Lying on your back with bent knees with a resistance band anchored to your leg and the other end held firmly in your affected arm.
Place a rolled-up towel under your affected elbow/upper arm and move your arm away from your body at 45-90 degrees with your palm pointing down towards the ground.
Pull the rubber band up/backwards (external rotation in the shoulder joint) as far as possible, using your elbow as a pivot point.
Hold briefly and then slowly return to starting position.
