Ah, the truth about exercise? Well I suspect that exercise is more often a marker of health than its cause—healthy people like to exercise more than unhealthy people to start with. And the real value of it is not in terms of abstract health benefits like longevity—an extra few hours or maybe months—but because it feels good when you do it or when it's over. To hell with Hygeia, the truth lies in the pleasure.
Richard A Friedman, attending psychiatrist and psychopharmacologist, Cornell-Weill Medical School