In his MF cover story, The Biggest Loser trainer Bob Harper told us he fell in love with CrossFit because of its straight-up efficiency. “Jumping into CrossFit was like jumping into the deep end of a pool. These workouts are so compact. I used to do long sessions all the time, and my body started to get beat up. But with CrossFit, it's almost like my body is finally getting a chance to rest while, at the same time, I'm pushing it harder than I've ever pushed it."