Extreme exercise programs like P90X, CrossFit, and Insanity will without a doubt kick you into the best shape of your life in a very short amount of time—but only if you stick with their crazy-for-most routines. The majority of people (trainers I've spoken with say something like 9 out of 10) give up on these workouts because they're really intense and require an hour almost every day to do them. More »
