Stand behind arm pad and face lever handles on opposite side. Place one foot forward under arm pad and opposite foot back on foot bar. Lean over arm pads and grasp handles with slightly narrower than shoulder width underhand grip. Squat down and position back of upper arms on arm pads.
Raise lever handles toward shoulders. Lower handles until arms are fully extended. Repeat.
Position armpit to rest near top of pad. Back of upper arm should remain on pad throughout movement. Notice that this machine has secondary lever so elbows are not aligned with primary fulcrum. Also see movement performed with narrow grip. The particular machine shown doubles as Triceps Extension Machine by placing weight on opposite side of fulcrum.
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. Long head of Triceps Brachii is only significantly activated as antagonist stabilizer when it approaches passive insufficiency as elbow nears full flexion.
Antagonist Stabilizers (see comments)