This exercise works all three muscles, however the hammer position works the brachialis to a greater degree than other positions and concentrates particularly on the brachioradialis.
Straighten the legs keeping the- back straight as you lift the dumbbells to the thighs.Let your arms hang straight down at your sides with your palms facing inward. Keep your elbow in at your side.
Concentric contraction: Breathe out. Flex elbow fully.
Eccentric contraction: Breathe in. Lower the dumbbe