What is the primary muscle action associated with the biceps, innervated by C5?

The primary muscle action associated with the biceps is elbow flexion and supination. The biceps brachii muscle, which is innervated by the C5 nerve root, is primarily responsible for bending the elbow (flexion) and turning the palm upward (supination). This muscle has two heads that originate from the shoulder area and insert on the radius, allowing it to effectively perform these actions.

Elbow flexion is critical in various activities, such as lifting and pulling movements, while supination is essential for actions like turning a screwdriver or holding a cup. The C5 nerve root's role in innervating the biceps emphasizes the importance of this muscle in upper extremity movements. Overall, the combination of these actions makes the biceps an essential muscle for functional tasks involving the arms.