The influence of acute exercise on sleep following high caffeine intake

The purpose of this study was to examine the influence of vigorous acute ex ercise on nocturnal sleep that had been disrupted by high doses (1200 mg) o f caffeine throughout the daytime. Eight moderately fit, young males with a history of moderate caffeine use completed four conditions in a within-sub jects, counterbalanced design: 60 min of (i) cycling at 60% VO2peak or (ii) quiet rest following placebo consumption, (iii) cycling, or (iv) quiet res t following the consumption of a high dose of caffeine. Each condition was performed twice from 1615-1715 h and followed by all-night polysomnographic recording. Subjects consumed two blinded 200-mg capsules of either lactose placebo or caffeine upon awakening, at 1600 h, and 2 h before bedtime. Sta te anxiety was assessed at bedtime. Criterion scores consisted of the mean data across the two days in each condition. Sleep data were analyzed using a condition (exercise versus quiet rest) by drug (caffeine versus placebo) repeated-measures ANOVA. Caffeine elicited sleep disturbance that was less than previously reported. Exercise attenuated selected sleep disturbances t o a small degree. In general, the effects of exercise on sleep were not gre ater following caffeine compared to placebo. Indeed, increases in slow-wave sleep after exercise were approximately 1/3 smaller following caffeine tre atment compared to placebo. (C) 2000 Elsevier Science Inc. All rights reser ved.