While exercise is often linked with a restful night’s sleep, whether performed at particular times of the day or soon before bed, it may also change our sleeping patterns. Despite years of research, however, there is still much unknown regarding the connection between the two.
A recent meta-analysis conducted by researchers at Concordia University in Canada and published in the journal Sleep Medicine Reviews examined the effects of a single session of intensive exercise on individuals. In the hours before night, healthy young and middle-aged people.
And, although no two bodies are identical, the researchers discovered that a variety of variables combine to increase or decrease exercise’s impact on sleep.
“When we conducted a study of the literature on this subject, we discovered many contradictory findings,” says Melodee Mograss, a cognitive neuropsychologist, and researcher at the PERFORM Sleep Laboratory. “Some were dependent on the time of exercise, while others depended on the research participants’ fitness level or even the kind of exercise.
Emmanuel Frimpong, a postdoctoral researcher at the Sleep, Cognition, and Neuroimaging Laboratory and the study’s lead author, says that the study’s primary goal was to determine if high-intensity exercise affected subsequent sleep and what variables could impact it.
The researchers pooled the data from the 15 trials. They conducted a statistical analysis, examining factors such as the time of exercise – early or late afternoon – and the hours between exercise cessation and the end of the day, approximately two hours before bedtime, about two hours before bedtime, and between two and four hours before bedtime.
Other factors were:
The individuals’ physical state (sedentary or physically active).
The threshold intensity.
The length of the activities.
Additionally, they examined the effect of various kinds of exercise on sleep.
“Overall, our study revealed that when activity was stopped two hours before bedtime, there were sleep advantages, including improved sleep onset and duration,” Frimpong adds. “However, when exercise was discontinued less than two hours before night, sleep was compromised. Participants took longer to fall asleep and slept for shorter periods.
A more thorough study showed that high-intensity exercise done first thing in the evening promoted the start and duration of sleep, particularly in inactive individuals, as did high-intensity exercise performed between 30 and 60 minutes. Cycling activities are the most effective for individuals in terms of sleep onset and depth.
However, regardless of the period, high-intensity exercise led to a slight reduction in the rapid eye movement (REM) phase of sleep, often linked with sleep experiences.
Reduced REM sleep has been shown to negatively affect cognitive activities when the material is complex and emotionally arousing, but not when the content is neutral or straightforward.
“Our study concluded that healthy, young and middle-aged people with no history of sleep problems should do night workouts first thing in the evening, if possible,” Frimpong writes.
“Individuals should also adhere to a regular exercise routine, since exercising at various hours of the night may result in sleep disturbances,” he says. “You must also consider if you are a morning or evening person. Late afternoon exercise at a high-intensity level may induce sleep problems in morning persons.
“And lastly, sleep hygiene measures such as bathing between exercise cessation and bedtime should be used, as should avoiding big meals or drinking lots of fluids before night,” he advises.