This exercise works all three muscles. It can also be performed in a bent over standing position, curling the arm from a straight arm hanging position, with no support against the thigh.
Seated, lean forward to allow one arm to rest against your inner thigh for support. Your arm should be straight and the dumbbell held in a palms up position. Keep your elbow down and your arm against your inner thigh.
Concentric contraction: Breathe out. Flex elbow fully.
Eccentric contraction: Brea