Grasp dumbbell and sit on preacher bench. With arm bent and palm facing shoulder, place back of arm down on pad.
Lower dumbbell until arm is fully extended. Raise dumbbell until forearm is vertical. Repeat. Continue with opposite arm.
Seat should be adjusted to allow arm pit to rest near top of pad. Back of upper arm should remain on pad throughout movement. Long head (lateral head) of biceps brachii is activated significantly more than short head (medial head) of biceps brachii since short head enters into active insufficiency as it continues to contract.