Acute capsaicin supplementation neither interferes with strength endurance nor jumping performance in advanced resistance-trained individuals

Background Experimental evidence suggests that capsaicin supplementation improves calcium metabolism in skeletal muscle, suggesting an ergogenic potential. Previous studies, however, have numerous methodological biases. Aim We investigated the effect of acute capsaicin supplementation on countermovement jump (CMJ) height and strength endurance in trained individuals, addressing previous methodological limitations. Methods Sixteen young (24 ± 4 years; 73.9 ± 2.7 kg; 1.73 ± 0.06 m), advanced resistance-trained men underwent: (1) one-repetition maximum (1-RM) tests to fulfill eligibility and to determine the strength endurance test intensity; (2) strength endurance tests (4 sets, 70% 1-RM) in the 45° leg press; and (3) CMJ tests. After successive familiarizations, the participants performed strength endurance and CMJ tests with a ≥ 72 h inter-session interval, under three different conditions, in a double-blind, counterbalanced crossover design: (1) Control (CON, no supplementation), (2) Placebo (PLA), and (3) Capsaicin (CAP, 12 mg). The capsules were ingested 40 min before the tests. Mixed models were used to analyze the intervention effect, with a significance level set at p ≤ 0.05. Summary No significant differences were detected between the experimental conditions, neither for the total number of repetitions in the strength endurance test (CAP: 55 ± 15 vs PLA: 52 ± 16 vs CON: 54 ± 16; p = 0.854), nor for jump height in the CMJ test (CAP: 36.0 ± 3.3 cm vs PLA: 36.3 ± 3.6 cm vs CON: 36.2 ± 3.7 cm; p = 0.976). Neither positive nor negative expectancy effects (both p > 0.05) from capsaicin ingestion were detected on performance outcomes. We conclude that acute capsaicin supplementation does not represent an effective strategy to improve CMJ height or strength endurance in advanced resistance-trained individuals.