A controlled trial found a narrow performance signal, not an across-the-board CrossFit boost. Phenylcapsaicin is a synthetic, microencapsulated analogue of capsaicin, the pungent compound in chili peppers. It is designed to activate similar biological pathways at a lower dose and with less irritation than purified capsaicin. In this study, the clearest effects appeared in strength-related tests and post-exercise soreness; performance in the workout of the day did not improve.
The design was stronger than a simple before-and-after comparison. The researchers enrolled 50 CrossFit-trained adults aged 18–35, evenly divided between women and men. All had at least three years of CrossFit experience and trained for at least six hours per week. In a randomized, triple-blind crossover design, every participant completed both conditions: 2.5 mg of phenylcapsaicin and a matched placebo, taken in four capsules 45 minutes before exercise. The sessions were separated by a one-week washout, and food intake during the preceding 24 hours was standardized.
The test session combined lifting, gymnastics, and conditioning. After warm-up and baseline countermovement jumps, participants completed nine rounds of bar-facing burpees followed by an increasingly heavy squat clean and jerk. They then performed the CrossFit Open 21.3 workout, which combined front squats, thrusters, and progressively harder gymnastics movements. The researchers also assessed a deep squat at 70% of one-repetition maximum, jump performance, heart rate, blood lactate, perceived effort, perceived recovery, and muscle soreness 24 and 48 hours later.
Phenylcapsaicin helped some strength-related outcomes. Compared with placebo, participants lifted more weight and completed more repetitions in the 70%-of-maximum squat test. They also maintained performance better across the nine weightlifting rounds: the average load in the final round was 73.1 kg after phenylcapsaicin versus 55.5 kg after placebo. The fall in countermovement-jump performance after the session was smaller with phenylcapsaicin, which suggests less loss of explosive power under fatigue.
The main workout result was negative. Phenylcapsaicin did not improve the number of repetitions completed in any part of the Open 21.3 workout. Heart rate, blood lactate, perceived exertion, and perceived recovery also did not differ between conditions. This matters because the study cannot support the broader claim that one dose improves overall CrossFit performance; the benefit was confined to selected strength and fatigue measures in this particular protocol.
Muscle soreness was modestly lower, but the time-point results were mixed. Average soreness scores were 3.08 after phenylcapsaicin versus 3.76 after placebo at 24 hours, and 3.10 versus 3.46 at 48 hours. The overall condition effect was statistically significant, while the individual 48-hour comparison was not. That pattern is more cautious than saying the supplement clearly accelerated recovery at both time points.
Tolerance and commercial ties deserve attention. Six participants—12% of the sample—reported heartburn or acid reflux after phenylcapsaicin, compared with none after placebo. The study was supported by Axichem, a phenylcapsaicin supplier, although the authors state that the sponsor did not collect or enter data and placed no restrictions on analysis or publication. Two authors were scientific advisors to Life Pro Nutrition, the supplement brand that prepared the study capsules.
The results are interesting but preliminary. This was a single acute dose in young, experienced athletes during one standardized session. It does not establish long-term safety, training adaptation, benefit in recreational exercisers, or superiority to established approaches such as adequate carbohydrate intake, sleep, and programmed recovery. The sex-stratified findings—less jump-height loss in men and a higher squat load in women—were secondary analyses in groups of only 25 and should not yet guide sex-specific recommendations.
Bottom line. A 2.5 mg dose taken 45 minutes before exercise improved selected lifting and fatigue outcomes and slightly reduced reported soreness, but it did not improve the workout-of-the-day result and caused heartburn in some participants. Independent replication across different workouts and longer training periods is needed before phenylcapsaicin can be considered a reliable performance aid.
Medical note. This article is for general education purposes only and is not intended as personal medical advice.