Potential ergogenic aid of capsaicinoid or capsinoids in healthy adults: a systematic review with meta-analysis

Capsaicinoids and capsinoids (CAP) have been proposed as ergogenic aids, with mechanisms suggesting benefits for resistance or aerobic exercise performance. The objective of this systematic review with meta-analysis was to verify the effects of CAP on resistance or aerobic exercise performance in healthy adults, and to explore potential variables influencing these outcomes. We hypothesize that CAP supplementation may acutely and chronically improve aerobic and resistance performance in adults. This review followed PRISMA guidelines and was registered in PROSPERO (CRD42023460579). Searches were conducted in PubMed, Web of Science, Embase, and SPORTDiscus. Eligible studies included healthy adults (18-59 years) receiving acute or chronic CAP supplementation with resistance or aerobic exercise, reporting outcomes on aerobic exercise performance (time trial or time to exhaustion), resistance exercise performance (total volume load or repetitions to failure), and rating of perceived exertion (RPE). Meta-analysis showed improvements in acute resistance exercise performance (standardized mean difference [SMD] = 0.198; 95% confidence interval (CI) = 0.083-0.313; P = .001), and acute aerobic exercise performance, where CAP improved time-to-exhaustion (SMD = 0.487; 95% CI = 0.089-0.885; P = .016) but without overall effect (SMD = 0.055; 95% CI = −0.128 to 0.238; P = .554). For RPE, there was a significant reduction for overall effect (SMD = −0.183; 95% CI = −0.318 to −0.047; P = .008). Three chronic resistance training studies were identified, with one showing increased strength. Two chronic aerobic studies were included, but neither improved. In conclusion, acute CAP supplementation may enhance resistance exercise performance and time-to-exhaustion during acute aerobic exercise, while lowering RPE, but chronic effects are limited.