Anyone who’s suffered a heart attack—or loves someone who has—knows that exercise is a key component of cardiac rehabilitation. It turns out, though, that too much of anything—including exercise—can be problematic: Scientists have found there is a point at which exercise seems to do more harm than good.
In fact, the study’s lead scientists—Paul T. Williams of the Lawrence Berkeley National Laboratory and Paul D. Thompson of Hartford Hospital—determined a specific turnaround point. In their study of 2,400 physically active heart attack survivors, the physicians found that deaths were reduced by 65% with around 30 miles of running per week, or 46 miles of walking. Beyond those numbers, though, the benefits didn’t just stop accumulating: Participants who clocked higher mileage suffered higher rates of death than those exercising less. Williams and Thompson also found that competitive athletic events seemed to increase the risk of an “acute event.” In short: An infinite amount of exercise isn’t an infinite good.
The study suggested that their findings could apply to 1 in 20 people; of course, as they also point out, 1 in 2 people aren’t getting the minimum recommended amount of physical activity, about 150 minutes of moderate exercise per week. The glory of moderation might not be the sexiest conclusion, but it is, in this case, probably the most accurate. “For patients with heart disease, almost all should be exercising, and generally most should be exercising 30-40 minutes most days, but from a health standpoint, there is no reason to exercise much longer than that and especially not more than 60 minutes on most days,” says Carl “Chip” Lavie, a cardiologist and co-author of a separate study published in the same issue of Mayo Clinic Proceedings. (Lavie’s study similarly established the importance of moderation in achieving optimal cardiac health.)
The doctors did warn that because their study focused on survivors of heart attacks, their findings “cannot be readily generalized to the entire population of heavy exercisers.” One element of the study primed for that sort of extrapolation, though, was evidence that walking offered the same health advantages as running—the only caveat being that walkers had to exercise for a longer period of time. In other words, if walkers are willing to put in the hours—about twice as many as runners—they can expect all the same health benefits as their more fleet-footed friends.
Are you getting in the recommended 150 minutes of moderate exercise per week? Share your fitness strategies in the comments below!