You can find this exercise on page 95 of the book Synergistic Golf.
Exercise Type: BIG BALL
Exercise Category: ABDOMINALS, LOW BACK, STRENGTH
Lie on your left side propped up on your midsection and hip on big ball. Place both hands across chest or behind ears for a challenge. Extend legs with left leg crossed behind right for support. Exhale and lift your torso off ball pushing left hip into ball. At the same time, draw your ribcage toward your hip. Pause and return to relaxed position on ball. Complete 10-15 repetitions each side.