You can find this exercise on page 10 of the book Synergistic Golf.
Exercise Type: DYNAMIC STRETCH
Exercise Category: BALANCE, FLEXIBILITY, LEGS - FEET, LOW BACK, POSTURE, RHYTHM - TIMING
Stand tall with feet together and arms overhead and fingers clasped together. Lengthen right arm forward while lifting left leg and try to touch toward toe. Return leg and arm and repeat with other side. Exhale during reach forward and try not to hunch over. Maintain posture and keep abdominals tight.