1 - Lie on your side on a flat bench or the floor, with your bottom arm supporting your head or resting on the bench.
2 - Hold a light dumbbell in your top hand with your elbow bent at 90 degrees and your upper arm resting against your side.
3 - Allow the dumbbell to hang down toward the floor in front of you as the starting position.
4 - Keeping your elbow bent at 90 degrees and your upper arm stationary against your side, rotate your forearm upward by externally rotating your shoulder.
5 - Continue rotating until the dumbbell points toward the ceiling or until you feel a slight stretch in your shoulder — avoid letting your elbow lift away from your body.
6 - Slowly lower the dumbbell back to the starting position in a controlled motion.
7 - Complete all reps on one side before switching to the other.
