Shoulder external rotation with supination: This exercise can be done with a dumbbell but is best accomplished with a piece of resistance tube or a cable column. Standing with The Pronator held in a neutral grip, rotate your hand away from your body, while keeping your elbow by your side. It is important to maintain a 90 degree angle at the elbow during the exercise. While rotating your hand away from your body, turn your hand palm up. To complete this exercise return to the starting position and repeat.