During the concentric phase of a biceps curl, which muscle acts as the prime mover?

The biceps brachii is the prime mover during the concentric phase of a biceps curl because it is the primary muscle responsible for flexing the elbow and raising the forearm toward the shoulder. In this phase, the biceps brachii contracts concentrically, meaning it shortens as it generates force to lift the weight. This action primarily targets the flexor muscles of the arm, with the biceps brachii being the most significant contributor to the curl movement.

Other muscles, such as the triceps brachii and deltoids, may play supportive roles or stabilize the shoulder joint during the curl but are not the main muscles acting to perform the movement itself. The triceps brachii is involved in extension, while the anterior and posterior deltoids assist with shoulder movement but do not actively contribute to the elbow flexion during this exercise. Thus, it is the biceps brachii that directly performs the primary action in a biceps curl.