A chili-derived pre-workout compound just got a rigorous test, and the results are more interesting than the usual supplement hype. In a triple-blind, placebo-controlled crossover trial of 50 CrossFit-trained athletes, a single 2.5 mg dose of phenylcapsaicin improved post-session squat performance, blunted jump-height loss, and left athletes less sore for two days afterward. It did not change how they performed in the workout of the day (WOD).
That split is the whole story, so read on before you add it to your cart.
What Is Phenylcapsaicin?
Phenylcapsaicin (PC) is a capsaicin analog, a relative of the compound that gives chili peppers their heat. The researchers frame it as a candidate for high-intensity training because it may reduce perceived exertion, increase mechanical output, and limit muscle damage. Those are hypotheses stated in the paper's background. The trial was designed to see whether anything shows up in real athletes doing a real CrossFit session.
The Setup: Who, What, and When
The study, published in the Journal of the International Society of Sports Nutrition, used a randomized crossover design. Each of the 50 CrossFit athletes (half of them women) completed the session twice, once with PC and once with a placebo. Neither the athletes nor the researchers knew which was which.
- Dose: 2.5 mg of phenylcapsaicin
- Timing: 45 minutes before the session
- Session: a standardized CrossFit workout with a warm-up, a weightlifting block, and a WOD
- Measures: countermovement jump (CMJ) before and after, a deep squat at 70% of 1RM after the session, heart rate, capillary lactate, rating of perceived exertion (RPE), perceived recovery status, and delayed-onset muscle soreness (DOMS) at 24 and 48 hours
The Headline Findings
Squats got better after the session
Compared with placebo, PC improved deep squat performance at 70% 1RM in both load and repetitions (P ≤ 0.035). Athletes were lifting more, for more reps, after already working through the session.
Jump height held up better
CMJ typically falls after hard training, a common proxy for neuromuscular fatigue. PC attenuated that decline (P < 0.001), the strongest statistical signal in the paper.
The weightlifting block stayed stronger
The PC group maintained weightlifting performance across the block (P interaction = 0.011), with significantly higher load in round 9 (P = 0.030). The advantage appeared late, when fatigue accumulates, not at the start.
Soreness was lower for two days
DOMS was significantly lower with PC at both 24 and 48 hours (P = 0.030).
What Didn't Change
Here is the reality check. There were no differences during the WOD (P interaction ≥ 0.826). If you hoped for a faster conditioning piece, this trial doesn't support it.
Also unchanged were blood lactate, RPE, perceived recovery status, and heart rate (P interaction ≥ 0.340). That is notable because reduced perceived exertion was one of the proposed mechanisms. Athletes didn't report the work as feeling easier, even though some outputs were better. The abstract doesn't explain why, so any mechanism remains speculation.
Men vs. Women
In the sex-stratified analysis, PC reduced CMJ loss in men (P = 0.043) and increased squat load in women (P = 0.021). It's tempting to say the compound works differently by sex, but treat this cautiously. Subgroup analyses of 25 people each are exploratory and shouldn't be read as proof of sex-specific effects.
Conflict of Interest and Caveats
Two authors, Jimenez-Martinez and Alix-Fages, disclosed that they are scientific advisors of a supplement brand, Life Pro Nutrition (Madrid, Spain). That doesn't invalidate the data, and the trial's blinded, crossover design is a strength. But it's a reason to want independent replication before treating the effect as settled.
Other limits to keep in mind:
- It's an acute study. One dose before one session. Nothing here shows what happens with weeks of use, or whether the soreness benefit translates into better long-term adaptation.
- The population is specific. These were CrossFit-trained athletes, so the results may not carry over to beginners, older adults, or other sports.
- Mechanisms are unproven here. The proposed pathways (less perceived exertion, less muscle damage) come from the paper's background reasoning and prior research. This trial measured outcomes, not mechanisms, and the unchanged RPE sits awkwardly with the exertion idea. Don't treat lab or animal findings on capsaicin-type compounds as proof of what happens in your training.
- Effect sizes aren't in the abstract. We know the differences were statistically significant, but not how large they were in practical terms.
Practical Takeaways
The protocol that was tested: 2.5 mg of phenylcapsaicin, taken 45 minutes before training.
Who it might suit: trained CrossFit-style athletes who do heavy lifting blocks and want to protect strength output late in a session or reduce next-day soreness. That is the population studied, and only that population is covered by the evidence.
Who should skip or be careful:
- Anyone who doesn't tolerate capsaicin or spicy foods well. The abstract doesn't report side effects, so check the full text.
- Anyone who is pregnant or on medication, or has a medical condition. Talk to a clinician first.
- Anyone chasing a faster WOD time. This trial found no WOD benefit.
- Beginners, since no evidence covers them, and basics like sleep, protein, and progressive training will beat any pre-workout.
The Bottom Line
Phenylcapsaicin isn't a magic pre-workout, but this is better evidence than most supplements get: a blinded crossover trial with a balanced sex split and consistent signals across squat, jump, and soreness outcomes. The authors conclude that acute supplementation enhances performance and recovery in CrossFit athletes. The more careful reading is that it showed benefits in specific outputs (strength maintenance, jump retention, soreness) and none in the WOD itself. With industry-linked advisors on the author list and no long-term data, independent replication should come before any big claims.
