Ergogenic Effects of Caffeine on Simulated Time-Trial Performance Are Independent of Fitness Level

Abstract

Background: The primary aim of this study was to compare the ergogenic effects of caffeine on cycling performance in endurance-trained and recreationally active participants. Methods: Endurance-trained [n=8, VO2max=57.5±3.9 mL/(kg·min)] and active [n=8, VO2max=46.5±6.3 mL/(kg·min)] participants initially completed two familiarization trials separated by at least 48 hours. Over the next three trials, they completed a 10 km cycling time trial preceded by ingestion of drinks containing caffeine (5 mg/kg ingested on 2 separate days) or placebo. Treatments were ingested using a single-blind, crossover design, and participants were deceived as to the content of all drinks. During exercise, heart rate (HR), rating of perceived exertion (RPE), and time were recorded every 1.6 km. Repeated measures analysis of variance was used to assess differences in cycling time, HR, and RPE between treatments, with fitness level used as a between-subjects variable. Results: Caffeine increased (p<0.05) cycling performance by 0.3%–2.0% versus placebo, with no effect (p>0.05) of fitness level. Magnitude of performance improvement in both caffeine trials (−0.21 and −0.23 minutes, respectively) was similar versus placebo. Compared with placebo, exercise HR was higher (p<0.05) with caffeine, although RPE was similar (p>0.05) across treatments. Conclusions: In active men of varying fitness, data reveal a small caffeine-mediated improvement in cycling performance that was similar in magnitude.