Lie supine on the floor with your hands by your side, head firmly planted, and legs on top of the stability ball so that only your heels and lower legs are in contact with it.
While keeping your head firmly on the ground, exhale and curl the ball toward you by bending your legs and gradually shifting the part of your feet that make contact with the ball.
Allowing your hips to raise as you curl, continue to curl the ball until you can no longer do so while still keeping your head and arms firmly on the ground.
Inhale and extend your legs while lowering your hips, allowing the ball to return to the starting position.