It’s well established that physical activity—especially aerobic exercise like biking or running—helps people to sleep better.
For example, one research study examined the effects of aerobic exercise among people with chronic insomnia who were sleeping on average less than 6 hours per night. The researchers divided participants into two groups. Both received education about good sleep habits, but one of the groups also was assigned to do aerobic exercise.
As expected, sleep education alone did little to improve sleep. After 16 weeks, the average person in that group got just 12 minutes more sleep per night. However, the group that added exercise saw a tremendous benefit from treatment—on average, an additional hour and 15 minutes of sleep per night.
Armed with this sort of knowledge, people with insomnia might work out with the hope that they'll sleep well that night. However, we often sleep no better on days we exercise than on days we don’t.
How can we reconcile these seemingly contradictory observations?
In a follow-up to the study described above, the same group of researchers set out to determine how exercise might have improved sleep: Specifically, did exercise improve sleep on the same day?
Perhaps surprisingly, the answer was no: Exercise did not have a same-day effect on sleep. 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 size of the studies and the fact they the participants were primarily older women. But assuming that the results are reliable and can generalize to other groups (especially younger adults and males), they have important implications for individuals battling insomnia. Specifically, 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 of the sleep benefits of exercise, and not be discouraged if same-day sleep is unaffected. Don't give up on exercise too soon if you're battling insomnia. The time and energy invested may still be well worth the effort since exercise helps not only with insomnia, but with conditions like depression and anxiety—not to mention the benefits for your general health.
Portions of this post appeared on sethgillihan.com.