External Dumbbell Rotation
Lie on the opposite side/shoulder your training, and keep the upper arm against the body. Hold dumbbell (palm down) with elbow bent at 90 degrees. Forearm starts against the abs. In a controlled motion, keeping the upper arm against the body, rotate the forearm up and away from the abs as far as possible. While maintaining the controlled motion, return to starting position. Do not allow muscles to relax before next repetition.