Start by sitting on the ball, and then walking the ball so that your low back is resting on it. Cross your hands in front of your chest, keeping your neck in-line with your spine. Leaning forward, move into a crunch. Remember to exhale on the crunch. Continue for a series of 10.
Human Rolling Pin
Kneel down on the mat and reach forward on the ball so you just have your fingertips on it. Then roll, down on the ball gradually resting the back of your arms on it as you come down. Keep your body in a straight line the entire time. Then roll back in. Work straight down on your abdominals in the front while emphasizing and strengthening your back muscles. Go through a slow series of 10.
Starting with your body forward over the ball, slowly move forward to the point where your hips are on the ball. Then roll your legs right on top of the ball until you are in a knee tuck. The series is a combination of a tuck and extension back. Go through a series of 10.
A modification on this exercise is to come into a Pike position once you have rolled your legs on top of the back, changing the combination to a tuck, pike, tuck, and extension back. Again, a series of 10 is a good starting point for this exercise.