Caffeine Ingestion Increases Mean Power But Not Critical Power In Female College Students

Abstract

Caffeine may increase performance during prolonged endurance exercise as well as during shorter, higher-intensity exercise bouts. PURPOSE: This study tested whether caffeine affects critical power (aerobic component) and the curvature constant (anaerobic component) in female college students. METHODS: Nine subjects (60.8 ± 9.0 kg) underwent a 3-min, all-out cycling effort 1 hour after ingesting either anhydrous caffeine (3 mg/kg) or placebo. Resistance on the cycle ergometer was 3% of the subject’s body weight. Treatments were randomly assigned and administered two weeks apart in a double-blind manner. Critical power and the curvature constant were determined from the intercept and slope, respectively, of the linear regression of power vs. time-1. Additionally, we determined maximum, average or minimum power for the 3-min, all-out exercise bout. RESULTS: Neither critical power (p = 0.771) nor the curvature constant (p = 0.288) differed between treatments. Average power increased with caffeine compared to placebo (Caf, 154.1 ± 31.3 W; Pla, 148.9 ± 28.3 W; p = 0.039). Neither maximum (p = 0.398) nor minimum power (p = 0.767) differed between groups. We also tested whether critical power differed between the subjects’ first and second trials. Critical power increased on their second trial compared to their first (Trial 1, 98.0 ± 32.2 W; Trial 2,106.3 ± 34.4 W; p = 0.024) regardless of whether they consumed caffeine or placebo. Maximum, average and minimum power did not differ between trials 1 and 2. CONCLUSIONS: Results from this study suggest that caffeine increases average power without affecting maximum, minimum or critical power in a 3-min all-out cycling effort. The increase in critical power on the subjects’ second trials suggest that the subjects may have paced themselves during their second trial due to extreme discomfort experienced during their first trial.