You can find this exercise on page 172 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: ABDOMINALS, LOW BACK, POSTURE, STRENGTH
Lie on back with legs straight in the air over hips squeezing inner thighs together. Arms at sides with palms down. Inhale to prepare. As you exhale, flex upper spine off floor while reaching arms slightly off ground. Extend straight legs away from body while maintaining a flat back to floor. Keep body still as arms pulse up-down an inch off floor counting to 100. Inhale on 5 breaths, exhale on 5 breaths.