Caffeine intake enhances peak oxygen uptake and performance during high-intensity cycling exercise in moderate hypoxia

Purpose We investigated whether caffeine consumption can enhance peak oxygen uptake ((V)over dotO(2peak)) by increasing peak ventilation during an incremental cycling test, and subsequently enhance time to exhaustion (TTE) during high-intensity cycling exercise in moderate normobaric hypoxia. Methods We conducted a double-blind, placebo cross-over design study. Sixteen recreational male endurance athletes (age: 20 +/- 2 years, (V)over dotO(2peak): 55.6 +/- 3.6 ml/kg/min, peak power output: 318 +/- 40 W) underwent an incremental cycling test and a TTE test at 80% (V)over dotO(2peak) (derived from the placebo trial) in moderate normobaric hypoxia (fraction of inspired O-2: 15.3 +/- 0.2% corresponding to a simulated altitude of similar to 2500 m) after consuming either a moderate dose of caffeine (6 mg/kg) or a placebo. Results Caffeine consumption resulted in a higher peak ventilation [159 +/- 21 vs. 150 +/- 26 L/min; P < 0.05; effect size (ES) = 0.31]. (V)over dotO(2peak) (3.58 +/- 0.44 vs. 3.47 +/- 0.47 L/min; P < 0.01; ES = 0.44) and peak power output (308 +/- 44 vs. 302 +/- 44 W; P = 0.02, ES = 0.14) were higher following caffeine consumption than during the placebo trial. During the TTE test, caffeine consumption enhanced minute ventilation (P = 0.02; ES = 0.28) and extended the TTE (426 +/- 74 vs. 358 +/- 75 s; P < 0.01, ES = 0.91) compared to the placebo trial. There was a positive correlation between the percent increase of (V)over dotO(2peak) following caffeine consumption and the percent increase in TTE (r = 0.49, P < 0.05). Conclusion Moderate caffeine consumption stimulates breathing and aerobic metabolism, resulting in improved performance during incremental and high-intensity endurance exercises in moderate normobaric hypoxia.