Brachialis Muscle: Function, Location & Nerve Supply

Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

The brachialis muscle is the primary flexor of the forearm. Learn what this means, as well as many other facts about the brachialis, by checking out this lesson.

The Real Muscle of Bicep Curls

Have you ever been to a gym or workout area and seen people doing bicep curls? Many people do this exercise in order to build and strengthen their biceps muscle. However, did you know that the biceps muscle is not the primary muscle being worked while doing a bicep curl?

The primary muscle being worked is actually the brachialis muscle, which is a long muscle of the upper arm, located directly underneath the biceps brachii muscle. Therefore, maybe the bicep curl exercise should be renamed the 'brachialis curl'.

The bicep curl exercise actually involves the brachialis muscle more than the biceps brachii muscle.

Location of the Brachialis

The brachialis is located in the upper arm, directly underneath the biceps brachii muscle. More specifically, it extends from about the middle and front surface of the humerus (the long bone of the upper arm) all the way down to the top of the ulna (the long bone of the forearm).

The brachialis (shown in blue) extends from the middle of the humerus to the top of the ulna.

Function of the Brachialis

The primary function of the brachialis muscle is to flex the forearm. Flexion of the forearm is the same motion used to perform bicep curls, which involves bringing the hand upward by bending at the elbow. Contrary to what you might think, the brachialis is actually stronger than the biceps brachii and functions as the primary flexor of the forearm.

You perform forearm flexion constantly each day. For example, you must flex your forearm in order to eat, drink, brush your teeth, and bathe (imagine trying to perform all these daily tasks without bending your elbows). Because the brachialis muscle is used so frequently, it oftentimes becomes irritated, inflamed, or damage from overuse.

Note that the brachialis does not also extend the forearm, only to flex it.

The brachialis functions to bend/flex the elbow, which is required for many everyday activities such as eating.

Nerve Supply of the Brachialis

In order for the brachialis to perform its primary function of forearm flexion, it must first receive electrical impulses from the brain through a nerve called the musculocutaneous nerve, which contains nerve fibers from the fifth and sixth cervical nerves (C5 and C6).

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