The prime mover of the elbow flexion is the brachialis muscle on the anterior side of the humerus. The prime mover of a muscle is the one that applies the most amount of force on that particular joint. The biceps brachii muscle also aids in the flexing of the elbow.
The muscles of the elbow provide strength and flexibility to the arm. Seven major muscles are located in the elbow that work to extend, flex or rotate the forearm. The flexor group includes the brachialis, brachioradialis and the biceps brachii. The extensors include the triceps brachii and the anconeus. The rotation is achieved through the pronator teres and the supinator.