Reminds me a lot of Overtraining Syndrome (OTS), the condition where your body stops responding positively to the stress of endurance sports and essentially stops recovering quickly. A 20 mile run no longer makes you faster, instead the fatigue from it just settles inside your body.

I remember reading that while training for an ironman and getting a bit spooked. But then I realized that the folks who suffer from OTS are taking it to such an extreme. This article reminded me a lot of that - it sounds like you can take anything too far. At the 99.99th percentile, probably any healthy activity can become an obsessive act that can ruin your life. But anywhere in between the 50th and 99th percentile it's probably still a good thing.