Using a Thera-Band or elastic tubing wrapped around a doorknob or in a closed door at approximately elbow height, hold each end of the tubing and stand at a distance so that the tubing is straight with a bit of tension.
Bend your arms, driving your elbows back and squeezing your shoulder blades together to pull the tubing to either side of you. Pause, and slowly return to start. Perform 12-15 repetitions.
If this exercise is too hard with the resistance of the tubing, simply do not use the tubing and just work on drawing your shoulder blades back together.
Lie back on a flat surface. Have your arm extended at shoulder height, with your elbow bent at 90 degrees to point up to the ceiling.
Slowly rotate your arm around your elbow in the arc displayed in the picture, so that the palm of your hand touches the surface in one direction, and the back of your hand contacts the surface in the other direction. Stop the motion if you experience pain.
Repeat 12-15 times. If this exercise is too easy, try holding a 2-3 lb weight.