Gretchen Reynolds, writer of the New York Times Phys Ed column and author of The First 20 Minutes, answers questions and debunks myths about exercise.

Gretchen Reynolds writes the "Phys Ed" column for the New York Times and is the author of The First 20 Minutes: Surprising Science Reveals How We Can: Exercise Better, Train Smarter, Live Longer. She joins us to discuss what science is proving and disproving when it comes to exercise. 

Gretchen Reynolds writes the "Phys Ed" column for the New York Times and is the author of The First 20 Minutes: Surprising Science Reveals How We Can: Exercise Better, Train Smarter, Live Longer. She joins us to discuss what science is proving and disproving when it comes to exercise. 

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.