A new study says that when it comes to leisure time physical activity, the more the better—but that doesn't mean that cranking out 10 times the minimum activity recommendations makes you 10 times more likely to live longer than someone who just meets the recommendations (or exceeds them by a bit).

Researchers compared mortality rates with activity levels among 661,137 men and women over 14.2 years in an effort to gauge the dose-response relationship between leisure time physical activity (LTPA) and mortality generally, with a focus on finding out if an "upper limit" of activity exists in which the longevity benefits level off—or actually decrease.

Some of what they found is already widely accepted: namely, that adhering to the 2008 Physical Activity Guidelines for Americans of 75 vigorous-intensity or 150 moderate-intensity activity minutes a week significantly reduces mortality. Other findings were new, particularly when it came to how much activity produces the biggest longevity payoff. Results were published in the April 6, 2015, online version of JAMA Internal Medicine (abstract only available for free).

By using self-reported activity data from 6 large-scale studies and then converting those data to metabolic equivalent of task (MET) numbers, researchers were able to compare results even when the studies asked slightly different questions about physical activity. The study sample consisted of 291,485 men and 369,652 women, although with a rate of 95% Caucasian participants it was not representative of the US population.

The analysis found that individuals who met or engaged in twice the guideline recommendations (7.5 to 14.9 METs per week) lowered their risk of mortality by 31%, and those who exceeded recommendations by 2 to 3 times (15 METs to 22.4 METs per week) saw a 37% drop. However, that benefit tapered off and finally plateaued at 3 to 5 times the minimum. From that point on, no additional activity—even activity that exceeded the guidelines by 10 times or more—seemed to make a dent in longevity rates.

PT in Motion (04/07/2015)