Transparent Labs Bulk

Protocol and duration

single acute dose, 40 to 60 minutes before training

Studied context

Studied for resistance-exercise repetition performance/muscular endurance, cycling performance, muscle-damage recovery, and muscle soreness. A 2021 critical review notes a single acute 8 g dose "may, albeit not consistently, increase muscular endurance-strength performance," with a meta-analysis finding an average 6.4% increase in repetitions with 6-8 g dosed 40-60 minutes pre-exercise, with a stronger trend for lower-body than upper-body exercises.

Limitations

The same review states there is "little evidence to advocate its use in the production and maintenance of muscular power, maximal strength, recovery of muscular function, or supporting muscular adaptations," calls cycling-performance effects "scarce," and says claims about reduced muscle soreness lack consistent support. Overall efficacy is called "ambiguous." The review also flags a real-world quality-control problem: commercial products often do not match the citrulline:malate ratio used in the research they cite.

Selected evidence: A critical review of citrulline malate supplementation and exercise performance, 2021 · Open source

Protocol and duration

per day in divided doses, for at least 2 to 4 weeks, not as a single pre-workout dose

Studied context

Studied for high-intensity exercise capacity in the 60-240 second range via elevation of muscle carnosine, which acts as an intracellular pH buffer against acidosis. ISSN 2015 position stand: greatest performance benefits in "open end-point" tasks/time trials lasting 1-4 minutes; some benefit noted in aerobic exercise up to roughly 25 minutes; attenuation of neuromuscular fatigue, particularly noted in older adults.

Limitations

Strength/resistance-training outcomes remain mixed; training volume may increase without a clear strength gain. Tasks under 60 seconds do not show benefit. Endurance benefit beyond about 25 minutes is not established. Long-term safety data beyond roughly a year, and effects in special/tactical populations, are flagged as needing more research.

Selected evidence: ISSN position stand on beta-alanine, 2015 · Open source

Protocol and duration

per day, studied for up to 15 days

Studied context

NIH ODS describes betaine as studied for strength- and power-based performance in bodybuilders and cyclists, with "potential but modest" improvements from a limited set of small, sometimes conflicting studies. A 2024/2025 systematic review focused specifically on endurance performance (VO2max, time-to-exhaustion, time-to-completion, power output).

Limitations

The endurance systematic review explicitly states "limited and inconclusive evidence regarding the definitive ergogenic effect of betaine supplementation on endurance exercise performance". Only 2 of 5 reviewed studies showed a significant improvement, and the authors call for "additional, more rigorous research."

Selected evidence: NIH ODS, Dietary Supplements for Exercise and Athletic Performance · Open source

Protocol and duration

per day, acutely across 6 to 15 days

Studied context

Studied for aerobic performance (VO2max, time-to-exhaustion, time-trial performance), anaerobic/strength performance, exercise-induced muscle damage, and recovery. A 2018 review ("Taurine in sports and exercise," PMC8152067) reports small-to-moderate improvements across several of these outcomes in some studies.

Limitations

The 2018 review states plainly: "limited and varied findings prohibit definitive conclusions regarding the efficacy of taurine on aerobic and anaerobic performance," and separately notes no peer-reviewed evidence exists for an independent role of taurine in skeletal-muscle hypertrophy.

Selected evidence: Taurine in sports and exercise, 2018 · Open source

Protocol and duration

per day for five days, in the cadet study

Studied context

Studied as the dietary precursor to norepinephrine for mitigating cognitive performance decrements under acute stress. A 2015 Military Medicine evidence review (rapid evidence assessment, 14 trials: 10 RCTs + 4 controlled clinical trials) issued a "weak recommendation" in favor of tyrosine for cognitive stress specifically, stating "all studies showed a positive effect" on that outcome. A widely cited primary study (Deijen et al. 1999, Brain Research Bulletin) gave cadets 2 g tyrosine daily for five days during a combat training course and found better memory and tracking-task performance, plus lower systolic blood pressure, versus a carbohydrate control.

Limitations

The 2015 Military Medicine review states explicitly that "no recommendation could be made" for tyrosine's effect on physical performance under stressful physical conditions, and concludes "available evidence is insufficient to make confident recommendations on the effectiveness of tyrosine for mitigating stress effects on physical/cognitive performance" overall, despite the positive signal on cognition. A separate heat-stress study found tyrosine ingestion did not influence cognitive function or physical performance during exercise heat stress despite raised serum tyrosine. NIH ODS's exercise/athletic-performance fact sheet does not cover tyrosine at all.

Selected evidence: Deijen et al., Brain Research Bulletin, 1999

Protocol and duration

single dose, 30 to 90 minutes before testing or training

Studied context

Studied for acute cognitive performance (e.g., Stroop-test measures) and for acute power output/strength in resistance exercise. A 2024 study found both 300 mg and 600 mg doses improved Stroop-test performance in healthy young men. Separate studies cited 600 mg dosed 90 minutes pre-exercise increasing post-exercise growth hormone and peak bench-press force, and 600 mg/day over 6 days increasing lower-body isometric strength by over 3%.

Limitations

NIH ODS's Choline Health Professional fact sheet does not mention alpha-GPC at all, and states no studies have compared relative bioavailability across the choline supplement forms it does cover (choline bitartrate, phosphatidylcholine, lecithin). Alpha-GPC's comparative bioavailability is outside what NIH has assessed in that document. A large 2021 observational study (JAMA Network Open, South Korean national-insurance cohort, n=12,008,977 adults 50+) found an association between alpha-GPC use and 10-year stroke risk (adjusted HR 1.46, 95% CI 1.43-1.48 for total stroke) in a dose- and duration-response pattern, but the authors explicitly flag confounding limitations: alpha-GPC users were older with more comorbidities at baseline, and the study is observational (association, not proven causation).

Selected evidence: Acute alpha-GPC supplementation and cognitive performance, 2024

Protocol and duration

per day across trials, with most using 200 mg

Studied context

Studied for attention/reaction-time measures and for stress-related relaxation without sedation. A meta-analysis/systematic review of 31 randomized controlled trials (n=1,168) found a single 200 mg dose taken 30-60 minutes before testing significantly improved choice reaction time (SMD = 0.51, 95% CI 0.25-0.77); a subset of 5 RCTs in 148 healthy adults found a dose-dependent effect on rapid visual information processing and recognition visual reaction time.

Limitations

The review describing itself as "promising, but not completely conclusive" signals the overall evidence base has not reached firm consensus strength despite the positive reaction-time finding.

Selected evidence: Systematic review and meta-analysis of L-theanine on cognitive performance · Open source

Protocol and duration

Not recorded in the selected comparison

Studied context

EFSA's Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF), in its 2017 opinion on xanthine alkaloids from the flavoring priority list, treats theobromine as a major metabolite of caffeine. Roughly 11% of an ingested caffeine dose converts systemically to theobromine. And states that because "only limited toxicity data in humans are available" for theobromine directly, its safety assessment leans on the extensive caffeine safety literature (EFSA's 2015 caffeine opinion) rather than an independent human-efficacy dataset for theobromine as a standalone ergogenic ingredient.

Limitations

No sports-performance-specific position stand or ISSN evaluation of theobromine as a standalone ergogenic ingredient was located in this research pass. EFSA's own framing acknowledges limited independent human toxicity data on theobromine itself.

Selected evidence: EFSA Flavouring Group Evaluation 49 Revision 1, 2017 · Open source

Protocol and duration

2 to 6 mg per kg body mass, 15 to 60 minutes before exercise, shown here for a 70 kg adult

Studied context

Studied for endurance-type aerobic exercise (moderate to large ergogenic effect, most consistent evidence category per ISSN 2021), muscular endurance and movement velocity in resistance exercise (small to moderate effects), sprinting/jumping/throwing (2-7% improvements), and cognitive attention/vigilance under fatigue. NIH ODS notes it "might enhance performance in endurance-type activities... And intermittent, long-duration activities."

Limitations

Minimal effective dose remains unclear. Repeated-sprint performance benefit is inconsistent and the ISSN position stand says this "requires further research." Effects of habitual/chronic caffeine use on the ergogenic response are described as equivocal.

Selected evidence: ISSN position stand on caffeine and exercise performance, 2021, with NIH ODS · Open source