Lie on your side with your exercising arm bent to 90 degrees at the elbow just above your rib cage so there is a gap between your body and your elbow. Set your shoulder blade back and down. Rotate the arm upwards towards the ceiling, pivoting at the elbow as an axis point (make sure the elbow stays bent at 90 deg). Don't let the elbow move out of position or let the shoulder blade move. Slowly return arm back to start position.