You can find this exercise on page 58 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: BALANCE, LOW BACK
Stand with feet together and big ball over head with arms straight. Shift weight to left leg. Slowly allow right leg to extend straight out behind body while arms and ball lean forward. Goal is to form a capital T with right leg and body parallel with the floor. Hold for 5 seconds, then return to start. Repeat 5x each leg. Focus on controlled breathing and form.