This article at RW destroys the claims by the authors of the study. The claim that running more than 20 mpw at 8 min/mile is bad for you has no basis if the study has intentionally eliminated any health benefits that might derive from running longer or faster than that.
hold the phone wrote:
"What this means is that they used statistical methods to effectively "equalize" everyone's weight, blood pressure, cholesterol, and so on. But this is absurd when you think about it. Why do we think running is good for health? In part because it plays a role in reducing weight, blood pressure, cholesterol, and so on... They're effectively saying, 'If we ignore the known health benefits of greater amounts of aerobic exercise, then greater amounts of aerobic exercise don't have any health benefits.'"
We were not able to identify an upper limit of physical activity, either moderate or vigorous, above which more harm than good will occur in terms of long-term life expectancy benefits.