You can find this exercise on page 181 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: ABDOMINALS, FLEXIBILITY, LOW BACK, POSTURE, STRENGTH
Lie face down with hands by shoulders and legs slightly apart and toes pointed. Inhale prepare. Exhale curl head, neck, and ribcage off floor using hands for added assistance. Feel stretch in front of body while activating gluteals and lengthening through spine. Inhale returning back to floor. Repeat 10x focusing on opening up through ribcage.