HOW: Start by lying on your side with your head supported and your knees either straight or bent up together, whichever is more comfortable for you. With your arm at your side, have your palm either facing the front of you or facing the ground. Bring your arm up and go as much as you can until your knuckles are at least facing the sky. Reset and repeat for the prescribed amount of reps.
FEEL: You should feel your shoulder muscles working.
COMPENSATION: Keep your arm straight and in line with your side, don’t bring it forwards or backward on the way up.