There was an article from the Wall Street Journal yesterday about the health risks of endurance running. This is apparently based on data from a couple of recent studies on endurance athletes. I'm always somewhat skeptical about these exercise studies, especially when they make broad conlcusions. The article mentioned a cardiologist who believes there is an agenda behind the "too much exercise" hypothesis and that the authors of the original study are manipulating the data to prove their point.
This afternoon an article from Alex Hutchinson was published on the Runner's World site explaining how the health risks might be exaggerated based on the statistical methods used. Here is a quote from that article
I think it's possible to overdue exercise, but I wonder how many people are actually training at the level and intensity that might be detrimental.But this scaremongering about relatively modest amounts of exercise in favor of "hunter-gatherer" exercise is silly. We can speculate all we want about "potential" risks and benefits, but the real-world epidemiology is crystal-clear: if you exercise for an hour a day, you're likely to live longer than if you exercise less than an hour a day.