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˙O2peak = 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% V˙O2peak, immediately followed by a 7-kJ·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·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.
1School of Public Health, Griffith University, Queensland, AUSTRALIA; 2Research Centre for Clinical and Community Practice Innovation, Griffith University, Queensland, AUSTRALIA; 3School of Physiotherapy Exercise Science, Griffith University, Queensland, AUSTRALIA; and 4School of Pharmacy, Griffith University, Queensland, AUSTRALIA
Address for correspondence: Ben Desbrow, Ph.D., A.P.D., School of Public Health and Research Centre for Clinical and Community Practice Innovation, Griffith University, Gold Coast Campus, Queensland 4222, Australia; E-mail: firstname.lastname@example.org.
Submitted for publication October 2008.
Accepted for publication February 2009.