Proceedings of The Physiological Society

Sleep Sleep and Circadian Rhythms (London, UK) (2018) Proc Physiol Soc 42, C15

Poster Communications

Effects of sleep extension and sleep restriction on the performance and cardiac autonomic function of endurance cyclists

S. Roberts1, W. Teo1, B. Aisbett1, S. A. Warmington1

1. Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia.

Sleep is considered the most important recovery behaviour for athletic success(1). While there is evidence that sleep may affect endurance performance(2), no study has investigated the effects of sleep on the sport-specific performance of trained endurance athletes. In addition, while indices of cardiac autonomic function are increasingly being used to monitor athlete wellbeing(3), little is known of the effects of sleep on such indices. In a balanced crossover experiment, endurance cyclists (n=9) completed three trials; normal sleep (NORS), sleep restriction (SRES), and sleep extension (SEXT). Each trial required cyclists to complete a time trial (TT) - based on predicted work achievable in one hour when cycling at anaerobic threshold - on four consecutive mornings (TT1 - TT4). Cyclists slept habitually prior to TT1 of each trial. However, on the three subsequent nights time in bed either; remained as normal (NORS), was restricted by 30% (SRES), or was extended by 30% (SEXT). A 7-day washout period separated each trial. Actigraphy (sleep-wake threshold 40 counts/min) was used to monitor sleep. Performance time (to the nearest second) and rating of perceived exertion (6-20 scale) were recorded for each TT. Prior to each TT, resting heart rate (HR), HR variability (Ln rMSSD), maximal rate of HR increase during submaximal exercise, HR recovery following submaximal exercise, mean response time during a psychomotor vigilance task (PVT), and mood disturbance were recorded. Data were analysed using a Generalised Estimating Equations approach. On each of the three sleep intervention nights, total sleep time was higher (P=0.000) in the SEXT trial compared with both NORS and SRES, and lower (P=0.000) in the SRES trial compared with NORS. TT4 was faster in the SEXT trial (mean±SD, 3409±187sec) compared with both the NORS (3521±204, P=0.013), and SRES (3718±312, P=0.010) trials. Rating of perceived exertion, resting HR, resting Ln rMSSD, maximal rate of HR increase at the onset of submaximal exercise, and HRR following submaximal exercise were unchanged between trials. Prior to TT4, total mood disturbance was higher in the NORS (13±18au, P=0.002) and SRES (28±12, P=0.000) trials compared with SEXT (4±10). Prior to TT3, mean response time was faster in the SEXT trial (346±27ms) compared with SRES (374±31, P=0.008) and NORS (360±28, P=0.021). Prior to TT4, mean response time was faster in the SEXT trial (332±29) compared with both NORS (363±28, P=0.000) and SRES (392±40, P=0.000). Sleep extension for three nights enabled cyclists to better maintain performance compared with normal sleep and sleep restriction. Cardiac autonomic indices were not sensitive to changes in sleep duration. Better mood and vigilant attention following sleep extension suggests psychological factors may explain the effects of sleep on endurance performance.

Where applicable, experiments conform with Society ethical requirements