Biceps Brachii

The biceps brachii is likely most well-known for its physical appearance when flexed for presentation. Many people flex their biceps as a display of their suggested strength (e.g., a football player breaks a tackle and scores, and he stands up and flexes his biceps to suggest his strength overcoming the defense).

In its name, the word biceps identifies that this muscle classically has two segments (called “bellies” or “heads”) and brachii describes its location on the upper arm; the word brachium describes the arm or humerus bone. The primary function of the biceps brachii is flexion of the elbow, but it is also significant in supination of the forearm and may assist in flexion of the shoulder.

Anatomy

As previously mentioned, the biceps brachii classically has two segments*; they are called the long head and the short head. Despite being named “brachii,” a reference to the brachium or upper arm, basic anatomy suggests that the biceps brachii does not attach on the humerus (upper arm bone). There are, of course, anatomical variants—one of which may include a 3rd attachment that arises off the humerus.

Variants aside, both heads of the biceps brachii begin on the scapula (shoulder blade) and attach into the radius (forearm bone that can rotate). The two bellies of this muscle may fuse into one, but again, anatomical variants exist, and it is possible that the muscle bellies stay separate and attach into the forearm in slightly different positions.

The proximal long head of the muscle attaches just above the shoulder joint and lines up with the humerus. The proximal short head attaches on a bony projection of the scapula a few inches inward from the shoulder joint and just below the clavicle (collar bone).

When the muscles do not fuse into one belly, the long head tendon attaches closer to the elbow and may have a more prominent role in supinating the forearm. The short head attaches further from the elbow suggesting it is a stronger flexor of the elbow. When the muscles do fuse, they attach, collectively, into an area on the forearm. In this instance, the long head is likely still more prominent in its role in forearm supination while the short head is likely more prominent in its role in elbow flexion. Both parts of the muscle will perform both actions, regardless.

Movements

Since it crosses the elbow, shoulder, and proximal radioulnar joint (the joint just below the elbow that allows the forearm to rotate), the biceps brachii can create or assist movement at all three joints. In the elbow and shoulder, the movement is called flexion. Additionally, due to its attachment on the radius, the biceps brachii will also supinate of the forearm.

The primary function is flexion of the elbow and secondary function is supination of the forearm. The biceps brachii is not a powerful flexor of the shoulder, although it can assist in that action.

When acting on the elbow joint to create flexion, the biceps brachii forms a class 3 lever system. If you refer back to the page on lever systems, you will be reminded that class 3 levers create a mechanical disadvantage for overcoming resistance. Therefore, it is important to check your ego and avoid dumbbells and barbells that are too heavy when training this muscle. You should also consider supination during biceps curls; these nuances for optimizing your training will be discussed further in the Sculpting Your Body section of this website.

Training the biceps brachii

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