The Effects of Caffeine Supplementation and Withdrawal on Muscle Power, Strength, and Endurance in Physically Active, Habitual Caffeine Consumers Open Access
Caffeine has strongly demonstrated to be an ergogenic aid in aerobic activity and equivocally found beneficial for anaerobic activity. This study compared independent effects of caffeine withdrawal, chronic and acute caffeine supplementation on muscle peak torque, average power, perceived exertion (RPE) and perceived pain index (PPI) during isokinetic exercises in habitual caffeine consumers. Physically active subjects (n=33) participated in a placebo-controlled study with four independent sessions. Repeated-measures ANOVA and paired t-tests were used for analyses with an alpha <0.05. Subjects withdrew from caffeine for 4 days, supplemented 5mg·kg of caffeine for 3 days and consumed 6mg·kg of caffeine or matched placebo 1 hour before final testing. Caffeine withdrawal showed significant decreases in knee extension peak torque 7.5 N-m (60°·s-1), 3.9 N-m (30-repetitions at 180°·s-1) 5.5 N-m (isometric @30°) and 8.2 N-m (isometric @90°). Knee flexion peak torque decreased 2.8 N-m (180°·s-1) and 3.0 N-m (30-repetitions at 180°·s-1). Average power for extension decreased 6.6 N-m (60°·s-1) and flexion by 8.1 N-m (180°·s-1). Average power decreased 5.9 N-m and 7.5 N-m during 30-repetitions at 180°·s-1. Following chronic and acute caffeine supplementation there were no differences in RPE, PPI, peak torque or average power. The current study demonstrated that caffeine withdrawal significantly decreased performance in moderate-to-high caffeine consumers, while chronic and acute caffeine consumption did not significantly affect performance.
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