You can find this exercise on page 241 of the book Synergistic Golf.
Exercise Type: DB STRENGTH
Exercise Category: ARMS - HANDS, CLUB CONTROL - ACCURACY, STRENGTH
Stand tall with feet hip distance apart. Hold a 5-10-15lb dumbbell in each hand with arms straight to sides with palms facing inward. Curl dumbbells up to chest-shoulder area keeping torso erect. Lower dumbbells to starting position. Repeat 10-15 repetitions in sets of 3. at a controlled speed. Do not sway body.