Hold a light stick (like a yardstick or broom handle) behind your back with one hand. Lightly grasp the other end of the stick with your other hand. Pull the stick horizontally toward the side of the grasping hand so that the target shoulder is passively rotated internally. Continue pulling until you feel a stretch in the front or back of the shoulder, but stop before feeling any pain. Maintain an upright posture throughout the movement; do not lean or twist your torso. Hold the stretch for 30 seconds, then relax and repeat on the other side.