
isometric shoulder external rotation in standing, resisting outward rotation with opposite hand at the wrist.
Stand, bend the elbow to 90 degrees such that hand facing forward, rotate the arm inward close to the stomach. Place other hand outer aspect of the wrist, further rotate the arm away from the body against the resistance of other hand. Release the pull and repeat.
Nothing here is a prescription. Your physiotherapist decides which of these are yours, and when.