Which muscle is primarily involved in flexing the elbow?

The biceps brachii is the primary muscle responsible for flexing the elbow joint. This muscle is a biarticular muscle, meaning it crosses two joints: the shoulder and the elbow. It originates from the scapula and inserts into the radius bone of the forearm. When the biceps brachii contracts, it pulls the forearm up towards the shoulder, resulting in elbow flexion.

Additionally, the biceps brachii is especially active during movements where the forearm is being lifted, such as in lifting objects or performing curls. It is most effective when the forearm is in a supinated position (palm facing up), which enhances its ability to produce force during elbow flexion. Hence, its anatomy and function make it the primary muscle for this specific action.

Other muscles involved in elbow flexion include the brachioradialis, which assists but is not the primary mover, and the triceps, which is primarily responsible for elbow extension. The deltoid muscle is largely involved in shoulder movements and does not play a direct role in elbow flexion.