Sit on an exercise ball, with both feet firmly on the ground. Gently lie back under your back is supported by the exercise ball. Place both hands gently on either side of your head. This is your start position. Without straining your neck, lift your torso slightly off the ball by contracting your abdominals, exhale as you do so. Gently return to the start position, inhaling as you do so. Repeat the movement for the required number of reps (or time).