Rhomboid Major: Function, Action & Insertion

Instructor: Dan Washmuth

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

Do you know the shape of a rhomboid? If so, then you already know the shape of the rhomboid major, a muscle located in the back. Learn other interesting facts about the rhomboid major in the lesson, including the insertion, function, and action of this muscle.

The Rhomboid Major

Does your rhomboid major muscle work? In order to find out, try this quick physical assessment test:

  1. Stand up with your arms hanging naturally at your sides
  2. Pinch your shoulder blades together

Now look at your shoulder blades in a mirror (you'll probably need to use your mirror on your bathroom wall as well as a smaller, hand-held mirror). Are your shoulder blades protruding far out from your body?

If you were able to do the first two steps easily and your shoulder blades are not protruding far out from your body, then your rhomboid major muscle seems to be working well.

The rhomboid major is a muscle located on both sides of the back, between the spine and the shoulder blades. As you can probably tell by its name, the rhomboid major muscle is shaped like a rhomboid. A rhomboid is a four-sided figure in which opposite sides and angles have equal measurements, and none of the angles are right angles.

The rhomboid major muscle is located on both sides of the back, between the spine and the shoulder blades.
rhomboid muscle

It should be noted that there is also a rhomboid minor muscle, which has a similar shape and function compared to the rhomboid major, only it is much smaller.

Rhomboid Major: Insertion

The rhomboid major muscle inserts on the scapula, the official name for the shoulder blade. Specifically, this muscle attaches to the inside border just below the spine of the scapula. The spine is a ridge that runs across the top of the scapula.

The insertion point of the rhomboid major is shown in red, which is on inner border of the scapula, just below the spine.
scapula

Rhomboid Major: Function & Action

The main action of the rhomboid major muscle is to retract and elevate the inner border of the scapula. When you pinched your shoulder blades together during the physical assessment test at the beginning of this lesson, that motion is termed a scapular retraction. The rhomboid major also rotates the outer part of the scapula downward.

These actions of the scapula caused by the rhomboid major function to keep the scapula pressed against the thoracic wall and rib cage. Without this muscle, the scapula would protrude out from the body.

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