Sleep Health | Sleep Review
Exercise is often positively associated with a good night’s sleep. But when done at certain times of the day or just before bedtime, it can also alter our sleep. And yet, despite years of study, we still don’t know much about how the two are connected.
A new meta-analysis by Concordia researchers published in the journal Sleep Medicine Reviews evaluated data from 15 published studies to see how a single session of vigorous exercise affected young and medium-sized healthy adults in the hours leading up to bedtime affects.
And while no two bodies are alike, the researchers found that the combination of factors worked together to improve or modulate the effects of exercise on sleep.
“When we reviewed the literature on this work, we found that there were a lot of mixed results,” said Melodee Mograss, PhD, a cognitive neuropsychologist and researcher at PERFORM Sleep Lab, in a press release. “Some depended on the training time, others on the fitness level of the study participants or even on the type of exercise.”
Timing is (almost) everything
Emmanuel Frimpong, postdoctoral fellow at Sleep, Cognition and Neuroimaging Lab and lead author of the study, says their main goal is to assess whether high-intensity exercise affects sleep afterwards and what factors might affect that sleep.
The researchers combined data from the 15 studies and performed a statistical analysis that included variables such as when to exercise – early evening or late evening – and the hours between stopping exercise and bedtime – less than two hours, about two hours and two to four hours.
Further variables were the fitness level of the participants (sedentary or physically active), the threshold intensity and the duration of the exercises. They also analyzed how certain sports affected sleep.
“Overall, our analysis showed that there were sleep benefits when training ended two hours before bed, including encouraging falling asleep and staying longer,” says Frimpong.
“On the other hand, sleep was negatively affected if training ended less than two hours before bedtime. It took longer for the participants to fall asleep and the duration of sleep was shortened. “
The further analysis provided the following results:
- High-intensity exercise in the early evening promoted falling asleep and improved sleep time, especially when performed by sedentary people.
- High-intensity exercise done between 30 and 60 minutes also improved onset and duration.
- It was found that cycling exercises benefited participants the most in terms of onset and deep sleep.
- However, regardless of the point in time, high-intensity training contributed to a slight decrease in the REM sleep phase (rapid eye movement phase), the sleep phase that is often associated with dream experiences. Studies suggest that reducing REM sleep can negatively impact cognitive tasks when the information is complex and emotionally stimulating, but not when the information is simple or neutral.
Various effects for early risers and night owls
“Based on our review, healthy young and mid-adult adults with no history of sleep disorders should be given evening exercises in the early evening whenever possible,” says Frimpong.
“The individual should also adhere to a uniform training plan, as training at different times of the evening can lead to sleep disorders. Individuals should also consider whether they are morning or evening people. High-intensity exercise in the late evening can cause insomnia in morning people.
“And last but not least, sleep hygiene strategies should also be implemented, such as showering between stopping exercising and going to bed and avoiding heavy meals or drinking a lot of water before bed.”
Master’s student Tehila Zvionow and Thien Thanh Dang-Vu, Professor at the Department of Psychology and the Concordia University Research Chair in Sleep, Neuroimaging and Cognitive Health, also contributed to the work.
Photo above: “Our analysis showed that there were sleep benefits when training ended two hours before bed, including encouraging falling asleep and sleeping longer,” say Emmanuel Frimpong (left) and Melodee Mograss. Photo credit: University of Concordia