The exercise-sleep mystery

There remains little compelling evidence that acute or chronic exercise promotes sleep. However, a major limitation of the literature is that studies have focused on good sleepers for whom improved sleep is implausible. Thus, the fact that consistent, albeit small, effects of exercise on sleep have been found in this population may be reason for optimism. More promising sleep effects have been found for chronic exercise in poor sleepers, but such evidence has not clearly demonstrated that these effects can be attributed to exercise per se, and not other associated factors such as environmental bright light exposure. Exercise might, indeed, have a uniquely potent effect on sleep, but this must be established empirically, with careful experimental control and exploration of potential mechanisms. The payoff for such findings would be great since the health and life benefits of exercise are so well-established. This review will begin with a brief discussion of the definition and measurement of sleep. Next, the paper will discuss the incidence and consequences of insomnia, and the risks and limitations associated with pharmacologic and other nonpharmacologic sleep treatments. Finally, the paper will review the evidence that exercise promotes sleep.