Sidelying External Rotation - arguably the best exercise for the posterior rotator cuff (teres minor and infraspinatus). Several key points are needed when explaining this exercise. For one, you should roll up a couple of towels and place them in your armpit (see entry on the “wringing out effect”). Second, make sure that you don’t flex/extend your wrist or flex/extend your elbow. If you feel this exercise in the front of the shoulder, you are not doing it right, or you potentially have joint range of motion limitations (from arthritis or loss of motion after surgery). If it hurts in front, you are likely substituting the bicep to perform this exercise and that is not our target.
Standing External Rotation - similar exercise in sidelying, but sidelying will be tougher because it is against gravity. Same rules apply as in sidelying. To tweak this exercise to make it tougher, turn your body slightly in the direction you are performing the exercise. Turning your body “prestretches” the back of the shoulder and requires a greater range for the muscle to work. A rare but crucial instruction for you to do when performing.