I had a supraspinatus issue for a while which is now - finally- resolved. Basically what i learned was many climber shoulder injuries are just the result of not enough space under the acromium (the bony protrusion next to your shoulder) which irritates the supraspinatus and other rotator cuff tendons/muscles. If you don't fix the cause it will just keep happening. I finally fixed it (pretty quickly) through focusing on some fundamental mobility issues:
1. Scapular stability exercises (basically pinching your shoulder blades together through various upper body exercises -- see youtube for exercises). If your shoulder blade wings out or up it reduces this subacromial space. Bad scapular position also forces over-reliance on the rotator cuff during big moves and gastons.
2. Thoracic spine mobilization. This made the most difference. (Mobility WOD videos by the sadist Kelly Starrett are the real deal - facing the wall squats (Steve Bechtel has some stuff on this), laying the spine on 2 tennis balls duct-taped together. If your thoracic spine is hunched (like every climber), it pushes your scapula up into the subacromial space. You've got to learn to loosen it up and un-hunch this part of the spine. Also, with this good posture you kind of magically appear to be a confident effective person and women will pay attention to what you are saying and your boss will give you a raise.
3. Your shoulder is a ball and socket - in climbers the ball is too far forward and high in the socket due to all the strong internal rotators. You want it down and back. Do pec doorway stretches (EXRX.com) and sub scapularis stretches (EXRX) and interior capsule stretches (on you tube - this one is amazing) and the one Dave MacLeod recommends - shoulder slides against the wall
4. All the other familiar pre-hab rotator cuff strengthening exercises (stretchy band door opening closing, Y's, H's, etc.) are all good but what I found was that unless you make more space, a bigger stronger rotator cuff will just get irritated again.
