CAFFEINE ALTERS PACING STRATEGIES WITHOUT IMPROVING 100-KM CYCLING TIME-TRIAL PERFORMANCE

Abstract

Aim This study analysed the effect of caffeine on 100 Km intermittent intensity cycling time trial performance. Methods Eight elite cyclists ingested 6 mg/kg of adrenergic caffeine prior to starting the cycle ride (for one of the two cycling time trials), followed by a maintenance dose of 0.33 mg/kg every 15 minutes throughout the ride. The 100 km time trial consisted of five 1-km sprints after 10, 32, 52, 72 and 99 km, as well as four 4-km sprints after 20, 40, 60, and 80 km. Subjects were required to complete the 100 km time trial and all sprints in the fastest time possible. Results Plasma [caffeine] were highly significant between groups (p < 0.01), (pre-and post-ride for placebo were 0.43 + 0.56 and 1.11 + 1.78 μM and for caffeine were 47.32 + 12.01 and 72.43 + 29.08 μM respectively). No significant differences were found in the time and average power to complete the sprints and the final time to complete the 100km. However, the overall profile of the caffeine group displayed faster times and higher work output in the first section of the trial and slower times and smaller work output in the latter. Significant differences (p < 0.05) in heart rate (HR) were found between groups. No significant differences were found for either EMG amplitude (IEMG) or mean power frequency spectrum (MPFS), however in the last two sprints there is a reduction in IEMG in the caffeine group whilst there was an increase in the control group and MPFS shifted to the upper part of the spectrum in the caffeine group. Conclusion The caffeine effect was clearly stimulatory as HR was elevated and the earlier sprints were insignificantly faster than the non-caffeine trials. However this early bout of exercise caused late-race deterioration, which is supported by the EMG data that shows increased levels of fatigue in the caffeine group. Hence caffeine interfered with the pacing strategy without improving performance.