You can find this exercise on page 37 of the book Synergistic Golf.
Exercise Type: HEAVY BALL
Exercise Category: BALANCE, POSTURE, STRENGTH
Stand with your feet firmly planted a little wider than hip distance apart and extend your arms in front of you while holding heavy ball. Rotate 180 degrees facing behind you keeping your arms straight out in front of you and maintain weight centered between both feet. Focus on lifting through the spine and be sure to lift your trailing heel for easier rotation. Repeat 5 times each direction. Ribcage and spine stay lifted with shoulders back and chin up.