The Claim: Exercise More During the Day, and You Will Sleep Better at Night

THE FACTS It has long been said that regular physical activity and better sleep go hand in hand. Burn more energy during the day, the thinking goes, and you will be more tired at night.

But only recently have scientists sought to find out precisely to what extent. One extensive study published this year looked for answers by having healthy children wear actigraphs — devices that measure movement — and then seeing whether more movement and activity during the day meant improved sleep at night. The results should be particularly enlightening to parents.

The study found that sleep onset latency — the time it takes to fall asleep once in bed — ranged from as little as roughly 10 minutes for some children to more than 40 minutes for others. But physical activity during the day and sleep onset at night were closely linked: every hour of sedentary activity during the day resulted in an additional three minutes in the time it took to fall asleep at night. And the children who fell asleep faster ultimately slept longer, getting an extra hour of sleep for every 10-minute reduction in the time it took them to drift off.

Studies on adults have reached generally similar results, showing that an increase in physical activity improves sleep onset and increases sleep duration, particularly in people who have trouble sleeping.

THE BOTTOM LINE Studies suggest that being more physically active can lead to better sleep.