Exercise and the law of diminishing returns

I always warn of the dangers of extreme exercise. It can cause permanent damage to the muscle fibers and nerves in your heart. Indeed, several studies I presented over the past few years show how “highly trained” athletes often suffer potentially fatal heart abnormalities as they grow older.  And now, instead of just recommending it, researchers at the Mayo Clinic have finally gotten around to actually studying the effects of exercise on heart attack patients.

For this brand-new study, researchers followed about 2,400 heart attack survivors for about 17 years. Over this time, they tracked the survivors’ exercise habits and their mortality rates.

The researchers found that survivors who ran regularly (but fewer than 30 miles per week) or walked regularly (but less than 46 miles per week) experienced significant reductions in mortality. In fact, they reduced their risk of dying from a heart attack by up to 65 percent.

But exercising beyond these amounts had the opposite effect. In fact, mortality rates in this study showed the typical “J-shaped curve.” And survivors who engaged in excessive exercise had higher death rates.

So–as I’ve always said–there is no health reason to run marathons. The current Physical Activity Guidelines for Americans recommend about 150 minutes per week (20 minutes per day) of moderate exercise or about 75 minutes per week (10 minutes per day) of vigorous exercise.

Most cardiologists do recommend exercise to their heart disease patients. But from a health standpoint, there appears to be no reason to exceed 30 minutes per day a few days a week.

Most current studies show the greatest health benefits in the general population happen when you get up off the couch and engage in some regular, light-moderate physical activity–such as walking, swimming, house work, or yard work. Adding more exercise on top of that amount may offer some marginal benefits. But, as research has shown, there is a point where you can get “too much.” In fact, going that “extra” mile shows no benefit. And it can actually harm you.

So, go out and get some exercise this weekend while the early autumn weather is pleasant. But don’t overdo it.


  1. “Increased Cardiovascular Disease Mortality Associated With Excessive Exercise in Heart Attack Survivors,” Mayo Clinic Proceedings, published online: August 12, 2014