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Exercise 3  Ball Crunch

The exercise ball is an excellent tool to have strong abdominals  and comes out number three for working the rectus abdominis. To do it right and get more efficience here are some tips:
a). Lie face-up with the ball resting under your at the middle of you back.
b). Place your arms behind the head or put them on your chest. 
c) Contract your abdominals to lift your torso off the ball, pulling the bottom of your ribcage down toward of your hips.
d) As you curl up, keep the ball stable if you make it correctly then you shouldn't roll.
e) Lower back down, getting a stretch in the abdominals, and repeat for 10-14 repetitions.