Exercise ball back extension with hands behind head

Place the stability ball on the ground and lie face down on top of it with your hips resting on the ball. Position your feet against a wall or other stable surface for support. Cross your arms behind your head, with your hands touching the back of your head. Engage your core and slowly lift your upper body off the ball, extending your back until your body forms a straight line from your head to your hips. Pause for a moment at the top of the movement, then slowly lower your upper body back down to the starting position. Repeat for the desired number of repetitions.