There’s a lively debate between walking and running fanatics about which one’s better, with people arguing passionately on both sides of the issue.

While there’s evidence supporting both arguments, we like James O’Keefe’s opinion.  It matters because he’s done both, and having tried both, has ultimately settled on the walking side of the debate.

O’Keefe is a cardiologist and a self-described exercise enthusiast, who used to spend several hours a day running and working out.  After a period of intensive research on the long-term effects of intense physical activity on the heart and body, he decided to trade in his running shoes for a comfortable pair of walking shoes.

Studies show that running doesn’t actually improve your mortality rate, while walking 1-2.5 hours a week can lower your risk of death by up to 25 percent.

As O’keefe explains:

“We’re not meant for sustained levels of exercise for long periods of time.  After 60 minutes of intense physical activity, like running, the chambers of your heart begin to stretch and overwhelm the muscle’s ability to adapt.”

It gets worse.  Over the longer terms, intense training can permanently damage your heart, because the increased blood flow to your heart leads to microtears.  If you only run occasionally, that’s not a huge deal, because they heal after a few days. If you do it repeatedly and over a long period of time, it can cause scarring in the heart that can accelerate aging.

Not only that, but excessive endurance training can also short circuit your immune system, making it more likely that you’ll get sick.  It sounds counterintuitive, but it’s true!

The bottom line is, while there’s no doubt that exercise is good for you, too much of a good thing can turn into a bad thing.  As ever, moderation is the key.