This torso transformer was inspired by the floor-wiper exercise from the famed "300 workout," the über-intense regimen that (more than the magic of CGI) carved Gerard Butler and his fellow Spartans into sinewy warriors. It fiercely works your chest, upper and lower back, shoulders, arms, abs, and obliques while forcing you to maintain balance. In short, it's the perfect pre-beach mid-and-upper-body sculptor. But know this: It requires intense focus on form, so start slow and go light with load at first. To maximize its fat-burning potential, cycle this muscle builder between up-tempo cardio intervals. Do 8 to 10 reps for a total of three sets, either in a row or as part of a larger circuit. Take a few minutes of rest between consecutive sets.