You can find this exercise on page 242 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: ABDOMINALS, HIPS, LOW BACK, STRENGTH
Sit on ball with feet hip distance apart and directly under knees. Place hands on ribcage with thumbs facing up to help stabilize and ensure no movement of upper body. Find neutral spine and placement of hips. Inhale. Exhale and pull belly button into spine which tilts hip bones backwards. Inhale tilt hips forward. Repeat F and B 20x. Using muscles on side of torso directly under ribcage, tilt hips right and left repeating 20x. Use control of breath and muscles to control body, not momentum.