Marathons: maybe mildly bad for you

2022 August 31

What negative effects does running marathons have on one’s general health? Humans are better than other animals at long-distance running, but that doesn’t mean that extreme endurance events don’t hurt you. Although exercising, even in large amounts, is better than being sedentary, it’s unclear whether an extreme level of exercise is better than a moderate level.

There’s obviously the risk for skeletal and muscular injury when running a lot. Less obvious is that running marathons may incur mild heart damage. This article in the New Yorker and these two articles by Alex Hutchinson are non-alarmist sources discussing this topic for a general audience. This talk targeted at cardiologists seems good as well, but some parts were too technical for me to understand.

The most convincing risk is a well-documented increase in the rate of atrial fibrillation by a few percentage points among older endurance athletes. A majority of marathon runners also temporarily have elevated levels of troponin, a protein associated with heart damage, after their race. But it’s not clear that exercise-induced troponin indicates something bad—troponin levels can rise 60 minutes into a marathon-paced run, and I don’t see anyone suggesting that regular bouts of 60-minute runs are harmful.

An optimistic guess about the effect of marathons on health would be that the high volume of running typical of serious marathon training has sharply diminishing returns for your health, and a pessimistic guess would be that so much running causes mild heart damage. My uneducated and uncertain guess is that running and training for lots of marathons is a little bad and at the very least is not an effective use of time compared to running, say, 20 miles per week.

Of course, even if running a lot is mildly bad for the heart, there are still other compelling reasons to run marathons: to enjoy the act of running itself, to reach a satisfying athletic achievement, to spend time with friends from a running club. Being happy is an intrinsic good, and it’s good for one’s health too if we’re still measuring by that yardstick. Moreover, having races on your calendar is a good motivator to do exercise in the first place. I signed up for a (non-marathon) race in November, and I might not be doing any cardiovascular exercise at all if it weren’t for that.

I don’t think this research on health risks from exercise suggests any interesting changes in behavior. If you’re regularly performing extreme endurance exercise, you probably enjoy it a lot and wouldn’t be deterred by mild health risks anyway. Meanwhile, if you’re exercising primarily for general health and longevity, it isn’t worth your time to perform extraordinary amounts of exercise even if there aren’t health risks.