Sleep and exercise: A reciprocal issue?

Summary

Sleep and exercise influence each other through complex, bilateral interactions that involve multiple physiological and psychological pathways. Physical activity is usually considered as beneficial in aiding sleep although this link may be subject to multiple moderating factors such as sex, age, fitness level, sleep quality and the characteristics of the exercise (intensity, duration, time of day, environment). It is therefore vital to improve knowledge in fundamental physiology in order to understand the benefits of exercise on the quantity and quality of sleep in healthy subjects and patients.

Conversely, sleep disturbances could also impair a person's cognitive performance or their capacity for exercise and increase the risk of exercise-induced injuries either during extreme and/or prolonged exercise or during team sports.

This review aims to describe the reciprocal fundamental physiological effects linking sleep and exercise in order to improve the pertinent use of exercise in sleep medicine and prevent sleep disorders in sportsmen.

Introduction

Over the last decade exercise has been extensively recommended as a major factor for improved health in the general population, in the elderly and in many groups with chronic diseases such as obesity, type 2 diabetes, cardiovascular diseases, depression and even cancer [1], [2]. Increasing exercise has been found beneficial for reducing weight, preventing pain, improving mood and enhancing the quality of sleep in patients with insomnia [1], [3], [4], [5].

Getting sufficient sleep has also been recommended as insufficient sleep has been identified as an associated risk factor for major public health concerns: obesity, type 2 diabetes, cardiovascular diseases, depression and accidents [6], [7], [8]. Sleeping 7–8 h has systematically been found to be associated with lower risks of morbidity and mortality.

However it is still difficult to understand exactly how exercise impacts on sleep and vice versa. In particular, very frequent associations have been found between sleep loss and exercise-induced injuries [9], [10] suggesting physiopathological interactions between sleep and injuries. Conversely, good sleeping habits and moderate physical activity could be mutually beneficial [11], [12], [13] and trigger a virtuous circle that improves fitness, particularly in sleep disorders patients.

The aim of this review is therefore: 1) to understand how exercise affects sleep physiology, via its impact on temperature, cardiac and autonomic function and the endocrine and immune systems; 2) to clarify how the duration of sleep affects exercise (exploring the impact of sleep loss, sleep restriction ad sleep extension); 3) to observe the reciprocal influence between sleep disorders (insomnia and sleep apnea) and exercise.