What Am I Doing?

Sweating, screaming, pumping, pushing: It's no secret that CrossFit is an extreme form of exercise. A combination of rapid-fire bodybuilding, gymnastics, and track and field moves, the workout has attracted a global following, and celebrities like Cameron Diaz and Jessica Alba swear it's a sure way to a hard body.

Alongside the acolytes, though, there are critics: Not just the folks who disliked the fitness regimen enough to start an "I Hate CrossFit" website, but people who say they have been badly injured during CrossFit.