This is a more popular ab exercise with the fitness ball.
Lying on your back, have your knees bent, and your feet flat on the floor. Your arms should be straight up holding the ball between both hands.
Exhale and lift the ball slowly up, keeping your arms straight. Stop just before the ball reaches your knees, hold for 2 seconds, and slowly lift back down. Continue with desired reps.
Do 10-12 reps.