The worst time to exercise for a good night's sleep

IF YOU'D like to sleep well tonight, you should probably avoid exercising this evening, especially if your workout will be intense.

- GRETCHEN REYNOLDS

That's the takeaway from a new study of almost 15 000 active men and women. It found that exercising within about four hours of bedtime makes it harder to fall asleep and reduces how long you spend slumbering by as much as 43 minutes.

The effects were most pronounced when workouts were long, intense or both, but almost any evening exercise influenced how well people slept.

“I do my best now to avoid exercising late in the evening,” said Josh Leota, a researcher at Monash University in Australia, who led the new study.

But there may be ways to minimise the effects if evening happens to be the only time you can — or care to — work out.

For decades, researchers have been puzzled by the relationship between sleep and exercise. According to most past research, active people sleep better than the sedentary, but not always. Some studies suggest morning workouts improve sleep, while later workouts don’t.