Scapula retraction/protraction sitting - arm on stability ball (Scapular protraction/retraction strengthening, rolling stability ball, sitting)

Sit up straight on a chair.
Do not lean back against the chair.
Place your weaker arm onto a stability ball so that your arm is just below shoulder level.
Place your other arm on your lap.
Use a small movement to bring your shoulder blades back and down.
Slowly roll the ball forwards, allowing your shoulder blade to move around your body.
Then roll the ball backwards as your pull your shoulder blade back and down again.
Maintain a straight back throughout this movement.