Starting Position: Begin in an all-fours position with your torso on the ball and hands and feet on the floor. Lengthen your legs and stretch your heels to the back of the room. Your hands should be under your shoulders.
Take a few deep breaths. Notice how your abdominals want to rest on the ball when you inhale.
Exhale and pull your abdominals away from the ball. Try to keep them pulled away even when you inhale. This is your abdominal engagement. Try to maintain this engagement throughout the exercise.
Upward Phase: Gently exhale. With your abdominals engaged, slowly walk yourself forward until your hips lie directly over the top of the ball. With your feet together, lift your legs off the floor until they are in line with your torso. In this position, your body weight is distributed over the ball and supported by both hands placed on the floor. Press and hold your legs together so they move at the same time.
Lowering Phase: Inhale. Keeping your legs pressed together, and slowly lower both legs back to the floor. Knees should be straight throughout the movement.
Do not bring your legs above parallel with the torso. This will cause your low back to arch.