Acute effects of caffeine supplementation on resistance exercise, jumping, and Wingate performance: no influence of habitual caffeine intake

Randomized, double-blind, counterbalanced crossover study in 24 resistance-trained adult men from Australia. Participants were classified by habitual caffeine intake into low users (n = 13) and moderate-to-high users (n = 11), and all completed the testing protocol without dropout.

Caffeine was given as a single oral capsule at 3 mg/kg, taken 60 minutes before the exercise session. Participants completed caffeine and placebo trials in a randomized, double-blind, counterbalanced crossover design; placebo contained 3 mg/kg dextrose.

Caffeine improved resistance-exercise, jumping, and Wingate performance overall, and habitual caffeine intake did not significantly blunt these acute effects. Compared with placebo, caffeine increased mean power at 25% 1RM by 123 (66, 180) W, mean velocity at 25% 1RM by 0.03 (0.01, 0.05) m/s, and CMJ height by 0.9 cm; muscular endurance also improved, with condition effects p < 0.001. Wingate peak, mean, and minimum power all favored caffeine, with condition effects p < 0.001, p < 0.001, and p = 0.012, respectively. No group × condition interaction was significant, and correlations between habitual caffeine intake and performance change were not significant.

Small sample size and only male resistance-trained participants limit generalizability. The study tested an acute single-dose caffeine challenge rather than chronic use, and habitual caffeine intake was estimated from questionnaire data. The trial also does not address whether responses differ in women, less-trained individuals, or other exercise contexts.