The stability ball hyperextension works to strengthen the lower back. Begin by placing your stomach/chest on a stability ball. Your legs should be shoulder width apart and fully extended against a wall behind you. The wall is used to provide leverage during the back extension. Place your hands either on side of the ball or crossed in front of your chest. Next, lift your chest off the ball until the lower back is fully flexed, then slowly return to the starting position. To add difficulty to this exercise, place your hands behind your head.