Washington DC, Dec 16(DC): Turns out, exercising four hours before going to bed does not have a negative effect on sleep.

Even among sleep researchers, it is a widely held belief that sleep quality can be improved by avoiding exercise in the evening. However, according to researchers from the Institute of Human Movement Sciences and Sport, it is not generally true.

The scientists concluded that "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."

By combining the data from the different studies, the researchers showed that in the night after study participants had done some sport in the evening, they spent 21.2 percent of their sleeping time in deep sleep. Following an evening without exercise, the average figure was 19.9 percent. While the difference is small, it is statistically significant. Deep sleep phases are especially important for physical recovery.

However, vigorous training within an hour before bedtime is an exception to the rule.