A New Study Just Debunked This Common Myth About Exercise & Sleep

You've probably heard the popular belief that working out close to bedtime can mess with your sleep/wake cycle, since it gives you a boost of energy right as you're trying to catch some Z's. However, research is showing that this common thinking is actually a misconception after all. Exercise before bed won't actually keep you awake at night, says the study published in Sports Medicine. In fact, it may even have a positive impact when it comes to getting restful sleep.

Researchers from the Institute of Human Movement Sciences and Sport at ETH Zurich analyzed and collected data from 23 studies that pertained to exercising at night, and potential sleep issues, according to a press release. Interestingly, they discovered that working out within four hours of bedtime generally doesn't negatively impact quality of sleep.

"It is well known that doing exercise during the day improves sleep quality. Now we have shown that, at the very least, exercising in the evening doesn't have a negative effect," Dr. Christina Spengler, the Deputy Head of the Exercise Physiology Lab at ETH Zurich, said in the press release. "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."

After analyzing their data, Spengler and the other researchers found that people who exercised even a small amount in the evening spent 21.2 percent of their time asleep in deep sleep. However, after going an evening without exercise, that number decreased to 19.9 percent. So, though it's only a small difference, exercise before bed may be a good thing — despite what most of us were told.

Nevertheless, the new research did indicate one exception: High intensity exercise sessions at night could still have a slightly negative impact when it comes to quality of sleep. In one study analysis, people who completed a rigorous workout close to bedtime had a more difficult time falling asleep, which was attributed to not enough recovery time before hitting the hay. On average, their heart rate was still 20 beats per minute above a normal resting heart rate. However, Spengler explained in the press release, "This preliminary observation [surrounding rigorous exercise at night] is based on just one study."

Spengler added that, "As a rule of thumb, vigorous training is defined as training in which a person is unable to talk," and is typically how professional athletes train. Most of us, whether doing cardio or weightlifting, would still most likely fall within the zone of moderate exercise.

"People can do exercise in the evening without hesitation. The data shows that moderate exercise in the evening is no problem at all," said Jan Stutz, a doctoral student and lead author of the study.

Ultimately, this analysis of close to two dozen studies dispels the myth that exercising too close to bedtime will mess with your sleep. When it comes down to it, it's all about your personal preference: Whether you like exercising in the A.M., or at night, your fitness routine will most likely help you sleep better in the long run.