It’s well established that exercise–especially aerobic exercise like biking or running–helps people to sleep better. However, people with insomnia sometimes find that they sleep no better on days they exercise than on days they don’t. Recent studies may help us to reconcile these seemingly contradictory observations.
In a 2010 study researchers compared the effects of 16 weeks of aerobic exercise plus education about good sleep habits versus sleep education alone; all participants had chronic insomnia, sleeping on average less than 6 hours per night. After 16 weeks, the average person in the exercise condition was sleeping an hour and 15 minutes longer per night, compared to just 12 minutes longer among the group that got only sleep education.
In a more recent study, the same group of researchers explored how exercise might have improved sleep. Specifically, did it improve sleep on the same day as the person exercised? The answer was surprising: Exercise did not have a same-day effect on sleep quality. However, people exercised longer after having gotten a better night’s sleep–that is, better sleep led to better exercise, not the reverse.
Certain caveats should be kept in mind, such as the relatively small sample sizes in the studies and the fact they the research participants were primarily older women.
Assuming that the results are reliable and generalize to other groups (especially males and younger men and women), they have important implications for individuals battling insomnia. While adding aerobic exercise–around 30 minutes 3 times per week–is likely to improve sleep, the effects probably won’t be immediate. For this reason it’s important to take a long view on the sleep benefits of exercise, and not be discouraged if same-day sleep is unaffected. The time and energy may be well worth the effort since exercise helps not only with insomnia but with other conditions like depression and anxiety–not to mention the effects on general health.