Effects of Exercise on Sleep

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Top Contributors - Sai Kripa, Pacifique Dusabeyezu, Kim Jackson and Sehriban Ozmen  

Introduction

Sleep is defined as a reversible behavioral state of perceptual disconnection from and impassiveness to the surroundings. It is usually divided into two sleep states, namely rapid eye movement (REM) sleep, non-rapid eye movement (NREM) sleep. While sleeping at night there is a sequential rotation occurs quite a lot of times (5 to 6 times) among these two sleep states. According to American sleep association, there are many sleep disorders that humans suffer from; including dyssomnias such as Sleep Apnea, Hypersomnia and Insomnia; Bruxism; parasomnias such as REM Behavior Disorder and sleepwalking, and circadian rhythm sleep disorders. Furthermore, sleep disorders are so common among individuals and it could lead to chronic sleep deprivation which is completely dangerous. There are numerous pharmacological interventions available to treat these sleep disorders, however one of the best non-pharmacological intervention approved by American Sleep Disorders Association regarding improving your sleep is considered to be Exercise, Wide epidemiological studies indicate that the general population recognizes the therapeutic and sleep promoting advantages of moderate to regular physical activity. Also, there are few researches that has been conducted on subjects to identify the effects of exercise upon sleep quality and quantity. Since exercise induces physical exhaustion, moreover its physiological and psychological calming effects are well known, it can be obvious to assume that exercise promotes sleep. 

Exercise and Insomnia

Two recent studies suggest improvement in sleep that has been performed to test the effect of exercise training among insomniacs. Guilleminault et al randomly allocated 3 separate 4-week therapies to 30 individuals (average age 44) who had psychophysiologic insomnia. The first set of intervention included sleep hygiene education, such as motivating the individuals to maintain a fixed sleep-wake schedule and to ignore daytime napping. The second set of intervention included sleep hygiene education and light therapy that involved individuals to sit in front of a bright light (3,000 lux) for 45 minutes beginning 5 minutes after awakening. The third set of intervention included sleep hygiene education and 45 minutes of brisk daily walking in the early evening. According to evidence, there has been an exercise-related improvement in sleep probably due to individual's exposure to outdoor light during exercise and at other times of the day. Apart from outdoor exposure, the improvement would have also been due to individual's different expectations for improved sleep associated with each protocol.

In another report, King et al randomly assigned 43 older people (age 50 to 76) with moderate sleep complaints to an exercise program for 16 weeks or to a waiting list control condition. During the day or early evening, the exercise group performed 30-40 minutes of moderate aerobic exercise 4 times per week. Based on sleep diaries and the Pittsburgh Sleep Quality Index, the exercise group showed considerably higher improvements in sleep. Nevertheless, on observing at these handful of evidences that have been performed suggest that exercise significantly improves the sleep of people with insomnia. 

Acute Exercise and Sleep

A recent meta-analysis of 38 studies carried out by Youngstedt et al examined the mean impact of acute exercise on sleep. Additionally, these studies pay attention exclusively on subjects who are good sleepers. Even the sleeping pills can have little effect on healthy sleepers. The small size of the results relating to exercise does not inherently undermine their meaning.

In all studies, sleep was assessed by polysomnography and the analysis concluded that:

• No effects on the amount of time it took to fall asleep;
• Statistically significant yet marginal improvement in overall sleep time (average 10 minutes) and slow-wave sleep time (average 4 minutes)
• Statistically significant but limited decrease in rapid eye movement ( REM) sleep (average 7 minutes), increases in the time for REM sleep to occur following sleep onset (average, 13 minutes).

Although the research focused on healthy sleepers, the results reveal nothing about the impact of acute exercise on sleep disorder sufferers. Furthermore, there are lack of evidence to prove the effects of acute exercise in such individuals.

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