Primary Muscle Group: Abdominals
Muscle Groups Worked in This Exercise: Lower Back
Preparation: Roll out onto ball in a supine position. The ball should be on your upper back. Keeping your hips and body parallel to the floor (no sagging of the hips) rotate your shoulders to the right with your arms extended. Remember to keep your trunk parallel with the floor.
Execution: Now rotate towards your left and repeat back and forth until the desired number of repetitions is met. The ball should pretty much stay in one place. Keep your body in a straight line and parallel with the floor. No sagging of the hips.