Can you exercise too much? There is no doubt that exercise is good for you. The list of benefits could take up half a page. Given that, many people are led to the belief that if exercise is good, more of it must be better. Mounting research, however, shows that you can exercise too much.
Research has shown that excessive high-intensity exercise (beyond 1-2) hours a day can cause micro tears in the heart and lead to heart problems over time. A recent study showed that runners have a 19% lower risk of death than non-runners. However, if you break down runners into groups based on how many miles a week they run, you find that people who run more than 20 miles a week are only slightly better off than non-runners (after all that work!). People who run between 5- 20 miles a week have the best health outcomes (see chart below).
Not only that, but other studies have shown that runners who run at a fast pace (a 7:30 minute mile or faster) enjoy significantly less health benefit as those who run at a slower pace (about a 10 minute mile pace). Research also shows that people who run 2-5 days a week are healthier than those who run 6 or 7 days a week.
So… unless you are doing it for other reasons, you might want to cancel that next marathon.
Note: Light to moderate exercise has no ill effects at high levels. So walk, take the stairs, etc. as much as you can.