Short Bursts of Exercise Can Add up to Better Health

We should all be familiar by now with the government’s official Physical Activity Guidelines for Americans, which recommend that for substantial health benefits, adults should get at least 150 minutes per week of moderate exercise (or at least 75 minutes per week of vigorous exercise). Additionally, the guidelines state that this exercise should be performed in episodes of at least 10 minutes each; exercise performed in episodes of less than 10 minutes has been said to be ineffective when it comes to health benefits.

But a new analysis of data from the National Health and Nutrition Examination Survey is casting some doubt on that latter recommendation.

“For about 30 years, guidelines have suggested that moderate-to-vigorous activity could provide health benefits, but only if you sustained the activity for 10 minutes or more,” says Professor William E. Kraus of the Duke University School of Medicine. “That flies in the face of public health recommendations, like taking the stairs instead of the elevator, and parking farther from your destination. Those don’t take 10 minutes, so why were they recommended?”

Kraus is a co-author of the new study (Moderate-to-Vigorous Physical Activity and All-Cause Mortality: Do Bouts Matter?), which suggests that these short episodes of exercise may be just as beneficial as longer ones, as long as the total minutes of weekly exercise reaches that 150 minute target.

In the survey that provided the data, the activity levels of participants were tracked using accelerometers. To be counted in the study, people had to wear the accelerometer for between one day and one week, for at least ten hours in the day. Nearly 5,000 people over the age of 40 participated.

The new analysis paired this accelerometer data with death records of participants in the ten years since the study ended, and found striking correlations:

  • Getting about 60 minutes per day of moderate to vigorous physical activity cut the risk of death in half.
  • Getting 100 minutes per day of moderate to vigorous physical activity cut the risk of death by 75%.

And just as important, it didn’t matter whether these participants got their exercise in episodes of at least 10 minutes each, or if the exercise came in much smaller blocks. As long as the total minutes of exercise reached those 60 and 100 minute thresholds, the reduction in risk of death was the same.

The caveat, of course, is that the study only showed a correlation — it didn’t determine that exercise was the cause of reduced death risk. It’s possible, for example, that people already at higher risk of death were unable to exercise as much or as intensely as other participants.

Still, these results suggest new areas for further study, and imply that it’s still a good idea to take those stairs or walk that extra distance, even if the effort is less than ten minutes.