Dumbbell concentration curls
Sit on the end of a flat bench with your legs apart and lean forward slightly. Grab a dumbbell in one hand with your palm facing upward and rest your elbow on the inside of your thigh letting the dumbbell hang. Slowly curl the weight up while keeping your elbow locked in place against your thigh. As you are curling, twist your wrist to the outside (i.e., supinate). Squeeze the muscle at the top of the movement for a one-count and then slowly return to the start position and repeat.