By Ken Mallows
The argument about exercising at night and its effect on sleep seems endless. Some health care professionals believe that exercising at night only serves to energize you, raise heart rate and body temperature, releases stimulating epinephrine, and therefore keeps you awake when you want to fall asleep.
The question is an important one because some people can only find the time to exercise after work, after chores, after dinner. At night. And, some folks are just not morning exercise types. They simply can't do it.
A 2011 study published in the Journal of Sleep Research suggests that night exercise may impair sleep, but in ways that may not matter so much. The report stated: "This study showed that relatively short vigorous exercise 2-2.5 hours before bedtime did not influence HRV [heart rate variability] or objective sleep quality but was sufficient to increase HR [heart rate] and stress vector during the first hour of sleep. Thus, our results are consistent with the general view that late-night exercise may impair sleep, and indicate that physiological stress reactions caused by exercise may be reflected in cardiac autonomic variables during sleep." That doesn’t mean that you're getting a bad night's sleep, just that your heart rate may be elevated and that may or may not be an issue for your particular sleeping regimen during the early hours of sleep.
Confused? Hold that thought…
A National Sleep Foundation 2013 poll found that 83 percent of people who exercised any time during the day – including night time – reported sleeping better than those who didn't exercise at all. Sounds simple but keep in mind that unlike the first study, the data here was self reported and subject to people's biases and opinions.
It appears that we're getting mixed messages. So what's the answer?
(There's also discussion in medical circles about what time of day you exercise yields the best fitness results, but that's another story.)
For the most part, exercising at any time will help you sleep better – but with a caveat. If you exercise at night, allow yourself time to wind down before getting into bed. Give your body the opportunity to relax, allow adrenaline levels to drop and give your brain a chance to quiet down. Ditto for your heart rate. You may be still mentally amped up from your exercise session where you were on high alert guarding against injuries, dodging pedestrians or keeping pace with an unrelenting treadmill's movement.
Most important, in this age of personalized medicine, do what works for you. If you find that evening or night exercising keeps you up, then don’t do it. Simple. If it makes no difference, then have at it.
One size does not fit everyone.