Proceedings of The Physiological Society

Sleep Sleep and Circadian Rhythms (London, UK) (2018) Proc Physiol Soc 42, C14

Poster Communications

High intensity interval running increases cardiac autonomic activity but does not disrupt subsequent night's sleep in trained runners.

C. Thomas1

1. Research institute for sport and exercise sciences, Liverpool John Moores University, Liverpool, United Kingdom.

Background: Observational studies have shown sleep quality in athletes is reduced after training sessions. As such, this period is considered a big obstacle to athletes' recovery, which could hinder future performances. High intensity exercise training in the evening is one of several factors that may explain this phenomenon through its effect on cardiac autonomic activity. Yet, no research has studied the impact of high intensity exercise on sleep within a trained cohort, making it impossible to discern whether it has a positive or negative effect on sleep. The aim of this study was to investigate the effect of exercise intensity on cardiac autonomic activity and subsequent night's sleep in trained runners. Methods: Eight trained male runners (age: 27.8±6.9yrs; height: 1.8±0.1m; weight: 73.5±5.3kg and VO2 max: 57± completed three experimental trials in a randomised, counterbalanced study design. Following a standardised afternoon meal (2g participants either performed: i) a 1h high intensity interval running session (6x5 min @60% VO2 max interspersed with 6x5 min @90% VO2 max); ii) a 1h low intensity running session (45% VO2 max); iii) no exercise. Exercise sessions were performed at 18.00h prior to a fixed bedtime of 22:30h. Sleep was assessed in a temperature controlled laboratory using overnight polysomnography and cardiac autonomic activity was recorded via electrocardiography. A one-way repeated measures ANOVA was performed to compare sleep variables and measures of cardiac autonomic activity between exercise intensities. Results: There were no changes in average nocturnal heart rate variability after exercise but average nocturnal heart rate was higher after high intensity interval running than low intensity running (50±5 bpm v 47±5 bpm, p = 0.02) and no exercise (50±5 bpm v 47±5 bpm, p = 0.028). In the polysomnography analysis, total sleep time, sleep efficiency and wake after sleep onset were improved after high intensity interval running and low intensity running compared with no exercise (p < 0.05). Conclusions: High intensity interval running increases cardiac autonomic activity but does not disrupt subsequent night's sleep compared to no exercise in trained runners. It should be considered that poor sleep on the night following a single training session in the evening is not caused by exercise intensity. Future research is warranted to determine if other stressors that are encountered by athletes after intense exercise training cause sleep disruption such as muscle damage and glycogen depletion.

Where applicable, experiments conform with Society ethical requirements