How does exercise affect sleep duration and quality?
Max Hirshkowitz, PhD
Experts universally endorse sleep, exercise, and nutrition as the building blocks for good health. The interrelationship between these three elements also provides grist for the mill of scientific inquiry. The manner in which exercise alters sleep has long been researched. The obvious, widely recognized, and commonly self-realized sleep quality improvements associated with exercise has lead to adopting the canon “maintain a regular exercise program” as one of the veritable 10-commandments of sleep. Furthermore, studies show that this applies not just to young, but to older adults as well .
In addition to self-rated sleep quality and overall sleep duration, sleep scientists like to spotlight the underlying sleep architecture. Sleep is not one thing; it is composed of several different processes. It appears that each of these different types of sleep seem to be independently important. Each has its own homeostatic process; that is, selectively depriving a person of a particular type of sleep leads to preferential rebound of that sleep process when the person is allowed to sleep normally. And although the exact underlying function for each type of sleep remains an item of debate, sleep experts generally agree each is important. The types of sleep include slow wave sleep (often characterized as important for body repair and maintenance), rapid-eye-movement (REM) sleep (during which dreams typically occur), and N2 sleep which constitutes more than half of our overall sleep time.
To summarize consistent trends in current body of knowledge, researchers apply meta-analytic techniques to systematically distill major findings. In one meta-analysis, Youngstedt, O’Connor, and Dishman  reviewed 38 separate studies exploring the relationship between sleep and exercise. Consistent findings included exercise-related increased total sleep time, increased slow wave sleep time, decreased REM sleep time, and prolonging latency to REM sleep. Changes were small but consisted but did occur in subjects who were already good sleepers. While Youngstedt and colleagues reviewed studies focused on acute exercise, another meta-analysis found similar changes resulting from chronic exercise .
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