You can find this exercise on page 21 of the book Synergistic Golf.
Exercise Type: PILATES
Exercise Category: ABDOMINALS, FLEXIBILITY, HIPS, STRENGTH
Begin on your back with belly button to spine. Exhale and pull your right knee to your chest as you lift your shoulders off the mat and try to kiss your knee. Extend you leg outward. Maintain a rounded upper back and ribs flat to ground. Keep belly button to spine as you switch sides. Repeat 10 times.