Find out whether your exercise routine is too much, too fast.
There is an ongoing debate about whether some types of exercise push people too far. So-called “extreme” fitness activities—from CrossFit to marathons to adventure runs like Tough Mudder and Spartan Race—have been blamed for incidents in which participants suffered illness, injury, or even death. But nearly every kind of physical movement carries some risk of injury. Are these vigorous activities any more dangerous than other forms of exercise?