It’s pretty well established now that exercise is good for sleep. Compared with couch potatoes, exercisers generally fall asleep more quickly, sleep more soundly, and feel more alert during the day.
The timing of your workout can also affect your sleep. Lack of exposure to sunlight can be a setup for insomnia, and now that the days are short, you may be able to improve your sleep by making exercise more regular or exercising at a different time of day.
First, let’s look at a new study that turns conventional thinking on its head. You’ve probably read that you shouldn’t exercise too close to bedtime. Exercise increases your heart and breathing rate, increases the stress hormones circulating in the blood, and delays secretion of melatonin. None of this is compatible with sleep—when your body is in rest-and-relax mode.
Still, there’s little evidence that vigorous exercise in the run-up to bedtime is harmful to sleep. So Swiss researchers set out to study the effects of evening exercise on 52 young adults who routinely exercised 2 or 3 nights a week. Specifically, they wanted to find out if the amount of exertion in the hours before bedtime would have a negative effect on sleep.
Following an evening of normal exercise, subjects were hooked up to an EEG machine for the recording of brain activity during sleep. In bed, they completed a questionnaire to assess how vigorously they’d exercised and how they felt. Then the EEG recordings began, no more than 70 minutes after exercise stopped.
Surprisingly, the more vigorous the exercise,
- the more tired subjects felt
- the more quickly they fell asleep
- the deeper and more efficient their sleep was, and
- the fewer awakenings they had.
Not only did the results show that vigorous exercise late in the evening was not harmful to sleep. On the contrary, it actually improved sleep in many ways.
This study shows that evening workouts may be beneficial to the sleep of healthy young adults. Whether the results would generalize to other populations is still unknown, but the results bode well for people who want to exercise but can’t find time during the day.
Exercise and the Circadian System
What about people with insomnia and older adults? Evening exercise may be OK for us (or not), but when should we exercise to maximize our chances for sound sleep? Following is the gist of what little is known.
One key to using exercise to benefit sleep is to make the activity regular. Scheduled exercise is known to improve the function of the circadian system, and sleep tends to be more stable when internal rhythms are in sync.
Sunlight is the main external cue that keeps your internal circadian rhythms in sync with the earth’s 24-hour light/dark cycle. But exercise has a lesser synchronizing effect on circadian rhythms. Especially near the winter solstice, when you’re exposed to the least amount of sunlight all year, regular exercise may be a good way to keep insomnia at bay.
The Best Time of Day
Regarding optimal timing, one study found that long-term fitness training in the middle of the day improved the consolidation of the sleep/wake cycle in older men.
Other studies suggest that in older adults with insomnia, sleep quality is more likely to improve with exercise scheduled late in the afternoon or early in the evening. Research from the 1980s is supportive of this claim. Exercise heats the body up and eventually triggers an internal cooling mechanism favorable to sleep—specifically, deep sleep. So you may be able to improve the quality and depth of your sleep by scheduling exercise sessions later in the day. I have.
But the timing of your workout may be less important to sleep than doing it at the same time every day. So experiment to find out when exercise is more appealing (or least unappealing!) and seems to help with your sleep. Then make it part of your routine.
If you exercise, when do you do it, and does it help your sleep?