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Muscle

What research found here. What was shown to help comes first, then the risks reported, most common first.

Muscle

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help105

AcupunctureStrong

Chronic pain across conditions

Shown to ease chronic pain about 0.5 standard deviations more than no acupuncture and about 0.2 more than sham acupuncture, with effects lasting a year.

Compared with sham acupuncture [2][3]; no acupuncture [2][3]

The numbers and sources
Effect
In individual patient data from 39 trials, acupuncture was superior to both sham and no acupuncture for each pain condition (all P < .001). The difference was close to 0.5 standard deviations against no acupuncture and close to 0.2 against sham, and about 15% of the effect was lost at 1 year. Effects were smaller in trials whose sham used a penetrating needle [2]. The earlier analysis of 29 trials found pain scores lower than sham by 0.23 SD for back and neck pain, 0.16 SD for osteoarthritis and 0.15 SD for chronic headache, and lower than no acupuncture by 0.55, 0.57 and 0.42 SD [3].
Population
20,827 patients with nonspecific musculoskeletal pain, osteoarthritis, chronic headache or shoulder pain in 39 trials [2]. 17,922 patients in 29 trials [3].
Sources
[2], [3]
Caveats
The two analyses come from the same collaboration and the later one contains the earlier trials. Patients and acupuncturists cannot be blinded when the comparison is no acupuncture, so the larger effect includes expectation. The authors say factors beyond needling contribute to the effect [3].
BCAAs and EAAsStrong

Muscle soreness and damage after hard exercise

Shown to reduce muscle soreness 24 to 96 hours after damaging exercise in active adults, with larger effects at higher doses and longer use.

The numbers and sources
Effect
Across 18 RCTs, BCAAs reduced soreness at 24 hours (g -1.34), 48 hours (g -1.75), 72 hours (g -1.82) and 96 hours (g -0.82). Creatine kinase was lower immediately (g -0.44) and at 72 hours (g -0.99), but not at 24, 48 or 96 hours; LDH did not change. Higher daily and total doses and longer use were linked to larger effects [4]. A second meta-analysis of 9 RCTs found reduced soreness 24 to 72 hours after exercise, mainly in trained people with mild to moderate damage, at doses up to 255 mg per kg a day [5].
Population
Healthy active adults after damaging resistance or endurance exercise [4][5].
Sources
[4], [5]
Caveats
The authors of [5] report high variability between studies by training status, dose and timing. Soreness is self-rated.
Beta-alanineStrong

High-intensity exercise lasting about 1 to 10 minutes

Shown to improve high-intensity exercise lasting about 1 to 10 minutes, by a median of about 3%, more in capacity tests than in time trials.

The numbers and sources
Effect
Across 40 placebo-controlled studies (1,461 participants), the overall effect size was 0.18 (95% CI 0.08 to 0.28). Within efforts of 0.5 to 10 minutes, exercise capacity tests improved more (0.50, 95% CI 0.25 to 0.75) than performance tests (0.11, 95% CI -0.20 to 0.42) [1]. An earlier meta-analysis found improvement in exercise of 60 to 240 seconds and over 240 seconds, none under 60 seconds, and a median 2.85% improvement after a median total of 179 g [2]. In 331 trained young men, the effect size for maximal efforts of 0.5 to 10 minutes was 0.39 (95% CI 0.09 to 0.69) [3].
Population
Healthy trained and untrained people; mostly men [1][2][3].
Sources
[1], [2], [3]
Caveats
Capacity tests (time to exhaustion) move more than performance tests (time trials), and performance is closer to competition [1]. Training status and total dose did not moderate the effect [1].
CaffeineStrong

Endurance performance

Shown to improve endurance time-trial power by about 3% and completion time by about 2% in mostly young, trained men. Responses varied.

The numbers and sources
Effect
Across 46 placebo-controlled studies, caffeine improved time-trial mean power output by 3.03% (± 3.07, effect size 0.23) and completion time by 2.22% (± 2.59, effect size 0.41). Two studies reported slower times and five reported lower power on caffeine [1]. An umbrella review of 21 meta-analyses rated the endurance evidence moderate quality and found effects generally larger for aerobic than anaerobic exercise [2].
Population
Mostly young, trained men [1][2].
Sources
[1], [2], [3]
Caveats
Individual responses varied, including some slower performances. Most trials were in young men, and the umbrella review notes few data in women and older adults [2]. A 2026 meta-analysis of 19 trials in 235 women found a small cycling gain (SMD 0.21, 95% CI 0.11 to 0.29) [4]. In 17 studies, people given a placebo they believed was caffeine also performed better (d 0.49, 95% CI 0.28 to 0.69), on low-quality evidence [5]. Not every pooled estimate gave a definite direction across its 95% prediction interval [2]. Reference [3] is an ISSN position stand, a narrative consensus rather than a systematic review.
CaffeineStrong

Muscle strength and power

Shown to improve maximal strength and jump power slightly in mostly resistance-trained young men. Lower body strength alone did not reach significance.

The numbers and sources
Effect
Across 10 studies, 1RM strength improved by SMD 0.20 (95% CI 0.03 to 0.36) and vertical jump power by SMD 0.17 (95% CI 0.00 to 0.34). Upper body strength improved (SMD 0.21, 95% CI 0.02 to 0.39); lower body did not reach significance (SMD 0.15, 95% CI -0.05 to 0.34) [6]. The umbrella review rated strength, muscular endurance and anaerobic power evidence moderate quality [2].
Population
Mostly resistance-trained young men [2][6].
Sources
[2], [6]
Caveats
Effects are small. The authors flag that blinding was rarely checked, and caffeine is often detectable by its feel [6].
Cold water immersionStrong

Muscle soreness after exercise

Shown to reduce muscle soreness for up to 96 hours after exercise compared with rest, in pooled trials rated low in quality.

The numbers and sources
Effect
A Cochrane review of 17 trials (366 participants) found less soreness than passive rest at 24 hours (SMD -0.55, 95% CI -0.84 to -0.27), 48 hours (SMD -0.66, 95% CI -0.97 to -0.35), 72 hours (SMD -0.93, 95% CI -1.36 to -0.51) and 96 hours (SMD -0.58, 95% CI -1.00 to -0.16). Cold water did not differ from contrast or warm water immersion [1]. A meta-analysis of 9 RCTs described cold water immersion as slightly better than passive recovery for immediate and delayed soreness [2]. An update with 44 trials found it superior to control for delayed soreness in every subgroup except the longest immersions [3]. Across 52 studies, soreness was lower 24 hours after high-intensity exercise (SMD -0.89, 95% CI -1.48 to -0.29) and perceived recovery was higher (SMD 0.66, 95% CI 0.29 to 1.03) [4].
Population
366 participants in 17 small trials [1]. Participants in 9 RCTs [2]. Athletes and non-athletes in 44 trials [3]. Physically active people in 52 studies [4].
Sources
[1], [2], [3], [4], [5]
Caveats
Soreness is self-rated and nobody can be blinded to cold water. Study quality was low and results were heterogeneous [1]. A 2026 umbrella review of 14 reviews found the same primary studies reused across reviews, so their agreement is not independent replication. It rated confidence low in 2 reviews and critically low in 12, and called the clinical importance of the soreness effect uncertain [5].
CreatineStrong

Lean mass during resistance training

Shown to add about 1 kg of lean mass over placebo alongside resistance training, and almost none without exercise.

The numbers and sources
Effect
Across 35 RCTs (1,192 participants), creatine raised lean body mass by 0.68 kg over placebo overall, and by 1.10 kg (95% CI 0.56 to 1.65) when combined with resistance training. With no exercise the difference was 0.03 kg (95% CI -0.65 to 0.70) [1]. In older adults training 2 to 3 days a week, the gain was 1.37 kg (95% CI 0.97 to 1.76) [2]. In postmenopausal women it was 0.37 kg (95% CI 0.05 to 0.69) [3].
Population
Healthy adults of all ages [1]; 721 adults with mean ages of 57 to 70 across 22 trials lasting 7 to 52 weeks [2]; 608 postmenopausal women in 7 trials lasting 12 to 104 weeks [3].
Sources
[1], [2], [3]
Caveats
Men gained 1.46 kg (95% CI 0.47 to 2.46) and women 0.29 kg (95% CI -0.43 to 1.01), a difference that did not reach significance for women [1]. Lean mass by DXA counts water, and creatine raises muscle water, so lean mass is not the same measure as contractile tissue. Several authors of [3] also authored the ISSN position stand [4]. In a 2026 analysis of 11 RCTs in adults aged 60 and over, the added muscle mass was not significant (g 0.35, 95% CI -0.09 to 0.78, low certainty) [5].
CreatineStrong

Strength

Shown to add a small amount of strength on upper and lower body lifts, including in older adults.

The numbers and sources
Effect
For upper body exercises under 3 minutes, the effect size for bench and chest press at the end of supplementation was 0.265 (95% CI 0.132 to 0.398) [6]. For the lower body, effect sizes were 0.336 (95% CI 0.047 to 0.625) for squat and 0.297 (95% CI 0.098 to 0.496) for leg press [7]. In older adults, leg press SMD was 0.24 (95% CI 0.05 to 0.43) [2]. Postmenopausal women gained 7.5 kg more on leg press 1RM (95% CI 2.2 to 12.8, 3 trials, 111 women) [3].
Population
53 trials with 1,138 people for upper limb [6]; 60 trials with 1,297 people for lower limb [7]; older adults [2]; postmenopausal women [3].
Sources
[2], [3], [6], [7]
Caveats
Effect sizes in the 0.24 to 0.34 range are small by conventional thresholds. The strength trials pool short protocols and long training blocks together. In 69 studies (1,937 participants), creatine with resistance training raised bench press by 1.43 kg and squat by 5.64 kg over placebo, and handgrip and leg press did not differ. Gains were significant in younger adults and men, and not in older adults or women [8]. A 2026 analysis limited to adults aged 60 and over found a small strength gain (g 0.31, 95% CI 0.18 to 0.45, moderate certainty) [5].
CuppingStrong

Chronic pain, compared with no treatment or usual care

Shown to ease chronic pain by a large amount against no treatment in the short term, and neck pain and fibromyalgia pain against no intervention or usual care.

Compared with no treatment [2]; no intervention [7]; usual care [6]

The numbers and sources
Effect
Against no treatment, cupping had a large short-term effect on pain (SMD -1.03, 95% CI -1.41 to -0.65) and a medium effect on disability (SMD -0.66) [2]. For neck pain, pain fell more than with no intervention (mean difference -2.42, 95% CI -3.98 to -0.86) and function improved [7]. In fibromyalgia, pain at day 18 was 12.4 points lower than with usual care (95% CI -18.9 to -5.9) [6].
Population
1,172 people in 18 trials [2]. 18 trials of people with neck pain [7]. 141 patients with fibromyalgia [6].
Sources
[2], [7], [6]
Caveats
Without a sham, participants know they were treated. The same reviews and trials found no difference from sham cupping [2][6]. The neck pain reviewers rated the evidence low in quality [7].
Daily stepsStrong

Activity and fitness in step-count programs

Shown to add about 1,800 to 2,500 steps a day in trials of pedometers and activity trackers, with a small gain in fitness.

Compared with control participants [8]; control groups the source does not describe [9]; control groups in randomized trials [10]

The numbers and sources
Effect
In randomized trials, pedometer users raised their activity by 2,491 steps a day more than controls (95% CI 1,098 to 3,885). Having a step goal such as 10,000 steps predicted a larger rise [8]. Across 39 reviews, activity trackers raised physical activity (SMD 0.3 to 0.6), about 1,800 extra steps a day, and fitness (SMD 0.3) [9]. In people with type 2 diabetes, step counters added 1,822 steps a day (95% CI 751 to 2,894), and 3,200 when paired with a goal [10].
Population
2,767 participants in 26 studies, 8 of them randomized, mean age 49, 85% women, mean 18 weeks [8]. 163,992 participants in 39 reviews of all ages [9]. 861 people with type 2 diabetes in 7 trials [10].
Sources
[8], [9], [10]
Caveats
People in trials could not be blinded to wearing a counter. Programs lasted months, and the earliest review called long-term durability undetermined [8].
Dietary nitrateStrong

Recovery from muscle damage

Shown to speed strength and jump recovery after damaging exercise with beetroot juice, in small trials. The reviews disagree on creatine kinase.

The numbers and sources
Effect
In 6 pooled studies, beetroot juice sped isometric strength recovery at 72 hours (SMD 0.54) and countermovement jump recovery at 24 to 72 hours (SMD 0.75 to 1.32), and raised pressure pain threshold at 48 and 72 hours. Creatine kinase and oxidative stress did not change; C-reactive protein was higher than placebo at 48 hours (SMD 0.55) [12]. In 7 trials, beetroot juice lowered creatine kinase by 98.67 IU/L (95% CI -122.14 to -75.21, I² 74.2%) and improved recovery of isometric strength (8.93%, I² 81.2%), jump height (4.72%) and pressure pain threshold (7.22%) against placebo. CRP, IL-6 and TNF-α did not change [13].
Population
Adults after damaging exercise [12][13].
Sources
[12], [13]
Caveats
Both reviews pooled 6 or 7 small, overlapping trials, and heterogeneity was high for creatine kinase and strength [13]. The two disagree on creatine kinase. All pooled trials in [12] had some concerns for risk of bias and used beetroot juice rather than isolated nitrate, so other juice compounds cannot be ruled out [12].
Dry needlingStrong

Musculoskeletal pain, all comparisons pooled

Shown to ease musculoskeletal pain more than no treatment, sham needling and other therapies pooled together, from 72 hours to 24 weeks, in low-quality evidence.

Compared with no treatment, sham dry needling and other therapies, pooled together [3][4]

The numbers and sources
Effect
Across 42 trials, pain fell more than in the comparison groups within 72 hours (SMD -0.81, 95% CI -1.21 to -0.40), at 1 to 3 weeks (SMD -0.69, 95% CI -1.02 to -0.35), at 4 to 12 weeks (SMD -0.85, 95% CI -1.30 to -0.40) and at 13 to 24 weeks (SMD -0.81, 95% CI -1.64 to -0.03) [4]. An earlier review of 13 trials found less pain and higher pressure pain thresholds than control, sham or other treatment up to 12 weeks. At 6 to 12 months the difference in pain was not significant. Function improved against no treatment or sham, and did not differ from other physical therapy treatments [3].
Population
42 trials of dry needling by physical therapists for musculoskeletal pain [4]. 13 trials of musculoskeletal pain conditions [3].
Sources
[3], [4]
Caveats
Both reviews pooled sham, no-treatment and other-treatment comparisons together, so the share of the effect beyond sham cannot be read from them. Heterogeneity downgraded the evidence to low quality at most time points [4], and the earlier review rated it very low to moderate [3]. The sham-controlled trials alone are in the next block.
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High-protein dietStrong

Lean mass during weight loss

Shown to keep about 0.3 to 0.4 kg more lean mass during calorie-restricted weight loss than standard-protein diets, including in adults over 50.

Compared with diets with less protein

The numbers and sources
Effect
Energy-restricted high-protein diets reduced the loss of fat-free mass by 0.43 kg (95% CI 0.09 to 0.78) and of resting energy expenditure by 595.5 kJ a day against standard-protein diets [1]. Protein above the RDA reduced lean mass loss during energy restriction by 0.36 kg (95% CI 0.06 to 0.67, 14 comparisons) and added 0.77 kg with resistance training (95% CI 0.23 to 1.31), with no effect when people neither dieted nor trained (0.08 kg, 95% CI -0.59 to 0.75) [2]. In a network meta-analysis of 83 articles, high-protein diets raised lean body mass 0.34 kg against normal-protein diets (95% CI 0.11 to 0.57) [3]. In adults over 50, higher protein during weight loss kept more lean mass and lost more fat [4].
Population
1,063 adults in 24 trials lasting a mean of 12.1 weeks [1]; healthy adults in 18 trials of at least 6 weeks [2]; adults in randomized trials [3]; adults over 50 in 20 RCTs [4].
Sources
[1], [2], [3], [4]
Caveats
A 2026 review of 22 trials in adults without kidney disease found no significant change in fat-free mass [5]. The abstract of [4] gives no effect sizes.
Hypnotherapy and clinical hypnosisStrong

Chronic pain

Shown to ease chronic pain moderately (Hedges' g -0.42) against control treatments, with larger effects after 8 or more sessions.

Compared with control interventions the source abstract does not describe [13]; standard care, and other psychological interventions [14]

The numbers and sources
Effect
In chronic musculoskeletal and nerve pain, hypnosis lowered pain intensity (Hedges' g -0.42 after treatment, -0.37 at short-term follow-up) and pain interference (-0.39). With 8 or more sessions the effect was g -0.555, and with fewer it was smaller and not significant [13]. An earlier meta-analysis found a moderate benefit over standard care, and a moderate benefit over other psychological treatments in people with pain other than headache [14].
Population
530 adults in 9 trials [13]. Trials in chronic pain [14].
Sources
[13], [14]
Caveats
Heterogeneity across trials was large [14].
Massage therapyStrong

Muscle soreness after exercise

Shown to reduce muscle soreness 24 to 72 hours after strenuous exercise compared with no massage, in three meta-analyses.

Compared with no intervention [8]; control conditions the source abstracts do not describe [9][10]

The numbers and sources
Effect
Against no intervention, soreness was lower at 24 hours (SMD -0.61, 95% CI -1.17 to -0.05), 48 hours (SMD -1.51, 95% CI -2.24 to -0.77) and 72 hours (SMD -1.46, 95% CI -2.59 to -0.33) after intense exercise [8]. Across 99 studies of recovery techniques, massage had the largest effect on soreness and perceived fatigue [9]. Across 29 studies with 1,012 participants, massage was linked to small improvements in soreness and flexibility [10].
Population
504 participants in 11 trials [8]. 99 studies of recovery methods [9]. 1,012 participants in 29 randomized studies [10].
Sources
[8], [9], [10]
Caveats
Soreness is self-rated and participants know they had a massage. The three reviews share many of the same small trials.
Muscle relaxantsStrong

Acute low back pain

Shown to lower acute low back pain by about 8 points on a 100-point scale within 2 weeks, with no gain in disability and more side effects.

The numbers and sources
Effect
In acute low back pain, non-benzodiazepine muscle relaxants lowered pain intensity at 2 weeks or less by 7.7 points on a 0 to 100 scale against control (95% CI 3.3 to 12.1), with no significant change in disability (-3.3, 95% CI -7.3 to 0.7). Adverse events were more frequent (RR 1.6, 95% CI 1.2 to 2.0) [1]. An earlier Cochrane review found non-benzodiazepine relaxants better than placebo for pain relief after 2 to 4 days (RR 0.80, 95% CI 0.71 to 0.89) and global efficacy (RR 0.49, 95% CI 0.25 to 0.95), with more adverse events (RR 1.50, 95% CI 1.14 to 1.98) [2]. For cyclobenzaprine, people were more likely to report improvement by day 14 than on placebo (OR 4.7, 95% CI 2.7 to 8.1), a number needed to treat of 2.7, with effect sizes of 0.38 to 0.58 that were largest in the first 4 days [3].
Population
6,505 adults with non-specific low back pain in 31 pooled trials, from 49 reviewed [1]; 30 trials, 24 of them in acute low back pain [2]; randomized placebo-controlled trials of cyclobenzaprine in adults with back pain [3].
Sources
[1], [2], [3]
Caveats
The most recent review rated its evidence very low certainty and described the pain reduction as not clinically important, with most trials at high risk of bias [1]. A separate review found fair evidence for cyclobenzaprine and tizanidine in acute back or neck pain and very limited or inconsistent data for methocarbamol and baclofen [4].
NappingStrong

Physical performance after a nap

Shown to improve physical test performance after an afternoon nap in two meta-analyses of athletes and active adults. Muscle force did not change.

Compared with a no-nap condition in randomized trials [3]; no-nap conditions [5]

The numbers and sources
Effect
After a normal night, a nap improved physical performance (SMD 0.99, 95% CI 0.67 to 1.31), with larger benefits for naps of 30 to under 60 minutes and when testing came more than an hour after waking [3]. In the 5-m shuttle run test, napping raised highest distance (effect size 1.026) and total distance (0.737) and lowered the fatigue index (0.839). Muscle force did not change (effect size 0.175, p = 0.267) [5].
Population
291 males aged 18 to 35, 164 trained athletes and 127 active adults, in 22 trials [3]. Physically active people and athletes in 18 studies after 7 to 9 hours of night sleep [5].
Sources
[3], [5]
Caveats
Small crossover studies, mostly in young men. Heterogeneity was high (I² 89.1%) [3]. Sprint, jump and endurance results rested on one to three studies each [5].
Physical therapy and exercise therapyStrong

Chronic low back pain, compared with no treatment, usual care or placebo

Shown to ease chronic low back pain about 15 points on a 100-point scale against no treatment, usual care or placebo, with a smaller gain in function.

Compared with no treatment, usual care or placebo [2]; no-exercise true control [3]

The numbers and sources
Effect
Exercise lowered pain by 15.2 points on a 100-point scale at earliest follow-up (95% CI -18.3 to -12.2), a difference the reviewers called clinically important, and functional limitation by 6.8 points (95% CI -8.3 to -5.3), short of their clinical threshold [2]. In a network meta-analysis against true control, Pilates had the largest pain effect (SMD -1.86), and resistance and stabilization or motor control exercise the largest function effects (SMD -1.14 and -1.13). Stretching and McKenzie exercise did not differ from true control for pain or function [3].
Population
249 trials of adults with chronic low back pain, mean age 43.7, 59% women [2]. 5,578 patients in 89 trials [3].
Sources
[2], [3]
Caveats
Most trials were at risk of performance bias because exercise cannot be blinded, and heterogeneity and publication bias lowered certainty [2]. The network meta-analysis rated its evidence low quality [3].
Protein powderStrong

Muscle mass and strength during resistance training

Shown to add about 2.5 kg of strength and 0.3 kg of fat-free mass during resistance training, with no extra gain above 1.62 g per kg of total protein.

The numbers and sources
Effect
Across 49 RCTs (1,863 participants), protein supplements increased 1RM strength by 2.49 kg (95% CI 0.64 to 4.33) and fat-free mass by 0.30 kg (95% CI 0.09 to 0.52) over control. Gains in fat-free mass did not rise further once total protein intake passed 1.62 g per kg a day. The effect fell with age and was larger in trained lifters (0.75 kg, 95% CI 0.09 to 1.40) [1]. An earlier meta-analysis of 22 RCTs (680 people) found 0.69 kg more fat-free mass (95% CI 0.47 to 0.91) and 13.5 kg more leg press 1RM (95% CI 6.4 to 20.7) [2]. In 12 studies of adults aged 18 to 30 (261 participants), whey raised bench press by 8.87 kg (95% CI 5.95 to 11.79) and squat by 9.60 kg (95% CI 5.61 to 13.60), and neither whey nor soy significantly changed lean body mass [3].
Population
Healthy adults in resistance training programs of 6 weeks or longer [1][2]. Young adults [3].
Sources
[1], [2], [3]
Caveats
The supplement effect depends on how much protein the diet already provides; the 1.62 g per kg breakpoint is total intake from food plus powder [1]. Trials mix whey, casein, soy and blends. The smaller 2025 review of young adults did not find the lean mass gain the two larger reviews report [3].
SNRIsStrongCommon

Fibromyalgia

Shown to raise the share with 50% pain relief in fibromyalgia from about 21% to 31%, a gain Cochrane reviewers judged not clinically relevant.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
On duloxetine or milnacipran, 31% reported pain relief of 50% or greater against 21% on placebo (risk difference 0.09, 95% CI 0.07 to 0.11), a number needed to treat of 11. More people rated themselves much or very much improved (52% vs 29%, number needed to treat 5). Fatigue changed little (SMD -0.13) [16]. For duloxetine 60 mg alone, the risk ratio for 50% pain relief was 1.57 (95% CI 1.20 to 2.06) at 12 weeks, a number needed to treat of 8 [13]. Across chronic pain conditions, with fibromyalgia the most studied, duloxetine 60 mg raised the odds of substantial pain relief (OR 1.91, 95% CI 1.69 to 2.17) [15].
Population
7,903 participants in 18 studies, 7 of duloxetine, 9 of milnacipran and 1 of desvenlafaxine [16]; 2,249 participants with fibromyalgia in 6 studies [13]; 4,490 participants in 16 studies for the pain relief outcome [15].
Sources
[16], [13], [15]
Caveats
Evidence quality was rated low for all comparisons with placebo, over concerns about publication bias [16]. The pooled figures mix duloxetine with milnacipran, which is outside this page. The band above uses the 9 to 10 point gain in responders.
Strength trainingStrong

Muscle strength, lean mass and physical function

Shown to raise muscle strength by a large amount and lean mass by about 1.1 kg in older adults in pooled trials, with small gains in everyday physical function.

Compared with control groups in randomized trials [9]; before training, in the same people, in randomized and nonrandomized studies [10][11]

The numbers and sources
Effect
Progressive resistance training had a large effect on strength (SMD 0.84, 95% CI 0.67 to 1.00, 73 trials), a small effect on physical ability (SMD 0.14), a gait speed gain of 0.08 m/s and a moderate to large effect on rising from a chair (SMD -0.94) [9]. Strength rose 29% in leg press, 24% in chest press, 33% in knee extension and 25% in lat pull, more with higher intensity [10]. Lean body mass rose 1.1 kg (95% CI 0.9 to 1.2), more with higher volume and less in older participants [11].
Population
6,700 older adults in 121 trials, mostly training 2 to 3 times a week at high intensity [9]. 1,079 adults 50 and older in 47 studies [10]. 1,328 adults 50 and older in 49 studies [11].
Sources
[9], [10], [11]
Caveats
Heterogeneity was high (I² 84% for lean mass) [11]. The two strength and lean mass reviews included nonrandomized studies and before-and-after changes [10][11].
Tai chi and qigongStrong

Falls in older adults

Shown to reduce the rate of falls in older adults by about 19% to 43% in pooled trials, and the number of people who fall by about 20%.

Compared with control interventions not thought to reduce falls [1]; other treatments [2]; control groups the source abstract does not describe [3]

The numbers and sources
Effect
In a Cochrane review, tai chi reduced the rate of falls by 19% (rate ratio 0.81, 95% CI 0.67 to 0.99, 7 trials, 2,655 participants, low certainty) and the number of people who fell by 20% (risk ratio 0.80, 95% CI 0.70 to 0.91, 8 trials, high certainty) [1]. Another meta-analysis found falls cut over the short term (incidence rate ratio 0.57, 95% CI 0.46 to 0.70) and less over the long term (0.87), with fewer injurious falls (0.50 short term). Time to first fall did not change (hazard ratio 0.98, 95% CI 0.69 to 1.37) [2]. A third found fewer fallers (risk ratio 0.80) and a lower fall rate (0.69, 95% CI 0.60 to 0.80), larger with more frequent practice [3].
Population
Community-dwelling adults aged 60 and over, mean age 76, 77% women [1]. Older and at-risk adults in 10 trials [2]. 3,824 older adults in 18 trials [3].
Sources
[1], [2], [3]
Caveats
Most trials had unclear or high risk of bias in at least one item [1]. Funnel plot asymmetry suggested publication bias [3]. The reviews share many trials.
TesamorelinStrong

Lean body mass

Shown to add about 1.4 kg of lean mass over placebo in people with HIV. Lean mass is a scan measure, not strength.

The numbers and sources
Effect
Two meta-analyses found lean body mass rose by 1.42 kg against placebo (95% CI 1.13 to 1.71) [4][5].
Population
909 people with HIV-associated lipodystrophy in 4 RCTs [4]; 5 RCTs against placebo [5].
Sources
[4], [5]
Caveats
Both reviews pooled largely the same trials in people with HIV. Lean mass is a scan measure, not strength.
Testosterone therapyStrongStudied in men

Fat-free mass and body fat in middle-aged and older men

Shown to add about 1.6 kg of fat-free mass and cut about 1.6 kg of body fat in middle-aged and older men, with no change in weight.

The numbers and sources
Effect
Testosterone raised fat-free mass by 1.6 kg (95% CI 0.6 to 2.6), a 2.7% rise over baseline, and cut total body fat by 1.6 kg (95% CI 0.6 to 2.5), a 6.2% drop. Body weight did not change [2]. A 2026 systematic review of 8 double-blind placebo-controlled trials in men with obesity and type 2 diabetes or metabolic syndrome found the most consistent effect was more lean mass and less fat mass [3].
Population
1,083 men in 29 RCTs, weighted mean age 64.5, mean baseline testosterone 10.9 nmol/L [2]; men with functional secondary hypogonadism, obesity and type 2 diabetes or metabolic syndrome in 8 RCTs [3].
Sources
[2], [3]
Caveats
The meta-analysis is from 2005, and dose and preparation explained some of the heterogeneity between trials [2]. The 2026 review was not pooled and rated certainty for lean and fat mass as low [3]. Fat-free mass counts water and organs as well as muscle.
YogaStrong

Balance and mobility in older adults

Shown to improve balance by a small to moderate amount in adults aged 60 and over, in two meta-analyses. Whether this prevents falls was not tested.

Compared with control groups the source abstract does not describe [13]; inactive controls such as a waiting list or education booklets [7]

The numbers and sources
Effect
Yoga improved balance performance (g = 0.40, 95% CI 0.15 to 0.65, 6 trials) and physical mobility (g = 0.50, 95% CI 0.06 to 0.95, 3 trials) [13]. In older adults without a specific condition, balance improved against inactive controls (effect size 0.7) [7].
Population
307 people aged 60 and over in 6 trials [13]. Older adults in 22 trials [7].
Sources
[13], [7]
Caveats
The reviewers state that whether balance gains translate into fewer falls is unknown [13].
AcupunctureModerate

Neck pain

Shown to ease neck pain slightly more than sham acupuncture in the short term, and more than a waiting list. The effect did not appear to last.

Compared with sham acupuncture [5]; inactive treatment [5]; waiting list [5]

The numbers and sources
Effect
For mechanical neck pain, pooled sham-controlled trials favored acupuncture in the short term (SMD -0.23, P = 0.0006). Acupuncture also eased pain more than inactive treatment, and pain and disability more than a waiting list, at short-term follow-up. The reviewers write that the effect does not seem sustainable over the long term [5].
Population
27 trials of adults with whiplash, myofascial, arthritic, nonspecific, radicular or mechanical neck pain [5].
Sources
[5]
Caveats
Evidence was rated moderate in quality. Few trials were large, and repeated courses were not studied [5].
AmitriptylineModerate

Fibromyalgia

Shown in very low quality evidence to make at least 50% pain relief about three times as likely as placebo, with about 4 treated for one extra responder.

Compared with placebo and other active treatments [6]

The numbers and sources
Effect
Using third-tier evidence, at least 50% pain relief was more likely on amitriptyline than placebo (RR 3.0, 95% CI 1.7 to 4.9), a number needed to treat of 4.1. Fatigue, sleep, quality of life and tender points showed no consistent differences. At least one adverse event occurred in 78% on amitriptyline and 47% on placebo [6].
Population
649 adults in nine studies of 6 to 24 weeks at 25 to 50 mg a day [6].
Sources
[6]
Caveats
No study had 50 or more participants per arm, and the review found no first or second tier evidence [6].
AshwagandhaModerate

Strength

Shown to raise muscle strength in physically active people but not in untrained people. Results leaned on single trials and certainty was low.

The numbers and sources
Effect
A Bayesian meta-analysis reported ashwagandha outperformed placebo on strength and power [11]. Across 20 trials, muscle strength rose (SMD 0.58, 95% CI 0.12 to 1.04, I² 56.9%), in physically active people (SMD 1.03, 95% CI 0.56 to 1.49) but not in untrained or special populations [8]. In 3 resistance-training trials, gains exceeded placebo for 1-RM bench press (SMD 0.60, 95% CI 0.20 to 1.01) and lower-body 1-RM (SMD 0.52, 95% CI 0.19 to 0.86), and body fat did not change [13]. In the three-level analysis, strength effects were positive but uncertain [12].
Population
Healthy men and women [11]. 1,249 participants [8]. 161 healthy adults in structured resistance training [13].
Sources
[11], [8], [13], [12]
Caveats
Under Hartung-Knapp-Sidik-Jonkman adjustment, both resistance-training estimates lost statistical significance, and each depended on one influential trial. Certainty was low [13].
BCAAs and EAAsModerate

Muscle protein synthesis

Shown to raise muscle protein synthesis for hours, by 22% in one trial of trained men, but less than complete protein. Lean mass did not change in older adults.

The numbers and sources
Effect
In 10 resistance-trained young men, 5.6 g of BCAAs after training raised myofibrillar protein synthesis to 0.110%/h against 0.090%/h on placebo, 22% higher [1]. A review of human studies found BCAAs transiently stimulate protein synthesis, but less than a complete protein source with all essential amino acids [2]. In older adults, leucine supplements raised the fractional synthetic rate (SMD 1.08, 95% CI 0.50 to 1.67) in 9 RCTs, with no change in lean body mass (SMD 0.18, 95% CI -0.18 to 0.54) or leg lean mass [3].
Population
Young trained men [1]; older adults [3].
Sources
[1], [2], [3]
Caveats
Synthesis rates over hours do not predict muscle gained over months, as the leucine meta-analysis shows [3]. The 2017 trial was funded in part by GlaxoSmithKline [1]. Reference [2] is a narrative review.
BCAAs and EAAsModerate

Muscle mass and strength in older adults

Shown to improve strength and muscle mass modestly in older adults, for supplements rich in BCAAs, including EAA and whey products.

The numbers and sources
Effect
Across 35 RCTs in older people, BCAA-rich supplements, a category that included EAA and whey protein products, improved strength (SMD 0.35, 95% CI 0.15 to 0.55), muscle mass (SMD 0.25, 95% CI 0.10 to 0.40) and physical performance (SMD 0.29, 95% CI 0.00 to 0.57). EAA supplements improved handgrip strength more than whey protein in subgroup analysis [7]. In 52 patients having knee replacement, 9 g a day of EAAs from 1 week before to 2 weeks after surgery left rectus femoris area at 134% of baseline at 2 years against 114% on placebo, and quadriceps strength at 159% against 125%. Clinical outcomes did not differ [8]. In 10 RCTs and one prospective study of people with sarcopenia, leucine groups differed from placebo in handgrip strength (p = 0.03), appendicular muscle mass and gait speed (p = 0.008) [9].
Population
Older adults [7]; knee replacement patients [8]; 1,133 people over 65 with sarcopenia [9].
Sources
[7], [8], [9]
Caveats
High heterogeneity, and 14 of 35 trials had potential bias [7]. The pooled supplements are not pure BCAA products. The leucine review rated its evidence low quality and found leucine alone of limited benefit without other therapy [9].
Beta-alanineModerate

Muscle carnosine

Shown to raise muscle carnosine at 4 to 6 g a day for 4 weeks, with nearly everyone responding in one lab's data.

The numbers and sources
Effect
A dose-response meta-analysis found muscle carnosine rises in a non-linear way and that common protocols may not approach saturation. In 99 individuals from one lab, 99.3% responded (95% CrI 96.2 to 100) [4]. The ISSN position stand reports that 4 to 6 g a day for 4 weeks raised muscle carnosine [5].
Population
Human muscle biopsy studies [4].
Sources
[4], [5]
Caveats
Carnosine is the mechanism, not a performance outcome. The individual data come from the authors' own lab [4]. Reference [5] is an ISSN position stand, a narrative consensus.
Biofeedback and neurofeedbackModerate

Tension-type headache

Shown to reduce tension-type headache with a medium to large effect (d 0.73) that lasted about 15 months, more than headache monitoring, placebo or relaxation.

Compared with headache monitoring, placebo, and relaxation therapies [5]

The numbers and sources
Effect
Across 53 studies, biofeedback gave an effect size of 0.73 (95% CI 0.61 to 0.84) that held over an average 15 months of follow-up. Headache frequency improved most, with gains in muscle tension, anxiety, depression and pain medication use. Biofeedback combined with relaxation gave the largest effects, and effects were especially large in children and adolescents [5].
Population
53 studies of tension-type headache [5].
Sources
[5]
Caveats
One meta-analysis from one research group. The abstract does not say how many studies were randomized [5].
Biofeedback and neurofeedbackModerate

Chronic back pain

Shown to reduce chronic back pain intensity with a moderate effect (Hedges' g 0.60) that held over about 8 months, alone or added to other treatment.

Compared with control conditions the source abstract does not describe, with before-and-after studies included [10]

The numbers and sources
Effect
Biofeedback reduced pain intensity (g 0.60, 95% CI 0.44 to 0.76), and the effect held at an average 8-month follow-up (g 0.62). It also reduced depression (g 0.40), disability (g 0.49) and muscle tension (g 0.44). Effects held when only controlled studies were analyzed [10].
Population
1,062 patients in 21 studies [10].
Sources
[10]
Caveats
The analysis included uncontrolled studies, and the abstract does not describe the controls [10].
CitrullineModerate

Strength and power during high-intensity sets

Shown to slightly improve resistance sets and short sprints in mostly strength-trained adults, with about 6% more repetitions to failure on 6 to 8 g.

The numbers and sources
Effect
Across 12 studies (13 samples, 198 participants) using at least 3 g taken at least 30 minutes before testing, citrulline improved resistance sets and sprints of 30 seconds or less by SMD 0.20 (95% CI 0.01 to 0.39), with no heterogeneity (I² 0%) [1]. In 8 studies (137 participants), 6 to 8 g of citrulline malate 40 to 60 minutes before training added 3 ± 5 repetitions to failure, 6.4% over placebo (SMD 0.196). Lower body trended up (SMD 0.27, p = 0.051) and upper body did not change (SMD 0.16) [2].
Population
Healthy, mostly strength-trained adults [1]; 101 trained men, 26 trained women and 9 untrained men in [2].
Sources
[1], [2]
Caveats
Every individual study's confidence interval crossed zero; only the pooled estimate did not [1].
CLAModerate

Lean mass

Shown to raise fat-free mass by about 0.3 kg in adults, under 1% of fat-free mass.

The numbers and sources
Effect
In the same 18 trials pooled for fat loss, fat-free mass rose 0.3 kg during CLA treatment, with no effect of dose or duration [4]. In 70 RCTs, fat-free mass rose 0.27 kg (95% CI 0.09 to 0.45) [3].
Population
Adults in RCTs [3][4].
Sources
[3], [4]
Caveats
The change was under 1% of fat-free mass [4].
DHEAModerate

Lean mass and fat mass

Shown to raise lean mass by about 0.45 kg in adults, though a 2-year trial in older adults found no change in body composition.

The numbers and sources
Effect
Pooled RCTs found DHEA raised lean body mass by 0.45 kg (95% CI 0.15 to 0.75) and lowered fat mass by 0.85% (95% CI 0.51 to 1.18). Body weight did not change [1]. In elderly men, fat mass fell by an SMD of -0.35 (95% CI -0.65 to -0.05), but the effect disappeared after adjusting for rises in testosterone and estradiol [2]. A 2-year RCT found no significant effect on body composition in men or women [3].
Population
Adults in randomized trials [1]; 1,353 elderly men in 25 placebo-controlled RCTs, mean follow-up 36 weeks [2]; 87 elderly men and 57 elderly women with low DHEA-S over 2 years [3].
Sources
[1], [2], [3]
Caveats
The pooled lean mass gain is small, and the one long trial did not find it.
Dry needlingModerate

Neck pain

Shown to ease neck pain in the short term against sham, placebo, waiting list or other needling pooled together. Neck function did not differ from physical or manual therapy.

Compared with sham, placebo, waiting list or another form of dry needling, pooled together [7]; manual therapy [7]; other physical therapy interventions [7]; sham dry needling, physical therapy or no treatment [8]

The numbers and sources
Effect
Against sham, placebo, waiting list or another form of dry needling, pain was lower immediately after treatment (mean difference -1.53 points, 95% CI -2.29 to -0.76) and in the short term (-2.31 points, 95% CI -3.64 to -0.99), and pain-related disability was lower in the short term (SMD -0.87). Against manual therapy, short-term pain was 0.51 points lower (95% CI -0.95 to -0.06) and disability did not differ. Against other physical therapy, no outcome differed. Nothing differed at mid-term, and neck range of motion did not change against any comparison [7]. In chronic nonspecific neck pain, function did not differ from control groups (mean difference 3.51, p = 0.14) and pain relief was borderline higher (mean difference 0.94, p = 0.05) [8].
Population
28 trials of people with neck pain and trigger points [7]. 5 trials of chronic nonspecific neck pain [8].
Sources
[7], [8]
Caveats
Sham and waiting-list comparisons were pooled together, so the effect beyond sham is not separable. No trial could blind the therapist [7]. Evidence was rated low to moderate [7].
Dry needlingModerate

Low back pain

Shown to ease low back pain more than other treatments right after treatment in 11 trials. Effects on disability were smaller and effects at later follow-up unclear.

Compared with other treatments the review abstract does not list [9]; laser, physical therapy and other combined treatments [6]

The numbers and sources
Effect
Across 11 trials, dry needling of trigger points lowered pain intensity (SMD -1.06, 95% CI -1.77 to -0.36) and functional disability (SMD -0.76, 95% CI -1.46 to -0.06) more than other treatments after the intervention. Dry needling combined with other treatments lowered pain more than dry needling alone (SMD 0.83, 95% CI 0.55 to 1.11) [9]. A second review found results against laser, physical therapy and other combined treatments mixed, and called the evidence not robust enough for a firm conclusion [6].
Population
802 people with low back pain and trigger points in 11 trials [9]. 16 trials of low back pain [6].
Sources
[9], [6]
Caveats
The reviewers call the effect on disability and at follow-up unclear [9]. Most trials were at high or unclear risk of bias [6].
Dry needlingModerate

Shoulder pain

Shown to ease nontraumatic shoulder pain by a small amount, about half a point, and disability by a larger amount, in the short term only.

Compared with comparison groups the review abstract does not describe [10]

The numbers and sources
Effect
Trigger point dry needling, alone or added to other treatment, lowered shoulder pain (mean difference -0.49 points, 95% CI -0.84 to -0.13, SMD -0.25) and pain-related disability (mean difference -9.99 points, 95% CI -15.97 to -4.01, SMD -1.14) more than the comparison groups. The effect on pain was found only in the short term [10].
Population
6 trials of nontraumatic shoulder pain [10].
Sources
[10]
Caveats
Evidence was moderate in quality for pain and low for disability, downgraded for heterogeneity [10].
Dry needlingModerate

Tennis elbow

Shown to ease tennis elbow pain and disability with large effects in the short term, and grip strength with a small effect.

Compared with comparison groups the review abstract does not describe [15]

The numbers and sources
Effect
Dry needling, alone or with other treatment, lowered pain (SMD -1.13, 95% CI -1.64 to -0.62) and related disability (SMD -2.17, 95% CI -3.34 to -1.01), and raised pressure pain thresholds (SMD 0.98) and grip strength (SMD 0.48, 95% CI 0.16 to 0.81). The largest effects were in the short term [15].
Population
320 people with lateral epicondylalgia in 7 trials [15].
Sources
[15]
Caveats
Evidence was low to moderate, downgraded for heterogeneity [15].
Energy drinksModerate

Exercise performance

Shown to improve muscle strength and endurance, endurance tests, jumping and sport-specific actions after one energy drink, in pooled studies, with no significant effect on sprinting.

Compared with control or placebo conditions the abstract does not describe [4]

The numbers and sources
Effect
Energy drink intake improved muscle strength and endurance (effect size 0.49), endurance exercise tests (0.53), jumping (0.29) and sport-specific actions (0.51), and not sprinting (0.14, p = 0.06). Performance was associated with taurine dose and not with caffeine dose in a meta-regression [4].
Population
34 studies published 1998 to 2015 [4].
Sources
[4]
Caveats
One review, with drinks varying in dose and ingredients. A different review found little evidence that ingredients other than caffeine improve performance [5]. Caffeine trials on their own are on the caffeine page.
Fish oilModerate

Muscle soreness and recovery after exercise

Shown to reduce muscle soreness and improve strength after eccentric exercise in healthy adults, though the wider review called recovery effects equivocal.

The numbers and sources
Effect
In 9 placebo-controlled eccentric exercise trials, long-chain omega-3 reduced delayed onset muscle soreness (Hedges' g -0.75, 95% CI -1.14 to -0.36), creatine kinase (g -0.40) and swelling (g -0.45), and improved strength (g 0.45, 95% CI 0.07 to 0.83) and range of motion (g 0.93) at peak impairment. Across all 43 studies reviewed, the effect on recovery was equivocal [30].
Population
Healthy young to middle-aged adults [30].
Sources
[30]
Caveats
The authors note significant methodological limits and could not assess dosing. One author reports product and placebo support from AkerBiomarine, a krill oil producer [30].
GabapentinoidsModerateVery common

Fibromyalgia

Shown to give at least 50% pain relief to about 22% to 24% of people with fibromyalgia on pregabalin, against about 14% on placebo.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
With pregabalin 300 to 600 mg a day, about 22% to 24% had at least 50% pain reduction after 12 or 13 weeks against about 14% on placebo, and 39% to 43% had at least 30% reduction against about 28%. Numbers needed to treat ranged from 7 to 14 [3]. For gabapentin, one 12-week trial found at least 30% pain reduction in 49% (38 of 75) against 31% (23 of 75) on placebo, and the reviewers judged the evidence insufficient to support or refute a benefit [4].
Population
3,283 participants in 5 pregabalin trials of 8 to 13 weeks [3]; 150 participants in one gabapentin trial [4].
Sources
[3], [4]
Caveats
The evidence is for pregabalin, rated high quality. The gabapentin trial was rated very low quality, and gabapentin is not approved for fibromyalgia. About 9 in 100 people gained substantial benefit beyond placebo.
Growth hormoneModerate

Body composition in healthy older adults

Shown to lower fat mass about 2.1 kg and raise lean body mass about 2.1 kg in healthy older adults, with no change in weight.

The numbers and sources
Effect
Against no growth hormone, fat mass fell 2.1 kg (95% CI 1.35 to 2.8) and lean body mass rose 2.1 kg (95% CI 1.3 to 2.9). Weight did not change (0.1 kg, 95% CI -0.7 to 0.8). Total cholesterol fell 0.29 mmol/L, not significantly after adjusting for body composition. Bone density and other lipids did not change [1].
Population
18 study populations with 220 treated participants, mean age 69, mean BMI 28, mean treatment 27 weeks [1].
Sources
[1]
Caveats
Most trials were small, and some outcomes were measured too rarely to pool [1]. The review was funded by AHRQ and the NIA. Lean body mass includes water, not only muscle.
Growth hormoneModerate

Visceral fat and thigh muscle in adults with obesity

Shown to lower visceral fat modestly and raise thigh muscle area with low-dose growth hormone in adults with obesity and no deficiency.

The numbers and sources
Effect
In adults with obesity and no growth hormone deficiency, low-dose growth hormone lowered visceral fat by an SMD of -0.34 (95% CI -0.57 to -0.12) and raised thigh muscle area by 6.33 cm² (95% CI 1.72 to 10.95) against placebo [4].
Population
420 adults aged 18 to 65 in 10 RCTs lasting 4 to 72 weeks [4].
Sources
[4]
Caveats
Small trials with wide differences in length. Fasting glucose rose (see Risks) [4].
Growth hormoneModerate

Lean mass and leg strength in orthopedic patients

Shown to raise lean body mass about 3.6% and leg strength about 3.2% in orthopedic and sports medicine patients.

The numbers and sources
Effect
Across orthopedic studies, lean body mass rose in 15 of 23 studies, a mean difference of 3.63% against placebo, and leg extension strength rose by a mean difference of 3.17%. IGF-1 rose by a mean of 133.2%, in a dose-dependent way [5].
Population
1,157 patients, mean age 54.3, in 22 studies of orthopedic surgery and sports medicine settings, mean dose 1.49 mg per day [5].
Sources
[5]
Caveats
The review rated its studies as moderate quality and pooled only where it could [5]. These were patients, not healthy athletes.
Growth hormoneModerate

Body composition and quality of life in growth hormone deficiency

Shown to lower body fat about 2.6 kg and raise lean mass about 1.4 kg in adults with growth hormone deficiency. Quality of life improved in most trials.

The numbers and sources
Effect
In adults with confirmed deficiency, growth hormone lowered weight by 2.31 kg (95% CI 1.96 to 2.66) and body fat by 2.56 kg (95% CI 2.16 to 2.97), and raised lean body mass by 1.38 kg (95% CI 1.10 to 1.65). BMI and bone density did not change. Quality of life improved in 11 of 16 trials, though the data could not be pooled [6].
Population
54 RCTs with more than 3,400 adults with growth hormone deficiency [6].
Sources
[6]
Caveats
Trial quality was rated fair [6]. These results describe people with a diagnosed deficiency, not healthy adults.
Heat therapyModerate

Acute low back pain, compared with an oral placebo

Shown to ease acute and subacute low back pain slightly against an oral placebo after 5 days, by about 1 point on a 0 to 5 scale, in two trials.

Compared with oral placebo [7]; a comparison the abstract does not describe, for a heated blanket [7]

The numbers and sources
Effect
In two trials of 258 people, a heat wrap reduced pain after five days against oral placebo (WMD 1.06, 95% CI 0.68 to 1.45, on a 0 to 5 scale). In one trial of 90 people, a heated blanket reduced acute pain immediately after use (WMD -32.20, 95% CI -38.69 to -25.71, on a 0 to 100 scale). There was not enough evidence to judge cold, and conflicting evidence on heat against cold [7].
Population
1,117 people in 9 trials, most with acute or subacute low back pain [7].
Sources
[7]
Caveats
The reviewers call the evidence moderate for a small short-term effect, from few trials. No pooled trial covered chronic low back pain [7].
Heat therapyModerate

Muscle soreness after exercise

Shown to ease muscle soreness after exercise when applied within an hour, in pooled trials, with hot packs ranking highest in a network analysis.

Compared with control groups the abstract does not describe [10]; passive recovery and other cold and heat methods [11]

The numbers and sources
Effect
Heat lowered soreness within 24 hours (SMD -1.17, as reported with a 95% CI of -2.62 to -0.09) and after 24 hours (SMD -0.82, 95% CI -1.38 to -0.26). Hot packs lowered it within 24 hours (SMD -2.31) and after (SMD -1.78), while other heat methods did not differ from control. Heat and cold did not differ from each other (P = 0.16) [10]. In a network analysis of ten methods, hot packs ranked first for pain relief at 24 and 48 hours [11].
Population
1,098 people in 32 trials [10]. 1,367 people in 59 trials [11].
Sources
[10], [11]
Caveats
Both reviews come from the same group and note limited trial quality [10][11].
HMBModerate

Muscle damage markers

Shown to lower the muscle damage markers creatine kinase and LDH after damaging exercise in healthy adults, mainly in studies over 6 weeks.

The numbers and sources
Effect
Across 10 studies (324 participants), HMB lowered creatine kinase by 60.71 U/L (95% CI -78.12 to -43.29) and, across 8 studies, LDH by 15.42 U/L (95% CI -22.2 to -8.6). The effect was significant in studies longer than 6 weeks [11].
Population
Healthy adults after damaging exercise [11].
Sources
[11]
Caveats
Blood markers, not soreness or performance.
Hyperbaric oxygen therapyModerate

Fibromyalgia pain

Shown to reduce pain in people with fibromyalgia in one meta-analysis of 9 small studies. Adverse events occurred in 23.8% of treated patients.

The numbers and sources
Effect
Across 9 studies (288 patients), hyperbaric oxygen reduced pain compared with control (SMD -1.56, 95% CI -2.18 to -0.93, I² 51%). Most studies also reported better tender points, fatigue, function and sleep disturbance. Adverse events occurred in 44 of 185 patients (23.8%), and 12 (6.5%) withdrew because of them [7].
Population
288 people with fibromyalgia in 9 randomized and non-randomized controlled trials [7].
Sources
[7]
Caveats
The pooled studies include non-randomized trials, and the abstract does not say how many used a sham. No serious adverse events were observed.
L-carnitineModerate

Muscle soreness and damage markers

Shown to lower muscle soreness for up to 96 hours after damaging exercise in adults, with damage markers lower at 24 hours only.

The numbers and sources
Effect
Across 7 RCTs, L-carnitine lowered muscle soreness at 0, 24, 48, 72 and 96 hours after damaging exercise, and lowered creatine kinase, myoglobin and LDH at 24 hours only [4].
Population
Adults after exercise-induced muscle damage [4].
Sources
[4]
Caveats
The abstract gives no effect sizes. Seven trials.
Massage therapyModerate

Pain across conditions

Shown to ease pain more than no treatment, by a large margin, and more than sham or active treatments, by smaller margins, in a meta-analysis of 67 trials.

Compared with sham treatments [2]; no treatment [2]; active treatments [2]

The numbers and sources
Effect
Massage lowered pain more than sham (SMD -0.44), no treatment (SMD -1.14) and active comparators (SMD -0.26) [2]. A map of 49 systematic reviews, 32 rated high quality, found their conclusions gave low strength of evidence for potential benefits in labor, shoulder, neck, low back, cancer, arthritis, postoperative and muscle soreness pain [3].
Population
67 randomized trials of people with pain in the general population, 60 rated high quality [2]. 49 systematic reviews [3].
Sources
[2], [3]
Caveats
The evidence map notes few large, rigorous trials and poor description of the massage given, so reviews could not say which type helps which pain [3]. Participants cannot be blinded to massage.
Massage therapyModerate

Low back pain

Shown to ease subacute and chronic low back pain more than inactive controls in the short term, with no lasting difference. Against active treatments the pain difference was small.

Compared with inactive controls [4]; active treatments [4]; usual care [5]

The numbers and sources
Effect
For subacute and chronic low back pain, massage lowered pain more than inactive controls in the short term (SMD -0.75, 95% CI -0.90 to -0.60, 7 trials, 761 participants) and improved function (SMD -0.72), with no difference in the long term. Against active controls, pain was lower in the short term (SMD -0.37, 12 trials, 964 participants) and long term (SMD -0.40), and function did not differ [4]. In 401 adults, Roland disability scores at 10 weeks were 2.9 points lower with relaxation massage and 2.5 points lower with structural massage than with usual care [5].
Population
25 trials with 3,096 participants, almost all with subacute or chronic low back pain [4]. 401 adults aged 20 to 65 with chronic low back pain in Seattle [5].
Sources
[4], [5]
Caveats
The reviewers rated the evidence low to very low and wrote that they have very little confidence in massage for low back pain [4]. The trial did not blind participants to massage versus usual care [5].
MK-677Grey marketModerate

Fat-free mass

Shown to add about 1.1 kg of fat-free mass over a year in older adults, against a 0.5 kg loss on placebo. Body weight also rose.

The numbers and sources
Effect
At 12 months, fat-free mass changed by +1.1 kg (95% CI 0.7 to 1.5) on MK-677 and -0.5 kg (95% CI -1.1 to 0.2) on placebo. Intracellular water, a marker of body cell mass, changed by +0.8 kg against -1.0 kg [1]. In obese men over 8 weeks, fat-free mass rose on MK-677 compared with placebo by DEXA and by a four-compartment model [2].
Population
65 healthy adults aged 60 to 81, over 2 years [1]; 24 obese men aged 18 to 50, BMI over 30 [2].
Sources
[1], [2]
Caveats
Fat-free mass includes water, organs and bone, not only muscle. Body weight also rose 2.7 kg against 0.8 kg on placebo [1].
NSAIDsModerate

Soreness and strength loss after muscle injury

Shown to reduce strength loss, soreness and creatine kinase modestly after acute muscle injury, more for lower body muscles, in studies including animals.

The numbers and sources
Effect
Across injury markers combined, NSAIDs produced a small to medium decrease (standardized effect size +0.34) in strength loss, soreness and blood creatine kinase after acute muscle injury. The effect was larger when lower body muscles were injured [1].
Population
41 studies of acute skeletal muscle injury, human and animal, including exercise-induced damage [1].
Sources
[1]
Caveats
Heterogeneity was moderate (I² 57%). The pooled result includes animal studies, and in animals the effect fell with longer use and longer follow-up [1].
Pet ownershipModerate

Walking and physical activity

Linked to more walking in dog owners in one meta-analysis. In a controlled study, getting a dog added about 2,600 daily steps at 3 months, gone by 8 months.

Compared with people without a dog [5]; people who delayed getting a dog and people with no plans to get one [6]; young people without a family dog [7]

The numbers and sources
Effect
Dog owners walked more (d 0.26) and were more physically active (d 0.16) than non-owners. About 60% of owners walked their dog, a median 160 minutes and 4 walks a week [5]. People who got a dog took 2,589 more steps a day at 3 months (p = 0.004), and the gain was not maintained at 8 months [6]. In children and teenagers, 7 of 9 studies found more activity with a family dog [7].
Population
29 studies, mostly cross-sectional, mostly in Australia and the US [5]. 71 adults, 17 of whom got a dog, followed 8 months [6]. 9 studies of youth [7].
Sources
[5], [6], [7]
Caveats
Most studies were cross-sectional, and active people may choose dogs. The controlled study let people choose their group and was small [6].
Protein powderModerate

Muscle and strength in older adults

Shown to raise lower-body strength slightly in older adults, with lean mass gains only when combined with resistance training.

The numbers and sources
Effect
In 25 trials (1,454 adults aged 64 to 84), whey raised lower-body strength (SMD 0.16, 95% CI 0.04 to 0.28, 19 trials) and did not change upper-body strength or body composition overall. Combined with resistance training, whey raised lean body mass [4].
Population
Older adults, with or without resistance training [4].
Sources
[4]
Caveats
One meta-analysis. The lean mass finding comes from a subgroup [4].
Protein powderModerate

Recovery of muscle function after training

Shown to speed recovery of muscle function modestly in the 4 days after hard resistance training in young adults, with half of studies reporting benefit.

The numbers and sources
Effect
Across 13 RCTs from 8 studies, whey protein produced effect sizes of 0.4 to 0.7 for restoring contractile function from under 24 to 96 hours after strenuous resistance training. Half of the individual studies reported a benefit [7].
Population
Young, healthy adults [7].
Sources
[7]
Caveats
One meta-analysis of a small pool of trials. Funded by Food Health Ireland, a dairy research partnership [7].
Red light therapyModerate

Neck pain

Shown to reduce chronic neck pain by about 20 mm on a 100 mm scale compared with placebo, lasting up to 22 weeks after treatment, in one meta-analysis.

The numbers and sources
Effect
Across 16 RCTs (820 patients), pain intensity fell 19.86 mm on a 100 mm visual analogue scale (95% CI 10.04 to 29.68) in 11 trials. In 7 trials with follow-up of 1 to 22 weeks, the reduction was 22.07 mm (95% CI 17.42 to 26.72). In chronic neck pain, the relative risk of improvement was 4.05 (95% CI 2.74 to 5.98) [8].
Population
820 patients with acute or chronic neck pain in 16 trials [8].
Sources
[8]
Caveats
One meta-analysis, published in 2009, of clinic laser treatment applied to painful sites.
Red light therapyModerate

Fibromyalgia

Shown to improve fibromyalgia symptom, pain and fatigue scores compared with placebo laser in one meta-analysis. It added nothing to an exercise program.

The numbers and sources
Effect
Across 9 RCTs (325 patients), low-level laser improved Fibromyalgia Impact Questionnaire scores (SMD 1.16, 95% CI 0.64 to 1.69), pain severity (SMD 1.18, 95% CI 0.82 to 1.54), tender points, fatigue, stiffness, depression and anxiety more than placebo laser. Laser plus a standardized exercise program gave no extra symptom relief over exercise alone [10].
Population
325 people with fibromyalgia in 9 RCTs [10].
Sources
[10]
Caveats
One meta-analysis of small trials.
SARMsGrey marketModerate

Lean body mass

Shown to add lean mass, about 1 to 1.5 kg across short trials, in healthy adults and people with cancer weight loss. Lean mass is not the same as strength.

The numbers and sources
Effect
LGD-4033 raised lean body mass in a dose-dependent way over 21 days [1]. Enobosarm raised total lean body mass in a dose-dependent way over 12 weeks, significant against placebo at the higher dose [2]. In people with cancer-related weight loss, lean mass rose by a median 1.5 kg and 1.0 kg in the two enobosarm groups by day 113, against 0.02 kg on placebo [3]. A 2026 review reports lean mass rising by roughly 1 to 1.5 kg across randomized trials [4].
Population
76 healthy men aged 21 to 50 [1]; 120 healthy men over 60 and postmenopausal women [2]; 159 men over 45 and postmenopausal women with cancer and at least 2% weight loss, 100 in the efficacy analysis [3].
Sources
[1], [2], [3], [4]
Caveats
The trials were short. In the cancer trial, the gains were changes from baseline within each group, and the trial was funded by GTx, the developer [3]. Lean mass by DEXA is not the same as muscle strength.
SNRIsModerate

Chronic back pain and osteoarthritis pain

Shown to lower back pain by about 5 points on a 100-point scale, which reviewers called not clinically important, and osteoarthritis pain by about 10 points.

The numbers and sources
Effect
On a scale from 0 to 100, SNRIs lowered back pain by 5.30 points more than placebo at 3 to 13 weeks (95% CI 3.30 to 7.31) and osteoarthritis pain by 9.72 points (95% CI 6.69 to 12.75). Back pain disability fell by 3.55 points. The authors judged the back pain effect small and not clinically important, and could not exclude a clinically important effect in osteoarthritis [17]. Across chronic pain conditions, duloxetine 60 mg lowered pain intensity against placebo (SMD -0.31, 95% CI -0.39 to -0.24) [15].
Population
5,318 participants with back pain, sciatica or osteoarthritis in 33 trials [17]; 4,959 participants in 18 studies for pain intensity [15].
Sources
[17], [15], [18]
Caveats
Certainty was moderate for back pain and low for osteoarthritis [17]. Duloxetine is the only SNRI with a chronic musculoskeletal pain approval [18]. Most trials were short and excluded people with low mood [15].
Tart cherryModerate

Recovery after strenuous exercise

Shown to speed recovery of strength after strenuous exercise in exercising adults and athletes. Reviews disagree on whether muscle soreness falls.

The numbers and sources
Effect
Across 14 studies, tart cherry reduced muscle soreness (ES -0.44, 95% CI -0.87 to -0.02) and sped recovery of strength (ES -0.78, 95% CI -1.11 to -0.46) and power (ES -0.53, 95% CI -0.77 to -0.29). Creatine kinase and TNF-alpha did not change [1]. A 2026 meta-analysis of 19 trials in trained athletes found faster recovery of maximal strength at every time point (ES 0.63 right after exercise to 4.82 at 96 hours) and lower CRP up to 48 hours (ES -0.46 to -0.73). Muscle soreness, creatine kinase, IL-6 and TNF-alpha did not change [2].
Population
Exercising adults in 14 studies to July 2020 [1]. Trained athletes in 19 trials to December 2025 [2].
Sources
[1], [2]
Caveats
The two meta-analyses disagree on soreness, and the later one reports strength effects several times larger, with I² of 69% to 93% [1][2]. Certainty in [2] ranged from very low to moderate, and several results depended on single studies. Products, doses and exercise protocols varied.
TaurineModerate

Endurance and exercise performance

Shown to improve endurance and time to exhaustion modestly in people, in small trials with low certainty.

The numbers and sources
Effect
Across 10 studies, taurine improved endurance performance by Hedges' g 0.40 (95% CI 0.12 to 0.67) and time to exhaustion by g 0.43 (95% CI 0.12 to 0.75). Dose and single versus repeated dosing did not change the effect [1]. A 2025 three-level meta-analysis of 23 trials of a single dose found g 0.25 (95% CI 0.10 to 0.39, I² 61%) across performance measures [2].
Population
10 studies at 1 to 6 g a day, single doses up to 2 weeks [1]; 308 participants with 69 effect sizes [2].
Sources
[1], [2]
Caveats
GRADE certainty in [2] was low to very low. Several subgroup effects weakened after influential studies were removed, and prediction intervals often included no effect [2]. Both analyses pool small trials.
TENSModerateVery common

Fibromyalgia pain with movement

Shown to lower pain with movement in women with fibromyalgia, by 1.0 point against placebo TENS and 1.8 points against no TENS, out of 10.

Compared with placebo TENS [12]; no TENS [12]; physical therapy alone [13]

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
After 4 weeks of home use during activity, pain with movement fell more with TENS than with placebo TENS (MD -1.0, 95% CI -1.8 to -0.2) or no TENS (MD -1.8, 95% CI -2.6 to -1.0), and fatigue with movement fell too. Global improvement was reported by 70% on TENS, 31% on placebo TENS and 9% with no TENS [12]. In a trial across 28 physical therapy clinics, adding TENS lowered pain with movement at day 60 (MD -1.2, 95% CI -1.6 to -0.7), and 41% against 13% had a reduction of 30% or more. At 180 days, 81% found TENS helpful [13].
Population
301 women with fibromyalgia on stable medicines [12]. 384 adults with fibromyalgia, 91% female [13].
Sources
[12], [13]
Caveats
The larger trial randomized clinics, not people, and had no placebo device [13].
TMGModerate

Muscle strength and power

Shown to raise maximal strength modestly, mostly lower body, in healthy people. Upper-body strength, sprint power and muscular endurance did not change.

The numbers and sources
Effect
Across 17 studies, betaine raised maximal strength (SMD 0.47, 95% CI 0.04 to 0.89), mostly in the lower body (SMD 0.49, 95% CI 0.01 to 0.98). Upper-body strength, cycling sprint power, bench throw power and muscular endurance did not change. Vertical jump improved (SMD 0.36, 95% CI 0.03 to 0.69) after one low-quality study was excluded [3].
Population
317 healthy people aged 15 to 60, 21% female, supplementing for at least 7 days [3].
Sources
[3]
Caveats
Small trials. The lower bounds of the intervals sit close to zero.
YogaModerate

Chronic low back pain, against no exercise

Shown to improve back function and pain slightly against no exercise in a Cochrane review, by amounts below the thresholds the reviewers set as clinically important.

Compared with waiting list, usual care or education [1]; a self-care book [2]; an educational book and newsletters [3]

The numbers and sources
Effect
At 3 months, back function improved 1.69 points on the 24-point Roland-Morris scale (95% CI -2.73 to -0.65, 11 trials, 1,155 participants, minimal clinically important difference 5 points) and pain fell 4.53 points on a 0 to 100 scale (95% CI -6.61 to -2.46, 9 trials, clinically important difference 15 points). More people rated their back pain improved or resolved (risk ratio 2.33, 95% CI 1.46 to 3.71) [1]. In 228 adults, function at 12 weeks was 2.5 points better with 12 yoga classes than with a self-care book (95% CI -3.7 to -1.3), and still 1.8 points better at 26 weeks [2]. In 320 mostly low-income adults, yoga was not superior to an educational book for function or pain at 12 weeks, and 21 percentage points fewer yoga participants used pain medication [3].
Population
2,223 adults in 21 trials, mostly women in their 40s or 50s [1]. 228 primary care patients [2]. 320 racially diverse adults at a safety-net hospital and 7 health centers [3].
Sources
[1], [2], [3]
Caveats
Every trial was at high risk of performance and detection bias, and no trial compared yoga with sham yoga. The reviewers judged it unlikely that blinded comparisons would find a clinically important benefit [1].
YogaModerate

Flexibility and leg strength in older adults

Shown to improve lower body flexibility and leg strength in older adults against both inactive controls and active exercise controls, in one meta-analysis.

Compared with inactive controls such as a waiting list or education booklets [7]; active controls such as walking or chair aerobics [7]

The numbers and sources
Effect
Against inactive controls, lower body flexibility improved (effect size 0.5) and lower limb strength improved (0.45). Against active controls, lower limb strength improved (0.49) and lower body flexibility improved (0.28) [7].
Population
Older adults with a mean age of 60 or above, not recruited for any condition, in 17 trials of physical function [7].
Sources
[7]
Caveats
The abstract gives no confidence intervals.
AcetaminophenLimited

Muscle growth with resistance training

One small trial found 4 g a day raised muscle and strength gains from 12 weeks of resistance training in older adults.

The numbers and sources
Effect
Over 12 weeks of knee extensor training, quadriceps volume rose 12.5% on acetaminophen 4 g a day and 8.6% on placebo, and strength rose 19 kg against 15 kg. Muscle protein content, water content and fiber type distribution did not differ between groups [18].
Population
36 adults aged about 64 to 67, 11 on acetaminophen, 13 on ibuprofen and 12 on placebo [18].
Sources
[18]
Caveats
One small trial in older adults. The dose, 4 g a day, is above the 6 caplets (3,000 mg) in 24 hours given in the over-the-counter directions [19].
AshwagandhaLimited

Recovery

One small trial found 600 mg a day raised recovery and sleep quality scores in 30 female footballers over 28 days.

The numbers and sources
Effect
A Bayesian meta-analysis reported ashwagandha outperformed placebo on fatigue or recovery [11]. In 30 professional female footballers, 600 mg a day of root extract for 28 days raised total quality recovery scores over placebo (group by time p = 0.026) and improved perceived sleep quality (p = 0.038) [14].
Population
Healthy men and women [11]. 30 female footballers [14].
Sources
[11], [14]
Caveats
One small trial, whose abstract reports p values without effect sizes [14]. The Bayesian abstract does not report effect sizes [11].
Beta-alanineLimitedStudied in women

Performance in women

Limited evidence: time to exhaustion improved in women, while other measures were imprecise, at very low certainty.

The numbers and sources
Effect
In 11 RCTs (312 women), time to exhaustion improved (8 studies, SMD 0.49, 95% CI 0.20 to 0.79). Pooled estimates for peak power, anaerobic performance, VO2max and body fat were imprecise [6].
Population
Women only [6].
Sources
[6]
Caveats
GRADE certainty was very low for all outcomes [6].
CholineLimited

Fatty liver and muscle damage when choline intake is low

Limited evidence: most adults on very low choline diets developed fatty liver or muscle damage, which reversed when choline was added back.

The numbers and sources
Effect
On a diet with under 50 mg of choline a day, 77% of men and 80% of postmenopausal women developed fatty liver or muscle damage, against 44% of premenopausal women. Organ function returned when choline was added back. Six men developed signs on 550 mg a day [8]. In people on long-term IV nutrition with low choline, 1 to 4 g a day of IV choline chloride resolved fatty liver within 6 weeks, and it returned in one patient after choline stopped [9].
Population
57 adults in a depletion study [8]; 4 adults on IV nutrition for about 10 years [9].
Sources
[8], [9]
Caveats
These are depletion and repletion studies, not trials of supplements in people eating normal diets.
FenugreekLimited

Muscle strength with training

Limited evidence: 4 of 6 small trials reported gains in strength, lean mass or lower body fat with fenugreek extracts alongside exercise.

The numbers and sources
Effect
A systematic review of 6 RCTs found 4 reported gains in muscle strength, repetitions to failure, lean mass or lower body fat with fenugreek extracts. Of two small glycogen trials, one found faster resynthesis and one did not [7].
Population
Participants in 6 RCTs of exercise or sport [7].
Sources
[7]
Caveats
Narrative synthesis without pooled effect sizes. Two of the trials had fewer than 10 participants [7].
Fish oilLimited

Muscle mass and function in older adults

Limited evidence: omega-3 added about 0.33 kg of muscle mass and slightly improved timed up and go in older adults.

The numbers and sources
Effect
Across 10 trials in older adults, omega-3 added 0.33 kg of muscle mass (95% CI 0.05 to 0.62) and shortened timed up and go by 0.30 seconds (95% CI -0.43 to -0.17). Above 2 g a day the muscle mass gain was 0.67 kg (95% CI 0.16 to 1.18) [34]. In 94 healthy older adults, 4 g a day of krill oil for 6 months increased muscle strength and size against a control oil, with similar responses by age, sex and BMI [35].
Population
Older adults in 10 RCTs [34]; adults 65 and older doing less than 1 hour of structured exercise a week [35].
Sources
[34], [35]
Caveats
Few trials, and the dose subgroup is post hoc. The search ended in July 2018 [34]. The krill oil report is a secondary analysis of one trial [35].
Gamma-glutamyl transferase (GGT)LimitedStudied in men

Heavy exercise

One small study found GGT was almost unaltered for 7 days after a weightlifting session that raised AST and ALT.

The numbers and sources
Compared with
The same men's results before exercise, and the laboratory's upper reference limit
Effect
After a single 1-hour weightlifting session in healthy men unused to lifting, GGT, bilirubin and alkaline phosphatase were almost unaltered over 7 days, and no man's GGT went above the upper reference limit. AST, ALT, lactate dehydrogenase, creatine kinase and myoglobin all rose significantly over the same days [16].
Population
15 healthy men, mean age 24.5, 14 analyzed [16].
Sources
[16]
Caveats
One small study of one kind of exercise in men not accustomed to it [16].
GardeningLimited

Physical activity

One randomized trial found a community garden plot added about 6 minutes a day of moderate to vigorous activity during the growing season, against a waiting list.

Compared with a waiting list for a community garden plot [7]

The numbers and sources
Effect
Moderate to vigorous physical activity showed a significant time-by-intervention effect (p = 0.012), with a mean between-group difference of 5.80 minutes a day (99.5% CI -4.44 to 16.05) by accelerometer. Sedentary time did not change [7]. Those who gardened the whole season reported a median 90 minutes a week at the garden [8].
Population
291 adults aged 18 and older who had not gardened in 2 years, 145 given a plot [7]. 145 people in the gardening group [8].
Sources
[7], [8]
Caveats
One trial, with a strict confidence interval that crosses zero at the second time point [7]. 67% of the gardening group gardened the whole season [8].
GingerLimited

Muscle soreness after exercise

Small trials found 2 g a day lowered arm muscle pain about 25% a day after eccentric exercise.

The numbers and sources
Effect
In two randomized, placebo-controlled experiments (34 and 40 volunteers), 2 g of raw or heat-treated ginger a day for 11 days lowered arm muscle pain 24 hours after eccentric exercise by 25% and 23% against placebo. Effects on other measures were smaller [9].
Population
74 adult volunteers [9].
Sources
[9]
Caveats
One research group, one elbow-flexor exercise model.
GlutamineLimited

Muscle soreness and strength recovery

One small trial found lower soreness and faster strength recovery over 72 hours after eccentric exercise in young adults.

The numbers and sources
Effect
In 16 young adults doing eccentric knee extensions, 0.3 g per kg a day for 72 hours gave lower soreness at 24 hours (2.8 against 3.4), 48 hours (2.6 against 3.9) and 72 hours (1.7 against 2.9), and higher fast-speed peak torque at 72 hours (91% against 86% of baseline) [2].
Population
8 women and 8 men, crossover design [2].
Sources
[2]
Caveats
One small trial in one muscle group. No meta-analysis of glutamine and soreness was located.
GroundingLimited

Pain

Limited evidence: two small studies reported less pain while grounded, one in 16 massage therapists compared with ungrounded weeks and one uncontrolled study of 12 adults.

Compared with weeks without grounding, in the same people [3]; before grounding, in the same people [2]

The numbers and sources
Effect
In a stepped wedge design, massage therapists reported significant decreases in pain, fatigue, tiredness and depressed mood and increases in physical function and energy while grounded at work and during sleep, compared with weeks not grounded [3]. Self-reported pain was reduced or eliminated in nearly all of 12 adults who slept grounded for 8 weeks [2].
Population
16 massage therapists, mean age 42.8, at one wellness center in California [3]. 12 adults [2].
Sources
[3], [2]
Caveats
Sixteen and 12 people. The massage therapist trial was led by an author who, in another paper, disclosed work as a contractor for the company that sponsors grounding research [3][4]. Outcomes were self-reported.
Heat therapyLimited

Acute low back pain, compared with ibuprofen and acetaminophen

One trial found a heat wrap eased acute low back pain more than ibuprofen 1,200 mg or acetaminophen 4,000 mg a day, on day 1 and days 3 to 4.

Compared with ibuprofen and acetaminophen [8]

The numbers and sources
Effect
Day 1 pain relief averaged 2 with the heat wrap, 1.51 with ibuprofen and 1.32 with acetaminophen. Relief on days 3 to 4 averaged 2.61, 1.68 and 1.95. Trunk flexibility and disability also improved more with heat [8].
Population
371 adults with acute nonspecific low back pain, 113 on heat, 106 on ibuprofen and 113 on acetaminophen [8].
Sources
[8]
Caveats
Only the investigator was blinded, and the placebo and unheated-wrap groups (20 and 19 people) were there for blinding, not for comparison [8].
Heat therapyLimited

Acute low back pain, heat with exercise

One trial found a heat wrap plus exercise restored function in 72% of people with acute low back pain, against about 20% with heat, exercise or a booklet alone.

Compared with an education booklet [9]; exercise alone [9]; a heat wrap alone [9]

The numbers and sources
Effect
Two days after 5 days of treatment, 72% of the heat plus exercise group had returned to pre-injury function, against 20% with heat alone, 20% with exercise alone and 19% with the booklet. Function improved 175% more than with the booklet [9]. A Cochrane review reports the same finding of added benefit from exercise [7].
Population
100 adults, mean age 31, with low back pain of less than 3 months [9].
Sources
[9], [7]
Caveats
One small trial with about 25 people per group [9].
HomeopathyLimited

Fibromyalgia

Limited evidence: four small trials found lower pain and fewer tender points than placebo, results the review authors call preliminary.

Compared with placebo [19]

The numbers and sources
Effect
Against placebo, homeopathy lowered tender point count (SMD -0.42, 95% CI -0.78 to -0.05), pain intensity (SMD -0.54, 95% CI -0.97 to -0.10) and fatigue (SMD -0.47, 95% CI -0.90 to -0.05) [19].
Population
4 randomized trials, plus case reports and observational studies [19].
Sources
[19]
Caveats
Few small trials. The authors write that any conclusions are preliminary [19].
Hyperbaric oxygen therapyLimited

Aerobic fitness in athletes

One sham-controlled trial found higher VO2 max after 40 sessions in middle-aged master athletes, with 31 of 37 randomized participants analyzed.

The numbers and sources
Effect
Compared with sham, 40 sessions at 2 ATA raised maximal oxygen consumption (p = 0.010, effect size 0.989) and oxygen consumption at the anaerobic threshold (effect size 0.837). Measures of mitochondrial respiration and mitochondrial mass in muscle also rose [15].
Population
37 healthy master athletes aged 40 to 50, of whom 16 hyperbaric and 15 sham participants were analyzed [15].
Sources
[15]
Caveats
One small trial with 6 randomized participants missing from the analysis. The abstract reports effect sizes without the size of the VO2 max change.
Infrared saunaLimited

Recovery after training

Small trials found less muscle soreness and a smaller drop in jump performance after a post-exercise infrared sauna, with no difference after a strength session in one study.

The numbers and sources
Effect
In 16 male basketball players, 20 minutes at 43°C after resistance exercise attenuated the drop in countermovement jump 14 hours later and lowered muscle soreness against passive rest (p < 0.01) [20]. In 10 active men, 30 minutes of far-infrared sauna after a strength session produced no difference in any recovery measure. After an endurance session, jump height at 30 minutes was 0.34 m with sauna and 0.32 m without (p < 0.05) [21]. In 40 female athletes, muscle soreness rose 36 hours after exercise only in the group without sauna [22].
Population
16 male basketball players in a randomized crossover [20]. 10 physically active men [21]. 40 female team sport athletes, pair-matched into two groups [22].
Sources
[20], [21], [22]
Caveats
Small samples, and soreness is self-rated by people who know whether they used the sauna. Temperatures were mild, 35°C to 50°C.
Infrared saunaLimitedStudied in women

Fibromyalgia

Limited evidence: pain fell by about half in 13 women with fibromyalgia given Waon therapy, in a study with no control group.

The numbers and sources
Effect
All 13 patients reported a reduction in pain of about half after the first session (range 11% to 70%), stable at 20% to 78% after 10 sessions. Pain and Fibromyalgia Impact Questionnaire scores fell significantly (p < 0.01) [26].
Population
13 women with fibromyalgia, mean age 45, treated 2 or 5 days a week [26].
Sources
[26]
Caveats
No control group and 13 participants, so the change cannot be separated from expectation.
Lymphatic drainage massageLimited

Muscle recovery after hard exercise

One trial of 36 combat athletes found drainage after jumping exercise raised pain thresholds and lowered creatine kinase and C-reactive protein more than passive rest.

Compared with passive rest [10]; intense sports massage [10]

The numbers and sources
Effect
Six 30-minute drainage sessions over 72 hours raised pressure pain thresholds more than passive rest at 24, 48 and 72 hours (p = 0.004 to < 0.001), with larger gains than sports massage at 24 hours. Creatine kinase and C-reactive protein were lower than with rest (p < 0.001 to 0.017). Sports massage increased muscle blood flow more [10].
Population
36 combat sports athletes, 24 men and 12 women, mean age 27.4 [10].
Sources
[10]
Caveats
One small trial with no sham. Perceived recovery was measured, and the abstract does not report its result [10].
Muscle relaxantsLimited

Methocarbamol for acute low back pain

One trial found 44% on methocarbamol stopped treatment early with complete pain relief, against 18% on placebo, in acute low back pain with spasm.

The numbers and sources
Effect
Over up to 8 days, 44% on methocarbamol and 18% on placebo ended treatment early because pain was gone, and 19% against 52% stopped because treatment was judged not to be helping. At the final visit 67% on methocarbamol and 35% on placebo rated the treatment as having helped. Adverse events were reported by 5 patients [7].
Population
202 adults with acute low back pain for at least 24 hours with spasm and restricted movement, 98 on methocarbamol and 104 on placebo [7].
Sources
[7]
Caveats
One trial, run in 2002 and analyzed after the fact for publication in 2015 [7]. A systematic review found very limited or inconsistent data for methocarbamol against placebo [4].
Protein powderLimited

Pre-sleep casein

Limited evidence: pre-sleep casein raised overnight muscle protein synthesis, with gains in size and strength in young men but not older men.

The numbers and sources
Effect
20 to 40 g of casein about 30 minutes before sleep raised overnight protein synthesis rates in young and older men. Over 10 to 12 weeks of training, pre-sleep protein increased fiber size, strength and muscle mass in young men but not in older men [8]. In 24 trained soccer players, 30 g of casein before sleep and the same dose right after training both improved next-day anaerobic performance against no casein, and the two timings did not differ [9]. After sleeve gastrectomy, casein-enriched milk before sleep or during the day did not change body composition, strength or physical performance over 12 weeks compared with no supplement [10]. In 9 trained adults, 40 g of casein before sleep did not change sleep measures against a carbohydrate control, while the same dose of whey shortened sleep onset and lengthened sleep [11].
Population
Nine studies, mostly men [8]. 24 male soccer players [9]. 45 adults after bariatric surgery [10]. 9 young adults, crossover [11].
Sources
[8], [9], [10], [11]
Caveats
Reference [8] is a systematic review without pooling. Its authors note uneven total protein intake between groups, so the timing effect cannot be separated from extra protein [8]. The three newer trials are small [9][10][11].
ReishiLimitedStudied in women

Stress and fitness

One small trial found better VO2 max, grip strength and mood scores than placebo in sedentary female students over 30 days.

The numbers and sources
Effect
In 78 female college students in India, 1,000 mg a day for 30 days improved heart rate, VO2 max, physical work capacity and right-hand grip strength against placebo, and anxiety, depression and well-being scores improved. The 500 mg dose differed from the 1,000 mg dose on VO2 max and work capacity [6].
Population
78 sedentary female students, mean age 20.6 [6].
Sources
[6]
Caveats
One small trial. The abstract does not report effect sizes or funding.
SaunaLimited

Endurance performance in trained runners

Small trials found longer run time to exhaustion and higher VO2 max in trained runners after 3 weeks of post-training sauna sessions.

The numbers and sources
Effect
In 6 male distance runners, 3 weeks of post-training sauna increased run time to exhaustion by 32% (90% confidence limits 21 to 43%) relative to control training, which the authors equate to about 1.9% in an endurance time trial. Plasma volume rose 7.1% [6]. In 20 middle-distance runners, 3 weeks of post-exercise sauna raised VO2 max by 0.27 L/min (p = 0.02) and running speed at 4 mmol/L blood lactate by 0.6 km/h (p = 0.01) more than training alone [7]. In 26 runners who all used the sauna, VO2 max rose 5% in both women and men [8].
Population
6 competitive male runners in a crossover study [6]. 20 trained runners, 13 of them women, mean age 20 [7]. 26 trained runners, 16 of them women [8].
Sources
[6], [7], [8]
Caveats
Very small samples. The abstract of [7] does not say that groups were randomized, and [8] had no control group. Sessions were about 30 minutes at 90°C to 108°C straight after training.
SaunaLimited

Low back pain

Limited evidence: pain scores fell from a median of 5 to 3 in 37 people after 10 sauna sessions, in a study with no control group.

The numbers and sources
Effect
After 10 sessions of 15 minutes at 90°C over 5 days, median pain on a verbal numerical rating scale fell from 5 (range 2 to 8) to 3 (range 0 to 8), and median Oswestry disability scores fell from 12 to 8 (P < 0.001 for both) [21].
Population
37 consecutive patients over 20 years of age with low back pain [21].
Sources
[21]
Caveats
No control group, so the change cannot be separated from natural recovery or expectation. One week of follow-up.
SchisandraLimited

Energy and endurance

Limited evidence: a review of Soviet-era studies reports more endurance and working capacity in healthy people and in animals, without figures in its summary.

The numbers and sources
Effect
The same review reports that Schisandra increased physical working capacity in animal studies, and in healthy people increased endurance, accuracy of movement, mental performance and working capacity [7]. In a 12-week trial in postmenopausal women, resting lactate, a fatigue-related marker, changed differently on Schisandra than on placebo [2].
Population
Animal studies and studies in healthy people in the former USSR, reviewed [7]. 45 postmenopausal women [2].
Sources
[7], [2]
Caveats
A narrative review of older studies, with no trial sizes or effect sizes in its abstract [7]. The lactate result was one measure among several in a small trial, and endurance itself was not tested [2].
Screen timeLimited

Activity and sleep after cutting family screen time

One trial found children were active about 46 minutes more a day after two weeks of strict family screen limits, with no change in sleep measured by EEG.

Compared with families told to carry on as usual [6]

The numbers and sources
Effect
Children's leisure non-sedentary activity rose by 45.8 minutes a day against controls (95% CI 27.9 to 63.6). Sleep measured by single-channel EEG did not differ between groups [6].
Population
181 children and 164 adults in 89 Danish families whose parent used screens for leisure over 2.4 hours a day [6].
Sources
[6]
Caveats
Two weeks, with phones and tablets handed in, which is stricter than most everyday limits. 97% of children complied [6].
SermorelinLimitedStudied in men

Strength in older men

One small study without placebo found 2 of 6 strength measures improved over 6 weeks in men aged 64 to 76. Muscle mass did not change.

The numbers and sources
Effect
Over 6 weeks, nightly sermorelin raised nighttime growth hormone release, with no change in IGF-1. Two of six strength measures (upright row and shoulder press) and one endurance test (abdominal crunch) improved. Muscle by DEXA and muscle histology did not change [4].
Population
11 healthy, non-obese men aged 64 to 76 with low baseline IGF-1 [4].
Sources
[4]
Caveats
One small study with no placebo group, comparing each man with his own baseline. The authors note that single nightly doses produced smaller hormone effects than multiple daily doses in earlier work [4].
Serum creatinineLimitedStudied in men

Type 2 diabetes at low levels

Limited evidence: one Japanese cohort of 8,570 men linked creatinine of 0.40 to 0.60 mg/dL to about twice the odds of type 2 diabetes over 4 years.

The numbers and sources
Effect
During 4 years, 877 men developed type 2 diabetes. Men with a creatinine of 0.40 to 0.60 mg/dL had an adjusted odds ratio of 1.91 (95% CI 1.44 to 2.54) against men at 0.71 to 0.80 mg/dL. The authors treat low creatinine as a possible stand-in for low skeletal muscle mass [8].
Population
8,570 Japanese men aged 40 to 55 without diabetes at entry [8].
Sources
[8]
Caveats
One observational cohort of men in one country. Muscle mass was not measured, so the link to muscle is the authors' interpretation [8].
Serum creatinineLimited

Death in intensive care at low levels

Limited evidence: one cohort of 11,291 intensive care patients linked a baseline creatinine of 0.6 mg/dL or below to about 2.6 times the odds of death.

The numbers and sources
Effect
After adjustment for predicted mortality, age, sex, surgery and body mass index, the odds ratio for death in hospital was 2.59 (95% CI 1.82 to 3.61) for a baseline creatinine of 0.6 mg/dL or below and 1.28 (1.03 to 1.60) for 0.6 to 0.8 mg/dL. Median baseline creatinine was 1.1 mg/dL. The authors treat low creatinine as a marker of low muscle mass [9].
Population
11,291 adults admitted to three intensive care units at two hospitals from 2003 to 2006, 1,185 deaths in hospital [9].
Sources
[9]
Caveats
Retrospective, in critically ill patients, so it does not describe a low result in a person who is well. Muscle mass was not measured [9].
StatinsLimited

Lean mass gain with resistance training

Limited evidence: one 12-week study linked statin use to greater lean mass gains with resistance training in adults aged 60 to 69, without randomizing statin use.

The numbers and sources
Effect
In a 12-week resistance training study, statin use was associated with greater gains in lean mass [4].
Population
49 community-dwelling adults aged 60 to 69 [4].
Sources
[4]
Caveats
Statin use was not randomized, and the abstract gives no effect size. It reports an association, not a cause.
Tai chi and qigongLimited

Falls, against other exercise

One trial of 670 adults at high risk of falling found a tai chi balance program cut falls 58% against stretching and 31% against a multimodal exercise program.

Compared with stretching exercises [4]; multimodal exercise combining balance, aerobic, strength and flexibility work [4]

The numbers and sources
Effect
Over 6 months, there were 152 falls in 85 people with tai chi, 218 falls in 112 people with multimodal exercise and 363 falls in 127 people with stretching. The incidence rate ratio was 0.42 (95% CI 0.31 to 0.56) for tai chi against stretching and 0.69 (95% CI 0.52 to 0.94) against multimodal exercise [4].
Population
670 community-dwelling adults aged 70 and over who had fallen in the past year or had impaired mobility, mean age 77.7, 65% women, in Oregon [4].
Sources
[4]
Caveats
One single-blind trial of a program tailored for balance, not classic tai chi forms [4].
Tai chi and qigongLimited

Fibromyalgia, against aerobic exercise

One trial of 226 adults with fibromyalgia found tai chi improved symptom scores more than aerobic exercise at 24 weeks, by 16.2 points when matched for time.

Compared with supervised aerobic exercise twice a week for 24 weeks [11]

The numbers and sources
Effect
Revised Fibromyalgia Impact Questionnaire scores improved 5.5 points more across the combined tai chi groups than with aerobic exercise (95% CI 0.6 to 10.4), and 16.2 points more when tai chi was given at the same dose (95% CI 8.7 to 23.6). Anxiety, self-efficacy and coping also improved more. Twenty-four weeks of tai chi improved scores more than 12 weeks [11].
Population
226 adults with fibromyalgia, 151 in four tai chi groups and 75 in aerobic exercise [11].
Sources
[11]
Caveats
One single-blind trial. Attendance was higher in tai chi than in aerobic exercise, which may explain part of the difference [11].
Testosterone therapyLimitedStudied in men

Muscle size and strength at high doses in young men

One small 1996 trial at high doses found more muscle size and strength in young men with normal testosterone, most with training.

The numbers and sources
Effect
Over 10 weeks without exercise, men on testosterone gained more triceps area (424 vs -81 mm²), quadriceps area (607 vs -131 mm²), bench press (9 vs -1 kg) and squat (16 vs 3 kg) than men on placebo. With training, the testosterone group gained 6.1 kg of fat-free mass, 22 kg on bench press and 38 kg on squat, more than either non-exercise group. Mood and behavior did not change in any group [5].
Population
43 healthy men with normal testosterone, in 4 groups, for 10 weeks [5].
Sources
[5]
Caveats
One small trial from 1996 at a dose the authors describe as supraphysiologic. It does not address men with low testosterone or use over years.
Tongkat aliLimited

Muscle strength

One small study without placebo found higher testosterone and grip strength over 5 weeks in active adults aged 57 to 72. The maker funded it.

The numbers and sources
Effect
In 25 physically active adults aged 57 to 72, 400 mg a day for 5 weeks raised total and free testosterone and handgrip force in men and women [7].
Population
13 men and 12 women, single group [7].
Sources
[7]
Caveats
No placebo group. Funded by Biotropics Malaysia [7].
TurmericLimited

Muscle soreness after exercise

Limited evidence: curcumin lowered soreness and muscle damage markers after hard exercise in some trials, but certainty was very low.

The numbers and sources
Effect
Curcumin reduced creatine kinase (WMD -48.54 IU/L, 95% CI -80.67 to -16.42) and a muscle soreness index (WMD -0.476, 95% CI -0.750 to -0.202) after muscle-damaging exercise [42]. A systematic review of 15 double-blind trials in active people and athletes found favorable results in 3 of 7 trials on soreness, recovery or fatigue, 4 of 6 on muscle damage and 4 of 8 on performance [43]. In 44 moderately active adults, 300 mg a day of a turmeric formulation for 5 days did not change soreness after downhill running, while soreness recovery from peak to 72 hours was 7.9% greater than placebo [44]. In 34 men, 1,500 mg a day of hydrolyzed curcumin was followed by greater reductions in pain, creatine kinase and IL-6 (p < 0.05), and slower muscle endurance recovery at 24 hours than 750 mg a day [45].
Population
Adults in RCTs of exercise-induced muscle damage [42]; active people and athletes [43]; 44 moderately active adults [44]; 34 recreationally active men [45].
Sources
[42], [43], [44], [45]
Caveats
The meta-analysis abstract does not report the number of trials or participants [42]. Certainty was very low for soreness, muscle damage and performance [43]. Soreness area under the curve, the primary outcome, did not differ from placebo [44].
Whole-body cryotherapyLimited

Fibromyalgia

Small trials found less pain and better quality of life scores in people with fibromyalgia after a course of sessions, compared with rest or usual care.

The numbers and sources
Effect
In 60 patients, pain fell 3.0 points on a visual analogue scale with cryotherapy against 0.3 with rest, and Fibromyalgia Impact Questionnaire scores fell 32.1 against 0.4 (all p < 0.001) [13]. In 24 patients, 10 sessions over 8 days improved health-related quality of life against usual care, lasting at least a month [14].
Population
60 patients in an open crossover trial, with only the first period analyzed [13]. 24 patients, 11 on cryotherapy and 13 controls [14].
Sources
[13], [14]
Caveats
Open trials with no sham, in a condition where symptoms respond strongly to expectation. A carry-over effect led one trial to discard its second period [13].
Whole-body cryotherapyLimited

Chronic low back pain

Limited evidence: pain and disability scores fell after a course of sessions in two studies with no control group.

The numbers and sources
Effect
In 41 adults with chronic low back pain, pain and disability scores fell significantly over 20 sessions in 5 weeks (p < 0.001) [17]. In 30 patients with lumbar spine osteoarthritis who also did therapeutic exercise, back pain fell significantly (p < 0.0001) and plasma cortisol rose (p = 0.0009) [18].
Population
41 adults aged 18 to 65 [17]. 30 patients with lumbar spine osteoarthritis [18].
Sources
[17], [18]
Caveats
Neither study had a control group, and one combined cryotherapy with exercise [18].

Reported risks42

Atypical antipsychoticsStrongVery common

Restlessness and movement side effects

Shown to cause restlessness in 25% on aripiprazole against 4% on placebo when added to an antidepressant, and in 8% against 4% in schizophrenia trials.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
On aripiprazole, akathisia-related events were reported by 25% against 4% on placebo as an add-on in depression, and by 8% against 4% in adult schizophrenia trials. Other movement events occurred in 13% against 12% in schizophrenia trials [10]. On quetiapine in bipolar depression trials, akathisia was reported by 4% against 1% and extrapyramidal disorder by 3% against 1% [3]. In maintenance trials across antipsychotics, movement disorders affected 16% against 9% on placebo [4]. A review of off-label use named akathisia as an adverse event of aripiprazole in adults under 65 [12].
Population
Adults in aripiprazole and quetiapine label trials [10][3]; 6,493 patients in 65 trials [4].
Sources
[10], [3], [4], [12]
Caveats
The band above is the akathisia rate on aripiprazole as an add-on in depression. Rates on quetiapine were lower.
StatinsStrongVery common

Muscle pain and weakness

Shown to raise muscle pain or weakness slightly in year 1, about 1 in 15 reports, with no excess after. In people with past symptoms, symptoms matched placebo.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
Over a median 4.3 years, 27.1% on a statin and 26.6% on placebo reported muscle pain or weakness (RR 1.03, 95% CI 1.01 to 1.06). In year 1 the excess was 7% (RR 1.07), or 11 more reports per 1,000 person-years, meaning about 1 in 15 reports on a statin was caused by it. After year 1 there was no significant excess. More intensive regimens had a higher RR (1.08) than moderate ones (1.03). Creatine kinase rose by about 0.02 times the upper limit of normal [5]. In people who had stopped statins over muscle symptoms, symptom scores did not differ between atorvastatin and placebo periods (MD -0.11, 95% CI -0.36 to 0.14). Withdrawals for intolerable symptoms were 9% during statin periods and 7% during placebo periods [6].
Population
123,940 participants in 19 placebo-controlled trials and 30,724 in 4 intensity trials [5]; 200 people in UK primary care, 151 analyzed, each randomized through six 2-month periods [6].
Sources
[5], [6]
Caveats
The n-of-1 series enrolled only people who had already reported muscle symptoms on statins [6]. The meta-analysis covers large trials of at least 1,000 people lasting at least 2 years [5].
Atypical antipsychoticsModerateVery common

Tardive dyskinesia

Linked to tardive dyskinesia in 20.7% of people on second-generation antipsychotics across studies, against 30.0% on first-generation drugs and 7.2% with no earlier first-generation exposure.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
Across 41 studies, the prevalence of tardive dyskinesia was 20.7% during current second-generation treatment (95% CI 16.6 to 25.4) and 30.0% during first-generation treatment (95% CI 26.4 to 33.8). In four studies of people never exposed to first-generation drugs, it was 7.2% [18]. Both labels warn that this syndrome of involuntary movements may be irreversible [3][10].
Population
11,493 people in 41 studies, mean age 42.8, 77% with schizophrenia-spectrum disorders [18].
Sources
[18], [3], [10]
Caveats
Prevalence in people treated long term, mostly for schizophrenia, with no placebo group. Many on second-generation drugs had earlier first-generation exposure, and prevalence rose with age and length of illness.
BisphosphonatesModerateVery common

Flu-like reaction after an infusion

Shown to cause fever, aches and flu-like symptoms within 3 days of a zoledronic acid infusion, with fever in 18% against 5% on placebo.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
In the main osteoporosis trial, fever was reported in 17.9% on zoledronic acid and 4.6% on placebo, muscle pain in 11.7% against 3.7%, and influenza-like illness in 8.8% against 2.7%. Most symptoms began within 3 days and resolved within 3 days. When acetaminophen was given, fever fell to 7%, and symptoms became less frequent with later doses [13]. In Paget's disease, zoledronate raised transient fever or fatigue against placebo (RR 2.57, 95% CI 1.21 to 5.44) [12].
Population
7,714 women in the main osteoporosis trial [13]; 176 people in one Paget's trial [12].
Sources
[13], [12]
Caveats
Applies to the infusion. Oral bisphosphonates were not linked to this reaction in these sources.
Chiropractic and spinal manipulationModerateVery common

Soreness, stiffness and headache after treatment

Shown in 50% to 67% of patients in large case series, as brief soreness, stiffness or headache. Pooled trials found mild events no more often than with control treatments.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
Minor, transient adverse events such as increased pain, muscle stiffness and headache were reported 50% to 67% of the time in large case series [6]. In 14 trials of neck manipulation, the rate of adverse events did not differ from control interventions, and every reported event was mild [15]. In one trial powered to look at harm, adverse events did not differ from sham manipulation (RR 1.24, 95% CI 0.85 to 1.81) [3].
Population
Large case series of patients treated with manipulation [6]. 14 randomized trials [15]. 183 participants in one trial [3].
Sources
[6], [15], [3]
Caveats
Most trials did not record adverse events systematically [3].
Dry needlingModerateVery common

Bruising, bleeding and pain at the needle site

Prospective surveys recorded mild effects after 19% to 37% of treatments, most often bleeding, bruising and pain during needling.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
Among 20,464 treatment sessions by 420 US physical therapists, 7,531 minor adverse events were reported, 36.7% of treatments. The most common were bleeding (16%), bruising (7.7%) and pain during needling (5.9%) [17]. Among 7,629 treatments by 39 Irish physiotherapists, mild events followed 19.18%: bruising 7.55%, bleeding 4.65%, pain during treatment 3.01%, pain after treatment 2.19%, worse symptoms 0.88% and drowsiness 0.26% [18]. A review of 59 studies found minor events after 0% to 48.15% of treatments [19].
Population
420 physical therapists over 6 weeks [17]. 39 physiotherapists over 10 months [18]. 59 studies including 1,947 patients in trials and observational studies [19].
Sources
[17], [18], [19]
Caveats
Therapists reported their own events, with no comparison group. Definitions of minor events varied between studies [19].
IsotretinoinModerateVery common

Joint, back and muscle symptoms

Shown in trials to cause joint or muscle symptoms in about 16%, with back pain in 29% of teenagers and marked creatine kinase rises in 24%.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
About 16% in a clinical trial had musculoskeletal symptoms, including joint pain. In a trial of teenagers, 29% had back pain, severe in 14% of those cases, and 22% had joint pain. Marked creatine kinase rises (350 U/L or more) occurred in about 24% of 924 trial participants, some linked to vigorous exercise, and rare rhabdomyolysis has been reported [3].
Population
358 patients aged 12 and older in a pediatric trial, and 924 participants in another trial [3].
Sources
[3]
Caveats
Uncontrolled label figures with no placebo rate.
Physical therapy and exercise therapyModerateVery common

Pain flare-ups and soreness

Shown to raise minor adverse events by 19% in pooled trials, about one extra for every 6 people. Most were increased pain or muscle soreness.

The numbers and sources
How common
Very common: more than 1 in 10 people.
Effect
Across exercise therapy trials, non-serious adverse events rose (RR 1.19, 95% CI 1.09 to 1.30), with one extra event for every 6 people treated [14]. In the hip osteoarthritis trial, 19 of 46 people (41%) on physical therapy and 7 of 49 (14%) on sham reported mild adverse effects [6]. In back pain trials that measured harms systematically, there was a median of 0.14 adverse effects per participant with exercise and 0.12 with comparison treatments, mostly minor, such as muscle soreness [2]. In knee and hip osteoarthritis trials, reported adverse events were increased knee, hip or low back pain [4][5].
Population
38,517 participants in 375 trials [14]. 95 adults with hip osteoarthritis [6]. 249 back pain trials [2]. Osteoarthritis trials [4][5].
Sources
[14], [6], [2], [4], [5]
Caveats
The 41% comes from one trial of a multi-part program [6]. Many trials did not report adverse events [2].
Osteopathy and osteopathic manipulative treatmentModerateCommon

Pain or discomfort after treatment

Shown at 2.5% of office visits, mostly as pain or discomfort, in patients asked right after treatment. Safety outcomes did not differ from sham in the largest back pain trial.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
Patients felt worse or much worse right after treatment at 45 of 1,847 visits, an adverse event rate of 2.5% (95% CI 1.3% to 4.7%). Pain or discomfort was the most common type (0.9%). Women reported adverse events more often than men (OR 13.9) [18]. In the largest back pain trial, safety outcomes did not differ between osteopathic treatment and sham [3]. Most systematic reviews reported no adverse events [17].
Population
884 patients at 1,847 visits [18]. 455 adults [3]. 9 systematic reviews [17].
Sources
[18], [3], [17]
Caveats
Effects were recorded before patients left the office, so later effects were not captured [18].
YogaModerateCommon

Adverse events in trials, mostly more back pain

Shown to raise adverse events, mainly more back pain, against no exercise in back pain trials, at about 4.3% against 0.9%. Rates matched other exercise and usual care.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
In back pain trials, adverse events at 6 to 12 months occurred in 43 per 1,000 with yoga and 9 per 1,000 with no exercise (risk ratio 4.76, 95% CI 2.08 to 10.89, low certainty), and in 84 per 1,000 with yoga and 91 per 1,000 with other exercise [1]. Across 94 trials with 8,430 participants, intervention-related, nonserious and serious adverse events did not differ between yoga and usual care or exercise. Against psychological or educational programs, yoga had more intervention-related (odds ratio 4.21) and nonserious adverse events (odds ratio 7.30), with similar serious events [15]. In the back pain trial against physical therapy, adverse events were mostly mild self-limited joint and back pain, as frequent as with physical therapy [3].
Population
1,037 participants in 8 back pain trials [1]. 8,430 participants in 94 trials [15]. 320 adults [3].
Sources
[1], [15], [3]
Caveats
Only 94 of 301 trials reported on adverse events [15].
YogaModerateCommon

Injuries reported by people who practice

Linked to injuries or other adverse events in 4.6% of practitioners over 12 months in observational studies, mostly sprains and strains, with 1.9% serious.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
Across 9 observational studies, 22.7% of practitioners reported an adverse event during a yoga class, 12-month prevalence was 4.6% (95% CI 3.8% to 5.4%) and lifetime prevalence ranged from 21.3% to 61.8%. Serious adverse events occurred in 1.9%. Against people who did not practice, falls (odds ratio 0.90) and fall injuries (odds ratio 1.04) did not differ, and meniscus injuries were more common (odds ratio 1.72, 95% CI 1.23 to 2.41) [16].
Population
9,129 yoga practitioners and 9,903 non-practitioners in 9 studies [16].
Sources
[16]
Caveats
Observational and self-reported. People who choose yoga may differ from those who do not.
Carnivore dietLimitedCommon

Self-reported symptoms and nutrient concerns

Limited evidence: in a self-report survey, 3.1% to 5.5% reported digestive symptoms, and fewer reported muscle or skin symptoms.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
Reported symptoms included gastrointestinal (3.1% to 5.5%), muscular (0.3% to 4.0%) and skin (0.1% to 1.9%) [1].
Population
2,029 survey respondents [1].
Sources
[1], [2], [6]
Caveats
No study located measured vitamin or mineral levels in people on the diet. A scoping review flagged potential shortfalls in vitamins C and D, calcium, magnesium, iodine and fiber [2]. An analysis of four modeled meal plans, with no people studied, fell short of reference intakes for thiamine, magnesium, calcium and vitamin C, sometimes for iron, folate, iodine and potassium, and well short for fiber [6].
30 more
Ezetimibe and fenofibrateLimitedCommon

Fenofibrate: muscle injury with statins

The label warns fibrates raise muscle injury risk with statins, most with gemfibrozil, and in trials creatine kinase rose in 3.0% on fenofibrate against 1.4% on placebo.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
Increased creatine kinase was reported in 3.0% on fenofibrate and 1.4% on placebo. Observational studies indicate rhabdomyolysis risk rises when fibrates, in particular gemfibrozil, are given with a statin [7].
Population
439 people on fenofibrate and 365 on placebo, and observational data cited in the label [7].
Sources
[7]
Caveats
The label gives no rate for the combination.
StatinsModerateUncommon

Liver enzyme rises and severe muscle injury

Shown to raise liver enzymes in about 0.2% on high doses. Severe muscle injury rose with dose, and myopathy was more frequent on simvastatin 80 mg.

The numbers and sources
How common
Uncommon: between 1 in 1,000 and 1 in 100 people.
Effect
Across 41 RCTs, transaminase elevation on high-dose statins occurred at a rate of 0.2% (95% CI 0.004 to 0.4%), and creatine kinase rises under three times the upper limit at 0.43% (95% CI 0.11 to 0.75%). Rhabdomyolysis risk rose with dose, and myopathy was more frequent on simvastatin 80 mg than on other statins [9].
Population
64,728 participants in 41 RCTs across several diseases [9].
Sources
[9]
Caveats
Rates varied by disease group, and the abstract does not give the rhabdomyolysis rate [9].
YogaLimitedRare

Emergency department visits for yoga injuries

Linked to 29,590 US emergency department visits from 2001 to 2014, mostly trunk sprains and strains, at the highest rate in people aged 65 and over.

The numbers and sources
How common
Rare: fewer than 1 in 1,000 people.
Effect
Of 29,590 yoga-related injuries seen in US emergency departments, 46.6% involved the trunk and 45.0% were sprains or strains. In 2014, the injury rate was 57.9 per 100,000 participants aged 65 and over, 17.7 at 45 to 64 and 11.9 at 18 to 44 [17].
Population
National Electronic Injury Surveillance System data, with participant numbers from national health surveys [17].
Sources
[17]
Caveats
Counts only injuries that reached an emergency department, and the participant denominators are survey estimates [17].
Alternate-day fastingModerateHow often is not known

Lean mass

Mixed results: one pooled analysis found no lean mass difference from daily restriction or control, and another found a lean mass difference against control without giving its size.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Lean body mass did not differ between alternate-day fasting and continuous energy restriction, time-restricted feeding or control [1]. The ratio of fat-free mass to total mass rose equally on alternate-day fasting and daily restriction over 24 weeks [11]. A second review found lean mass differed from control (p 0.002) [2].
Population
728 participants [1]; 100 adults [11]; 269 adults [2].
Sources
[1], [2], [11]
Caveats
The second review does not report the direction or size of the lean mass change in its abstract [2].
GrapefruitModerateHow often is not known

Higher blood levels of some statins

The FDA states grapefruit juice can interact with some statins. One glass daily raised simvastatin levels 3.6-fold in a small trial, and pravastatin was unaffected.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The FDA names simvastatin and atorvastatin among drugs grapefruit juice can interact with, and states that too much statin in the body raises the risk of liver and muscle damage [1]. Double-strength juice three times a day raised simvastatin exposure (AUC) 16-fold [6]. One 200 mL glass a day for 3 days raised simvastatin AUC 3.6-fold and simvastatin acid 3.3-fold [8]. Double-strength juice raised atorvastatin acid AUC 2.5-fold, and did not change pravastatin [7]. In 60 patients who kept their atorvastatin dose and added 300 mL a day for 90 days, serum atorvastatin rose 19% to 26%, lipids changed negligibly, and liver tests and creatine phosphokinase showed no adverse effects [9]. A modeling review estimated a daily glass raises simvastatin and lovastatin blood levels about 260% when taken together and atorvastatin about 80%, and judged the added rhabdomyolysis risk minimal [18].
Population
10 healthy volunteers [6]. 10 healthy volunteers [8]. 12 and 11 healthy volunteers [7]. 130 patients on stable atorvastatin [9]. A modeling analysis [18].
Sources
[1], [6], [8], [7], [9], [18]
Caveats
The pharmacokinetic studies were small and in healthy volunteers, and none measured muscle injury. The size of the interaction depended on the amount of juice and the statin [6][8][7].
Intermittent fastingModerateHow often is not known

Lean mass loss

Shown to lower fat-free mass by about 0.4 to 0.9 kg alongside fat loss in adults with overweight, with no loss found in resistance-trained adults.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In 30 studies with 1,341 participants, fat-free mass fell 0.86 kg (95% CI -1.23 to -0.49) against non-matched controls and 0.41 kg (95% CI -0.79 to -0.03) against calorie-matched controls [17]. In 20 trials, fat-free mass fell 0.58 kg on time-restricted eating against no restriction and 0.56 kg on time-restricted eating plus calorie restriction against calorie restriction alone [7]. In TREAT, appendicular lean mass index fell 0.16 kg/m² more than on three structured meals (95% CI -0.27 to -0.05) [9]. In 8 trials of resistance-trained adults, fat-free mass changed by 0.27 kg (95% CI -0.80 to 1.34) [18].
Population
Adults with overweight or obesity [17]; 1,242 adults [7]; 50 adults tested in person [9]; resistance-trained adults on 8 to 10 hour windows [18].
Sources
[7], [9], [17], [18]
Caveats
Fat-free mass falls with most weight loss, and the time-restricted groups often lost more weight than controls [17]. Lean mass did not differ between time-restricted eating with calorie restriction and calorie restriction alone over 12 months [3]. The resistance training trials were few, small and short [18].
Massage therapyModerateHow often is not known

More pain or soreness after treatment

Shown in trials as the most common side effect, with increased pain reported in 1.5% to 25% of participants across back pain trials.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In low back pain trials, increased pain intensity was the most common adverse event, in 1.5% to 25% of participants [4]. In neck pain trials, the 4 that reported side effects all reported pain after treatment, and one found low blood pressure after treatment in 22% of participants [6].
Population
25 low back pain trials [4]. 15 neck pain trials, 4 reporting side effects [6].
Sources
[4], [6]
Caveats
The range spans two frequency bands and no pooled rate was given. Most trials did not report side effects [6].
MetforminModerateHow often is not known

Blunted gains from exercise training

Shown to blunt gains from exercise training, including smaller rises in lean mass, VO2 max and insulin sensitivity, in older and at-risk adults. One trial found no blunting.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Over 14 weeks of resistance training, the placebo group gained more lean body mass and thigh muscle mass than the metformin group, with greater gains in thigh muscle area and density. Strength gains trended lower on metformin without reaching significance [13]. Over 12 weeks of aerobic training, metformin attenuated the rise in whole-body insulin sensitivity and VO2 max and abolished the rise in muscle mitochondrial respiration [18]. Pooled across controlled trials, metformin with exercise produced smaller gains in VO2 peak than exercise alone (MD -1.19, 95% CI -2.33 to -0.04) and smaller drops in systolic (3.76 mm Hg, 95% CI 0.63 to 6.89) and diastolic (1.98 mm Hg, 95% CI 0.42 to 3.55) blood pressure [19]. During exercise, metformin raised blood lactate (SMD 0.98, 95% CI 0.36 to 1.60) [17]. Over 16 weeks of low- or high-intensity aerobic training, VO2 max rose on placebo but not on metformin 2,000 mg a day, and metformin blunted the rise in vascular insulin sensitivity [15]. In the same trial, metabolic insulin sensitivity rose after high-intensity training on placebo but not on metformin [20]. Over 5 weeks of aerobic training, VO2 peak rose 0.11 L/min on metformin and 0.26 L/min on placebo, while fat oxidation rose more on metformin [16]. In a 12-week trial in prediabetes, metformin did not reduce the muscle changes seen on MRI with aerobic exercise [21].
Population
94 healthy adults aged 65 and older [13]; 53 older adults, mean age 62 [18]; 827 adults across the spectrum of glucose dysregulation in 9 studies [19]; 325 participants in 21 studies [17]; 91 adults at risk for metabolic syndrome [15][20]; 22 adults with metabolic syndrome completing [16]; 42 adults with prediabetes [21].
Sources
[13], [18], [19], [17], [15], [20], [16], [21]
Caveats
Body weight, glucose, HbA1c, insulin and lipids did not differ between groups in the pooled trials [19]. GRADE certainty was moderate for VO2 peak and blood pressure [19]. Responses in [18] were highly variable between people. [21] did not find the blunting seen in the other trials. The added trials were small.
Physical activityModerateHow often is not known

Minor adverse events in exercise trials

Shown to raise non-serious adverse events by about a fifth in exercise therapy trials, one extra event for every 6 people, with no rise in serious events.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Exercise therapy raised non-serious adverse events (RR 1.19, 95% CI 1.09 to 1.30), a number needed to harm of 6. Serious adverse events did not rise (RR 0.96, 95% CI 0.90 to 1.02) [21].
Population
38,517 participants in 375 trials for non-serious and 38,368 in 378 trials for serious events, drawn from 180 Cochrane reviews [21].
Sources
[21]
Caveats
Trials were of exercise therapy, often in people with a health condition, and recorded adverse events in different ways. The abstract does not name the events.
SemaglutideModerateHow often is not known

Lean mass loss

Lean mass made up about 25% of weight lost in one review and 15% to 60% in others. A 2026 review called the muscle evidence too uncertain.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Sources measure the loss and describe it differently. A network meta-analysis found GLP-1 receptor agonists reduced lean mass by 0.86 kg (95% CI 0.42 to 1.30), about 25% of weight lost, while relative lean mass as a percentage of body weight was unchanged. Semaglutide 2.4 mg and tirzepatide 15 mg produced the most weight and fat loss and ranked among the least lean-sparing [9]. In a tirzepatide substudy, about 75% of weight lost was fat and 25% lean, the same split as placebo [10]. A review reports that in some trials lean mass made up 40 to 60% of total weight lost, and in others about 15% or less. It notes that lean mass includes organs, bone and water [11]. A 2026 meta-analysis found the muscle evidence too heterogeneous and imprecise for firm conclusions, with low to very low certainty [12].
Population
22 RCTs with 2,258 adults with diabetes or overweight [9]; 160 adults with DXA scans in SURMOUNT-1 [10]; trials summarized in a narrative review [11]; 19 studies, 2 comparative for muscle [12].
Sources
[9], [10], [11], [12]
Caveats
[11] is a narrative review, not a systematic one. Lean mass by DXA is not the same as muscle, and few trials measured strength or function [12].
Strength trainingModerateHow often is not known

Muscle and joint complaints in trials

Reported in trials: mostly minor muscle and joint complaints such as joint pain and soreness, with serious adverse events rare and poorly recorded.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Across 121 trials in older adults, adverse events were poorly recorded. Joint pain and muscle soreness were reported in many trials that monitored them, serious adverse events were rare, and none was reported as directly related to training [9]. In falls prevention trials, reported events were mainly non-serious and musculoskeletal, with two serious events, a pelvic stress fracture and hernia surgery, in one trial [16]. The high-intensity bone trial recorded one minor back spasm [15].
Population
6,700 older adults in 121 trials [9]. 6,019 participants in 27 trials that reported adverse events [16]. 101 postmenopausal women [15].
Sources
[9], [16], [15]
Caveats
Most trials did not monitor adverse events closely in both groups, so rates cannot be given [9][16].
TesamorelinModerateHow often is not known

Joint pain, muscle pain and swelling

Shown to raise joint pain, muscle pain and leg swelling slightly in adults with HIV, such as muscle pain in 6% against 2% on placebo.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Over 26 weeks, joint pain occurred in 13% on tesamorelin and 11% on placebo, pain in a limb in 6% against 5%, muscle pain in 6% against 2%, swelling of the legs in 6% against 2%, and carpal tunnel syndrome in 1% against 0% [6]. A meta-analysis of 5 RCTs also linked tesamorelin with joint pain, muscle pain and tingling (paresthesia) [5].
Population
543 adults on tesamorelin and 263 on placebo [6]; 5 RCTs [5].
Sources
[6], [5]
Caveats
The label groups these as fluid retention effects [6].
TirzepatideModerateHow often is not known

Lean mass loss

Lean mass made up about 25% of weight lost in one substudy, the same share as on placebo, and 15% to 60% in others. A 2026 review called it uncertain.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Sources measure the loss and describe it differently. In a SURMOUNT-1 substudy, tirzepatide changed body weight by -21.3%, fat mass by -33.9% and lean mass by -10.9%, against -5.3%, -8.2% and -2.6% on placebo. About 75% of weight lost was fat and 25% lean on both tirzepatide and placebo [17]. A network meta-analysis found GLP-1 drugs reduced lean mass by 0.86 kg (95% CI 0.42 to 1.30), about 25% of weight lost, while relative lean mass was unchanged. Tirzepatide 15 mg and semaglutide 2.4 mg produced the most weight and fat loss and ranked among the least lean-sparing [18]. A review reports that in some trials lean mass made up 40 to 60% of total weight lost, and in others about 15% or less. It notes that lean mass includes organs, bone and water [19]. A 2026 meta-analysis found the muscle evidence too heterogeneous and imprecise for firm conclusions, with low to very low certainty [20].
Population
160 adults with DXA scans, 73% women [17]; 22 RCTs with 2,258 adults [18]; trials summarized in a narrative review [19]; 19 studies, 2 comparative for muscle [20].
Sources
[17], [18], [19], [20], [21]
Caveats
[19] is a narrative review, not a systematic one. Lean mass by DXA is not the same as muscle, and few trials measured strength or function [20]. Across 6 RCTs, self-reported physical function improved against placebo (SF-36 physical function MD 2.26 points, 95% CI 1.76 to 2.76), but heterogeneity was very high (I² 99.8%) [21].
5-HTPLimitedHow often is not known

Eosinophilia-myalgia syndrome and peak X contaminants

Limited evidence: EMS-like symptoms have been linked to 5-HTP, and contaminants called peak X were found in tested products. Sources disagree on whether peak X matters.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Eosinophilia-myalgia syndrome (EMS) was traced in 1989 to contaminated L-tryptophan from one manufacturer [9]. EMS-like symptoms have been associated with 5-HTP, and analysis of EMS-implicated 5-HTP found "peak X," a family of contaminants. All 8 commercial 5-HTP samples tested contained three or more peak X contaminants [10]. A 2004 review reported no definitive toxicity cases in 20 years of use, apart from one unresolved case, and described peak X as a chromatographic artifact at very small concentrations [9].
Population
Product analyses and case reports [9][10].
Sources
[9], [10]
Caveats
The sources disagree on peak X. The Cochrane review states the possible link between these substances and EMS has not been elucidated [1].
Beta-alanineLimitedHow often is not known

Liver enzyme and muscle taurine changes

Limited evidence: ALT rose slightly but stayed within reference ranges, and muscle taurine did not change in humans.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Beta-alanine raised circulating alanine aminotransferase slightly (effect size 0.274, 95% CrI 0.04 to 0.527), with mean values within clinical reference ranges. Muscle taurine (0.156, 95% CrI -0.38 to 0.72) and histidine did not change in humans. Taurine fell in mice only at 3% or more beta-alanine in drinking water [9].
Population
101 human and 50 animal studies [9].
Sources
[9]
Caveats
The abstract does not report trial durations. No trials of use over years were located.
BisphosphonatesLimitedHow often is not known

Bone, joint and muscle pain

The label warns of severe, sometimes incapacitating bone, joint or muscle pain reported after approval, while placebo-controlled alendronate trials found similar rates.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The alendronate label reports postmarketing cases of severe bone, joint or muscle pain beginning a day to months after starting, mostly relieved after stopping, with some recurrence on rechallenge. In its placebo-controlled trials, the share with these symptoms was similar on alendronate and placebo [15]. In the main zoledronic acid trial, bone pain was 5.8% against 2.3% on placebo [13].
Population
Postmarketing reports and trial populations [15][13].
Sources
[15], [13]
Caveats
Postmarketing reports cannot give a rate.
Black seed oilLimitedHow often is not known

Kidney injury and muscle breakdown

Case reports: one person had acute kidney injury, muscle breakdown and liver toxicity after drinking black seed oil.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
A 2024 case report describes acute kidney injury, rhabdomyolysis and liver toxicity after a person drank black seed oil [14].
Population
One case [14].
Sources
[14]
Caveats
A single case report cannot give a rate.
BuspironeLimitedHow often is not known

Restlessness and movement symptoms

The label reports a syndrome of restlessness soon after starting in a small fraction of patients, and rare voluntary reports of movement disorders.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The label states that controlled trials did not identify significant antipsychotic-like activity, and that a syndrome of restlessness appearing shortly after the start of treatment has been reported in a small fraction of patients. Voluntary reports since marketing include rare cases of dystonia, parkinsonism, akathisia, dyskinesia and restless leg syndrome [4].
Population
Controlled trials and postmarketing reports summarized in labeling [4].
Sources
[4]
Caveats
No rate is given, and the label says cause has not been established for the voluntary reports.
Calcium channel blockersLimitedHow often is not known

With simvastatin and other statins

Small studies found diltiazem, verapamil and amlodipine raise blood levels of simvastatin, about 5-fold with diltiazem. Labels warn of a higher risk of muscle injury.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
In 10 healthy volunteers, diltiazem raised simvastatin exposure 5-fold, and in another 10 it raised lovastatin exposure 3 to 4-fold and left pravastatin unchanged. The diltiazem label states that the risk of myopathy and rhabdomyolysis with statins metabolized by CYP3A4 may be increased [10]. The verapamil label reports simvastatin exposure 2.5 times that of simvastatin alone and sets dose limits of 10 mg for simvastatin and 40 mg for lovastatin [16]. The amlodipine label states that it increases simvastatin exposure and sets a limit of 20 mg of simvastatin a day [8].
Population
Healthy volunteers in small crossover studies described in the labels [10][16][8].
Sources
[10], [16], [8]
Caveats
The studies measured blood levels, not muscle injury. No rate of muscle injury is given.
ChromiumLimitedHow often is not known

Muscle breakdown (rhabdomyolysis)

Case reports: a bodybuilder developed rhabdomyolysis after 1,200 µg of chromium picolinate over 48 hours.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
A 24-year-old bodybuilder developed rhabdomyolysis after taking 1,200 µg of chromium picolinate over 48 hours. The authors describe it as the first reported case [14].
Population
One case report [14].
Sources
[14]
Caveats
Weight lifting is itself a cause of rhabdomyolysis [14].
Ezetimibe and fenofibrateLimitedHow often is not known

Ezetimibe: muscle problems

Mixed results: the label warns ezetimibe may cause muscle damage, mostly in people also taking a statin, while pooled trials were too uncertain to tell.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
It was uncertain whether adding ezetimibe to a statin changed myopathy (RR 1.31, 95% CI 0.72 to 2.38) or rhabdomyolysis, given few events [3]. The label reports myopathy and rhabdomyolysis after approval, mostly in people taking a statin or other drugs linked to it [2].
Population
20,581 people in 3 trials [3]; postmarketing reports [2].
Sources
[3], [2]
Caveats
Very low quality evidence [3].
MK-677Grey marketLimitedHow often is not known

Appetite, weight gain, swelling and muscle pain

One trial found more appetite, mild leg swelling and muscle pain, with weight up 2.7 kg against 0.8 kg on placebo, in older adults.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
The most frequent side effects were increased appetite that subsided within a few months, and transient, mild swelling of the legs and muscle pain. Body weight rose 2.7 kg against 0.8 kg on placebo, and limb fat rose 1.1 kg against 0.24 kg [1].
Population
65 healthy adults aged 60 to 81 [1].
Sources
[1]
Caveats
One trial.
NiacinLimitedHow often is not known

Serious side effects, infection and bleeding

One trial found more serious gut, muscle, skin, infection and bleeding events with niacin plus laropiprant. EMA suspended these products in 2013.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Against placebo, niacin with laropiprant raised serious adverse events of the gut (1.0 percentage point), muscles and joints (0.7), skin (0.3), infection (1.4) and bleeding (0.7), all P of .003 or less [2]. EMA suspended these products across the EU in 2013, stating their benefits no longer outweighed their risks [10].
Population
25,673 adults with vascular disease, median 3.9 years [2].
Sources
[2], [10]
Caveats
One trial of a combination with laropiprant [2].
Why limited
This rests on one trial, of 25,673 people. Strength counts independent studies that agree, so one trial is limited at any size.
One meal a dayLimitedHow often is not known

Muscle and strength

Limited evidence: short trials found no loss of strength or aerobic capacity, though in an 8-week training trial only the group eating normally gained lean tissue.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
One evening meal for 11 days did not impair aerobic capacity or strength, and fat oxidation during exercise rose [2]. In young men doing resistance training, a 4-hour eating window on 4 days a week cut intake about 650 kcal on those days and did not change total body composition. Muscle cross-sectional area and strength rose in both groups, and effect sizes showed a lean soft tissue gain of 2.3 kg only in the group training without the window [4].
Population
11 lean adults [2]; recreationally active young men over 8 weeks [4].
Sources
[2], [4]
Caveats
The training trial restricted eating 4 days a week, not daily [4]. Both trials were small and short.
StatinsLimitedHow often is not known

Interaction with some antibiotics

Limited evidence: statins with some antibiotics, mainly macrolides, were linked to about twice the muscle toxicity of a statin alone, in three observational studies.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Taking a statin with an interacting antibiotic, mainly macrolides, was associated with more statin-related muscle toxicity than a statin alone (OR 2.13, 95% CI 1.82 to 2.50) [13].
Population
3 observational studies [13].
Sources
[13]
Caveats
Only three studies, all observational [13].
StatinsLimitedHow often is not known

Blunted fitness gains from training

Small trials found mixed results: one found simvastatin blunted fitness gains from aerobic training, and others found similar gains in statin users and non-users.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Results differ by trial. Over 12 weeks of aerobic training, fitness rose 10% with exercise alone and 1.5% with simvastatin, and muscle citrate synthase rose 13% against a 4.5% fall [7]. Over 16 weeks of interval training, VO2 peak rose 12% in statin users and 19% in non-users, while metabolic syndrome scores, fat oxidation and mitochondrial enzymes improved similarly [15]. Over 12 weeks of endurance and resistance training, strength, fatigue resistance and capillarization improved with no differences between statin users and controls; citrate synthase improved less in statin users without symptoms [16].
Population
37 sedentary overweight adults with metabolic syndrome risk factors, randomized [7]; 106 adults with metabolic syndrome, statin users and matched non-users [15]; 32 statin users and 20 controls, mean age 63 to 64 [16].
Sources
[7], [15], [16]
Caveats
Small trials, and only [7] randomized statin use. No meta-analysis was sourced.
Strength trainingLimitedHow often is not known

Injuries in weight-training sports

Limited evidence: competitive weight-training sports reported about 0.24 to 7.5 injuries per 1,000 hours, mostly strains, tendinitis and sprains of the shoulder, lower back and knee.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Bodybuilding had the lowest rates, 0.24 to 1 injury per 1,000 hours. Strongman had 4.5 to 6.1 and Highland Games 7.5. The shoulder, lower back, knee, elbow and wrist or hand were most often injured [21].
Population
Competitive athletes in weightlifting, powerlifting, bodybuilding, strongman, Highland Games and CrossFit, in 20 studies [21].
Sources
[21]
Caveats
Most studies were retrospective and only 5 of 20 had a low risk of bias. These are competitive athletes, not people training for health [21].
Tai chi and qigongLimitedHow often is not known

Minor muscle and joint aches

Reported adverse events in randomized trials were mostly minor muscle and joint aches, such as knee and back pain. Two thirds of trials did not report adverse events.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Of 153 randomized trials, 50 (33%) reported adverse events and 18 (12%) described an explicit monitoring protocol. Reported events were typically minor, expected and musculoskeletal, such as knee and back pain [16].
Population
153 randomized trials, most in older adults [16].
Sources
[16]
Caveats
Reporting was poor and inconsistent, so no rate can be given [16].
Cold water immersionModerate

Smaller strength and muscle gains when used after lifting

Shown to reduce strength and muscle gains when used regularly after resistance training sessions, mostly in studies of young men.

The numbers and sources
Effect
Pooled trials found smaller strength gains (SMD -0.60, 95% CI -0.87 to -0.33) [7] and smaller hypertrophy (comparative SMD -0.22, 95% credible interval -0.47 to 0.04) [11] with cold water immersion after resistance training than with training alone. An umbrella review of 15 meta-analyses concluded that immersion impaired strength and hypertrophic gains [6].
Population
Participants in 8 controlled studies [7] and 8 randomized studies [11].
Sources
[7], [11], [6]
Caveats
The effect was studied with immersion straight after training. No trial tested immersion at other times of day. Endurance training gains were not reduced [7].
Cold water immersionLimitedStudied in men

Blood test changes after one ice-cold immersion

One small study found liver and muscle enzymes rose after a single immersion below 4°C in 13 young men, all staying within non-pathological limits.

The numbers and sources
Effect
After the immersion, aspartate transaminase, alanine transaminase, lactate dehydrogenase, creatine kinase, its CK-MB form and total bilirubin were higher, and urea, creatinine and uric acid were lower. The authors report all changes stayed within non-pathological limits [27].
Population
13 healthy young men [27].
Sources
[27]
Caveats
One immersion, no control group, healthy young men only.

Mixed results50

IGF-1Strong

Body composition and adverse events in trials of growth hormone

Shown in trials of growth hormone to shift fat and lean mass by about 2 kg in older adults, with more swelling, joint pain and carpal tunnel syndrome.

The numbers and sources
Effect
IGF-1 manages the effects of growth hormone in the body [1], and these trials gave growth hormone without aiming at an IGF-1 level. In community-dwelling adults with a mean age of 69 who were not being treated for a specific illness, growth hormone lowered fat mass by 2.1 kg (95% CI 1.35 to 2.8) and raised lean mass by 2.1 kg (1.3 to 2.9), with no change in weight, bone density or most blood lipids. Treated people were more likely to have soft tissue swelling, joint pain, carpal tunnel syndrome and breast growth in men, and somewhat more likely to develop diabetes or impaired fasting glucose [10]. In adults with confirmed growth hormone deficiency, it lowered weight by 2.31 kg (1.96 to 2.66) and body fat by 2.56 kg (2.16 to 2.97) and raised lean mass by 1.38 kg (1.10 to 1.65). Swelling had a relative risk of 6.07 (4.34 to 8.48) and joint stiffness 4.17 (1.4 to 12.38), with no significant change in bone density. Quality of life improved in 11 of 16 trials [11].
Population
220 treated participants in 18 study populations, mean treatment 27 weeks [10]. More than 3,400 patients in 54 randomized trials [11].
Sources
[10], [11], [1]
Caveats
A marker that tracks an outcome is not always one whose correction changes it. Low IGF-1 went with more deaths in cohorts, and these trials measured body composition, not deaths. The trials in older adults were small and short [10].
AlbuterolModerate

Strength and sprint performance in people without asthma

Mixed results: beta-agonists improved strength and sprint performance by about 5% overall in people without asthma, mostly with oral, weeks-long or prohibited use. Inhaled approved doses barely differed.

Compared with placebo [11]

The numbers and sources
Effect
Overall, beta-agonists improved anaerobic performance by about 5% (SDM 0.29, 95% CI 0.16 to 0.42). The effect was 0.14 (95% CI 0.00 to 0.28) for drugs and doses approved in sport and 0.46 for prohibited ones, 0.16 for inhaled and 0.51 for oral use, and 0.20 for a single dose against 0.50 over weeks. Strength (0.35) and sprint (0.17) both improved [11].
Population
34 randomized placebo-controlled studies with 472 participants without asthma [11].
Sources
[11]
Caveats
The authors state it is uncertain whether doses approved in sport improve performance. Results are pooled across beta-agonists [11].
AstaxanthinModerate

Exercise performance and recovery

Mixed results: one review found better performance alongside training, while another found no gain in VO2 max, time trials or power. Reviews disagree on creatine kinase.

The numbers and sources
Effect
Across 24 RCTs, astaxanthin lowered creatine kinase (SMD -0.45, 95% CI -0.83 to -0.07) and lactate dehydrogenase (SMD -0.93, 95% CI -1.39 to -0.48). Malondialdehyde and IL-6 did not change. VO2 max, time-trial performance and maximal power did not improve [1]. An earlier meta-analysis found better physical performance when astaxanthin was combined with training (SMD 0.62, 95% CI 0.17 to 1.06) and higher fat oxidation [2]. A 2026 meta-analysis of 7 RCTs found lower advanced oxidation protein products after exercise (SMD -1.06, 95% CI -1.49 to -0.62, I² 48%), with no change in creatine kinase, malondialdehyde, superoxide dismutase or IL-6 [3].
Population
Healthy participants and athletes in 24 RCTs [1]; 346 healthy participants in 11 RCTs [2]; 188 participants in 7 RCTs [3].
Sources
[1], [2], [3]
Caveats
The first two reviews disagree on performance, and [1] and [3] disagree on creatine kinase. Heterogeneity for lactate dehydrogenase was substantial [1]. One funder of [1] is a university and company joint laboratory for skin nutrition and anti-aging.
Coenzyme Q10Moderate

Statin-associated muscle pain

Mixed results: two reviews found no benefit for statin muscle pain, including one limited to diagnosed statin myalgia, while two others found less pain.

The numbers and sources
Effect
Statin therapy lowered plasma CoQ10 by 0.44 μmol/L across 8 placebo-controlled arms [1]. For muscle pain, a 2015 meta-analysis of 6 RCTs found no significant effect (SMD -0.53, 95% CI -1.33 to 0.28) and no change in creatine kinase [2]. A 2020 meta-analysis of 7 RCTs (321 patients) found no benefit for myalgia (WMD -0.42, 95% CI -1.47 to 0.62) and no change in staying on statins (RR 0.99) [3]. A 2018 meta-analysis of 12 RCTs (575 patients) found less muscle pain (WMD -1.60, 95% CI -1.75 to -1.44), weakness and cramps [4]. A 2025 meta-analysis of 7 RCTs (389 patients) found less pain intensity (WMD -0.96, 95% CI -1.88 to -0.03) [5].
Population
Adults taking statins, many with muscle symptoms [2][3][4]. The 2025 review covered 100 to 600 mg a day for 30 to 90 days [5].
Sources
[1], [2], [3], [4], [5]
Caveats
The four reviews pool overlapping small trials with different inclusion rules and reach opposite conclusions. The review restricted to patients with diagnosed statin myalgia found no benefit [3]. Creatine kinase did not change in any of them [2][4].
Coenzyme Q10Moderate

Muscle damage markers after exercise

Mixed results: two reviews found lower creatine kinase and malondialdehyde in athletes after exercise, while a 2026 review found no change.

The numbers and sources
Effect
In 17 trials (440 athletes), CoQ10 lowered creatine kinase by 71.81 IU/L (95% CI -124.33 to -19.3), lactate dehydrogenase by 69.99 IU/L and the oxidative stress marker malondialdehyde by 0.61 µmol/L. Total antioxidant capacity did not change [15]. In 14 RCTs (433 participants), creatine kinase fell (SMD -1.532, 95% CI -2.856 to -0.209) and malondialdehyde fell (SMD -0.289) [13]. A 2026 review of athlete trials found malondialdehyde unchanged in its primary analysis (SMD -0.96, 95% CI -2.07 to 0.15, I² 73%), and creatine kinase, IL-6 and total antioxidant capacity unchanged [12].
Population
Athletes [12][15]; exercising adults [13].
Sources
[15], [13], [12]
Caveats
Sources disagree on creatine kinase. Evidence quality was low to very low [15]. These are blood markers, not measured recovery or performance.
Cold water immersionModerate

Recovery of power and performance

Mixed results: pooled trials found small gains in next-day muscular power and no effect on strength recovery, and umbrella reviews call performance findings inconsistent.

The numbers and sources
Effect
Cold water immersion improved recovery of muscular power 24 hours after eccentric exercise (SMD 0.34, 95% CI 0.06 to 0.62) and high-intensity exercise (SMD 0.22, 95% CI 0.004 to 0.43), and lowered creatine kinase 24 hours after high-intensity exercise (SMD -0.85, 95% CI -1.61 to -0.08). Recovery of strength did not differ from passive recovery after either type of exercise [4]. An umbrella review of 15 meta-analyses reported better muscular power and jump performance at 24 to 48 hours despite impaired jumping in the first hours after immersion, and no improvement in strength performance [6]. A second umbrella review judged findings for objective performance inconsistent, time-dependent or comparator-dependent [5].
Population
Physically active people in 52 studies [4]. 161 unique studies across 15 meta-analyses [6]. 14 reviews [5].
Sources
[4], [6], [5]
Caveats
Certainty of evidence was rated low to very low, mainly for inconsistency and imprecision [6]. The lower confidence limit for power after high-intensity exercise sits at zero [4].
CuppingModerate

Chronic pain, compared with other active treatments

Mixed results: one meta-analysis found no pain difference from other active treatments, while reviews of neck and low back pain trials found cupping ahead.

Compared with other active treatments [2][7]; medication [8]; usual care [8]

The numbers and sources
Effect
Against other active treatments, chronic pain did not differ significantly (SMD -0.24, 95% CI -0.57 to 0.09), while disability was lower (SMD -0.52) [2]. In neck pain trials, pain fell more than with active controls (p = 0.0009) [7]. In low back pain trials, pain fell more than with medication (d 1.8, 8 trials) and usual care (d 1.07, 5 trials) at 2 to 8 weeks, with no difference at 1 month or 3 to 6 months [8].
Population
18 trials [2]. 18 neck pain trials [7]. 921 participants in 11 low back pain trials [8].
Sources
[2], [7], [8]
Caveats
Heterogeneity was high across the low back pain subgroups [8].
Dry needlingModerate

Musculoskeletal pain, compared with sham needling

Mixed results: in adequately blinded trials, pain did not differ from sham needling. Less well blinded sham trials favored dry needling, as did two small low back pain trials.

Compared with sham dry needling, penetrating or non-penetrating [5]; sham needling [6]

The numbers and sources
Effect
Across 24 sham-controlled trials, the 3 adequately blinded comparisons found no difference in short-term pain (SMD -0.40, 95% CI -0.96 to 0.15, 122 participants), and the 4 adequately blinded comparisons at 1 to 6 months found none in long-term pain (SMD -0.30, 95% CI -0.62 to 0.02, 202 participants). Inadequately blinded comparisons favored dry needling in the short term (SMD -0.71, 95% CI -1.05 to -0.38, 504 participants) and the long term (SMD -1.14, 95% CI -1.64 to -0.65, 284 participants). The one adequately blinded comparison measured right after treatment, in 31 people, favored dry needling (SMD -0.76) [5]. In low back pain, 2 sham-controlled trials favored dry needling for pain after treatment (SMD -2.74, 95% CI -3.77 to -1.71) and at follow-up (SMD -1.05, 95% CI -1.70 to -0.40), and disability at follow-up did not differ [6].
Population
24 trials comparing dry needling with a sham that simulated it, searched to February 2016 [5]. 2 sham-controlled trials within 16 low back pain trials [6].
Sources
[5], [6]
Caveats
19 of the 24 trials were at high or unclear risk of bias, and no trial tried to blind the therapist. The reviewers say the subgroups were small and the results are uncertain [5]. Most low back pain trials were at high or unclear risk of bias [6].
Dry needlingModerate

Low back pain, compared with acupuncture

Mixed results: low back pain eased more than with acupuncture right after treatment in 6 trials, and pain and disability did not differ at follow-up.

Compared with acupuncture, including wrist-ankle acupuncture in one trial [6]

The numbers and sources
Effect
Across 6 trials with 467 participants, pain intensity after treatment was lower with dry needling than with acupuncture (SMD -0.96, 95% CI -1.80 to -0.12). At follow-up, pain and disability did not differ. In one trial of 60 people with acute low back pain, one 5-minute session lowered pain more than wrist-ankle acupuncture [6].
Population
467 people with low back pain in 6 trials [6].
Sources
[6]
Caveats
Most trials were at high or unclear risk of bias, and the reviewers say the evidence is not robust [6].
Dry needlingModerate

Headache

Mixed results: headache pain did not differ from other treatments in the short term, while headache-related disability improved more in tension-type and cervicogenic headache.

Compared with other interventions [16]

The numbers and sources
Effect
Short-term headache pain did not differ from other interventions in tension-type headache (SMD -1.27, 95% CI -3.56 to 1.03, 230 participants), cervicogenic headache (SMD -0.41, 95% CI -4.69 to 3.87) or mixed headache including migraine (SMD 0.03, 95% CI -0.42 to 0.48). Disability improved more in tension-type headache (SMD -2.28, 95% CI -2.66 to -1.91) and cervicogenic headache (SMD -0.72, 95% CI -1.09 to -0.34) [16].
Population
11 trials, 9 pooled, of people with tension-type, cervicogenic or migraine headache [16].
Sources
[16]
Caveats
Only 4 trials were of high quality, and the evidence on pain was rated very low quality [16].
HMBModerate

Muscle mass and strength in older adults and patients

Mixed results: HMB raised muscle mass and strength slightly in older adults and patients, but not when added to resistance training.

The numbers and sources
Effect
In 9 RCTs (448 older adults), HMB raised fat-free mass (ES 0.37, 95% CI 0.16 to 0.58), with no change in fat mass. HMB alone raised fat-free mass (ES 0.59); HMB added to exercise did not (ES 0.06, 95% CI -0.26 to 0.38) [5]. In 21 RCTs (1,935 people over 50), HMB raised appendicular muscle mass by 1.56 kg (95% CI 0.03 to 3.09), lean mass by 0.28 kg, handgrip strength by 0.54 kg and gait speed by 0.06 m/s [6]. In 5 RCTs in sarcopenia, muscle mass index (SMD 0.32, 95% CI 0.00 to 0.64) and handgrip strength (SMD 0.65) rose, and gait speed did not change [7]. In 15 RCTs (2,137 patients with muscle-wasting conditions), HMB or HMB-containing supplements raised muscle mass (SMD 0.25, 95% CI -0.00 to 0.50) and strength (SMD 0.31, 95% CI 0.12 to 0.50) [8].
Population
Older adults [5][6]; people with sarcopenia [7]; hospital and clinical patients [8].
Sources
[5], [6], [7], [8], [9], [10]
Caveats
Many trials gave HMB in multi-ingredient nutrition drinks, so the effect of HMB alone is unclear [8]. No trial in [8] had low risk of bias in every category. Review [6] searched Chinese databases. Added to resistance training, HMB did not change muscle mass (SMD 0.05, 95% CI -0.10 to 0.20, 13 RCTs, 561 adults over 50) or strength [9], and a second review of 10 trials (596 older adults) found no change in lean mass, a borderline handgrip gain (SMD 0.24, 95% CI 0.00 to 0.48) and better physical performance scores (SMD 0.54), with half the trials at high risk of bias [10].
Low-dose naltrexoneModerate

Fibromyalgia pain

Mixed results: two meta-analyses found less fibromyalgia pain than placebo, while a third and two later trials found no difference.

The numbers and sources
Effect
In 4 RCTs (222 patients), pain scores fell more than on placebo (MD -0.86, 95% CI -1.20 to -0.51, I² 33%), while the revised Fibromyalgia Impact Questionnaire did not differ [1]. A meta-analysis of 5 RCTs found less pain than placebo (SMD -0.61, 95% CI -1.14 to -0.08) and no change in mechanical pain threshold [2]. A third meta-analysis of 8 trials found no difference from placebo in pain (SMD -0.50, 95% CI -1.19 to 0.19, I² 91%) or symptom severity [3]. In a crossover trial of 58 patients, 4.5 mg a day did not differ from placebo in pain ratings or questionnaire scores [4]. In 98 women followed for 12 months, pain at 3 months fell 0.33 points on LDN and 0.64 on placebo (difference 0.49, p 0.236) [5].
Population
Adults with fibromyalgia in small RCTs [1][2][3], 58 patients in a crossover trial with treatment periods of about 3 weeks [4], and 98 women over 12 months [5].
Sources
[1], [2], [3], [4], [5]
Caveats
The meta-analyses reach different answers from overlapping trials. Most trials were crossover designs with fewer than 60 people. The two trials published after the meta-analyses found no difference [4][5].
38 more
Massage therapyModerate

Strength, sprint and performance recovery

Mixed results: one meta-analysis found no effect on strength, jump, sprint or endurance, while others found small gains in force or short-term performance recovery.

Compared with no intervention [8]; control conditions the source abstracts do not describe [10][11]

The numbers and sources
Effect
Across 29 studies, massage did not improve strength, jump, sprint, endurance or fatigue [10]. In another pooled analysis, maximal isometric force (SMD 0.56) and peak torque (SMD 0.38) were higher after massage [8]. Across 22 trials, performance recovery effects were small: +6.6% with 5 to 12 minutes of massage and +1.0% with more than 12 minutes, larger for recovery periods of up to 10 minutes (+7.9%) than more than 20 minutes (+2.4%) [11].
Population
1,012 participants in 29 studies [10]. 504 participants in 11 trials [8]. 22 randomized trials [11].
Sources
[10], [8], [11]
Caveats
The authors of [11] called the effects rather small and partly unclear, larger in untrained people than in trained athletes.
Muscle relaxantsModerate

Spasticity in multiple sclerosis

Mixed results: one review found fair evidence that baclofen and tizanidine reduce spasticity against placebo, and a Cochrane review called the evidence in multiple sclerosis poorly documented.

The numbers and sources
Effect
A systematic review of 101 randomized trials found fair evidence that baclofen and tizanidine reduce spasticity against placebo, mainly in multiple sclerosis, and that the two are roughly equivalent, with more dry mouth on tizanidine and more weakness on baclofen. None of the trials met its top quality rating [4]. A Cochrane review of 26 placebo-controlled and 13 comparative studies in multiple sclerosis found that of the 8 placebo-controlled trials using the Ashworth scale of muscle tone, 3 showed a significant difference, and that spasms and function were assessed with unvalidated scores [8].
Population
People with spasticity, mostly from multiple sclerosis, in 101 randomized trials of muscle relaxants [4]; people with multiple sclerosis in 39 studies of anti-spasticity drugs [8].
Sources
[4], [8]
Caveats
Both reviews date from 2003 and 2004. Neither pooled an effect size.
NMNModerate

Muscle and physical function

Mixed results: one review found no change in muscle mass, strength or gait speed in older adults, while others found better endurance or gait speed.

The numbers and sources
Effect
In adults with a mean age over 60, NMN did not change skeletal muscle index (MD -0.42, 95% CI -0.99 to 0.14), grip strength, gait speed (MD -0.01 m/s, 95% CI -0.08 to 0.06) or chair-stand time. Knee extension strength, SPPB scores and thigh muscle mass did not improve [4]. A network meta-analysis of NAD precursors reported higher endurance with NMN at medium dose (SMD 0.66, 95% CI 0.09 to 1.23) and high dose (SMD 1.02, 95% CI 0.43 to 1.60), with no change in strength [5]. One trial reported a longer six-minute walk on 300 to 900 mg a day than placebo [1]. A 2025 meta-analysis of 9 RCTs (412 middle-aged and older adults) found faster gait speed on NMN (SMD 0.34, 95% CI 0.03 to 0.66) and lower ALT (SMD -0.29, 95% CI -0.55 to -0.03) [6].
Population
Randomized trials in adults with mean ages of 60.9 to 83 years [4]; 27 studies with 1,599 adults across NR, NMN, NADH and nicotinamide [5]; 80 middle-aged adults [1]; 412 middle-aged and older adults [6].
Sources
[4], [5], [1], [6]
Caveats
The reviews disagree on endurance and on gait speed [4][5][6]. The pooled muscle analysis included 2 to 5 studies per measure [4]. The network analysis mixes precursors and populations [5].
Ozone therapyModerate

Joint and muscle pain, compared with corticosteroid injections

Mixed results: across musculoskeletal conditions, steroid injections eased pain more in the short term, while in knee osteoarthritis alone ozone eased pain more.

Compared with corticosteroid injections [8][9]

The numbers and sources
Effect
Across 11 studies of musculoskeletal pain of several kinds, short-term pain fell more with corticosteroid injections (d 0.31, 95% CI 0.01 to 0.60), and medium-term pain did not differ (d -0.17, 95% CI -0.42 to 0.07) [8]. In 7 knee osteoarthritis trials, ozone injections reduced pain more than corticosteroid injections in the short and medium term and improved function in the medium term [9].
Population
534 people with musculoskeletal pain in 11 studies [8]. 409 people with knee osteoarthritis in 7 trials [9].
Sources
[8], [9]
Caveats
Both reviews describe the included trials as limited in quality [8][9]. The knee review abstract gives no effect sizes [9].
Physical therapy and exercise therapyModerate

Chronic low back pain, compared with other treatments

Mixed results: exercise eased pain about 9 points on a 100-point scale more than other conservative treatments, below the clinical threshold, and did not differ from manual therapy.

Compared with other conservative treatments [2]; education alone [2]; non-exercise physical therapy [2]; manual therapy [2]

The numbers and sources
Effect
Against all other conservative treatments, pain fell 9.1 points more (95% CI -12.6 to -5.6) and functional limitation 4.1 points more, neither meeting the reviewers' threshold for clinical importance. By subgroup, pain fell more than with education alone (-12.2) and non-exercise physical therapy (-10.4), and did not differ from manual therapy (1.0, 95% CI -3.1 to 5.1) [2].
Population
249 trials of adults with chronic low back pain [2].
Sources
[2]
Caveats
Low-certainty evidence for these comparisons [2].
Red light therapyModerate

Low back pain

Mixed results: one meta-analysis found pain reduction with higher-dose laser in chronic low back pain, and a later one found the effect against sham clinically unimportant.

The numbers and sources
Effect
Across 15 sham-controlled studies (1,039 participants), pain fell by up to 1.40 cm on a 10 cm scale (95% CI -1.91 to -0.88) in trials using at least 3 J per point and in people with pain for under 30 months [15]. Across 12 RCTs (1,046 participants), the effect on pain and disability compared with sham was clinically unimportant in acute, subacute and chronic low back pain, and did not differ meaningfully from exercise [16].
Population
Adults with chronic non-specific low back pain [15]. People with acute, subacute or chronic non-specific low back pain [16].
Sources
[15], [16]
Caveats
The earlier review's benefit appeared only in dose and duration subgroups [15]. The later review concluded current evidence does not support its use for this condition [16].
Red light therapyModerate

Exercise performance

Mixed results: pooled trials found small gains in muscle endurance and cycling time to exhaustion, and no effect on strength, sprinting, running or swimming performance.

The numbers and sources
Effect
Across 37 double-blind crossover studies (586 participants) of light applied before exercise, muscle endurance in single-joint exercise improved (SMD 0.27, 95% CI 0.12 to 0.41) and so did cycling time to exhaustion (SMD 0.35, 95% CI 0.10 to 0.59). Strength (p = 0.92), cycling sprints (p = 0.96), running and swimming measures did not change [17]. An earlier review of 39 trials (861 participants) found some effect in favor of phototherapy on time to exhaustion, repetitions, peak torque and lactate, at very low to moderate quality [18]. In athletes, a meta-analysis of 24 studies reported better lower-limb strength up to 8 weeks when laser was applied before exercise [19].
Population
Healthy young adults [17]. Healthy people in 39 trials [18]. Physically active athletes in 24 studies [19].
Sources
[17], [18], [19]
Caveats
The reviews disagree on strength. Light doses, wavelengths and exercise tests varied widely, and samples were small [18].
Red light therapyModerate

Muscle soreness and damage after exercise

Mixed results: one meta-analysis found no substantial effect on exercise-induced muscle pain or strength loss, and another in athletes found lower soreness and creatine kinase.

The numbers and sources
Effect
Across 15 studies (317 participants) of a single session before or after exercise, creatine kinase was lower only when laser was applied before exercise (SMD -0.66, 95% CI -1.30 to -0.02). Swelling, range of movement and strength did not differ from placebo, and the authors concluded phototherapy may not have a substantial effect on exercise-induced muscle injury and pain [20]. A meta-analysis in athletes reported a lower soreness index, creatine kinase and interleukin-6 with laser therapy [19].
Population
317 participants in 15 placebo-controlled studies [20]. Athletes in 24 studies [19].
Sources
[20], [19]
Caveats
Substantial heterogeneity limited the pooled analyses [20]. The athlete review gives no effect sizes in its abstract [19].
Strength trainingModerate

Falls in older adults

Mixed results: programs combining balance and strength exercises probably cut falls by about a third, while the effect of strength training alone was uncertain.

Compared with control interventions not thought to reduce falls [16]

The numbers and sources
Effect
Programs with several exercise types, most often balance and functional exercises plus resistance exercises, probably reduced the rate of falls by 34% (RaR 0.66, 95% CI 0.50 to 0.88) and the number of people falling by 22% (RR 0.78). Balance and functional exercises reduced the rate of falls by 24%. The review was uncertain of the effect of programs that were mainly resistance training [16].
Population
23,407 people 60 and older living in the community, average age 76, in 108 trials [16].
Sources
[16]
Caveats
Evidence for mixed programs was rated moderate in certainty, and for resistance training alone too uncertain to judge [16].
Vitamin DModerate

Muscle strength

Shown to raise muscle strength slightly in older adults and those with low vitamin D, with no change in younger people. A newer review found no change.

The numbers and sources
Effect
Across 30 RCTs (5,615 people, mean age 61.1), vitamin D raised global muscle strength by an SMD of 0.17. Muscle mass (SMD 0.058) and power (SMD 0.057) did not change. The effect was larger with baseline 25-hydroxyvitamin D below 30 nmol/L and at 65 or older (SMD 0.25, 95% CI 0.01 to 0.48) than in younger people (SMD 0.03, 95% CI -0.08 to 0.14) [23]. Across 7 RCTs in adults 60 and older, vitamin D did not raise skeletal muscle mass index, lean mass or handgrip strength [24]. In 152 postmenopausal women with 25-hydroxyvitamin D below 30 ng/mL, 20 µg calcifediol or 3,200 IU vitamin D3 a day for 6 months did not differ from placebo on gait speed, knee strength and sit-to-stand tests (success in 53.6%, 55.5% and 61.4%) [25].
Population
Adults in 30 RCTs, with or without calcium [23]; adults with mean age 60 to 74 in 7 RCTs of 3 to 36 months [24]; women aged 50 to 70 with osteopenia or osteoporosis [25].
Sources
[23], [24], [25]
Caveats
An SMD of 0.17 is small, and the search for that review ended in January 2014 [23]. The newer review did not find a change in handgrip strength [24].
Volunteering and purposeModerate

Physical function in older volunteers

Mixed results: one meta-analysis linked volunteering after 65 to 17% less functional disability, while an earlier review found no favorable effect on physical health.

Compared with non-volunteers [3]; non-volunteers [2]; people who volunteered 0 hours a year [4]

The numbers and sources
Effect
Volunteers had less new functional disability (HR 0.83, 95% CI 0.72 to 0.97) and kept functional competence more often (OR 0.81, 95% CI 0.70 to 0.94). Decline in daily living tasks did not differ significantly (OR 0.73, 95% CI 0.53 to 1.01) [3]. Cohort studies did not show favorable effects on physical health [2]. Volunteering 100 hours or more a year was linked to fewer physical functioning limitations and more physical activity [4].
Population
Adults 65 and older in 3 disability and 3 functional competence studies [3]. 17 cohort studies [2]. 12,998 US adults over 50 [4].
Sources
[3], [2], [4]
Caveats
Observational. People with better function are more able to start and keep volunteering, which is reverse causation.
Whole-body cryotherapyModerate

Muscle soreness after exercise

Mixed results: a Cochrane review found insufficient evidence that whole-body cryotherapy reduces soreness, and two placebo-controlled trials found it no better than a sham treatment.

The numbers and sources
Effect
A Cochrane review of 4 trials (64 participants) found lower soreness at 1 hour (SMD -0.77, 95% CI -1.42 to -0.12). At 24 hours (SMD -0.57, 95% CI -1.48 to 0.33), 48 hours (SMD -0.58, 95% CI -1.37 to 0.21) and 72 hours (SMD -0.65, 95% CI -2.54 to 1.24) the intervals included no difference [2]. A review of 16 studies reported muscle pain was reduced in 80% of them [3]. After a marathon, 31 runners randomized to cryotherapy, cold water immersion or a placebo showed no advantage of either cold treatment over placebo for functional recovery or perceived training stress [4]. After a resistance session in 24 men, cryotherapy lowered soreness at 24 hours compared with cold water and placebo, and neither cold treatment sped recovery more than placebo overall [5].
Population
64 physically active young adults, all but 4 of them men [2]. Healthy, physically active people in 16 studies [3]. 31 endurance-trained men [4]. 24 resistance-trained men [5].
Sources
[2], [3], [4], [5]
Caveats
Cochrane rated all evidence very low in quality, with a high risk of bias in every trial, and concluded there was insufficient evidence [2]. The 16-study review counted positive studies and did not pool them [3]. The placebo-controlled trials suggest belief in the treatment may account for part of the reported benefit [4].
ACE inhibitorsLimited

Physical function in older adults

Small trials found mixed results: perindopril raised 6-minute walking distance by 31 m in one trial and did not change physical performance in another.

The numbers and sources
Effect
Over 20 weeks, 6-minute walking distance improved by 31.4 m more on perindopril than on placebo (95% CI 10.8 to 51.9) in older adults with mobility problems [18]. Over 12 months in older adults with sarcopenia, perindopril 4 mg did not change the short physical performance battery score (difference -0.1 points, 95% CI -1.2 to 1.0) or any secondary outcome [19].
Population
130 adults aged 65 and older with functional impairment, 95 completing [18]; 145 adults aged 70 and older with sarcopenia [19].
Sources
[18], [19]
Caveats
Both trials tested perindopril. The sarcopenia trial recruited 145 of a planned 440 people, and adherence to perindopril was lower than to placebo [19].
Alpha-GPC and choline supplementsLimitedStudied in men

Strength and power

Small trials found mixed effects on strength and power in young men, with one gain in lower body pull force. All were funded by alpha-GPC makers.

The numbers and sources
Effect
In 13 college-aged men, 600 mg a day for 6 days raised mid-thigh pull peak force by 98.8 N versus a 39.0 N fall on placebo. Upper body force did not differ significantly [9]. In 48 men over 7 days, 250 mg or 500 mg a day did not change isometric strength or psychomotor vigilance. Countermovement jump velocity and power differed between groups, with the largest change at 250 mg [10]. Jumps, bench throws and growth hormone did not differ after single doses [8].
Population
Young men [8][9][10].
Sources
[8], [9], [10]
Caveats
All three trials were funded by alpha-GPC manufacturers (Chemi Nutra [9][10], NNB Nutrition [8]). Samples were small and outcomes were mixed.
CitrullineLimited

Muscle soreness and perceived effort

Limited evidence: perceived effort and soreness at 24 hours fell in one review, while a larger review found no effect on perceived effort.

The numbers and sources
Effect
Across 13 articles (206 participants), citrulline lowered rating of perceived exertion (7 studies, p = 0.03) and muscle soreness at 24 hours (7 studies, p = 0.04), but not at 48 hours (p = 0.25) or 72 hours (p = 0.62). Blood lactate did not change (8 studies, p = 0.17) [4].
Population
Healthy adults; 8 g citrulline malate was the most common dose [4].
Sources
[4]
Caveats
The abstract reports p-values without effect sizes. The results sentence groups soreness at 24 and 48 hours as reduced, but the 48-hour p-value is 0.25 [4]. A 2026 three-level meta-analysis of citrulline malate (30 RCTs, 644 participants) found no significant pooled effect on perceived exertion, so sources disagree on effort [5].
CollagenLimited

Muscle mass and strength with training

Limited evidence: one review found gains in fat-free mass and strength with training, while 8 training trials found collagen added no strength gain.

The numbers and sources
Effect
Across 19 RCTs (768 healthy adults) training for 8 weeks or more, collagen peptides improved fat-free mass (SMD 0.48), muscle architecture (SMD 0.39), maximal strength (SMD 0.19) and 48-hour reactive strength recovery (SMD 0.43) [1]. A 2025 meta-analysis found muscle performance improved (SMD 0.60, 95% CI 0.05 to 1.15) [10]. In 8 training RCTs, strength rose with training in every trial, and collagen added no further gain [2].
Population
Healthy adults over 17 in exercise programs [1]; people in RCTs of collagen with or without calcium and vitamin D [10]; trained adults aged 18 to 52 [2].
Sources
[1], [10], [2]
Caveats
Sources disagree on strength. GRADE certainty was moderate for body composition and low for the other outcomes [1]. A systematic review found collagen did not raise muscle protein synthesis compared with isonitrogenous higher-quality proteins [3].
CuppingLimited

Recovery and flexibility in athletes

Limited evidence: small trials against mostly untreated controls reported less pain and more range of motion, and a sham-controlled study found no change in hamstring flexibility.

Compared with mostly untreated control groups [9]; sham cupping and no treatment [10]

The numbers and sources
Effect
Across 11 trials in athletes, cupping was reported to lower pain and disability, increase range of motion and reduce creatine kinase against mostly untreated controls [9]. In 25 adults with tight hamstrings, 10 minutes of cupping did not change flexibility compared with sham or control (p = 0.35 and 0.36) [10].
Population
498 amateur and professional athletes in 11 trials [9]. 25 healthy adults in a crossover study [10].
Sources
[9], [10]
Caveats
Most athlete trials were at unclear or high risk of bias, and none reported safety [9].
Fisetin and quercetin (senolytics)Limited

Physical function and cognition

Small trials found mixed results: walking improved in an uncontrolled pulmonary fibrosis study, cognition did not change in Alzheimer disease, and quercetin results in older adults varied.

The numbers and sources
Effect
In idiopathic pulmonary fibrosis, six-minute walk distance, 4 m gait speed and chair-stand time improved significantly after 3 weeks of intermittent dosing [5]. In mild Alzheimer disease, cognitive and brain imaging outcomes did not differ from baseline after 12 weeks [6]. With quercetin alone, 26 older adults doing 6 weeks of resistance training on 200 mg a day of quercetin glycosides gained more knee extension force than on placebo (115.1% against 105.3% of baseline), with no change in muscle mass [7]. In 38 older adults, a single 500 mg dose before low or moderate intensity resistance exercise produced a larger drop in electrically elicited muscle torque afterward than placebo, and not at high intensity [8].
Population
14 adults with idiopathic pulmonary fibrosis [5]; 5 adults with early Alzheimer disease, mean age 76 [6]; healthy older adults [7][8].
Sources
[5], [6], [7], [8]
Caveats
The dasatinib plus quercetin studies were open-label with no placebo group, built to test feasibility [5][6]. The two quercetin-only trials are small and from one research group [7][8].
GABALimited

Growth hormone and lean mass

Small trials found 3 g raised growth hormone in trained men, but 200 mg a day did not change body fat or lean mass in women with obesity.

The numbers and sources
Effect
In 11 resistance-trained men, 3 g of GABA raised peak resting growth hormone about 400% and area under the curve about 375% compared with placebo, and growth hormone was also higher after exercise [7]. In 21 men training twice a week for 12 weeks, 10 g of whey plus 100 mg of GABA increased fat-free mass more than whey alone [8]. In 26 women with obesity training 3 days a week for 90 days, 200 mg of GABA a day did not change body fat, fat mass, fat-free mass or growth hormone compared with placebo. Within the GABA group, BMI and waist circumference fell and sit-up performance rose [9].
Population
11 men aged 18 to 30, crossover [7]. 21 men aged 26 to 48 [8]. 26 women with obesity [9].
Sources
[7], [8], [9]
Caveats
All three trials were small. The within-group changes in the women's trial were not differences from placebo [9]. The lean mass trial was funded by Pharma Foods International, which supplied the GABA and employed four authors [8]. A rise in growth hormone was not shown to change muscle in [7].
GroundingLimited

Muscle damage and soreness after exercise

One sham-controlled trial of 32 young men found creatine kinase did not rise after damaging exercise with grounding, while it rose with sham. Pain occurred in both groups.

Compared with sham grounding, with the same equipment not connected to the earth [4][5]

The numbers and sources
Effect
After 200 half-knee bends, men grounded for 4 hours on days 1 and 2 had no significant rise in creatine kinase on day 2, while the sham group did (P < 0.01). The between-group difference was significant (P = 0.04). Both groups had pain on every day after exercise [4]. In an 8-person pilot, pain scores and creatine kinase were among the measures that differed by 10% or more between grounded and sham groups [5].
Population
32 healthy young men, 16 grounded and 16 sham [4]. 8 healthy adults, 4 per group [5].
Sources
[4], [5]
Caveats
The trial was funded by Earth FX Inc., which also supplied the products, and both authors named in its disclosure worked as contractors for Earth FX. The authors state the funder had no role in the study [4]. The pilot set its own 10% threshold rather than testing significance [5].
IV vitamin therapyLimitedStudied in men

Exercise performance, IV fluids against drinking

Small crossover trials disagreed: one found IV rehydration sped a 40 km cycling time trial by 3.5% against drinking, and another found drinking gave a faster time trial.

Compared with drinking fluids, sports drink and water [5]; drinking water [6]

The numbers and sources
Effect
After dehydration by 4% of body weight, rehydrating half with IV saline cut 40 km time trial time by 3.5% against oral rehydration, and oral glycerol by 3.7%. Combining IV fluid with oral glycerol restored the most plasma volume and did not improve performance over either alone [5]. During 90 minutes of cycling in 35°C heat, 25 mL of saline infused every 5 minutes left people thirstier and hotter, with a slower 12 km time trial (19.6 minutes) than drinking 25 mL of water every 5 minutes (17.7 minutes, P = 0.05) [6].
Population
9 endurance-trained men [5]. Recreationally active men, mean age 29, number not given in the abstract [6].
Sources
[5], [6]
Caveats
Two small crossover trials with different designs. Neither tested recovery on the following days.
L-arginineLimited

Exercise performance

Limited evidence: one review reported better aerobic and anaerobic performance but was found to contain errors, and strength trials found no effect.

The numbers and sources
Effect
A meta-analysis of 15 studies reported improved aerobic performance (SMD 0.84, 95% CI 0.12 to 1.56, I² 89%) and anaerobic performance (SMD 0.24, 95% CI 0.05 to 0.43) [10]. A 2025 published comment identified errors in that analysis, including outlier effect sizes, effect estimates that needed recalculating with standard deviations, and one included study that appeared to compare arginine with citrulline rather than placebo [11]. A meta-analysis of 3 trials of acute arginine alone in strength training found no effect on muscular endurance (0.26, 95% CI -0.13 to 0.65) or peak torque [12]. In a crossover trial of 4 days at 3.2 to 9.6 g a day, total biceps curl repetitions, volume load, fatigue and plasma nitric oxide did not differ from placebo [13].
Population
Athletes and active adults [10][12]. 16 recreationally trained young men [13].
Sources
[10], [11], [12], [13]
Caveats
Sources disagree. Aerobic results had very high heterogeneity [10].
L-arginineLimitedStudied in men

Growth hormone and muscle growth

Mixed results: small trials found oral arginine raised resting growth hormone but blunted its rise after lifting, and lean mass did not change in athletes over 45 days.

The numbers and sources
Effect
In 8 healthy men, 5 g and 9 g of oral arginine raised the growth hormone area under the curve over placebo at rest, while 13 g did not and caused stomach upset in most [16]. In 8 men, 7 g of arginine before resistance exercise gave a smaller growth hormone response than exercise alone [17]. In 14 strength-trained men, arginine before lifting blunted growth hormone (area under the curve 288.4 against 487.9 on placebo, p < 0.05), with no difference in IGF-1 [18]. In 56 male soccer players, 2 g a day for 45 days did not change lean body mass, fat mass or BMI against placebo [19].
Population
Healthy young men [16][17]. Strength-trained men [18]. Male soccer players aged 16 to 35 [19].
Sources
[16], [17], [18], [19]
Caveats
Small, short trials in men. Growth hormone was measured for hours after a single dose, and no trial measured muscle growth over a training program [16][17][18].
L-carnitineLimited

Endurance and exercise metabolism

Limited evidence: some small trials reported better endurance, one only with added carbohydrate, while a CrossFit trial found no change.

The numbers and sources
Effect
In 30 publications in healthy people, carnitine raised blood carnitine and changed resting VO2, with no change in blood lactate at rest or after exercise [5]. In 14 healthy men, 2 g of L-carnitine L-tartrate with 80 g of carbohydrate twice daily for 24 weeks raised muscle carnitine 21%, cut muscle glycogen use 55% at low intensity, and raised work output 11% from baseline; carbohydrate alone did not change it [6]. A 2026 systematic review of 18 randomized placebo-controlled trials in active people reported better endurance performance after single doses of 2 to 15 g and after 2 to 3 g a day for 2 to 24 weeks, with no change in fat oxidation during exercise [7]. In 20 trained men, 3 g of L-carnitine L-tartrate 90 minutes before a 20-minute CrossFit workout did not change repetitions completed (202.4 against 204.5) [8].
Population
Healthy adults [5]; 14 young men [6]; active people in 18 trials [7]; 20 recreational CrossFit athletes [8].
Sources
[5], [6], [7], [8]
Caveats
The single trial is small, and the carbohydrate was needed to raise insulin and move carnitine into muscle [6]. The meta-analysis reports dose in "g/dL", which appears to be a unit error [5]. The 2026 review did not pool results, and none of its trials was at low risk of bias [7].
MacaLimited

Physical performance

Limited evidence: large effects came mostly from animal tests, and a small trial in basketball players found no difference from placebo.

The numbers and sources
Effect
A meta-analysis of 16 studies reported large effects on forced swimming, rota-rod and grip strength tests and lower blood lactate [8]. In a crossover trial in 10 well-trained college basketball players, 2,000 mg a day for 2 weeks did not differ from placebo in jump height, shooting accuracy, repeated sprints, fatigue index or lactate clearance [9].
Population
Animal and human studies [8]. 10 male basketball players [9].
Sources
[8], [9]
Caveats
The outcomes are largely animal tests. The abstract does not report a separate human effect [8]. The basketball trial was small and short [9].
Massage therapyLimited

Neck pain

Limited evidence: very low-quality trials suggested some massage techniques improved function and tenderness more than control or placebo, and reviewers called the effect uncertain.

Compared with control or placebo treatment [6]; education [6]

The numbers and sources
Effect
Very low-quality evidence suggested traditional Chinese massage and strain-counterstrain techniques may improve function and tenderness more than control or placebo, and massage may ease pain bothersomeness more than education in the short term. Most trials measured outcomes immediately after treatment [6].
Population
15 trials of adults with mechanical neck disorders [6].
Sources
[6]
Caveats
All trials were rated low or very low in quality, and only 4 of 15 described the massage adequately. The reviewers made no recommendation [6].
NSAIDsLimited

Muscle growth and strength with resistance training

Small trials found mixed results: ibuprofen raised muscle gains in older adults, lowered them in young adults against aspirin, and made no difference in another.

The numbers and sources
Effect
Results differ by trial. In older adults training for 12 weeks, ibuprofen 1.2 g a day increased quadriceps volume 10.9% against 8.6% on placebo, and strength 19 kg against 15 kg [6]. In young adults training for 8 weeks, ibuprofen 1,200 mg a day increased quadriceps volume 3.7% against 7.5% on low-dose aspirin, and strength gains on the maximal-effort leg were smaller [7]. In young adults training for 6 weeks, ibuprofen 400 mg after each session did not change biceps thickness or strength against placebo [8]. A systematic review of 7 athlete trials found NSAIDs did not raise collagen synthesis or satellite cell activity after exercise [9].
Population
36 adults aged about 64 to 67 [6]; 31 adults aged 18 to 35 [7]; 18 adults aged about 24, each arm its own control [8]; 346 athletes in 7 RCTs [9].
Sources
[6], [7], [8], [9]
Caveats
Small trials with different doses, ages and comparators. [7] compared ibuprofen with 75 mg aspirin, not placebo. No meta-analysis of training adaptations was sourced.
Osteopathy and osteopathic manipulative treatmentLimited

Neck pain

Limited evidence: four small trials pooled against no treatment or sham found less neck pain, at very low quality, and a 2024 sham-only review found no difference.

Compared with no intervention or sham treatment, pooled together [9]; sham or placebo interventions [2]

The numbers and sources
Effect
Against no intervention or sham, osteopathic treatment lowered pain (effect size -1.57, 95% CI -2.50 to -0.65) and improved function (-1.71), with very low quality evidence for every outcome [9]. The 2024 review, which pooled neck and low back pain against sham or placebo only, found no difference in pain or disability [2].
Population
5 trials, 4 pooled, of adults with nonspecific neck pain [9]. 9 trials in neck or low back pain [2].
Sources
[9], [2]
Caveats
None of the neck pain trials was judged at low risk of bias in every domain [9].
Red meat and processed meatLimited

Muscle and strength with resistance training in older adults

Mixed results: one trial in older women found more lean mass and strength with lean red meat during training, while a larger trial found no added gain.

Compared with a daily serving of pasta or rice [5]; rice, pasta or potato on training days [6]

The numbers and sources
Effect
In women aged 60 to 90 doing resistance training twice a week, about 160 g of cooked lean red meat 6 days a week gave greater gains in total lean mass (0.45 kg, 95% CI 0.07 to 0.84), leg lean mass and strength (18%), and a 10% greater rise in IGF-1, over 4 months [5]. In adults 65 or older training 3 days a week, lean red meat on training days did not add to gains in lean mass, thigh muscle, strength or executive function over 24 weeks. Arm lean mass, gait speed and muscle density improved slightly more [6].
Population
100 women in 15 retirement villages, cluster randomized [5]. 154 community-dwelling adults aged 65 or older [6].
Sources
[5], [6]
Caveats
Two trials from the same research group with different results. Both combined meat with exercise, so neither tests meat alone.
Reiki and therapeutic touchLimited

Pain, compared with sham Reiki

Mixed results: a fibromyalgia trial found Reiki no different from sham given by actors, and a knee pain trial found more people improved with Reiki than with sham.

Compared with sham Reiki given by actors, with or without touch [7]; sham Reiki and a waiting list [8]

The numbers and sources
Effect
In 100 adults with fibromyalgia treated twice weekly for 8 weeks, pain and every secondary outcome were nearly identical whether a Reiki master or an actor gave the treatment, with touch or at a distance [7]. In 164 adults with knee osteoarthritis, symptoms improved more with Reiki than with a waiting list (P = .02), and a reduction of more than 30% was reported by 55% given Reiki, 20% given sham Reiki and 13% on the waiting list [8].
Population
100 adults with fibromyalgia in Seattle [7]. 164 adults with knee osteoarthritis [8].
Sources
[7], [8]
Caveats
The knee trial abstract does not report a direct test of Reiki against sham [8].
SARMsGrey marketLimited

Physical function and strength

Limited evidence: one trial found better physical function in healthy older adults, and a review found improvement inconsistent across trials.

The numbers and sources
Effect
In healthy older adults, physical function improved on enobosarm against placebo (P = 0.013) [2]. The 2026 review reports that physical function improved inconsistently across trials [4].
Population
120 healthy older adults over 12 weeks [2]; trials summarized in a review [4].
Sources
[2], [4]
Caveats
One phase 2 trial plus a narrative review.
SaunaLimited

Recovery after hard training

Mixed results: swimmers were slower the morning after a post-training sauna, while a sauna before eccentric exercise reduced strength and motion losses in one small trial.

The numbers and sources
Effect
In 20 competitive swimmers and triathletes, a 4 x 50 m all-out swim the next morning was 1.69 s slower after 3 x 8 minutes of sauna at 80°C to 85°C, against 0.66 s faster after a placebo treatment (P = .02). Perceived stress was higher after sauna [25]. In 28 young adults, a sauna before eccentric wrist exercise led to smaller deficits in range of motion, grip strength and wrist extension strength than no sauna (P < 0.05) [26].
Population
20 swimmers and triathletes in a randomized crossover [25]. 28 adults with a mean age of 20.9, randomized to sauna or control [26].
Sources
[25], [26]
Caveats
Two small trials asking different questions, one of sauna after training and one of sauna before it. The authors of [25] put the smallest meaningful change in this swim test at 1.2 s.
Slow breathing and breathworkLimited

Exercise performance with hyperventilation breathwork

Mixed results: a systematic review of Wim Hof Method trials found mixed effects of its breathing on exercise performance and on breathing during exercise.

Compared with control conditions the source abstract does not describe [19]

The numbers and sources
Effect
In a narrative synthesis of 9 papers from 8 trials, the effect of Wim Hof breathing on exercise performance was mixed, as were effects on minute ventilation, tidal volume and breathing frequency after exercise [19].
Population
Healthy people and people with medical conditions aged over 14 in 8 trials [19].
Sources
[19]
Caveats
No pooled estimate. Trials were small.
Testosterone therapyLimitedStudied in men

Muscle strength in middle-aged and older men

Limited evidence: strength gains in middle-aged and older men were small and varied widely across trials.

The numbers and sources
Effect
Strength results were heterogeneous. Leg and knee extension and dominant-hand grip showed a pooled effect size of 0.3 SMD (95% CI 0.0 to 0.6) [2].
Population
Middle-aged and older men in the strength subset of 29 RCTs [2].
Sources
[2]
Caveats
The interval reaches zero, and trials varied widely.
Total testosteroneLimitedStudied in men

Sexual function, vitality and walking in a trial that raised testosterone in older men

One trial found raising low testosterone in men 65 and older improved sexual function moderately, with no benefit for vitality or walking distance.

The numbers and sources
Effect
In 790 men aged 65 or older with testosterone below 275 ng/dL and symptoms, testosterone gel for 1 year raised levels to the mid-normal range for men aged 19 to 40. Sexual activity increased (P below 0.001), as did sexual desire and erectile function. The share of men gaining at least 50 meters in the 6-minute walk did not differ significantly in the Physical Function Trial, and was 20.5% against 12.6% when men from all three trials were pooled. There was no significant benefit for vitality, and mood and depressive symptoms were slightly better [21].
Population
790 men aged 65 or older, mean of two testosterone results below 275 ng/dL, treated for 1 year [21].
Sources
[21]
Caveats
One trial of 1 year. The authors state that it enrolled too few men to draw conclusions about the risks of treatment [21].
Vitamin CLimited

Muscle soreness after exercise

Limited evidence: antioxidant supplements lowered soreness slightly up to 72 hours after exercise, in trials mostly at high risk of bias, not specific to vitamin C.

The numbers and sources
Effect
Across 50 trials of antioxidant supplements, soreness was slightly lower up to 6 hours (SMD -0.30), at 24 hours (SMD -0.13, 95% CI -0.27 to 0.00), 48 hours (SMD -0.24) and 72 hours (SMD -0.19). At 96 hours there was little difference [12].
Population
1,089 participants aged 16 to 55, 88% male, in trials of several kinds of antioxidant supplements and antioxidant-rich foods [12].
Sources
[12]
Caveats
Not specific to vitamin C. 47 of 50 trials carried a high risk of bias, and all used doses above the daily amount set for the general population [12].
Whole-body cryotherapyLimited

Recovery of muscle function

Mixed results: a review counted better performance recovery in most studies, while a marathon trial found worse muscle function after cryotherapy than after cold water immersion.

The numbers and sources
Effect
In a review of 16 studies, measures of athletic capacity and performance improved in 71% of studies using controlled exercise [3]. After a marathon, cryotherapy had a harmful effect on muscle function compared with cold water immersion and was no better than placebo [4]. After resistance exercise, peak force at 48 hours was higher with cryotherapy than with cold water or placebo, and most other outcomes were trivial, unclear or favored placebo [5]. In 14 academy soccer players, peak power, soreness and perceived recovery did not differ from seated rest after one session [6].
Population
Physically active people in 16 studies [3]. 31 male marathon runners [4]. 24 resistance-trained men [5]. 14 professional academy soccer players in a crossover [6].
Sources
[3], [4], [5], [6]
Caveats
Small trials with different temperatures, timings and exercise models. Only the two Wilson trials used a placebo.
Whole-body cryotherapyLimited

Performance when used before exercise

Limited evidence: a systematic review of 12 controlled studies found the effect of cryotherapy before exercise on performance unclear.

The numbers and sources
Effect
Of 12 controlled studies of whole-body or partial-body cryotherapy before exercise, 6 tested performance, 4 oxidative stress and 2 lysosomal enzymes. The reviewers judged the potential for favorable physical responses unclear, with little high-quality research available [24].
Population
Healthy or athletic participants in 12 studies [24].
Sources
[24]
Caveats
No pooled estimate. Protocols were not standardized across studies.

Not shown to help51

Coenzyme Q10Strong

Exercise performance

Not shown to improve VO2 max or exercise performance in athletes or healthy adults, though it raised blood CoQ10.

The numbers and sources
Effect
Across 24 studies, CoQ10 consistently raised blood CoQ10. Performance effects were small and inconsistent. A small chronic benefit was no longer stable after outliers were removed, and acute dosing showed no benefit [11]. In athletes, VO2max did not change (7 studies, SMD 0.03, 95% CI -0.32 to 0.39), nor did anaerobic threshold [12]. Across 14 RCTs (433 participants), VO2max and blood lactate did not change [13]. In 33 trials (3,317 participants) in adults aged 40 and over, VO2peak rose 0.73 mL/kg/min (95% CI -0.07 to 1.54), compatible with no benefit, and estimates for walking distance, grip and leg strength, chair rises and lean mass were uncertain [14].
Population
Healthy adults in randomized trials [11]; athletes and trained people [12]; exercising adults [13]; middle-aged and older adults [14].
Sources
[11], [12], [13], [14]
Caveats
Certainty was very low to low [11][14]. Risk of bias raised some concerns in 23 of 24 athlete studies [12].
Cold water immersionStrong

Strength gains from resistance training

Shown to reduce strength gains when used after resistance training sessions, in two meta-analyses. Whole-body immersion on its own showed no significant difference.

The numbers and sources
Effect
Across 8 controlled studies, regular cold water immersion with resistance training reduced gains in one-repetition maximum, isometric strength and strength endurance (SMD -0.60, 95% CI -0.87 to -0.33) and in ballistic efforts (SMD -0.61, 95% CI -1.11 to -0.11) [7]. Across 10 studies (170 participants, 92% men), it attenuated strength gains (effect size -0.23, 95% CI -0.45 to -0.01). The effect was -0.31 (95% CI -0.61 to -0.01) when only the trained limbs were immersed and -0.08 (95% CI -0.53 to 0.38) with whole-body immersion [8]. In 21 men training for 12 weeks, strength rose more with active recovery than with 10 minutes of cold immersion after each session (P < 0.05) [9]. In 16 men training for 7 weeks, leg press gains were similar with and without 15 minutes at 10°C [10].
Population
Participants in 8 controlled studies of immersion at 15°C or colder [7]. 170 participants in 10 studies [8]. 21 physically active men [9]. 16 men [10].
Sources
[7], [8], [9], [10], [6]
Caveats
The two meta-analyses draw on an overlapping set of small trials, almost all in young men. The whole-body subgroup did not reach significance [8], and one trial found strength unaffected while muscle fiber growth was blunted [10]. An umbrella review reached the same conclusion on strength at low to very low certainty [6].
DHEA sulfate (DHEA-S)Strong

Body composition, physical performance and quality of life in trials that raised DHEA-S

Not shown to change body composition, physical performance, sexual function or quality of life in a meaningful way when DHEA-S was raised with DHEA in older adults.

The numbers and sources
Effect
In a 2-year trial in older adults with low DHEA-S, DHEA raised the level by a median of 3.4 µg/mL in men and 3.8 µg/mL in women, which is 340 and 380 µg/dL. It had no significant effect on body composition, and did not change peak oxygen consumption, muscle strength, insulin sensitivity or quality of life. Bone density rose at the femoral neck in men and at the ultradistal radius in women [8]. Across 25 trials in older men, DHEA reduced fat mass slightly (standardized mean difference -0.35, 95% CI -0.65 to -0.05), an effect that disappeared after adjusting for the rise in testosterone and estradiol, with no effect on blood lipids, blood sugar, bone, sexual function or quality of life [9]. A review of 8 trials called the effect on muscle strength and physical function inconclusive [10]. In postmenopausal women, 23 trials found no significant improvement in libido or sexual function (0.35, -0.02 to 0.73) and no significant effect on lipids, glucose, weight or bone density [11]. A Cochrane review found no improvement in quality of life (0.16, -0.03 to 0.34) and more androgenic side effects, mainly acne (odds ratio 3.77, 1.36 to 10.4) [12].
Population
87 older men and 57 older women with low DHEA-S, treated for 2 years [8]. 1,353 older men in 25 trials, mean follow-up 36 weeks [9]. 661 adults aged 50 or older in 8 trials [10]. 1,188 postmenopausal women in 23 trials [11]. 1,273 women in 28 trials [12].
Sources
[8], [9], [10], [11], [12]
Caveats
A marker that tracks an outcome is not always one whose correction changes it. Low DHEA-S went with more deaths in cohorts. The trials measured body composition, function and quality of life, not deaths. The reviewers of the trials in women rated confidence in the evidence as low [11].
HMBStrong

Strength and fat-free mass in trained athletes and young lifters

Not shown to change strength, fat-free mass or fat mass in trained athletes or young adults in resistance training.

The numbers and sources
Effect
In 6 RCTs of trained and competitive athletes (193 participants), effect sizes were trivial and not significant for bench press (0.00), leg press (0.09), fat-free mass (0.16) and fat mass (-0.20) [1]. In 11 studies of adults aged 18 to 45 in resistance training, HMB raised total body mass slightly but did not change fat-free mass, fat mass or strength [2]. In 5 studies of athletes, fat-free mass trended up (0.30, 95% CI -0.07 to 0.68, p = 0.08), apparently only when protein intake was under 1.6 g per kg a day [3].
Population
Trained and competitive athletes [1][3]; young adults in training [2].
Sources
[1], [2], [3]
Caveats
Small pooled samples. The ISSN position stand [4] reports body composition improvements across ages and training levels, but several of its authors disclose employment, consulting or patents tied to HMB.
Menopausal hormone therapyStrongStudied in women

Muscle strength

Not shown to increase muscle strength in postmenopausal women, though very high variation leaves a small effect possible.

The numbers and sources
Effect
Hormone therapy was not associated with strength gain (SMD 0.352, 95% CI -0.098 to 0.803, I² 95.3%). Results were unchanged by treatment type, muscle group and duration [10]. A 2025 systematic review found 2 of 6 RCTs suggesting better grip strength and 1 of 6 better physical performance, with no consistent evidence of benefit [9].
Population
9 RCTs with 2,476 postmenopausal women [10]; 15 RCTs and 28 observational studies [9].
Sources
[10], [9]
Caveats
Heterogeneity was very high, so a small effect cannot be ruled out. The systematic review rated risk of bias high to severe [9].
Protein powderStrong

Plant protein compared with animal protein

Not shown to differ in strength by protein source. Soy matched milk protein for muscle, while non-soy plant proteins trailed animal protein in 5 trials.

The numbers and sources
Effect
In 16 RCTs, protein source did not change absolute lean mass or strength; adults under 50 gained 0.41 kg more lean mass (95% CI 0.08 to 0.74) on animal protein [5]. In 30 RCTs, plant protein produced lower muscle mass than animal protein (SMD -0.20, 95% CI -0.37 to -0.03). Soy and milk protein did not differ (SMD -0.02, 17 RCTs). Non-soy plant proteins such as rice, oat and potato trailed animal protein (SMD -0.58, 5 RCTs). Strength (14 RCTs) and physical performance (5 RCTs) did not differ [6].
Population
Adults of all ages, most with protein intakes above the RDA [5][6].
Sources
[5], [6]
Caveats
Few trials tested pea, rice or other non-soy powders, so the non-soy estimate rests on 5 trials [6].
AlbuterolModerate

Endurance performance in people without asthma

Not shown to improve aerobic performance, time trials, time to exhaustion or VO2 max in people without asthma, whatever the beta-agonist, dose or route.

Compared with placebo [10]

The numbers and sources
Effect
Beta-agonists did not change aerobic performance against placebo (SDM 0.051, 95% CI -0.020 to 0.122), with no heterogeneity (I² 0%). The result did not depend on drug type, dose, route, treatment length or athletic level [10].
Population
47 randomized trials with about 680 participants without asthma [10].
Sources
[10]
Caveats
The analysis pooled several beta-agonists, not albuterol alone [10].
Beta-alanineModerate

Body composition and muscle gain

Not shown to change body mass, fat mass or fat-free mass in adults in training, across 20 trials.

The numbers and sources
Effect
Across 20 RCTs (492 participants), beta-alanine did not change body mass (-0.15 kg, 95% CI -0.78 to 0.47), fat mass (-0.24 kg, 95% CI -1.16 to 0.68), body fat percentage (-0.06%) or fat-free mass (0.05 kg, 95% CI -0.71 to 0.82). Results were the same across training type, duration and dose [7].
Population
Adults in resistance, endurance or combined training [7].
Sources
[7]
Caveats
Certainty ranged from low to moderate. The authors report no funding [7].
Beta-alanineModerate

Repeated sprints

Not shown to change repeated sprint performance or fatigue across 17 trials, at any dose or duration tested.

The numbers and sources
Effect
Across 17 RCTs, beta-alanine taken for 2 weeks or more did not change mean repeated sprint performance (SMD -0.018, 95% CI -0.207 to 0.170), peak repeated sprint performance (0.205, 95% CI -0.073 to 0.483) or fatigue decrement (-0.020, 95% CI -0.516 to 0.476). Total dose, duration, exercise type and training status did not moderate the result [8].
Population
Healthy people in 17 placebo-controlled trials [8].
Sources
[8]
Caveats
One meta-analysis. The abstract does not report the pooled number of participants [8].
ChromiumModerateStudied in men

Strength and muscle with resistance training

Not shown to add to strength or muscle gains from resistance training in men, in two small trials.

The numbers and sources
Effect
Over 8 weeks, strength, fat-free mass and muscle mass rose with training, and chromium chloride or picolinate did not add to the gains [10]. Over 12 weeks in older men, 924 µg a day did not add to strength, muscle size or lean mass. The placebo group gained more knee-extension power [11].
Population
36 men [10]; 18 men aged 56 to 69 [11].
Sources
[10], [11]
Caveats
Both trials were small.
CitrullineModerate

Aerobic endurance

Not shown to change aerobic performance, perceived effort or lactate in healthy adults across 10 trials.

The numbers and sources
Effect
Across 10 placebo-controlled studies, citrulline did not change aerobic performance (SMD 0.15, 95% CI -0.02 to 0.32), perceived exertion (-0.03), oxygen uptake kinetics (0.01) or lactate (0.25, 95% CI -0.10 to 0.59) [6].
Population
Healthy adults in aerobic tests [6].
Sources
[6]
Caveats
The authors note chronic protocols showed a positive tendency that has not been tested in enough trials [6].
Cold water immersionModerate

Muscle growth from resistance training

Not shown to help muscle growth. Used after resistance training, it was associated with smaller gains in pooled trials, a difference whose interval narrowly included zero.

The numbers and sources
Effect
A meta-analysis of 8 randomized studies found smaller hypertrophy with cold water immersion plus resistance training than with training alone (comparative SMD -0.22, 95% credible interval -0.47 to 0.04), with a 95.7% probability that the difference was below zero [11]. In 21 men over 12 weeks, muscle mass increased more with active recovery, and type II fiber cross-sectional area rose 17% with active recovery and did not rise with cold immersion [9]. In 16 men over 7 weeks, the increase in type II fiber area was smaller with cold immersion (effect size -1.37) [10].
Population
Healthy adults in 8 randomized studies of at least 4 weeks [11]. 21 physically active men [9]. 16 men training 3 days a week [10].
Sources
[11], [9], [10], [6]
Caveats
The authors of the meta-analysis rated the evidence fair to poor in quality [11]. Trials were short and mostly in young men. An umbrella review also concluded that hypertrophic gains were impaired [6].
39 more
Cold water immersionModerate

Endurance training adaptations

Not shown to change gains from endurance training, for better or worse, in one meta-analysis and a later 5-week trial.

The numbers and sources
Effect
Regular cold water immersion with endurance training had no effect on time-trial mean power or maximal aerobic power (SMD -0.07, 95% CI -0.54 to 0.53) or on time-trial duration (SMD 0.00, 95% CI -0.58 to 0.58) [7]. In 16 men doing interval training 3 times a week for 5 weeks, 15 minutes at 11.2°C after each session did not change VO2 max, running time to failure, or muscle markers of adaptation and inflammation relative to training alone [12].
Population
Participants in controlled endurance training studies [7]. 16 healthy men, 9 using cold immersion and 7 controls [12].
Sources
[7], [12], [6]
Caveats
Few small trials with wide intervals. An umbrella review found endurance performance improved immediately after immersion with no later benefit and no effect on adaptations [6].
CuppingModerate

Chronic pain, compared with sham cupping

Not shown to ease chronic pain more than sham cupping, in two meta-analyses and three later trials of back pain, knee osteoarthritis and fibromyalgia.

Compared with sham cupping [2][3][4][5][6]

The numbers and sources
Effect
Against sham cupping, pain did not differ significantly (SMD -0.27, 95% CI -0.58 to 0.05) and neither did disability (SMD -0.26) [2]. In 5 trials of dry against placebo cupping, the short-term pain difference was -9.9 points on a 100-point scale (95% CI -30.5 to 10.7), very uncertain at every time point [3]. In 90 people with chronic low back pain, pain differed by 0.0 to 0.6 points on a 0 to 10 scale over 8 weeks [4]. In 62 women with knee osteoarthritis, no outcome differed from sham at any time point [5]. In 141 people with fibromyalgia, pain at day 18 differed from sham by -3.0 points (95% CI -9.9 to 3.9) [6].
Population
1,172 people with chronic pain in 18 trials [2]. 281 adults with musculoskeletal complaints in 5 trials [3]. 90 adults [4]. 62 women aged 50 to 75 [5]. 141 patients, 139 of them women [6].
Sources
[2], [3], [4], [5], [6]
Caveats
Few sham-controlled trials exist and most are small. The second meta-analysis rated certainty very low and four of its trials at high risk of bias [3].
D-aspartic acidModerateStudied in men

Strength and muscle with training

Not shown to add to strength or muscle gains from resistance training in trained men over 28 days to 12 weeks.

The numbers and sources
Effect
Over 28 days of heavy resistance training, body composition and strength rose in both groups and did not differ between 3 g of D-aspartic acid and placebo [2]. Over 12 weeks of supervised training, isometric strength rose 17% and quadriceps and calf muscle size increased similarly in both groups on 6 g a day or placebo [4].
Population
Resistance-trained men [2][4].
Sources
[2], [4]
Caveats
Small samples, 22 randomized in [4].
DHEAModerate

Strength and physical function in older adults

Not shown to change strength or physical function in most studies of adults aged 50 and older, including a 2-year trial.

The numbers and sources
Effect
A systematic review of 8 studies found single improvements in grip, chest press, leg press and knee strength, with similar numbers of studies showing no effect on each. Four of five studies of physical function found no difference from control [4]. Over 2 years, DHEA did not change muscle strength or peak oxygen uptake [3].
Population
661 adults aged 50 and older in 8 studies [4]; 144 elderly men and women [3].
Sources
[3], [4]
Caveats
The review was not pooled, and its trials differed in population and exercise.
Estimated GFR (eGFR)Moderate

Creatine supplements

Shown to raise serum creatinine about 0.13 mg/dL in pooled trials. Creatinine-based GFR estimates fell in one analysis while GFR measured with a tracer did not.

The numbers and sources
Compared with
GFR measured with Cr-EDTA, a tracer method that does not rely on creatinine
Effect
In 26 randomized trials, creatine supplementation raised serum creatinine by 0.14 mg/dL (95% CI 0.05 to 0.22) and lowered GFR assessed by creatinine-based methods by 10.75 mL/min (95% CI -17.48 to -4.02). GFR assessed by Cr-EDTA did not differ significantly (5.89 mL/min, 95% CI -0.30 to 12.08), nor did serum urea, albuminuria or proteinuria [14]. A second meta-analysis of 20 randomized studies found serum creatinine 0.13 mg/dL higher (95% CI 0.07 to 0.18) and no significant difference in eGFR (-5.20 mL/min/1.73 m2, 95% CI -15.00 to 4.60) [15].
Population
1,036 participants in 26 trials, healthy people and people with chronic kidney disease [14]. 19 randomized trials and one randomized crossover study [15].
Sources
[14], [15]
Caveats
The authors of the first analysis attribute the changes to altered creatinine metabolism, not kidney injury, because the tracer measurement did not change [14]. The two analyses disagree on whether the fall in estimated GFR is statistically significant. The authors of the second call for trials longer than 1 year [15].
GlutamineModerate

Athletic performance and body composition

Not shown to change lean mass, body fat or VO2max in athletes. Body weight fell about 1.4 kg.

The numbers and sources
Effect
Across 25 trials in athletes over 18, glutamine did not change lean body mass, body fat percentage or VO2max. Body weight fell by 1.36 kg (95% CI -2.55 to -0.16) [1].
Population
Athletes, 47 studies reviewed and 25 pooled [1].
Sources
[1]
Caveats
One meta-analysis. The weight change is not explained by a lean mass or fat change in the same analysis [1].
Growth hormoneModerate

Strength and performance in healthy young athletes

Not shown to improve strength or exercise capacity in healthy young athletes, though lean body mass rose about 2 kg, mostly water. Sprint capacity rose slightly.

The numbers and sources
Effect
Lean body mass rose 2.1 kg (95% CI 1.3 to 2.9) against no growth hormone, but strength and exercise capacity did not appear to improve. Lactate during exercise was higher in 2 of 3 studies that measured it [2]. In recreational athletes given growth hormone for 8 weeks, sprint capacity rose 0.71 kJ (3.9%, 95% CI 0.0 to 7.7%), and 8.3% in men given testosterone as well. Endurance, strength and jump height did not change. The lean mass gain came from extracellular water, and the sprint gain was gone 6 weeks after stopping [3].
Population
27 study samples with 303 treated participants aged 13 to 45, mean 27, mean treatment 20 days [2]; 96 recreational athletes, 63 men and 33 women [3].
Sources
[2], [3]
Caveats
Few studies measured performance, and trial doses may differ from covert use [2][3]. [3] was funded by the World Anti-Doping Agency.
HomeopathyModerate

Bruising, swelling and pain after surgery or injury, arnica

Not shown to differ from placebo in a 1998 review of 8 trials. A 2021 meta-analysis found a small edge over placebo that fell short of statistical significance.

Compared with placebo [17][18]; active comparators and no treatment [18]

The numbers and sources
Effect
Eight placebo-controlled trials, most in tissue trauma and most with severe methodological flaws, did not suggest homeopathic arnica worked better than placebo [17]. In 18 placebo-controlled comparisons after surgery, the pooled effect was Hedges' g 0.18 (95% CI -0.007 to 0.373, P = 0.059). Active-comparator trials gave g 0.26 with high heterogeneity, an effect driven by nonrandomized studies that moved toward zero in randomized trials [18].
Population
8 trials [17]. 23 publications with 28 comparisons in surgical patients [18].
Sources
[17], [18]
Caveats
The 2021 authors read their result as a small effect, though the placebo-controlled interval included zero [18].
Hyperbaric oxygen therapyModerate

Exercise performance and recovery

Not shown to improve exercise performance or recovery when given before or after exercise. A Cochrane review found more muscle soreness at 48 hours with immediate treatment.

The numbers and sources
Effect
In a meta-analysis of physically active adults, hyperbaric oxygen before exercise had no significant effect on performance and after exercise had no significant effect on recovery (10 studies reviewed, 6 pooled with 69 participants) [22]. A Cochrane review of 9 trials (219 participants) found higher pain at 48 hours in people given hyperbaric oxygen straight after muscle-damaging exercise (mean difference 0.88 on a 0 to 10 scale, 95% CI 0.09 to 1.67), with no difference in swelling or strength. Two trials in ankle sprain and knee ligament injury found no difference from sham [23].
Population
166 physically active adults in 10 studies [22]. 219 participants in 9 small trials [23].
Sources
[22], [23]
Caveats
Small trials. Individual studies of oxygen breathed during exercise reported better muscle endurance, which could not be pooled [22].
MagnesiumModerate

Muscle cramps

Not shown to reduce idiopathic leg cramps in older adults. Pregnancy cramp trials conflicted, and none tested exercise cramps.

The numbers and sources
Effect
For idiopathic cramps, mostly nocturnal leg cramps in adults aged about 62 to 69, magnesium did not change the percentage change in cramps per week at 4 weeks (MD -9.59%, 95% CI -23.14% to 3.97%) or the number of cramps per week (MD -0.18, 95% CI -0.84 to 0.49). The share with a 25% or better reduction did not differ (RR 1.04, 95% CI 0.84 to 1.29, high certainty) [10].
Population
11 trials, 735 people, including pregnancy-associated and idiopathic cramps [10].
Sources
[10]
Caveats
Pregnancy cramp trials were conflicting and could not be pooled. No RCT tested exercise-associated cramps [10].
Menopausal hormone therapyModerateStudied in women

Muscle mass

Not shown to preserve lean mass in postmenopausal women, with no consistent benefit across trials.

The numbers and sources
Effect
Women on hormone therapy lost 0.06 kg less lean body mass than controls (95% CI -0.05 to 0.18), not a significant difference. Results were unchanged by treatment type, dose, duration or time since menopause [8]. A 2025 systematic review counted 7 of 12 RCTs suggesting more muscle on scans with hormone therapy, and found no consistent evidence of benefit overall [9].
Population
12 RCTs with 4,474 women, mean age 59, median follow-up 2 years [8]; 15 RCTs and 28 observational studies of community-dwelling women [9].
Sources
[8], [9]
Caveats
GRADE quality of evidence was low [8]. The systematic review rated risk of bias high to severe, and most data were over 20 years old [9].
Muscle relaxantsModerate

Added to an NSAID for acute low back pain

Not shown to improve function or pain at 1 week when added to naproxen or ibuprofen for acute low back pain in two emergency department trials.

The numbers and sources
Effect
In people sent home from an emergency department with naproxen, function at 1 week improved 10.1 points on a 24-point scale with cyclobenzaprine added and 9.8 points with placebo added (difference 0.3, 98.3% CI -2.6 to 3.2) [5]. In people sent home with ibuprofen, function improved 11.1 points with placebo added, 10.6 with baclofen, 10.1 with metaxalone and 11.2 with tizanidine. Moderate to severe pain at 1 week was reported by 30% on placebo, 33% on baclofen and 33% on tizanidine [6].
Population
323 adults with acute low back pain of 2 weeks or less, 108 assigned cyclobenzaprine 5 mg [5]; 320 adults with acute low back pain of 2 weeks or less in 4 groups [6].
Sources
[5], [6]
Caveats
Both trials came from emergency departments in one city and followed people for 1 week as the main outcome.
N-acetylcysteineModerate

Exercise performance

Not shown to change exercise performance in athletes and active adults, with a mean change of 0.29%.

The numbers and sources
Effect
Across 7 studies, mean performance changed by 0.29% (95% CI -0.67 to 1.25) [2].
Population
Athletes and active adults, typical dose 5.8 g a day, range 1.2 to 20 g [2].
Sources
[2]
Caveats
The authors note suboptimal reporting across trials [2].
Nicotinamide ribosideModerate

Muscle and physical function

Not shown to preserve muscle mass or function in adults over 60. One trial found a longer six-minute walk in peripheral artery disease.

The numbers and sources
Effect
A meta-analysis of randomized trials in adults over 60 found no support for NR or NMN preserving muscle mass or function. NR was linked to a longer six-minute walk in peripheral artery disease, and to lower SPPB scores and slower chair stands in mild cognitive impairment [5]. In the peripheral artery disease trial, six-minute walk changed by +7.0 m on NR and -10.6 m on placebo, a difference of +17.6 m (90% CI +1.8 to +∞) at 6 months [6].
Population
Randomized trials in adults with mean ages of 60.9 to 83 [5]; 90 people with peripheral artery disease for 6 months [6].
Sources
[5], [6]
Caveats
The walking result is one trial with a one-sided interval. ChromaDex supplied the NR and placebo for it [6].
ReflexologyModerate

Pain, compared with sham reflexology or plain foot massage

Not shown to ease pain more than sham reflexology or plain foot massage in three trials, in multiple sclerosis, Parkinson's disease and advanced breast cancer.

Compared with sham reflexology [4]; sham massage [5]; lay foot manipulation, and conventional care [6]

The numbers and sources
Effect
In 73 people with multiple sclerosis, pain fell by a median of 50% in both the reflexology and sham reflexology groups over 10 weeks, and reflexology was not superior to sham [4]. In 30 people with Parkinson's disease and chronic pain, pain fell 12.3 mm on a 100-mm scale with reflexology and 17.9 mm with sham massage, with no difference between groups (P = 0.88) [5]. In 385 women with advanced breast cancer, pain did not differ between reflexology, lay foot manipulation and conventional care [6].
Population
73 people with multiple sclerosis [4]. 30 adults with Parkinson's disease in France [5]. 385 women with advanced breast cancer at 13 US oncology clinics [6].
Sources
[4], [5], [6]
Caveats
Pain improved substantially in both arms of the sham-controlled trials, so touch and attention may account for much of the effect [4][5].
Serum creatinineModerate

Creatine supplements

Shown to raise serum creatinine about 0.13 mg/dL in pooled trials, with no significant change in kidney filtering measured by a tracer.

The numbers and sources
Compared with
Kidney filtering measured with Cr-EDTA, a tracer method that does not rely on creatinine
Effect
In 26 randomized trials, creatine supplementation raised serum creatinine by 0.14 mg/dL (95% CI 0.05 to 0.22). Filtering measured by Cr-EDTA did not differ significantly (5.89 mL/min, 95% CI -0.30 to 12.08), nor did serum urea, albuminuria or proteinuria [12]. A second meta-analysis of 20 randomized studies found serum creatinine 0.13 mg/dL higher (95% CI 0.07 to 0.18), with no difference in urea [13].
Population
1,036 participants in 26 trials, healthy people and people with chronic kidney disease [12]. 19 randomized trials and one randomized crossover study [13].
Sources
[12], [13]
Caveats
The authors of the first analysis attribute the rise to altered creatinine metabolism, not kidney injury, because the tracer measurement did not change. Results across its trials varied widely. The authors of the second call for trials longer than 1 year [12][13].
TribulusModerateStudied in men

Strength and sport performance

Not shown to improve strength, body composition or sport performance in active men. One small trial found a larger bench press gain.

The numbers and sources
Effect
In 30 CrossFit-trained men over 6 weeks, body composition and four of five workout tests did not differ from placebo. Bench press rose 19.2% with tribulus against 8.5% with placebo [5]. A systematic review of 7 studies in physically active men found no clear benefit on muscle damage markers or hormones, some lipid improvements and no reported toxicity [4]. A review of athlete use found that tribulus alone did not improve androgen status or physical performance [9].
Population
Physically active men [4][5][9].
Sources
[4], [5], [9]
Caveats
Few and small trials.
YogaModerate

Chronic low back pain, against other exercise

Not shown to improve back function or pain more than other back exercise, stretching classes or physical therapy. It was noninferior to physical therapy in one trial.

Compared with back-focused exercise such as physical therapy [1]; conventional stretching classes [2]; 15 physical therapy visits [3]

The numbers and sources
Effect
Against back-focused exercise at 3 months, back function differed by 0.38 points (95% CI -1.33 to 0.62, 4 trials, moderate certainty) and pain by 2.68 points on a 0 to 100 scale (95% CI -2.01 to 7.36, very low certainty) [1]. Yoga was not superior to conventional stretching exercises at any time point [2]. Yoga met the noninferiority margins against physical therapy for function and pain at 12 weeks, and both were maintained at 1 year [3].
Population
912 participants in 8 trials [1]. 183 adults in the yoga and stretching arms [2]. 320 adults [3].
Sources
[1], [2], [3]
Caveats
Participants were not blinded, and the physical therapy group had more loss to follow-up [3].
Alanine aminotransferase (ALT)Limited

Heavy exercise and muscle injury

Small studies found ALT rose for at least 7 days after one weightlifting session, and rose in muscle injury with no liver disease.

The numbers and sources
Compared with
The same men's results before exercise, and the laboratory's upper reference limit
Effect
After a single 1-hour weightlifting session in healthy men unused to lifting, ALT rose significantly and was still raised 7 days later. The highest value was 4.1 µkat/L against an upper reference limit of 0.7 µkat/L, and the median time to peak was 120 hours. At the follow-up visit 10 to 12 days after exercise, mean ALT was higher than mean AST [20]. In 16 patients with muscle necrosis from extreme exercise, polymyositis or seizures and no evidence of liver disease, ALT and AST were both elevated alongside markedly raised creatine kinase [21].
Population
15 healthy men, mean age 24.5, 14 analyzed [20]. 16 patients with muscle injury [21].
Sources
[20], [21]
Caveats
Both studies are small. The exercise study used men not accustomed to weightlifting, and people who train regularly may respond differently [20]. The muscle injury study also reports the ratio of AST to ALT, a separate quantity not placed on this page [21].
Aspartate aminotransferase (AST)LimitedStudied in men

Heavy exercise

One small study found AST rose above the laboratory's upper limit in every man 3 to 5 days after one weightlifting session.

The numbers and sources
Compared with
The same men's results before exercise, and the laboratory's upper reference limit
Effect
Healthy men used to moderate activity, not including weightlifting, did a single 1-hour weightlifting session. Six had AST above the upper reference limit the next day, and all 14 did on days 3, 4 and 5. The highest value was 16.0 µkat/L against an upper reference limit of 0.7 µkat/L. AST was still significantly higher than before exercise on day 7. Creatine kinase and myoglobin, which come from muscle, rose steeply over the same days, while bilirubin, GGT and alkaline phosphatase were almost unaltered [10].
Population
15 healthy men, mean age 24.5, 14 analyzed [10].
Sources
[10]
Caveats
One small study in men not accustomed to weightlifting. People who train regularly may respond differently, and the study did not test them [10]. The study also reports the ratio of AST to ALT, a separate quantity not placed on this page.
Aspartate aminotransferase (AST)Limited

Muscle injury and disease

Case series: 16 patients with muscle injury and no liver disease had raised AST, falling faster than ALT over the following days.

The numbers and sources
Compared with
Creatine kinase, lactate dehydrogenase and clinical review showing muscle, not liver, as the source
Effect
In a review of 16 patients with muscle necrosis from extreme exercise, polymyositis or seizures and no evidence of liver disease, AST and ALT were both elevated alongside markedly raised creatine kinase and lactate dehydrogenase. In acute cases AST was more than 3 times ALT. The two came closer within a few days because AST declined faster, and they were comparable in chronic muscle injury [11].
Population
16 patients with muscle injury, in three groups: extreme exercise, polymyositis and seizures [11].
Sources
[11]
Caveats
A retrospective review of 16 records. The abstract gives no AST values [11].
BCAAs and EAAsLimited

Lean mass during dieting

One trial found BCAAs did not significantly reduce lean mass loss over 16 weeks of dieting in 132 adults, and a high-protein diet lost the least.

The numbers and sources
Effect
In 132 adults with overweight or obesity on a 500 kcal daily deficit for 16 weeks, lean mass fell 4.39% with BCAAs (0.1 g per kg a day), 5.39% with placebo and 3.67% with a high-protein diet (p = 0.06). Insulin sensitivity did not differ among groups [6].
Population
132 Chinese adults aged 21 to 45 [6].
Sources
[6]
Caveats
One RCT. The high-protein diet group lost the least lean mass [6].
BenzodiazepinesLimited

Acute low back pain

One trial found diazepam added to naproxen did not improve acute low back pain or function more than placebo at one week or three months.

The numbers and sources
Effect
Disability scores improved by 11 points in both the diazepam and placebo groups at one week. Moderate or severe pain at one week was reported by 32% on diazepam and 22% on placebo, and at three months by 12% and 9%. Adverse events were reported by 21% on diazepam and 15% on placebo [17].
Population
114 emergency department patients with acute low back pain, all given naproxen [17].
Sources
[17], [8]
Caveats
One trial of 114 people. The diazepam label lists muscle spasm as an add-on use [8].
CholineLimited

Endurance and strength performance

One small trial found choline citrate did not change run time to exhaustion or squat performance in 14 soldiers.

The numbers and sources
Effect
Choline citrate before and during 4 hours of loaded treadmill marching raised plasma choline 128% and did not change run time to exhaustion, squat performance or perceived exertion [10].
Population
14 soldiers in a crossover trial [10].
Sources
[10]
Caveats
One small trial. Trials of alpha-GPC and citicoline, including memory and power output, are on the alpha-GPC page.
CitrullineLimited

Maximal strength

Limited evidence: 4 studies found no effect of citrulline malate on maximal muscle strength in resistance-trained adults.

The numbers and sources
Effect
In 4 studies (69 citrulline malate and 69 placebo assessments), there was no overall effect on muscle strength (SMD 0.13, 95% CI -0.21 to 0.46), for lower (0.06) or upper (0.17) limbs [3].
Population
Resistance-trained adults [3].
Sources
[3]
Caveats
Four studies. This and the repetition analysis [2] measure different things: maximal force versus reps to failure.
Estimated GFR (eGFR)Limited

Muscle mass

One study of 170 healthy adults found serum creatinine rose with lean mass while cystatin C, another filtration marker, did not.

The numbers and sources
Compared with
Serum cystatin C measured in the same people
Effect
In 170 healthy adults, serum creatinine correlated with body weight and more strongly with lean mass, and cystatin C correlated with neither. People with moderate or intense physical activity had more lean mass (55.3% against 48.5%) and higher serum creatinine (1.04 against 0.95 mg/dL) than sedentary people, with no difference in cystatin C. Lean mass stayed related to creatinine after adjustment for protein and meat intake and physical activity [11]. KDIGO lists body builders, extreme sport, eating disorders, above-knee amputation and spinal cord injury as settings where creatinine-based eGFR loses accuracy and a cystatin C-based estimate may be appropriate [3]. Laboratories print serum creatinine intervals by sex: 0.67 to 1.17 mg/dL for men and 0.51 to 0.95 for women in a US national survey laboratory manual, and 0.70 to 1.30 and 0.50 to 1.10 in an internal medicine board table [12][13].
Population
92 women and 78 men, healthy, grouped as sedentary, mildly active or moderately to intensely active [11].
Sources
[11], [3], [12], [13]
Caveats
The study did not measure GFR directly, so it shows that creatinine tracks muscle, not by how much any one eGFR is off [11]. Serum creatinine in mg/dL is a different quantity from eGFR, so its intervals are described here and not placed as ranges on this page.
Hyperbaric oxygen therapyLimitedStudied in children

Cerebral palsy in children

One trial of 111 children found no difference in motor function between 40 hyperbaric oxygen sessions and slightly pressurized room air.

The numbers and sources
Effect
Gross motor function scores rose 2.9% with hyperbaric oxygen at 1.75 ATA and 3.0% with air at 1.3 ATA (mean difference -0.40, 95% CI -1.69 to 0.90). Speech, attention, memory and functional skills improved in both groups without a difference between them. Ear problems occurred in 27 children on hyperbaric oxygen and 15 on pressurized air (p = 0.004) [26].
Population
111 children aged 3 to 12 with cerebral palsy, 57 on hyperbaric oxygen and 54 on pressurized air [26].
Sources
[26]
Caveats
One trial. Both groups improved, and the comparison was pressurized air, not no treatment.
Infrared saunaLimitedStudied in women

Muscle growth and power

One trial found no added muscle growth from a 10-minute infrared sauna after training for 6 weeks in 40 female athletes. Loaded jump height improved.

The numbers and sources
Effect
Six weeks of strength and power training improved performance and muscle size in both groups. Hypertrophy measures by DXA and ultrasound showed no group by time interaction. Countermovement jump with 15% added load improved in the sauna group (interaction p = 0.002 for height and p = 0.010 for peak power) [23].
Population
40 female team sport athletes, pair-matched to sauna (10 minutes at 50°C, 3 times a week) or control [23].
Sources
[23]
Caveats
Pair-matched, not described as randomized. One of several jump tests showed the effect.
IV vitamin therapyLimited

Fibromyalgia, Myers' cocktail

One small trial found weekly Myers' cocktail drips did not differ from a saline-type drip on any fibromyalgia measure at 8 or 16 weeks.

Compared with weekly infusions of lactated Ringer's solution [4]

The numbers and sources
Effect
No outcome differed between groups at 8 or 16 weeks: tender points, global pain, physical function, depression or quality of life. Both groups improved from baseline. The Myers' cocktail group improved in tender points, pain, depression and quality of life, and the placebo group in tender points only. One minor adverse event occurred in the treatment group [4].
Population
34 adults with fibromyalgia in Connecticut, treated weekly for 8 weeks [4].
Sources
[4]
Caveats
A pilot study. The authors note a high placebo response and a sample too small to show a difference [4].
MagnesiumLimited

Muscle strength and performance

Limited evidence: no significant change in strength or power across trials. One small trial in exercisers found lower VO2max and sprint power on magnesium.

The numbers and sources
Effect
Across 14 RCTs, magnesium did not significantly change isokinetic peak torque (WMD 0.87, 95% CI -1.43 to 3.18), muscle strength (WMD 0.87, 95% CI -0.12 to 1.86) or muscle power (WMD 3.28, 95% CI -14.94 to 21.50). Benefits appeared more pronounced in older adults and people with alcoholism than in athletes [11].
Population
215 athletes or active people, 95 untrained adults, and 232 older adults or people with alcoholism [11].
Sources
[11], [12]
Caveats
Fixed-effects pooling across mixed populations and outcomes. In a 2025 crossover RCT of 15 regular exercisers, 600 mg a day of magnesium chloride for 9 days lowered VO2max (44.4 vs 41.3 mL/kg/min, p = 0.005) and 30 second sprint power (439 vs 415 W, p = 0.03) against placebo, with no change in a 10 km time trial [12].
MagnesiumLimited

Recovery and muscle soreness

One trial found a topical magnesium gel did not differ from a placebo gel on soreness or strength after downhill running.

The numbers and sources
Effect
A topical magnesium gel applied to both thighs before and after 40 minutes of downhill running did not differ from a placebo gel on muscle soreness, knee extensor strength, creatine kinase or interleukin-6 at 24 or 48 hours [13].
Population
35 healthy active adults, double-blind parallel RCT [13].
Sources
[13]
Caveats
One small trial of one commercial gel. No trial of oral magnesium on recovery was located in this search.
MK-677Grey marketLimited

Strength and physical function

Limited evidence: added fat-free mass did not change strength in older adults, and after hip fracture only gait speed improved over placebo.

The numbers and sources
Effect
In healthy older adults, the gain in fat-free mass did not change strength or function [1]. After hip fracture, stair climbing power rose 12.5 W more than placebo (95% CI -10.95 to 35.88, not significant), and gait speed improved by a 0.7-point score difference (95% CI 0.17 to 1.28). Several other functional measures did not improve [3].
Population
65 older adults [1]; 123 older adults recovering from hip fracture, 24 weeks [3].
Sources
[1], [3]
Caveats
The older-adult trial was not powered for function [1]. The hip fracture trial was stopped early [3].
MSMLimited

Muscle damage and soreness after endurance exercise

One trial found no change in muscle damage markers or pain against placebo around a half-marathon.

The numbers and sources
Effect
Taking 3 g a day for 21 days before a half-marathon and 2 days after did not change oxidative stress, creatine kinase, LDH, or muscle and joint pain against placebo. The MSM group had pain reductions of more than 10 mm that the authors call clinically significant [5].
Population
22 healthy adults, 17 women, mean age 34 [5].
Sources
[5]
Caveats
One small trial. No time-by-treatment result reached significance [5].
PotassiumLimited

Muscle cramps

Limited evidence: no trial of potassium for cramps was located, and cohort studies found athletes who cramped had higher, not lower, blood potassium after races.

Compared with athletes who did not cramp [18][19]

The numbers and sources
Effect
A 2026 meta-analysis of 9 longitudinal studies (11,274 participants) found higher post-race serum potassium in people with exercise-associated cramps (moderate evidence). Apart from a history of cramps, no hydration, electrolyte or other factor was consistently linked to cramping [18]. An earlier review found that support for the electrolyte depletion explanation of exercise cramps came mainly from anecdotes, case series totaling 18 cases and one case-control study of 10, while four prospective cohort studies did not support it [19].
Population
11,274 participants in 9 longitudinal studies of athletes [18]. Studies of exercise-associated cramps [19].
Sources
[18], [19]
Caveats
Observational studies of blood levels, not trials of taking potassium. The authors of [18] rated most findings as limited or very limited evidence. Cramps in other settings, such as at night or during dialysis, were not covered.
RapamycinLimited

Physical function with exercise in older adults

Small trials found no gain in physical function with exercise, and one found smaller chair-stand gains on sirolimus than placebo in some analyses.

The numbers and sources
Effect
Over 13 weeks of home exercise, chair-stand repetitions rose in both groups. The difference was -2.13 repetitions (95% CI -4.61 to 0.34) for sirolimus 6 mg weekly against placebo. Complete-case (-2.46) and per-protocol (-3.44) analyses favored placebo significantly. Six-minute walk and grip strength also favored placebo, not significantly [3]. Handgrip and timed walk did not change on rapamycin 1 mg daily in the pilot [2].
Population
40 sedentary adults aged 65 to 85, mean 72.2 [3]; 25 adults aged 70 to 95 [2].
Sources
[3], [2]
Caveats
Small exploratory trials. [3] was funded by Dr Brad Stanfield Ltd.
Serum creatinineLimited

Muscle mass

One study of 170 healthy adults found serum creatinine rose with lean mass while cystatin C, another filtration marker, did not.

The numbers and sources
Compared with
Serum cystatin C measured in the same people
Effect
Serum creatinine correlated with body weight and more strongly with lean mass, and cystatin C correlated with neither. People with moderate or intense physical activity had more lean mass (55.3% against 48.5%) and higher serum creatinine (1.04 against 0.95 mg/dL) than sedentary people, with no difference in cystatin C. Lean mass stayed related to creatinine after adjustment for protein and meat intake and physical activity [10]. A kidney guideline lists body builders, extreme sport, eating disorders, above-knee amputation and spinal cord injury as settings where muscle mass alters creatinine apart from kidney function. It also lists anabolic steroids, medications that decrease secretion of creatinine by the kidney tubules, and low-protein, vegetarian, ketogenic and high-protein diets [11].
Population
92 women and 78 men, healthy, grouped as sedentary, mildly active or moderately to intensely active [10].
Sources
[10], [11]
Caveats
The study did not measure kidney filtering directly, so it shows that creatinine tracks muscle, not by how much any one result is shifted [10]. The reference ranges on this page are printed by sex and not by muscle mass [2][3].
Turkesterone and ecdysteroneLimitedStudied in men

Muscle growth with turkesterone

One small study found no significant change in IGF-1 or resting metabolic rate within 24 hours of turkesterone in 11 young men. No muscle growth trial was located.

Compared with placebo [8]

The numbers and sources
Effect
In 11 healthy men, mean age 23, turkesterone did not significantly change serum IGF-1, resting metabolic rate, or blood lipid and carbohydrate measures at 3 or 24 hours against placebo. IGF-1 rose non-significantly on both turkesterone conditions [8].
Population
11 healthy young men, with samples before and 3 and 24 hours after doses [8].
Sources
[8]
Caveats
One small, short study of single doses. IGF-1 and metabolic rate are markers, not muscle growth, and no training was involved [8]. Tested turkesterone products often held little or none of the labeled ingredient (see Risks) [4].
Vitamin CLimited

Training adaptation

One trial found muscle mitochondrial markers rose with endurance training on placebo but not with vitamin C plus E. VO2max rose 8% in both groups.

The numbers and sources
Effect
Over 11 weeks of endurance training, VO2max rose 8% with vitamin C plus E and 8% with placebo. Markers of mitochondrial growth in muscle rose on placebo (COX4 59%, PGC-1α 19%) but not with the vitamins (-13% and -13%) [13].
Population
54 young men and women given 1,000 mg vitamin C and 235 mg vitamin E a day [13].
Sources
[13]
Caveats
One trial of a combination, so the result cannot be assigned to vitamin C alone. Performance did not differ between groups. Funders included Sana Pharma AS and Smartfish AS [13].
Vitamin ELimited

Training adaptation

One trial found muscle mitochondrial markers rose with endurance training on placebo but not with vitamins C plus E. VO2max rose 8% in both groups.

The numbers and sources
Effect
Over 11 weeks of endurance training, VO2max rose 8% with vitamins C plus E and 8% with placebo. Markers of mitochondrial growth in muscle rose on placebo (COX4 59%) but not with the vitamins (-13%) [11].
Population
54 young men and women given 235 mg vitamin E with 1,000 mg vitamin C a day [11].
Sources
[11]
Caveats
One trial of a combination. Performance did not differ. Funders included Sana Pharma AS and Smartfish AS [11].

Checked, no increase found2

CreatineModerate

Side effects in clinical trials

Side effects were about as common on creatine as on placebo across 685 trials.

The numbers and sources
How common
Common: between 1 in 100 and 1 in 10 people.
Effect
Across 685 trials (12,839 on creatine, 13,452 on placebo), side effects were reported in 13.7% of creatine study arms and 13.2% of placebo arms. By participant, total side effect frequency was 4.60% on creatine and 4.21% on placebo. GI issues were 5.51% versus 4.05%, and muscle cramping or pain 0.52% versus 0.07%, neither significant by participant count [17].
Population
Clinical trial participants worldwide, plus adverse event databases [17].
Sources
[17]
Caveats
This is a pooled count, not a meta-analysis of randomized comparisons, and trials vary in how they collect side effects. The lead author also led the ISSN creatine position stand [4].
KetoanaloguesModerate

Nutritional status

Nutritional measures such as albumin and lean mass did not differ from a low-protein diet alone in adults with chronic kidney disease.

The numbers and sources
How common
How often is not known: the sources give no rate.
Effect
Albumin, mid-arm muscle circumference, lean body mass and subjective global assessment did not differ from a low-protein diet alone [1]. Albumin and cholesterol did not fall against placebo [3]. In the 15-month trial, nutritional measures did not change and no adverse reactions occurred [5]. Across protein restriction trials, 12 studies reported no protein energy wasting and 3 reported small numbers in each group [6].
Population
Adults with CKD [1][3][5][6].
Sources
[1], [3], [5], [6]
Caveats
The 15-month trial enrolled well-nourished patients who had followed the diet in a run-in phase [5]. Few studies reported weight [6].

Not studied in people3

BPC-157Grey marketUntested

Muscle injury

Not studied in people. Animal studies found faster recovery of cut and crushed leg muscles in rats.

No study in people. This rests on animal studies.

The numbers and sources
Effect
In rats whose quadriceps muscle was cut through, BPC-157 given by injection improved load to failure, walking recovery, muscle fiber regeneration and the muscle's appearance over 72 days [20]. In rats with a crushed calf muscle, BPC-157 given by injection or as a cream over 14 days reduced bruising and swelling and improved function, microscopic healing and muscle enzyme levels [21]. A 2019 review found that skeletal muscle injury models suggested a benefit after direct trauma [15].
Population
Rats [15][20][21].
Sources
[20], [21], [15]
Caveats
The two injury studies come from the same research group [20][21]. Cut and crushed muscles in rats do not show what happens after a muscle strain in people. The human studies located concerned knee pain, interstitial cystitis and intravenous safety [9].
InsulinUntested

Muscle gain in people without diabetes

Not studied in people. Bodybuilders report injecting insulin to build muscle, and a review found little evidence-based human data for the practice.

No study in people. This rests on what users report, how it acts in the body.

The numbers and sources
Effect
A review of hormones used for anabolic purposes describes insulin as commonly abused by professional and recreational athletes, and states that the belief in added muscle mass is widespread among users despite a paucity of evidence-based data in humans [17]. In a questionnaire study of 92 male recreational bodybuilders, 43% reported regular hormone use, and 38% of those reported using insulin [18].
Population
92 male recreational bodybuilders answering anonymous questionnaires [18]. No controlled trial in people without diabetes was located [17].
Sources
[17], [18]
Caveats
Not an approved use. What users report is not a measured effect. See the risk block on low blood sugar in people without diabetes.
MOTS-cGrey marketUntested

Endurance and physical capacity

Not studied in people. MOTS-c raised physical performance in young, middle-aged and old mice, and a single dose lengthened running in untrained mice.

No study in people. This rests on animal studies.

The numbers and sources
Effect
MOTS-c treatment enhanced physical performance in young (2 months), middle-aged (12 months) and old (22 months) mice [12]. In untrained mice, a single dose raised total running time by 12% and distance by 15% in an exercise test [13]. In people, exercise raised the MOTS-c the body makes, in skeletal muscle and in the blood [12].
Population
Mice [12][13].
Sources
[12], [13]
Caveats
A rise in the body's own MOTS-c with exercise is not a test of taking it. No study giving MOTS-c to people was located, and FDA found no human exposure data by any route [3].

Not yet researched4

CJC-1295 and ipamorelinGrey marketNo research yet

Muscle and strength

We haven't sourced research on this yet.

CJC-1295 and ipamorelinGrey marketNo research yet

Injury recovery

We haven't sourced research on this yet.

GHK-CuGrey marketNo research yet

Injury recovery

We haven't sourced research on this yet.

TB-500Grey marketNo research yet

Muscle healing

We haven't sourced research on this yet.