Exercise has had a Goldilocks problem, with experts debating just how much exercise is too little, too much or just the right amount to improve health and longevity.

New, impressively large-scale studies provide some clarity, suggesting that the ideal dose of exercise for a long life is a bit more than many of us currently believe we should get, but less than many of us might expect. The studies also found that prolonged or intense exercise is unlikely to be harmful and could add years to people’s lives.

These new studies, both of which were published last week in JAMA Internal Medicine, helpfully tackle those questions.In the broader of the two studies, researchers with the National Cancer Institute, Harvard University and other institutions gathered and pooled data about people’s exercise habits from six large, ongoing health surveys, winding up with information about more than 661,000 adults, most of them middle-aged.

Those who met guidelines precisely, completing 150 minutes per week of moderate exercise, enjoyed greater longevity benefits and 31 percent less risk of dying during the 14-year period compared with those who never exercised.

The sweet spot for exercise benefits, however, came among those who tripled the recommended level of exercise, working out moderately, mostly by walking, for 450 minutes per week, or a little more than an hour per day. Those people were 39 percent less likely to die prematurely than people who never exercised.

Still, the associations were strong and consistent and the takeaway message seems straightforward, according to the researchers.

Anyone who is physically capable of activity should try to “reach at least 150 minutes of physical activity per week and have around 20 to 30 minutes of that be vigorous activity,” says Klaus Gebel, a senior research fellow at James Cook University in Cairns, Australia, who led the second study. And a larger dose, for those who are so inclined, does not seem to be unsafe, he said.

Gretchen Reynolds
NY Times