The Too-Much-Running Myth Rises Again:

We are curious as to whether Wen and colleagues have data about long-term survival in individuals who did vigorous exercise for more than 50 min per day. Do the mortality benefits begin to erode away as the daily time spent doing vigorous physical activity increases beyond 1 h?

Wen and colleagues reply that yes, they do have data — and it doesn’t show what O’Keefe et al. hope:

By 120 min [per day], the hazard ratio for all-cause mortality was around 0·55 [which is better than it was for 60 min per day], with even better hazard ratios for cardiovascular diseases… The adverse effects of strenuous exercise for incremental efforts for more than an hour a day did not seem to outweigh the 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.

This exchange took place before the recent spate of review articles about the dangers of too much exercise was published. And yet the study is still being cited as evidence that doing more than an hour a day of exercise is bad for you. As a subsequent letter to the journal from Michael Bubb of the University of Florida put it, “The interpretation of the data provided in the review by O’Keefe et al is misleading, particularly given the response of the authors of the original data.”

To reiterate, I’m not flipping to the other extreme and arguing that there’s no point of the diminishing returns for exercise, or even that there’s no possibility of heart damage associated with extreme ultraendurance exercise. These are open and legitimate questions. 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.