Why fatigue and illness aren’t the same as “overtraining”


As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)


Got an interesting e-mail about overtraining from a Jockology reader named Nathan:

I used to train frequently and at a high exertion level, as a result I […] was often fatigued and sick. It also appeared that other athletes arround me who exercised frequently for sport specific activities (e.g., triathlons, distance running, cycling, etc.) were also sick frequently.

This is a pretty common observation — if exercise is a miracle drug, I guess this is the fine print. Nathan goes on to frame the question in terms of a hypothetical graph of health benefits versus amount of exercise. As activity increases, health improves — but at a certain point, it begins to plateau, and eventually more exercise actually makes you less healthy.

There’s an element of truth to this, but it’s not the full story.

Beyond a certain point, training is no longer about health — it’s about performance. Elite Ironman triathletes, for example, are always training at the very edge of their capabilities, a hair’s breadth away from injury or illness. If they simply wanted to maximize their short- and long-term health, it would no doubt make sense to cut back. In that sense, the health-versus-exercise curve does indeed go to a region with negative slope.

But that region is far, far removed from the experience of the vast majority of exercisers. You pretty much have to make training your full-time job to get there. We often read about “overtraining” (for instance, Gina Kolata did a nice article on it last fall), a poorly understood and hotly debated condition in which the body seems to be pushed past its normal limits and just gives up. Full-blown overtraining is something like chronic fatigue syndrome, and athletes can take many months to simply to return to normal functioning.

Catching a cold after a week where you pushed it hard at the gym, on the other hand, isn’t overtraining. It’s just a failure to recover, because you’re body wasn’t adapted to the new regimen. A runner who is used to running 20 kilometres a week might get a knee injury if they suddenly jump to 40 kilometres a week. That doesn’t that running more than 20 kilometres a week is bad rather than good for health — it just means the runner’s body wasn’t yet capable of running that mileage. In another year, 40 kilometres might seem perfect.

Another way of saying this is that the health-versus-exercise curve is not only unique to each individual, but changes constantly as you get fitter. Colds and the occasional injury may happen, but if you’re careful and push your limits gradually, there’s no reason you should ever encounter a region of truly negative returns.

Thanks for the question, Nathan!