Why do you feel your biceps in a pec deck fly?”Let’s understand. The pec deck fly is meant to target horizontal adduction—mainly the pectoralis major.During a pec deck fly, the machine applies resistance perpendicular to your forearms (especially in machines where the arms move in an arc). This resistance creates external torque at the elbow joint, even though you’re not actively flexing or extending the elbow.1. Elbow Joint Torque- Your forearm acts as a lever, and the line of force (resistance