You can find this exercise on page 249 of the book Synergistic Golf.
Exercise Type: DB STRENGTH
Exercise Category: BACK, SHOULDERS, STRENGTH
Stand with feet hip distance apart holding 3-5-8lb dumbbells in hands with palms facing outer thighs. Inhale lift arms straight out to side always keeping palms down. Exhale move arms parallel to floor directly in front of chest keeping arms straight. Inhale lower down to front of thighs. Exhale repeat triangle in reverse (front-side-down) alternating breaths. Repeat lifting sequence 5-10x each way. Do not allow body to sway or move during exercise.