ball crunch

-Lie on the ball, positioning it under the lower back.
-Cross your arms over the chest or place them behind your head.
-Contract your abs to lift your torso off the ball, pulling the bottom of your ribcage down toward your hips.
-As you curl up, keep the ball stable (i.e., the ball shouldn't roll).
-Lower back down, getting a stretch in the abs, and repeat for 1-3 sets of 12-16 reps.

 Notes:

-Do not do the exercises unless advised by your doctor.
-Repetitions of each exercise depend on your tolerance and condition, usually between 30-50 times.
-If you feel any pain while doing the exercises stop and ask your doctor.