Begin by kneeling in front of ball. Place hands on ab mat in shoulder-width push-up position. Place one leg back at a time until only toes and balls of your feet rest on stability ball. Focus your gaze on the floor. Flex abs and slowly pull knees toward chest until hips and knees are vertically aligned. Pause, and then extend legs back to starting position. Repeat this movement for all reps then dismount ball, stand up and recover.