Sit upright in a chair and rest your symptomatic arm out to the side on a table or solid work surface.
Your arm should be at approximately 90° to your body.
Bend your elbow to a right angle, and hold a stick in both hands.
Maintaining good posture and shoulder blade control, push with the stick to rotate your affected arm up so that your forearm moves off the table from horizontal to vertical.
Remove the support of the stick and slowly lower your affected arm back to the starting position.
Your elbow should remain on the table at a right angle and your posture should stay straight with your shoulder blades remaining back and down.
Repeat the exercise, remembering to always use the stick to raise the arm up.