Effect of caffeine on cycling time-trial performance in the heat

Abstract

Objectives: The purpose of this investigation was to determine whether a moderate dose of caffeine would improve a laboratory simulated cycling time-trial in the heat. Methods: Nine well-trained male subjects (VO2max 64.4±6.8mLmin-1kg-1, peak power output 378±40W) completed one familiarisation and two experimental laboratory simulated cycling time-trials in environmental conditions of 35°C and 25% RH 90min after consuming either caffeine (3mgkg-1 BW) or placebo, in a double blind, cross-over study. Results: Time-trial performance was faster in the caffeine trial compared with the placebo trial (mean±SD, 3806±359s versus 4079±333s, p=0.06, 90%CI 42-500s, 86% likelihood of benefit, d=-0.79). Caffeine ingestion was associated with small to moderate increases in average heart rate (p=0.178, d=0.39), VO2 (p=0.154, d=0.45), respiratory exchange ratio (p=0.292, d=0.35) and core temperature (p=0.616, d=0.22) when compared to placebo, however, these were not statistically significant. Average RPE during the caffeine supplemented time-trial was not significantly different from placebo (p=0.41, d=-0.13). Conclusion: Caffeine supplementation at 3mgkg-1 BW resulted in a worthwhile improvement in cycling time-trial performance in the heat. Design: Double-blind cross-over study. © 2013 Sports Medicine Australia.