In this anatomy lesson, I’m going to talk about an arm muscle that few people mention, the brachialis.
Brachialis Shape and Location
Like the biceps brachii, the brachialis muscle is a spindle-shaped muscle that is also located in the anterior (front) compartment of the arm. However, it lies just under the biceps brachii, and because it is somewhat hidden by the biceps, people almost never say, “Hey, show me your brachialis!”
However, if you look closely, you can often see the brachialis muscle on a bodybuilder, especially when you look at the lateral surface of the arm when it’s flexed, as you can see in the back double biceps pose below:
And if you want to build bulging biceps, you’ll want to build the muscle that’s going to help push them up even higher, the brachialis!
Brachialis Muscle Name Meaning
What does the name brachialis mean? The word brachialis comes from the same root as the “brachii” word that makes up the biceps and triceps name, and that’s because the word “brachi” comes from an old Latin word that means “arm” or “of the arm.”
So anytime you see that “brachi” prefix, you should be thinking: arm! Where is the brachialis? Arm. Where is the biceps brachii? Arm. Where is the brachial artery? It runs down the arm!
Brachialis Origin and Insertion
Unlike the biceps brachii, the brachialis attaches to the humerus, originating on the lower anterior (front) surface of the bone (that’s its strong anchor point), and it inserts at the coranoid process of the ulna, as well as the ulnar tuberosity (the insertion is the part it moves as it contracts).
Brachialis Action (Function)
What is the major function of the brachialis muscle? Remember, the insertion point is the part that the muscle is typically going to move during contraction, and this muscle inserts into the ulna.
Therefore, the main function of the brachialis is going to be to pull up on the ulna and cause elbow flexion (also called forearm flexion), bringing the forearm close to the arm, just like how the biceps brachii is attached to the radius and also caused forearm flexion. In fact, the brachialis muscle is a synergist (helper) to the biceps brachii in that specific movement.
Here’s a tip to help you remember the main function: The brachialis helps you drink from a chalice!
Because the brachialis is involved with elbow flexion, any exercise that involves curls will involve this muscle (“curls for the girls”), along with exercising the biceps brachii. However, by placing the wrist in a neutral or pronated position, you can reduce the involvement of the biceps brachii and place more emphasis on the brachialis.
This is due to the fact that the biceps brachii attaches to the radius and plays a role in supination, whereas the brachialis attaches to the ulna.
Two popular exercises that train the brachialis muscle include the following:
- Hammer curls – this is where you curl while the wrist is in a neutral position, facing medially. Keep your arm at your side, and curl the weight up. Perform this with a barbell or dumbbell.
- Reverse curls – Pronate the forearm so that the palms are facing down as you grip the bar, and curl the weight just as you normally would. You can use a barbell or dumbbell for this exercise.
Brachialis Nerve Supply
Like the biceps brachi, the brachialis is supplied by the musculocutaneous nerve. However, it is receives some innervation via the radial nerve as well.
Free Quiz and More Anatomy Videos
Take a free comprehensive quiz on the brachialis muscle to test your knowledge, or review our brachialis video. In addition, you might want to watch our anatomy and physiology lectures on YouTube, or check our anatomy and physiology notes.