Exercise Advice: Lie on your back on an exercise ball with your feet flat on the ground and your knees bent. Grab a medicine ball with both hands and hold it on your chest. Begin to roll your shoulders off the exercise ball. Continue to push down with your lower back. Your shoulders should come up off the ball only about four inches, and your lower back should always remain on the ball. As always, make sure you let your abs do the work in a slow and controlled fashion!