The latest study on exercise has me running scared. It shows that jogging more than 2.5 hours per week might be as bad as not exercising at all.
Yikes! If you count soccer, I’m running at least three hours a week. If you add biking, weight lifting, tennis and hiking I might be killing myself with exercise.
Is this possible? Haven’t we always been told about the endless benefits of movement?
There is definitely such a thing as too much running, says lead researcher Peter Schnohr of the Frederiksberg Hospital in Copenhagen, in a press release:
If your goal is to decrease risk of death and improve life expectancy, jogging a few times a week at a moderate pace is a good strategy. Anything more is not just unnecessary, it may be harmful.
2500 Years of Too Much Running
The study came out today in the Journal of the American College of Cardiology. But concerns about too much running go back a long way, at least to 490 B.C. That’s when, according to legend, Pheidippides ran 25-miles back to Athens from the battle of Marathon, only to die as soon as he announced the victory.
In recent years, teams of researchers have tried to figure out just how much is too much running by comparing groups of people — and animals — who exercise at different levels.
After shocking rats in the tail to make them run too much, one group found scarring in their hearts. Other studies have shown higher rates of heart disease among marathon runners. Just as you can get stress fractures and tendinitis from all the pounding of your feet, these researchers have concluded, you can get scars and malformations from all the pounding of your heart.
For today’s study, Schnohr and his colleagues followed for 12 years 1,098 people who jog and 413 who don’t.
The non-joggers were much older on average. After using statistical wizardry to adjust for that, the researchers found that the joggers who ran 1 to 2.4 hours per week were the least likely to die during the study. Those who ran more were just as likely to die as those who didn’t jog at all.
The same was true of frequency; the benefits topped out at less than once jogging session per week. And running much faster than average also proved as unhealthy as sitting around all day.
An Overexercise Epidemic?
We shouldn’t overlook the good news in the study. It found that a little bit of jogging can make a big improvement in your health.
Still, if the finding about too much running is supported by further research, it could have huge implications. The number of Americans finishing marathons has exploded in recent years to 541,000 in 2013.
And the problem of too much exercise could affect a huge number of serious swimmers, cyclists, triathletes, and essentially anyone else who trains hard for an aerobic sport. According to one earlier estimate, as many as one in 20 Americans may be exercising too much.
To find out if other exercise experts shared this concern, I checked in with Steven N. Blair, an exercise science professor at the University of South Carolina.
“I do not think we can conclude that marathon runners are less healthy than sedentary people,” he said. “Of course like any scientific issue there are usually some unclear data.”
He didn’t go into detail about the unclear data, but he referred me to a commentary on the new study in the Journal of the American College of Cardiology.
Reasons Not to Worry
That paper points out that the non-joggers in the study were not only older but also fatter, with higher blood pressure and more diabetes than the joggers. Although the researchers used statistical methods to control for these differences, that’s not as good as having groups that are better matched.
More important, there weren’t very many people in the study who jogged more than four hours a week, or more than three times. When you have very small numbers in a population, the statistics don’t have much significance.
This study also didn’t take into account other types of physical activity.
And finally, while some other studies support its conclusions, a few have found the opposite – that benefits of running continue far above the recommended amount.
Where does this leave us? I asked one of the commentary writers, Carl “Chip” Lavie, director of exercise laboratories at the University of Queensland, to give me the bottom line in plain language.
Here’s what he said:
From a pure health stand-point, one probably obtains maximal health benefits at low doses, certainly by 40-60 minutes of exercise, and more exercise may burn more calories (which could be good to prevent obesity as well as allowing greater caloric consumption without weight gain) and improves sport performance (e.g. racing time) but more does not achieve greater health (so more is certainly not better.) For running, which is a high intensity form of exercise, maximal health benefits occur at very low doses. High dose exercise may be associated with some health risks. Since these risks seem small overall, we should probably not go overboard to scare athletes, but still worth clinicians and the public recognizing these risks and understanding that extreme levels of exercise are not needed for health (but as we said in the editorial, we need more evidence to know if more really is worse).
In other words, it’s too early for me to take to my couch in panic. Fitness can be a goal separate from health. Being able to run far feels good. Exercising more improves the way I play soccer and tennis, and adds to my speed and endurance in skiing and biking.
Even if it turned out I was shortening my life a little by getting in shape for my favorite sports, I’d probably keep doing it.
The featured image on this page is “Le soldat de Marathon” by Luc Olivier-Merson