Does night-time exercise really disturb sleep?

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By Dr. Simon Kyle

Science supports a link between exercise and improved sleep quality but it is commonly believed that exercising too close to bedtime may actually disrupt sleep. Indeed, sleep hygiene advice – lifestyle and environmental recommendations to help optimize sleep – typically suggest avoiding exercise proximal to the sleep period. However, experimental evidence for this statement is actually quite sparse and indeed there are theoretical reasons – exercise-related reductions in anxiety and muscle tension, declining body temperature and sleep-onset – for thinking that exercise may actually improve sleep.

A new study published in the journal Sleep Medicine has examined whether evening exercise disrupts sleep in a large representative sample of 1000 adults in the US. Participants were asked about their sleep in the past two weeks, reporting information on sleep quality, total sleep time, latency to fall asleep and waking up feeling unrefreshed. A physical activity questionnaire was also completed, probing exercise intensity and timing (separating participants into three groups: exercise taking place more than 8 hours before sleep; taking place between 4-8 hours prior to sleep; and taking place less than 4 hours prior to sleep).

Results indicated that, overall, exercise intensity was related to improved sleep outcomes. When looking at exercise timing, it was found that evening moderate or vigorous exercisers did not differ in their sleep outcomes from non-exercisers. Moreover, the majority of evening exercisers felt that they slept better or that there was no difference, relative to when they did not exercise. Consistent with previous research morning vigorous exercisers reported the best sleep outcomes.

The authors suggest that sleep hygiene recommendations may need to be reviewed:

“In general, morning exercisers were most likely to report good sleep quality and optimal sleep duration and least likely to awaken unrefreshed. Thus, morning exercise may be an optimal time for regular exercise with respect to sleep quality. However, evening exercising was not associated with disturbed sleep, even among those who identified themselves as poor sleepers. These data suggest that, with respect to good sleep, it is better to exercise than not exercise, even if the only time to exercise is close to bedtime.”

Reference:
Buman, M.P., Phillips, B.A., Youngstedt, S.D., Kline, C.E., Hirshkowitz, M. (2014). Does nighttime exercise really disturb sleep? Results from the 2013 National Sleep Foundation Sleep in America Poll. Sleep Medicine, 15(7), 755-761.

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