Exercise Advice: Stand up with your feet about shoulder width apart and grab onto a squat rack or something sturdy. To perform this exercise, simply curl one of your legs back behind you so as to actually kick yourself in the butt with your heel. Be sure to keep your knee still and really focus on using your butt and hamstring to do the work. Again, be sure to really flex your butt and hamstring for a one-count when your leg is at the top of the movement back behind you. Return to the start position and repeat with the opposite leg.