You can find this exercise on page 188 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: BALANCE, LOW BACK
Start in regular superman position face down over ball with tips of toes on floor behind you and fingertips on floor under shoulders. Slowly lift opposite arm and leg up and away from body. Hold for 10 seconds trying to maintain balance. Return to center and repeat other side. Repeat each side 5 times keeping abdominals engaged.