To stretch/relax the Supraspinatus muscle running across the top of the shoulder blade and across the tip of the shoulder.
Stand with feet slightly apart, head in neutral position and shoulders relaxed. Place hand of affected side behind lower back, palm facing outward. Use other hand to clasp the wrist of affected side.
With torso remaining upright at all times. Pull the hand which is across your back downwards away from the affected side until a stretch is felt in affected shoulder. Hold in this position for 20 seconds whilst breathing slowly and deeply. Then return to start position and repeat as advised.
To increase the effectiveness of this stretch and to include neck muscles, gently tilt the head away from the side being stretched, at the same time as you are pulling the arm down.