You can find this exercise on page 53 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: ABDOMINALS, BACK, CHEST, FLEXIBILITY
Sit on ball with feet hip distance apart and directly under knees. Place hands on hips with thumbs facing back to help stabilize and ensure no movement of hips and lower body. Find neutral spine and placement of ribs. Inhale to prepare. Exhale and slide ribs side to side controlling direction and range of motion with muscles around ribs and mid spine. Repeat side to side 20x. Enhance control by popping ribs forward and back. Repeat 20x F and B. Use control of breath and muscles to move body, not momentum.