Taking a painkiller before you hit the track, the soccer field, or the bike path sounds like a smart move if you want to prevent pain and muscle soreness after a workout. But new studies suggest that you could actually be doing the opposite. To look at the effects of self-medicating before exercising, we talk to Gretchen Reynolds, who writes a weekly column for The New York Times Magazine. She also covers fitness for Women's Health and O, The Oprah Magazine.

Whereas most people think running is good exercise that aggravates knees and causes long-term damage, a new report reveals that it just might be good for your joints. Last spring, a European study revealed that people who run were actually protected from knee injuries. New York Times Magazine columnist Gretchen Reynolds explains.