You can find this exercise on page 302 of the book Synergistic Golf.
Exercise Type: DYNAMIC STRETCH
Exercise Category: CHEST, FLEXIBILITY, SHOULDERS
Stand with your feet in address position. Clasp hands behind your back opening up chest cavity. Slowly bend over from waist allowing arms to follow and point up toward sky. Hold belly button in to support spine and keep knees bent. Allow head to hang looking back through knees. Slowly roll back up to standing with head being last to roll. Repeat 3 times.