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Research · Supplements

Pre-workout blends

Small trials of individual products found a few more repetitions and better rated energy, with small effect sizes. Nearly half of listed ingredients sit in proprietary blends with undisclosed amounts. Analyses of products sold in the US found banned and never-tested stimulants, including DMAA, DMHA and BMPEA. FDA has issued warning letters and seized DMAA products.

Add to Bio HackChecked 2026-11-09
Status
Sold as dietary supplements in the US. FDA states DMAA is not a dietary ingredient and DMAA products marketed as supplements are illegal. FDA considers supplements containing DMHA adulterated.
Also called
pre-workout, preworkout, multi-ingredient pre-workout supplements, MIPS, pump products, stim pre-workout, proprietary blend, DMAA, 1,3-dimethylamylamine, methylhexanamine, geranium extract, DMHA, octodrine, 2-aminoisoheptane, DMBA, BMPEA, deterenol, synephrine pre-workout
Taken for
energy, focus, pump, muscular endurance, strength, power, training volume, fat loss

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 help2

Reported risks4

What people take it for, and what was found

Shown to help2

Limited

Acute resistance and sprint performance

Small trials found slightly more reps, volume and sprint power than placebo with single pre-workout products, and results do not carry across formulas.

The numbers and sources
Effect
In 12 men, a pre-workout product taken 30 minutes before training raised bench press repetitions in a final set to failure (9.8 versus 9.1) and total volume load (753 versus 710 kg), and raised mean sprint power, with effect sizes of 0.20 to 0.38 [1]. A review of the field found evidence for better muscular endurance and mood, and mixed results for force and power [2]. In 22 men and women with more than 2 years of high-intensity functional training, a pre-workout product raised total volume load about 4.4% and repetition rate about 2.2% over placebo in 5 and 15 minute workouts. Total repetitions did not differ [3].
Population
Resistance-trained young men [1]; studies reviewed in [2]; 12 men and 10 women, mean age 29, crossover [3].
Sources
[1], [2], [3]
Caveats
Each trial tests one formula, often with undisclosed amounts, so results do not carry from one product to another [2]. The authors of [1] described the practical significance as possibly minimal.
Limited

Rated energy, alertness and fatigue

One small trial found better fatigue and alertness ratings than placebo after a resistance session with a pre-workout product.

The numbers and sources
Effect
After a pre-workout product, subjective fatigue (d 3.78) and alertness (d 2.72) ratings were better than placebo after a resistance session [1]. Among 872 regular users surveyed, 89% took these products for energy and focus [4].
Population
12 men [1]; adult users responding to an online survey [4].
Sources
[1], [4]
Caveats
Subjective ratings in one small trial. The survey measured reasons for use, not effects.

Mixed results1

Limited

Body composition and strength over weeks

Limited evidence: small trials found strength gains in one, and no difference from carbohydrate in another, over 4 to 6 weeks of training.

The numbers and sources
Effect
In recreationally active men taking a caffeine, creatine, beta-alanine and amino acid product for 28 days, leg press 1RM rose in the supplement group only (218.8 to 228.8 kg). Body fat fell and fat-free mass rose over time in both groups. Maximal oxygen uptake fell in the supplement group only (47.3 to 45.6 mL/kg per minute) [5]. A review found chronic use with periodized training may add lean mass, and effects on force, endurance and aerobic performance were unclear [2]. In 43 middle-aged adults (26 peri- and postmenopausal women and 17 men), a caffeinated plant protein pre-workout taken before each session of a 6-week training program did not differ from carbohydrate alone on fat mass, fat-free mass, muscle thickness, strength, power or muscular endurance. Both groups improved. Only the pre-workout group reduced waist circumference (1.8 cm), with no difference between groups at the end [6].
Population
College-aged men [5]; studies reviewed in [2]; adults aged about 52 to 54 [6].
Sources
[2], [5], [6]
Caveats
Body composition changes in [5] were main effects for time, not differences between groups. The comparator in [6] was carbohydrate, not a placebo.

Doses studied

Among the top 100 products, the mean number of ingredients was 18.4, and 44.3% of all ingredients were in proprietary blends at undisclosed amounts. Listed amounts averaged 254 mg caffeine (in 86% of products), 2.0 g beta-alanine (87%), 4.0 g citrulline (71%), 1.3 g taurine (51%) and 2.1 g creatine (49%) per serving [7]. Among users, 14% took two or more servings at a time and 18% used them more than once a day [4].

Risks

Reported risks4

Limited

Side effects reported by users

Limited evidence: in a survey of 872 regular users, 54% reported side effects such as skin reactions, heart abnormalities and nausea.

The numbers and sources
Effect
Of 872 regular users, 54% reported side effects after use, including skin reactions, heart abnormalities and nausea. Women reported side effects more often than men [4].
Population
Adult pre-workout users, online survey [4].
Sources
[4]
Caveats
Self-selected, self-reported survey with no comparison group.
Moderate

Banned and untested stimulants in products

Product tests found banned or untested stimulants such as DMAA, DMHA and BMPEA in brands whose labels suggested them, some above former drug doses.

The numbers and sources
Effect
In 6 brands listing ingredients that might refer to DMAA analogs, testing found octodrine (DMHA) at 72 mg per serving, more than twice the largest former pharmaceutical dose, plus 1,4-DMAA at 21 to 94 mg, and the banned stimulants 1,3-DMAA and 1,3-DMBA [8]. In 17 brands listing deterenol, testing found 9 prohibited stimulants and 8 different mixtures, with up to 4 experimental stimulants in one product, including BMPEA at 5.7 to 92 mg per serving [9].
Population
Sports and weight loss supplements sold in the US [8][9].
Sources
[8], [9]
Caveats
Products were chosen because their labels suggested these ingredients, so the findings are not a market-wide rate.
Limited

Deaths and cardiovascular events

Case reports: two soldiers on DMAA supplements died of cardiac arrest during exertion, and synephrine products were tied to chest pain and arrhythmias.

The numbers and sources
Effect
Two soldiers taking multi-ingredient supplements containing DMAA collapsed from cardiac arrest during physical exertion and died [10]. A review of 30 case reports described 35 patients with adverse events after synephrine-containing supplements, most often chest pain, palpitations, syncope and dizziness, with ischemic heart disease, arrhythmias and cerebrovascular disease among the diagnoses. Five were left disabled or on medication [11]. In US emergency departments, weight loss or energy products were implicated in 71.8% of supplement-related visits for palpitations, chest pain or tachycardia [12].
Population
Case reports [10][11]; national surveillance from 63 emergency departments, 2004 to 2013 [12].
Sources
[10], [11], [12]
Caveats
Case reports cannot show causation. Caffeine and other ingredients may have contributed [11].
Strong

FDA actions on DMAA and DMHA

FDA states DMAA is not a dietary ingredient and can raise blood pressure and lead to heart problems, including arrhythmias and heart attack.

The numbers and sources
Effect
FDA states DMAA is not a dietary ingredient and that it can raise blood pressure and lead to cardiovascular problems including arrhythmias and heart attack. FDA has issued warning letters since 2012, detained two DMAA products (OxyElite Pro and Jack3d) and seized products in 2013, which were destroyed in 2020 [13]. On April 10, 2019, FDA issued 9 warning letters to companies selling supplements labeled to contain DMHA, which it considers either a new dietary ingredient for which FDA received no required notification, or a food additive without FDA approval [14].
Population
US market [13][14].
Sources
[13], [14]
Caveats
Regulatory actions, not measured harm rates.

Claims tested and not found

  1. That a pre-workout raises aerobic capacity. Maximal oxygen uptake fell in the supplement group over 28 days, from 47.3 to 45.6 mL/kg per minute [5].
  2. That a pre-workout adds to training gains over weeks in middle-aged adults. Body composition, strength and endurance gains did not differ from carbohydrate alone over 6 weeks [6].

Sources

  1. Jagim AR, Jones MT, Wright GA, et al. The acute effects of multi-ingredient pre-workout ingestion on strength performance, lower body power, and anaerobic capacity. Journal of the International Society of Sports Nutrition. 2016. https://doi.org/10.1186/s12970-016-0122-2
  2. Harty PS, Zabriskie HA, Erickson JL, et al. Multi-ingredient pre-workout supplements, safety implications, and performance outcomes: a brief review. Journal of the International Society of Sports Nutrition. 2018. https://doi.org/10.1186/s12970-018-0247-6
  3. Mangine GT, Staples C, Henley JW, et al. Acute effect of a multi-ingredient pre-workout supplement on pacing and kinetic expression during shorter and longer bouts of high intensity functional training. Journal of the International Society of Sports Nutrition. 2025. https://doi.org/10.1080/15502783.2025.2529906
  4. Jagim AR, Camic CL, Harty PS. Common Habits, Adverse Events, and Opinions Regarding Pre-Workout Supplement Use Among Regular Consumers. Nutrients. 2019. https://doi.org/10.3390/nu11040855
  5. Kendall KL, Moon JR, Fairman CM, et al. Ingesting a preworkout supplement containing caffeine, creatine, β-alanine, amino acids, and B vitamins for 28 days is both safe and efficacious in recreationally active men. Nutrition Research. 2014. https://doi.org/10.1016/j.nutres.2014.04.003
  6. Puente-Fernández J, Larumbe-Zabala E, Roberts J, et al. Pre-workout multi-ingredients or carbohydrate alone promote similar resistance training outcomes in middle-aged adults: a double-blind, randomized controlled trial. Journal of the International Society of Sports Nutrition. 2025. https://doi.org/10.1080/15502783.2025.2519515
  7. Jagim AR, Harty PS, Camic CL. Common Ingredient Profiles of Multi-Ingredient Pre-Workout Supplements. Nutrients. 2019. https://doi.org/10.3390/nu11020254
  8. Cohen PA, Travis JC, Keizers PHJ, et al. Four experimental stimulants found in sports and weight loss supplements: 2-amino-6-methylheptane (octodrine), 1,4-dimethylamylamine (1,4-DMAA), 1,3-dimethylamylamine (1,3-DMAA) and 1,3-dimethylbutylamine (1,3-DMBA). Clinical Toxicology. 2018. https://doi.org/10.1080/15563650.2017.1398328
  9. Cohen PA, Travis JC, Vanhee C, et al. Nine prohibited stimulants found in sports and weight loss supplements: deterenol, phenpromethamine (Vonedrine), oxilofrine, octodrine, beta-methylphenylethylamine (BMPEA), 1,3-dimethylamylamine (1,3-DMAA), 1,4-dimethylamylamine (1,4-DMAA), 1,3-dimethylbutylamine (1,3-DMBA) and higenamine. Clinical Toxicology. 2021. https://doi.org/10.1080/15563650.2021.1894333
  10. Eliason MJ, Eichner A, Cancio A, et al. Case Reports: Death of Active Duty Soldiers Following Ingestion of Dietary Supplements Containing 1,3-Dimethylamylamine (DMAA). Military Medicine. 2012. https://doi.org/10.7205/MILMED-D-12-00265
  11. de Jonge MLL, Kieviet LC, Sierts M, et al. Review of Case Reports on Adverse Events Related to Pre-workout Supplements Containing Synephrine. Cardiovascular Toxicology. 2023. https://doi.org/10.1007/s12012-022-09777-z
  12. Geller AI, Shehab N, Weidle NJ, et al. Emergency Department Visits for Adverse Events Related to Dietary Supplements. New England Journal of Medicine. 2015. https://doi.org/10.1056/nejmsa1504267
  13. U.S. Food and Drug Administration. DMAA in Products Marketed as Dietary Supplements. FDA. Accessed 2026. https://www.fda.gov/food/information-select-dietary-supplement-ingredients-and-other-substances/dmaa-products-marketed-dietary-supplements
  14. U.S. Food and Drug Administration. FDA Acts on Dietary Supplements Containing DMHA and Phenibut. FDA Constituent Update. 2019. https://www.fda.gov/food/hfp-constituent-updates/fda-acts-dietary-supplements-containing-dmha-and-phenibut

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