You can find this exercise on page 165 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: FLEXIBILITY, LEGS - FEET, LOW BACK, POSTURE
Sit tall with spine straight and legs out straight with feet flexed. Place hands by hips. Remain seated on sit bones, not behind. Goal is to keep body at 90 degree angle. Inhale sitting taller drawing chest up and belly button to spine. Exhale hinging from the hips (not rounding the back) and reach straight arms toward toes. Pause. Return back to starting position with hands at sides to stretch spine. Complete 5x. Great exercise to test starting flexibility before workout or round and after.