You can find this exercise on page 137 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: ABDOMINALS, FLEXIBILITY, LOW BACK, STRENGTH
Lie on back with legs directly up toward sky and arms down at sides. Inhale flexing hips and hinging legs toward torso. Then sequentially articulate spine off mat from tailbone to mid back reaching legs overhead parallel to mat. Exhale extend hips and reach legs toward sky. Inhale staying in place reaching toes toward sky. Exhale maintain extension in hips as much as possible and sequentially articulate spine back down to mat. Repeat entire sequence 5x.