Caffeine, Cycling Performa f fnce, and Exogenous CHO Oxidation: A Dose-Response Study

DESBROW, B., C. M. BARRETT, C. L. MINAHAN, G. D. GRANT, and M. D. LEVERITT. Caffeine, Cycling Performance, and Exogenous CHO Oxidation: A Dose-Response Study. Med. Sci. Sports Exerc., Vol. 41, No. 9, pp. 1744-1751, 2009. Purpose: This study investigated the effects of a low and moderate caffeine dose on exogenous CHO oxidation and endurance-exercise performance. Methods: Nine trained and familiarized male cyclists (mean +/- SD: 29.4 +/- 4.5 yr, 81.3 +/- 10.8 kg body weight [BW], 183.8 +/- 8.2 cm, (V) over dotO(2peak) = 61.7 +/- 4.8 mL.kg(-1).min(-1)) undertook three trials, with training and high CHO diet being controlled. One hour before exercise, subjects ingested capsules containing placebo and 1.5 or 3 mg.kg(-1) BW of caffeine using a double-blind administration protocol. Trials consisted of 120 min steady-state cycling at approximately 70% VO2peak immediately followed by a 7-kJ.kg(-1) BW time trial (TT). During exercise, subjects were provided with fluids containing C-14-glucose every 20 min to determine exogenous CHO oxidation. Results: No significant TT performance improvements were observed during caffeine-containing trials (mean SD: placebo = 30 min 25 s +/- 3 min 10 s; 1.5 mg.kg(-1) BW= 30 min 42 s +/- 3 min 41 s; and 3 mg.kg(-1) BW=29 min 51 s +/- 3 min 38 s). Furthermore, caffeine failed to significantly alter maximal exogenous CHO oxidation (maximal oxidation rates: placebo = 0.95 0.2 g.min(-1); 1.5 mg.kg(-1) BW= 0.92 +/- 0.2 g-min(-1); and 3 mg.kg(-1) BW = 0.96 +/- 0.2 g-min(-1)). Conclusion: Low and moderate doses of caffeine have failed to improve endurance performance in fed, trained subjects.