How do I perform a ball side sit-up?

Lie on your side on a stability ball with the ball placed under your hips and our feet anchored against a wall. Extend your legs, placing them in a staggered-stance position with your bottom foot placed slightly in front of the other. Cross your arms over your chest, draw-in your navel, contract your glutes and tuck-in your chin. Bend sideways at the waist, raising your upper body into a side crunch position. Return to the starting position and repeat.