Which muscle primarily contributes to forearm flexion at the elbow?

The brachialis is the primary muscle responsible for forearm flexion at the elbow. It lies underneath the biceps brachii and is specifically designed to flex the elbow joint regardless of the position of the forearm. This muscle is highly effective at this action because it attaches from the humerus to the ulna, exerting force directly on the ulna to create flexion.

While the biceps brachii also contributes to elbow flexion, it is more active when the forearm is in a supinated position, such as when performing a bicep curl. The triceps brachii, on the other hand, is primarily responsible for extension of the elbow and does not facilitate flexion. The brachioradialis assists in elbow flexion, particularly in a neutral position (thumbs up), but it is not the primary mover in this action. Thus, the brachialis is recognized for its main role in flexing the forearm at the elbow joint.