You can find this exercise on page 233 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: ABDOMINALS, FLEXIBILITY, LOW BACK
Stand with feet hip distance apart and ball overhead. Maintain even amount of weight in both heels. Lean to one side without shifting hips. Take top arm away for a moment to add a challenge to shoulders and forearms. Return arm to ball and stand back to center. Repeat each side 5x. Inhale on the way down, exhale on return to center.