What is the functional relationship between the brachialis and the biceps brachii?

The brachialis and biceps brachii are both muscles located in the upper arm that play crucial roles in elbow flexion. While the biceps brachii also assists in forearm supination, the brachialis is primarily responsible for flexing the elbow regardless of forearm position. Together, they work synergistically during movements that require bending the elbow, with the brachialis providing a strong, consistent force. The biceps brachii, although it contributes to flexion, is more active during activities that involve supinating the forearm.