Trapezius Muscle Anatomy and Function

Model of the human body showing trapezius muscle
Model of the human body showing trapezius muscle. SCIEPRO/Science Photo Library/Getty Images

Unless you're vigilant about it, work  — and life — in our frenetic 21st century can become all but devoid of movement. While this has its conveniences, you should be aware of the drawbacks, too. For one, muscles that remain inactive for most of the day are much more likely to go into spasm and give you pain.

One such muscle, called the upper trapezius — which is the one located at the tops of your shoulders - is particularly prone to this type of tension.

 

Check it for yourself by observing and asking yourself these two questions:

  • How well can you move your shoulders up and (especially) down?
  • Do you have pain at the top of either shoulder, or both?  

If your should movement is limited and/or there's pain in that area, you may have an upper trapezius muscle in spasm. (Fortunately, solutions exist that are, for most people, non-medical and can even feel good in some cases.)

Trapezius Muscle - The Bigger Picture

Most people don't know that the trapezius is not limited to the tops of your shoulders. It actually has 3 parts (described below) and is big as muscles go. It's just that the upper part is the one that speaks the loudest when we are misaligned or tight. This is in large part due to a sedentary lifestyle.

The 3 Areas of the Trapezius Muscle

The trapezius muscle is divided into 3 areas: The upper fibers (aka upper trapezius or upper traps), the middle fibers (aka the middle trapezius) and the lower fibers (you guessed it, the lower traps.

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The division into the separate, distinct parts of this muscle is about functionality.  In other words, each area does something different. Let's explore.

Functions of the Trapezius Muscle

The trapezius muscle acts as both a posture stabilizer and a movement muscle. Common actions you may recognize in which the trapezius is involved include shrugging your shoulders, tilting, turning and extending your neck, keeping your shoulders down and more.

Because the trapezius muscle (the middle and lower parts, at least) are superficially located on the back, they also work with other muscles to extend and side bend your trunk. In the same way, they may contribute to good posture by counteracting the downward pull of gravity, especially as it rounds your shoulders forward, increases the kyphosis in your upper back and/or draws your head down towards the floor.

But let's get specific in terms of the areas and what they do.

The upper trapezius, which is the part that goes across the tops of your shoulders, can elevate, or bring up, your shoulder girdle.  

While that's the official action of this area of the trapezius muscle, it is not always a good thing. If you work at a desk, or your job involves a lot of driving, you likely know first hand what I'm talking about.  When the shoulder girdle is pulled up in a constant and chronic way, it leads to misalignment that can makes the upper traps constantly and chronically tight. The result may well be pain, limited movement and a loss of neck flexibility in that area. Not fun!

The upper trapezius also (together with the lower) helps rotate your shoulder blade upward. This movement occurs when you lift your arm up to the side (provided your shoulders, neck and upper back are in good alignment and your muscles are flexible.

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The middle trapezius helps bring the shoulder blades back, toward the spine. Again, if you sit at a desk or drive all day this may prove a handy move for preventing or managing excessive kyphotic posture in that area.   The middle trapezius also helps with trunk side bending and rotation in the upper thoracic spine.

And finally the lower trapezius muscle is tasked with stabilizing action bringing the shoulder girdle down. This is the opposite action to that of the upper trapezius (discussed above. ) 

The Trapezius Muscle as a Breathing Muscle

The trapezius is an accessory breathing muscle. This means that it helps open up the small amount of breathing room in the upper chest area.

 Practically speaking, though, for back and neck pain management, it is best not to rely on the trapezius alone for breathing support, as this will likely lead to shallow breathing.  Instead, it's a good idea to develop the capacity of your most primary and powerful breathing muscle, the diaphragm, which is also a muscle of posture.

Tight Trapezius Muscles Love a Good Massage

Although the trap muscles tend to get very tight for most people, they often respond well to massage therapy. An added perk is that they are located such that you can reach your own.  Try a self-massage on your trapezius muscle now.

Source:

Kendall, Florence, McCreary, Elizabeth Kendall, Provance, Patricia Geise.  Muscles Testing and Function 4th ed.  Williams and Wilkins.  Baltimore, Maryland, 1993.

 

 

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