Guest: Gretchen Reynolds

Gretchen Reynolds is the author of "The First 20 minutes" and also writes the popular "Phys Ed" column for The New York Times, which posts online as part of the "Well" blog and appears in the print edition of the paper's "Science Times." The column regularly is among the week's most emailed stories and several columns have been among the most viewed and most emailed stories of the year at nytimes.com.

She also writes for a variety of other publications, including The New York Times Magazine, O: The Oprah Magazine, Men's Journal, Outside, Parade, Popular Science and others. Gretchen has won a number of awards for her writing and reporting, including two National Magazine Award nominations and one shared win in the Personal Service category.

Currently Gretchen lives in Santa Fe, New Mexico, with her husband, an artist, and their teenaged soccer player/swimmer/track sprinter/freestyle skier. She is also a committed if slowing athlete, with two marathons, a dozen century bike rides, many mountain bike races and a number of Fun Runs under her belt. Nowadays, though, she loses the Fun Runs to her son.