Is it possible that there is an upper limit to how much exercise the body can take? The answer seems to be yes:
For some time, exercise scientists, as well as a few highly committed exercisers and their spouses, have wondered if there might be an upper limit to the amount of exertion that is healthy, especially for the human heart. While the evidence is overwhelming that exercise improves heart health in most people and reduces the risk of developing or dying of heart disease, there have been intimations that people can do too much. A 2011 study of male, lifelong, competitive endurance athletes aged 50 or older, for instance, found that they had more fibrosis — meaning scarring — in their heart muscle than men of the same age who were active but not competitive athletes.
Now the latest Vasaloppet study and a separate study of rats running the equivalent of several rodent marathons that was published this month in The Journal of the American College of Cardiology are likely to further the debate about possible upper limits to safe exercise. Providing some counterbalance, though, is another animal study, published this month in PLoS One, that suggests that even if strenuous prolonged exercise increases the chances of some arrhythmias, it may lessen the chance of suffering fatal heart problems.
I’m not training for an ultra-endurance event anytime soon…