Muscle Biomechanics: Trapezius Muscle

In this blog post from our muscle biomechanics series, we are going to discuss the Trapezius Muscle.

The trapezius muscle is one of the most important muscles of our upper back and shoulder girdle.

The trapezius has many different actions, involved in the movement of the cervical tract of the spine, scapula, and neck.

The Trapezius has the important function of the stabilizer of the scapula during many movements of our arm.

For example, during the exercise of hummer curl, which involved mainly the Biceps Brachaii Muscle, the upper part of the Trapezius contracts to stabilize the scapula preventing it from being pulled down from the weight acting on the arm.

Anatomy of the Trapezius Muscle

The Trapezius Muscle is formed by twin muscles disposed on the two sides of the upper and middle spine. It connects the two scapulas with the spine and head bones.

The Trapezius has different origin points such as:

  1. Superior nuchal line.
  2. External occipital protubrance.
  3. Nuchal ligaments.
  4. Spinosus processes of C7-C12.

The Trapezius Muscle has three attachment points:

  1. The lateral third of the clavicle.
  2. Acromion.
  3. The spine of the scapula.

The innervation of the Trapezius Muscle is the accessory nerve ( XI ).

Actions of the Trapezius Muscle

Since the Trapezius Muscle has its origin and insertion in multiple different points, it can make more movements of both the scapula and the head.

The main actions of the Trapezius Muscle are:

  1. Scapula Adduction.
  2. Scapula Elevation.
  3. Scapula Depression.
  4. Scapula Rotation.
  5. Vertebral column Extension ( Head Extension ).
  6. Vertebral column Lateral Flexion ( Head Lateral Flexion ).

These six different movements are permitted with the engagement of the different muscle fibers the trapezius muscle is composed of.

The scapula adduction is permitted when the whole muscle fibers of the trapezius muscle are engaged (watch the video ).

The scapula elevation is permitted when only the upper muscle fibers of the trapezius muscle are engaged (watch the video ).

The scapula’s depression is permitted when only the lower muscle fibers of the trapezius muscle are engaged (watch the video ).

The scapula’s rotation is permitted when only the upper muscle fibers of the trapezius muscle are engaged and fixing the head in a steady position (watch the video ).

The head or vertebral column extension is permitted when only the upper muscle fibers of the trapezius muscle ( both sides ) are engaged and fixing both scapulas in a steady position (watch the video ).

The head or vertebral column lateral flexion is permitted when only the upper muscle fibers of the trapezius muscle ( one side) are engaged and fixing scapulas of the same side in a steady position (watch the video ).

Injuries of the Trapezius Muscle

As the Trapezius muscle is linked with the cervical spine and scapulas, it can cause different injuries or conditions affecting the neck and shoulders.

Trapezius muscle injuries can be caused by many conditions such as overuse, poor posture, and trauma.

Here are some of the most common injuries and conditions associated with the trapezius muscle:

  1. Trapezius strain or sprain: Trapezius muscle strains or sprains are among the most common injuries. These can occur due to overuse, sudden or repetitive movements, or lifting heavy objects improperly. Symptoms may include pain, stiffness, and limited range of motion.
  2. Nerve Compression: In some cases, the trapezius muscle may compress nearby nerves or its own supplying nerve, leading to conditions like thoracic outlet syndrome. This can cause symptoms such as pain, numbness, and tingling in the arm and hand. It can be caused by poor posture, repetitive movements, or muscle injury.
  3. Trapezius Tendinitis: This is a condition of inflammation of the tendon, which is the connective tissue that connects the muscle to the bone. It can result from repetitive movement, overuse, or muscle strain during playing sports or lifting weights, for example.
  4. Trapezius Bursitis: This is an inflammation of the bursa, which is a small sac of fluid that cushions the muscle and bone. It can be caused by repetitive rubbing of the muscle against the bone, such as when carrying a heavy backpack or lifting heavy weights. Trapezius muscle can generally cause inflammation of the Subacromial Bursa.
  5. Whiplash Injury: Trapezius muscle injuries can occur as a result of whiplash, typically due to a car accident or other traumatic event that causes sudden acceleration and deceleration of the head and neck. Some tackles during rugby matches may be a similar cause of whiplash injury affecting the Trapezius muscle.
  6. Rotator Cuff Impingement: Trapezius muscle imbalances or overuse can contribute to rotator cuff impingement, a condition in which the tendons of the rotator cuff muscles become compressed. This compression can lead to rotator cuff tendon inflammation, with symptoms of pain and limited range of motion. 
  7. Cervicogenic Headaches: Dysfunction or tension in the Trapezius muscle can contribute to cervicogenic headaches, which are headaches that originate from the neck and may radiate to the head. So the trapezius muscle, together with other neck muscles such as Splenius Capitis, Splenius Cervis, and Levator Scapulae muscles, under excessive use or stress can be the main cause of this particular form of tensive headache.

Trapezius muscle injury treatment

Treatment for Trapezius muscle injuries and conditions typically involves a combination of rest, physical therapy, stretching exercises, strengthening exercises, sports therapy such as sports massage, and pain management techniques. In severe cases or when conservative treatments are ineffective, medical interventions such as injections or surgery may be considered.

We advise you to seek a healthcare professional help such as a sports therapist or physiotherapist for an accurate diagnosis and tailored treatment plan if you suspect you have a trapezius muscle injury or related condition.

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