You can find this exercise on page 86 of the book Synergistic Golf.
Exercise Type: HEAVY BALL
Exercise Category: HIPS, LOW BACK, POWER PRODUCTION, RHYTHM - TIMING, STRENGTH
Begin with feet hip distance apart back to back with a partner. Keeping the feet planted on the ground, rotate torso to the right and left direction focusing on maintaining torso stability. Pass the ball in one direction with partner, then turn to receive it in the opposite direction. The rear foot must pivot and heel will lift on turn. Repeat both ways 10x.