ZURICH — Worried a little late night fitness will keep your heart racing into the overnight? Contrary to popular and previous scientific belief, a new study finds that hitting the gym and exercising in the evening has no effect on sleep quality or duration.

Researchers at the Institute of Human Movement Sciences and Sport at ETH Zurich analyzed 23 studies that met their quality standards and found that exercising four hours before hitting the sack does not have negative effects on sleep. Combining the data from the studies, the researchers found that the night after participants exerted physical activity, they spent 21.2 percent of their sleep time in deep sleep. This figure is similar to the average 19.9 deep sleep percentage overall.

“If doing sport in the evening has any effect on sleep quality at all, it’s rather a positive effect, albeit only a mild one,” notes study co-author Christina Spengler, head of the Exercise Physiology Lab at ETH Zurich, in a media release.

There was one exception: Only vigorous training within an hour of bedtime has a definitively negative effect on sleep patterns, the authors found. Analysis showed that study participants took longer to fall asleep if they exercised vigorously shortly before bedtime because their bodies aren’t recovered in that 60 minutes. Their heart rates were on average 20 beats higher per minute than those who didn’t exercise an hour before bed or less.

“It is well known that doing exercise during the day improves sleep quality,” says Spengler. “Now we have shown that, at the very least, exercising in the evening doesn’t have a negative effect.”

Jan Stutz, a doctoral student in Spengler’s research group and lead author of the analysis, agrees that people shouldn’t hesitate to exercise in the evening if they’re up for it. But

“Not everyone reacts to exercise in the same way, and people should keep listening to their bodies. If they notice they are having problems falling asleep after doing sport, they should try to work out a little earlier,”

The study was published in the journal Sports Medicine.

About Ben Renner

Writer, editor, curator, and social media manager based in Denver, Colorado. View my writing at

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