Since ditching the gym for the yoga studio, you may have improved your flexibility, but Bob says your cardio has probably slipped, and your overall fitness level may not be as high as you think. Bikram can't provide the perfect workout—and neither can running, cycling, swimming or any other activity you do exclusively. In his book 20 Years Younger
, Bob found that the people in the absolute best shape were those who switched between three to five different exercises each week. That's the best way to work as many muscles as possible and avoid injuries from overuse, he says.