Lie on back on floor with feet balanced on a medicine ball, knees bent, aligned over ankles, arms by your side with palms facing up
Contract abdominals and lift hips off the floor so knees, hips & shoulders are in a straight line, squeeze glutes and hold for a second then lower hips to close up but not touching the floor, keeping the medicine ball as still as possible
Continue raising and lowering hips until all reps are complete
WARNING: You must consult your physician before you begin this or any other exercise program