You can find this exercise on page 121 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: ABDOMINALS, FLEXIBILITY, LEGS - FEET
Stand tall with feet together and arms overhead with ball. Lengthen ball forward as right leg lifts to touch toe to ball. Exhale during reach forward and try not to hunch over. Maintain posture and keep abdominals tight. Return with ball overhead and repeat with left leg. Switch legs 10x.