Although CrossFit was created almost two decades ago, it has been gaining popularity in the past few years as the antidote to boring gym workouts. What do fans say is so great about CrossFit? For starters, the program is a time-saver; it's not about how long you exercise, but the intensity of it. The workout incorporates weight lifting, kettlebell workouts, plyometrics, cardio, and more into bursts of high-intensity exercise. CrossFit also uses Tabata training as well as increasing intensity techniques (like lifting heavier weights for a lower number of reps) to help up strength and stamina. You get results fast, according to CrossFit's fans, who include more than a few buff celebrity devotees — yes, even Madonna has tried it. Check out a few more female celebrities who've shaped up with CrossFit!