Rock Doc

I’m not going to give you permission in this piece to live a sedentary life, sitting at a desk at work all day and then on the couch watching television each evening. But medical science increasingly has some evidence of a general principal your mother warned you about: there is such a thing as too much of a good thing.

A few folks really throw themselves headlong into aerobic exercise, running, biking, rowing or swimming for hours and hours each week. Most of these hard-core endurance athletes start young. Many fall by the wayside in middle age, but there are also those who keep going, comple...