Movement: Stand next to a doorway or the protruding corner of a wall. Place the upper arm against the side of this door frame or wall, with a 90 degree angle at both your upper arm and forearm. Now slowly lean your body forward, keeping your shoulder stable and being sure not to rotate your shoulder forward. To make the stretch more challenging, simply turn your head in the opposite direction.
Repetitions: Hold for the full prescribed time on one side, then switch sides and repeat. This counts as one set.