One study that looked at sleep quality and exercise in post-menopausal women found that 30 minutes of moderate intensity aerobics in the morning was most effective for improving sleep, while aerobic workouts in the evening made it more difficult to fall sleep – but not all studies concur.
Other research shows that evening workouts don’t make it harder to fall asleep, at least in normal healthy people without pre-existing insomnia problems. Exercise raises your core body temperature and floods your body with hormones like epinephrine and norepinephrine that hype you up, which isn’t necessarily a good thing when you’re trying to wind down. Exercise intensity may be a factor too. A 30-minute walk in the evening could make it easier to fall asleep, while a high-intensity interval workout might keep you awake.
A more recent study published in December of 2011 showed that aerobic exercise improved sleep in people with chronic insomnia regardless of whether they worked out in the morning or evening. Regular aerobic workouts out also improved their mood and overall quality of life. This would suggest that exercise makes for better sleep regardless of when you do it.
Does Weight Training Affect Sleep?
This isn’t an issue that’s been well-researched, but getting a good night’s sleep is important when it comes to building lean body mass. Growth hormone is secreted in a pulsatile fashion during sleep. This promotes tissue growth and repair, which is important for the strength-building process. It’s not clear whether strength-training has the same beneficial effects on sleep as aerobic exercise, but strength-training is a good stress reliever and that may contribute to better sleep.
The Bottom Line?
Regular moderate-intensity aerobic workouts are beneficial if you have problems sleeping. Most research shows that even exercise in the evening won’t keep you awake. On the other hand, it’s probably best to do high-intensity exercise earlier in the day to avoid greater increases in core body temperature and release of hormones that can hype you up.
Science Daily. “Moderate Exercise Can Improve Sleep Quality of Insomnia Patients” Sleep. 2003. Vol. 26, No. 7, pages 830-836. Journal of Applied Physiology. June 1978. Vol. 44. No. 6. 945-951. Sleep Med. 2011 Dec;12(10):1018-27. Epub 2011 Oct 22.