Too much exercise

Medical science increasingly has some evidence of a principal your mother warned you about: there really is too much of a good thing.

A few folks throw themselves headlong into aerobic exercise. 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, completing marathons and similar events well into retirement age.

What happens to the heart muscles of such titans of lifelong exercise?

A recent British study set out to address that question. It studied men ranging in age from 26 to 67 who were chronic and life-long...