Position yourself supine over the stability ball so that it presses into the middle of your back and your upper torso is leaned back.
With your legs bent in front of you and hands behind your head, exhale and curl your torso forward.
Continue to curl your torso forward while keeping your feet firmly planted on the ground and back pressed into the ball until your torso is almost upright. Do not allow your lower back to raise off the ball.
Inhale and lower your torso down, returning to the starting position.