The four muscles that facilitate elbow flexion are the biceps brachii, brachialis, brachioradialis and pronator teres, which each cross the front of the joint. Learning the anatomic structure and biomechanical function of each muscle can help you design a training program that will make them larger and stronger, enabling them to work properly and possibly preventing injuries. Consider hiring a personal trainer to develop a program that's appropriate for you.
Biceps Brachii
The biceps brachii contains two heads, the long head and short head, which attach to the upper rim of your shoulder socket and the coracoid process of the scapula bone, respectively. Both heads run down the front of your upper arm from those points and combine near your elbow, reattaching to the radius bone of your forearm. The biceps muscle contributes to elbow flexion most effectively when your forearm is supinated, with your palm facing forward while your arms are at your sides, because the muscle is fully lengthened in that position.
Brachialis
The brachialis muscle, which some call the workhorse of the elbow, is the strongest of the elbow flexors, according to Susan Hall, author of "Basic Biomechanics." The muscle attaches to the lower half of the front of the humerus bone of your upper arm on top and to the ulna bone of your forearm on the bottom. The brachialis is an effective elbow flexor regardless of whether your forearm is supinated or pronated, with your palm facing backward while your arms are at your sides.
Brachioradialis
The brachioradialis muscle attaches to the outside of the humerus bone on one end, just above your elbow joint, and to the styloid process of the radius bone on the other. It strongly contributes to elbow flexion when your forearm is in a neutral position between pronation and supination, according to Hall. The hammer curl, which involves flexing your elbows from your sides with your palms facing inward, is an effective exercise for the muscle.
Pronator Teres
Although it primarily facilitates forearm pronation, the pronator teres muscle assists the biceps, brachialis and brachioradialis with elbow flexion. The muscle attaches to the inside of your elbow joint and the inside of the ulna bone on top and to the middle and outside surfaces of the radius bone on the bottom.
References
- "Basic Biomechanics"; Susan J. Hall; 2007
- Get Body Smart: Muscles that Act on the Forearm
- "NSCA's Essentials of Personal Training"; Roger Earle and Thomas Baechle; 2004
- ExRx.net: Dumbbell Hammer Curl
