Triceps Brachii Muscle: Definition, Function & Location

Instructor: Dan Washmuth

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

What do the triceps brachii and Cerberus, the mythical dog that guards the Underworld, have in common? If you said they both have three heads, you are correct! Be sure to read this lesson to learn more interesting facts about the triceps brachii!

Triceps Brachii

Try this quick and easy physical assessment test:

  1. Stand up with your arms hanging naturally at your sides.
  2. Bending at the elbow, bring your hands up until your elbow makes a 90-degree angle.
  3. Straighten the arms back out.

If you were able to do these three steps, then your triceps brachii muscles seem to be working!

Triceps Brachii: Definition

The triceps brachii is a muscle located in the upper arm. This muscle gets its name because it has three muscle heads (tri means three). The 'head' of a muscle is a point of origin. Therefore, the triceps brachii muscle has three separate points of origin which includes one location on the scapula (shoulder blade) and two locations on the humerus (bone of upper arm).

The triceps brachii is located at the back of the humerus, the bone in the upper arm.
triceps brachii

Triceps Brachii: Location

As it was already mentioned, the triceps brachii is a muscle located in the upper arm. More specifically, this muscle is located at the back of the upper arm, between the shoulder and the elbow joints. Because the triceps brachii has three heads, it often appears in the shape of a horseshoe at the back of the arm.

The triceps brachii muscle can be visible in muscular people, oftentimes appearing like a horseshoe under the skin when this muscle is flexed.
body builder triceps brachii

Triceps Brachii: Function

The main function of the triceps brachii is to extend the forearm at the elbow. This means the triceps brachii functions to straighten the arm at the elbow joint, just like you did during the physical assessment test at the beginning of the lesson.

Have you ever been to the gym and seen people at a weight machine that forces them to press or pull their forearms down to a straight position? This machine is called a 'triceps extension', and it is used to strengthen the triceps brachii muscle.

Other functions of the triceps brachii include:

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