Brachialis Muscle: Origin, Insertion & Action

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 one of the most powerful muscles in the arm. To learn all about this muscle, including specifics on its placement in the arm and its action, be sure to check out this lesson.

Brachialis Muscle

Is your brachialis muscle working? To find out, do this quick physical assessment test:

  1. Stand up straight, with your arms naturally hanging down at your sides
  2. With your right hand, touch your right shoulder by bending at the elbow
  3. Repeat step 2 with your left hand

If you were able to do each of these steps, your brachialis muscle seems to be working just fine. The brachialis muscle is a muscle located in bottom half of the upper arm, underneath the biceps muscle. Since this muscle lies underneath the biceps muscle, its very hard to see the brachialis muscle when a person flexes.

Have you ever seen old body-building pictures of Arnold Schwarzenegger? His biceps muscles were huge. Part of the reason that his biceps looked so huge is that he also worked out and developed his brachialis muscles as well. As his brachialis muscles got bigger and stronger, these muscles caused his biceps to pop out even more. Therefore, even though you can't see the brachialis muscle, it still has a huge impact on how big a person's arm muscles appear.

The massive biceps of Arnold Schwarzenegger were so big partly because of the brachialis muscles that are located underneath his biceps.
arnold

Brachialis Muscle: Origin

The point of origin or beginning point of the brachialis muscle is on the humerus bone, which is the long bone that makes up the upper arm. Specifically, the brachialis originates from the front side of the humerus, about half-way down the bone.

The brachialis muscle originates from the front, middle of the humerus bone.
arm

Brachialis Muscle: Insertion

From the humerus bone, the brachialis muscle extends down the arm, through the inner elbow joint, and inserts or attaches to the ulna. The ulna is one of the long bones that make up the forearm (the other bone of the forearm is the radius). This muscle attaches to the coronoid process and tuberosity of the ulna. The coronoid process is a triangular-shaped prominence that sticks out from the top part of the ulna, and the tuberosity is a small, round prominence located on the coronoid process.

The brachialis muscles inserts on the coronoid process of the ulna, which is a triangular prominence at the top of the ulna.
ulna

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