Brachialis: Functional Anatomy Guide

The brachialis (G. brachion, arm.) is a lesser-known arm muscle located on the front of the humerus. It is the prime mover in elbow flexion.


Since it only crosses one joint, its contribution to elbow flexion is always the same, no matter the position of the shoulder joint or rotation of the forearm.

It’s the strongest elbow flexor due to its large cross-sectional area combined with the favorable leverages produced by its attachment points.

The aforementioned factors are why the brachialis is often described as the “workhorse of elbow flexion.”

Note: Although the brachialis is always the strongest elbow flexor, it’s not always the most active one. The biceps brachii is more active when the forearm is supinated. The brachioradialis is just as active as the brachialis when the forearm is pronated or neutral. The brachialis is most active when the shoulder is in flexion, as well as during isometric elbow flexion, regardless of forearm position.

The brachialis – which is part of the anterior compartment of the arm – is not a very “popular” muscle, and that’s mostly because it’s lies deep to the more well-known biceps brachii.

However, it is partially visible on the lower and outer portion of the upper arm, which can have a significant aesthetic impact by making the arm thicker viewed from the front. With low body fat, it creates a prominent bulge on the outer arm, giving the arm a more 3-D look when flexed.

The brachialis has a broad origin on the distal half of the humerus. Its parallel-oriented fibers run distally down the arm and insert on the proximal ulna, forming a flat fusiform muscle architecture.

Also Called

  • Brachialis anticus
  • Lower biceps
  • Outer biceps
  • Workhorse of elbow flexion

Origin, Insertion, Action & Nerve Supply

Muscle Origin Insertion Action Nerve Supply
Brachialis Distal half of the anterior surface of the humerus
  • Coronoid process of the ulna
  • Tuberosity of the ulna
Elbow flexion
  • Musculocutaneous nerve (C5-C6)
  • Radial nerve (C7)


Note: The chart below only includes exercises that target the brachialis directly, while minimizing the involvement of the biceps brachii and brachioradialis. For exercises where that train the brachialis more indirectly, see biceps brachii exercises and brachioradialis exercises.

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Stretches & Myofascial Release Techniques:


The brachialis physically cannot be stretched. Doing so would require extending your forearm back so far that the elbow bends in the opposite direction.

Self Myofascial Release Techniques

When using these techniques, give special attention to the common trigger points shown in the image below.
brachialis trigger points

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Common Issues:

  • Overactive/Short Brachialis: The brachialis is overactive and short in many people due to poor postural habits where the elbows are bent and the arms are tense (e.g. typing, writing, playing video games). This is amplified by putting too much of an emphasis on the elbow flexors during training (i.e. too many curl variations, or relying on arm strength during back training). As the brachialis and other elbow flexors become overactive and short, the triceps brachii tends to become weaker and lengthened due to reciprocal inhibition. If this imbalance becomes too extreme over time, strength gains on upper body push and pull exercises will eventually plateau. This is because the elbow extensors and flexors have an agonist/antagonist relationship and must be balanced to work together efficiently. If one lags too much, it becomes the weakest link. Lastly, overactive elbow flexors tend to take over during back exercises like rows and chin ups, which reduces back muscle activation.

Training Notes:

  1. If you have overactive/short brachialis, do the following:
    • Reduce training volume on biceps curl variations in general, and preacher or concentration curl variations in particular.
    • Release the brachialis. Release and stretch the biceps and brachioradialis as well. Do this on a daily basis, especially before and after training biceps or back.
    • Increase the amount of direct triceps training in your program. This will create more of a balance between the elbow flexors and elbow extensors.
    • Avoid postures where the elbow is bent for long periods of time (e.g. typing on a laptop, texting/browsing on your smartphone). When you can’t avoid being in such a position for an extended period of time, remember to straighten your elbows or stretch your brachialis every 15 minutes or so to allow your it to return to normal resting length.
  2. If you simply want bigger brachialis muscles, use the following training and technique tips:
    • Do isolation brachialis exercises 1-2 times per week, whenever you do biceps training. Start with 3-6 sets per session, using a moderately heavy weight that you can lift for at least 8 reps (I’ll explain why, in the next bullet point). Consider adding an extra 1-2 sets per workout if you fail to add weight or do more reps for two or more weeks in a row.
    • Don’t use heavy weight on brachialis exercises. This is especially important for preacher curls: Due to the mechanics of the movement, your distal biceps tendon is put under a large amount of stress at the bottom of the range of motion. This is a recipe for a nasty biceps rupture under the right circumstances. To avoid this, use a weight you lift for 8+ reps with good form, always warm up and never go to failure.
      • Note: If you have distal biceps tendinosis, your chances of a rupture are compounded and you shouldn’t be doing preacher curls in the first place).
    • Squeeze hard at the top of the range of motion for a full second on brachialis exercises. This is the point at which the brachialis is most isolated and under the greatest amount of tension, since there is no more biceps involvement.
    • Lower the weight slowly (e.g. a full 2 second negative) so that you don’t lockout too fast and hurt your elbows. If you can’t lower it that slowly, then you need to reduce the weight.
    • Don’t ignore hammer curls. Although the hammer curl is classified as a brachioradialis exercise, I consider them to be just as effective for the brachialis. Plus, lots of people could benefit from a bit of brachioradialis training as well.
    • Use an EZ-curl bar for barbell preacher curls instead of a straight bar. It puts your forearms in a slightly less supinated position, which reduces the strain on your wrists without impacting brachialis activation.

About the Author Alex

Hey! My name is Alex, and I'm the owner and author of King of the Gym. I started this website back in late 2009 during college, and it has been my pet project ever since. My goal is to help you learn proper weight training and nutrition principles so that you can get strong and build the physique of your dreams!

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