You can find this exercise on page 29 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: BACK, BALANCE, FLEXIBILITY
Sit on Big ball and slowly walk feet forward to bridge position with head and shoulders on ball. Reach arms overhead as feet walk back toward ball. Allow your spine to form to the ball reaching back to touch floor. Reverse it. Walk feet back out to bridge then back in to a seated position without using hands.