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Erschienen in:
01.12.2014 | Original Article
Combined caffeine and carbohydrate ingestion: effects on nocturnal sleep and exercise performance in athletes
Erschienen in: European Journal of Applied Physiology | Ausgabe 12/2014
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Purpose
In athletes, caffeine use is common although its effects on sleep have not been widely studied. This randomised, double-blind, placebo-controlled crossover trial investigated the effects of late-afternoon caffeine and carbohydrate-electrolyte (CEB) co-ingestion on cycling performance and nocturnal sleep.
Methods
Six male cyclists/triathletes (age 27.5 ± 6.9 years) completed an afternoon training session (TS; cycling 80 min; 65 % VO2max) followed by a 5 kJ kg−1 cycling time trial (TT). Caffeine (split dose 2 × 3 mg kg−1) or placebo was administered 1 h prior and 40 min into the TS. A 7.4 % CEB (3 ml kg−1 every 15 min) was administered during the TS, followed 30 min after by a standardised evening meal. Participants retired at their usual bedtime and indices of sleep duration and quality were monitored via polysomnography. Data: mean ± SD.
Results
All participants performed better in the caffeine TT (caffeine 19.7 ± 3.3; placebo 20.5 ± 3.5 min; p = 0.006), while ratings of perceived exertion (caffeine 12.0 ± 0.6; placebo 12.9 ± 0.7; p = 0.004) and heart rate (caffeine 175 ± 6; placebo 167 ± 11 bpm; p = 0.085) were lower in the caffeine TS. Caffeine intake induced significant disruptions to a number of sleep indices including increased sleep onset latency (caffeine 51.1 ± 34.7; placebo 10.2 ± 4.2 min; p = 0.028) and decreased sleep efficiency (caffeine 76.1 ± 19.6; placebo 91.5 ± 4.2 %; p = 0.028), rapid eye movement sleep (caffeine 62.1 ± 19.6; placebo 85.8 ± 24.7 min; p = 0.028) and total sleep time (caffeine 391 ± 97; placebo 464 ± 49 min; p = 0.028).
Conclusions
This study supports a performance-enhancing effect of caffeine, although athletes (especially those using caffeine for late-afternoon/evening training and competition) should consider its deleterious effects on sleep.