1. Stand on SBB with feet straight, shoulder-width apart.
2. Keep chest up, shoulders back, and abs engaged.
3. Hold medicine ball in front of you, at chest height with a slight bend in your elbows.
4. With your hips facing forward, rotate your abdominal and oblique muscles to your left, then to your right, and release to a partner.
5. Your partner immediately throws it back to you. As he or she does, engage the abs with the momentum of the ball as you rotate to other side and back around to your partner.
6. Continue for appropriate amount of reps then switch sides.
Tips: Keep a slight bend in the knees at all times. Use the momentum created by the weight of the medicine ball to fully engage your oblique muscles. Never over rotate, or go past the point of the lateral plane; this can place too much torque on the spine.