Resumen de Caffeine, Cycling Performance, and Exogenous CHO Oxidation: A Dose-Response Study

Ben Desbrow, Clare M. Barrett, Clare L. Minahan, Gary D. Grant, Michael D. Leveritt

• 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[spacing dot above]O2peak = 61.7 +/- 4.8 mL[middle dot]kg-1[middle dot]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[middle dot]kg-1 BW of caffeine using a double-blind administration protocol. Trials consisted of 120 min steady-state cycling at approximately 70% V[spacing dot above]O2peak, immediately followed by a 7-kJ[middle dot]kg-1 BW time trial (TT). During exercise, subjects were provided with fluids containing 14C-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[middle dot]kg-1 BW = 30 min 42 s +/- 3 min 41 s; and 3 mg[middle dot]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[middle dot]min-1; 1.5 mg[middle dot]kg-1 BW = 0.92 +/- 0.2 g[middle dot]min-1; and 3 mg[middle dot]kg-1 BW = 0.96 +/- 0.2 g[middle dot]min-1).

  Conclusion: Low and moderate doses of caffeine have failed to improve endurance performance in fed, trained subjects