Does Sport harm my sleep in the evening?

Jogging in the park, soccer on the football field, volleyball on the beach: the longer the days are, the more time there is left to play sports outdoors. Basically great - however, exercise before going to bed can, under certain circumstances, harm sleep.

Anyone who lifts weights in the evening or swings on a racing bike sleeps worse, that is a common belief. Disturbed sleep in turn increases the risk of accidents, heart attacks, overweight and mental disorders.

The German Society for Sleep Research and Sleep Medicine (DGSM) points out in a guidebook that sports too short of bedtime can disturb sleep. New studies show a contradictory picture.

No intensive training before bedtime

Sports scientists from ETH Zurich evaluated 23 studies for a meta-analysis published in February in the journal "Sports Medicine". As a result, those who spend less than an hour at bedtime are in danger of taking longer to fall asleep and less sleep. On the other hand, the movement did not affect other aspects such as deep sleep phases or the frequency of waking up.

And the negative effects, mind you, only refer to intensive training very shortly before going to bed. In general, evening sports - ie sports less than four hours before going to bed - do not affect sleep.

On the contrary, late exercise could even promote sleep quality. However, the effect is small. "Similar to normal fluctuations from night to night and therefore probably clinically irrelevant," the scientists write.

Compared to previous single studies, the meta-analysis is quite meaningful. But she has limitations. Above all, the researchers did not compare evening sports with morning or afternoon athletes - but with non-athletes. In addition, only studies with persons without sleep disturbance were included. And it was almost exclusively normal-weight men between 19 and 28 years old.

Better sport in the evening than in the afternoon

In a study overview from the year 2015, however, US psychologists have juxtaposed sports at different times of the day. In addition, the study participants were from different age groups.

The researchers showed that people who had driven less than three hours before going to bed Sport, even more rarely woke up as those who had trained in the afternoon or early evening (three to eight hours before going to bed).

Other factors, such as how long it takes to fall asleep, did not affect the time of day. And the positive results were only for occasional sports (less than once a week). "There were not enough studies on regular sports that considered the time of day," the researchers said.

Even less research is available with regard to people who already suffer from sleep disorders. And that is in Germany, according to the federal government almost every third. Australian researchers have recently looked at evening sports especially in overweight men with sleep disorders - and found no evidence of worse sleep after exercise in the evening than in the morning or afternoon.

Many studies, few subjects

On the other hand, movement may well affect the biorhythm and, like light, act as a timer - a new study from the USA suggests.

The German guidelines for the treatment of sleep disorders explicitly make no statement about exercise as a therapeutic method - to the data is too thin.

That the study situation is still ambiguous, should also be due to the fact that usually only a few subjects are examined. Although the Swiss meta-analysis includes 23 studies - but only 275 people, ie an average of twelve people per study.

With a small number of participants, the risk that the results in other samples would look different increases. In fact, the results changed in part when the researchers excluded individual studies from the analysis. Say: The results are anything but robust.

Incidentally, scientists are still wondering what mechanisms evening sports should impair sleep at all. Higher body temperature? Aching? Heartbeat? Nocturnal hunger? Again, previous studies are not clear.


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