Trapezius

Trapezius is a large, superficial back muscle that extends from the back of the head and the upper part of the spine to the shoulder blades and the clavicle. It is shaped like an inverted triangle and is functionally and anatomically divided into three parts: upper, middle, and lower trapezius.

Origin

Trapezius has a broad and complex origin. Each part of the muscle has its own attachment areas, which together form a large area of origin.

Upper trapezius:

• External occipital protuberance (posterior part of the skull)

• Superior nuchal line (upper nuchal line of the occipital bone)

• Ligamentum nuchae (strong connective tissue in the neck)

• Spinous processes of C1–C7

Middle trapezius:

• Spinous processes of T1–T5 (upper thoracic vertebrae)

Lower trapezius:

• Spinous processes of T6–T12 (lower thoracic vertebrae)

Explanation: These areas provide trapezius with a stable origin from both the neck and upper back. The ligamentum nuchae functions as a tendon-like structure that absorbs forces from head movements and transmits them to the trapezius.

Insertion

The muscle’s broad origin contrasts with more specific insertion areas on the shoulder and clavicle.

• Upper trapezius inserts laterally on the clavicle

• Middle trapezius inserts on the acromion and the upper part of the spine of the scapula

• Lower trapezius inserts on the medial part of the spine of the scapula

Clinical context: This three-part anchoring allows the muscle to precisely control scapular movements in all directions – a crucial function for positioning of the arm.

Innervation

Trapezius is one of the few muscles in the body that is not innervated by a spinal nerve via the brachial plexus, but instead by a cranial nerve.

• Nerve: Accessory nerve (cranial nerve XI), together with contributions from spinal nerves C3 and C4, which provide sensory information (proprioception).

Explanation: The accessory nerve originates from the brainstem and provides motor control. The interaction between cranial and spinal nerves gives trapezius both strength and precision.

Clinical tip: Injury to the accessory nerve, for example after neck surgery, can result in clear trapezius atrophy and reduced ability to elevate the shoulder.

Blood supply

The blood supply mainly comes from three sources:

• Transverse cervical artery (from the thyrocervical trunk, a branch of the subclavian artery)

• Dorsal scapular artery (may have variable origin, often from the subclavian artery)

• Segmental contributions from intercostal arteries and the occipital artery

Explanation: This rich vascularization makes trapezius well suited to tolerate sustained load over time, especially during postural activity.

Function and fiber direction

Trapezius is unique among the back muscles because it has three distinct functional parts that act in different directions and with different roles. This makes the muscle central to nearly all movements of the scapula. Scapular mobility is essential for arm reach and function, and trapezius is the key muscle ensuring this coordination.

Functional division and fiber direction

The muscle is divided into:

Upper trapezius

Fiber direction: Slants downward and laterally – from the neck region to the clavicle.

Primary function:

• Elevation of the scapula (lifts the shoulder blade, for example when shrugging the shoulders)

• Together with the lower part: Upward rotation of the scapula during arm elevation above head level

Secondary function:

• Stabilizes the head and neck during postural activity

• Can contribute to rotation and lateral flexion of the head during unilateral contraction

Clinical relevance: During static activities, such as prolonged screen use, the upper trapezius often becomes overactive and tight. This increases muscle tone and can lead to tension, headaches, and neck pain.

Middle trapezius

Fiber direction: Horizontal – from the thoracic spine straight out to the acromion.

Primary function:

• Retraction (adduction) of the scapula – pulls the shoulder blades together

Secondary function:

• Stabilizes the scapula against the thorax during arm movements

• Partial assistance in upward rotation of the scapula in combination with the other parts

Clinical relevance: Weakness in the middle trapezius is often seen in scapular dyskinesis – the scapula moves away from the chest wall and contributes to impingement syndrome and pain during overhead activities.

Lower trapezius

Fiber direction: Upward and lateral – from the lower thoracic vertebrae toward the medial part of the spine of the scapula.

Primary function:

• Depression of the scapula

• Stabilizes and upwardly rotates the scapula (together with the upper part)

Secondary function:

• Contributes to maintaining proper scapular positioning during overhead arm use

• Counteracts overdominance of the upper trapezius

Clinical relevance: The lower trapezius is often underactive in individuals with poor scapular control. During shoulder stability training, activation of this part is often prioritized, especially in rehabilitation after rotator cuff injuries.

Cooperation with other muscles

Trapezius never works alone – it continuously functions in coordination with other muscles around the shoulder and neck:

• Serratus anterior: Together with trapezius, it is responsible for upward rotation of the scapula, which is necessary to lift the arm above head level

• Levator scapulae and rhomboid major/minor: These muscles cooperate and balance trapezius in tasks such as retraction and elevation

• Deltoid: Trapezius ensures correct scapular positioning so that the deltoid can function effectively during abduction

Example: When you lift the arm straight out to the side (abduction), the deltoid performs the main action, but trapezius upwardly rotates the scapula and keeps it stable. Without this interaction, arm elevation would stop at approximately 90 degrees – movement above head level requires scapular motion controlled by the trapezius.

Clinical relevance and dysfunction

Trapezius is one of the most clinically significant muscles in the upper body. Not only is it active in nearly all movements of the scapula and neck, but it is also a frequent site of muscle tension, trigger points, postural overload, and neurogenic dysfunction. Its dual role in both mobility and stability makes it particularly vulnerable to faulty movement patterns, sedentary work, and injury.

Common dysfunctions in the trapezius

1. Muscle tension and trigger points (especially the upper part)

The upper trapezius is often overactive in individuals who:

  • Work statically in front of a screen

  • Maintain constant shoulder elevation (e.g. due to stress)

  • Have reduced function in the lower or middle trapezius

Chronic overload commonly leads to localized trigger points, which may cause:

  • Local pain in the neck, shoulders, and occipital region

  • Referred pain toward the temple or behind the eye

  • Tension-type headaches and stiffness during head rotation

2. Scapular dyskinesis and imbalance

When activity in the middle and lower trapezius is reduced, an imbalance between the different parts often develops. This may result in:

  • Excessive elevation of the scapula (upper trapezius dominance)

  • Insufficient retraction and depression

  • Compensatory overuse of the levator scapulae and rhomboids

This pattern is commonly referred to as scapular dyskinesis and is frequently observed in:

  • Impingement syndrome

  • Rotator cuff injury

  • Labral injury

  • Postural pain and movement restrictions

3. Neurogenic involvement – peripheral nerve injury

The trapezius is innervated by the accessory nerve (cranial nerve XI). Injury to this nerve (e.g. after neck surgery, lymph node removal, or trauma) may result in:

  • Visible scapular winging (lateral and inferior displacement)

  • Reduced ability to elevate the arm above 90 degrees

  • Weakness of both elevation and retraction

  • Pain and functional impairment throughout the shoulder complex

This condition is known as accessory neuropathy and may easily be misinterpreted as a rotator cuff disorder if scapular position and movement are not examined carefully.

Common compensation patterns

When trapezius function is impaired, the body often attempts to compensate through other muscles:

• Upper trapezius overactivity may compensate for weak lower fibers, but results in inefficient scapular motion and increased risk of neck pain.

• Levator scapulae and rhomboids often attempt to substitute for middle and lower fibers, but lack the ability to contribute effectively to upward rotation.

• Serratus anterior may become overloaded, particularly during overhead stability demands.

The overall result is frequently asymmetric scapular movement, reduced force production during arm elevation, and impaired postural control of the shoulder region.

Clinical observation and examination

During clinical assessment, the following should be evaluated:

  • Asymmetry in scapular position at rest and during movement

  • A scapula that appears to “hang” or elevate excessively

  • Failure of retraction or depression during shoulder abduction

  • Reduced strength during resisted retraction testing

  • Palpation tenderness in the upper trapezius and active trigger points

A useful clinical tool is the Scapular Assistance Test (SAT) to assess whether improved scapular mechanics reduce pain and improve motion. In addition, isometric strength testing of individual trapezius parts may reveal selective weakness.

Trapezius – exercises

The trapezius consists of three functionally distinct parts, making it essential to select exercises that specifically target each component. The primary goal is not only strength, but also control, coordination, and inter-muscular balance, particularly in cases of postural dysfunction, shoulder pathology, or scapular instability.

Upper trapezius – activation and strength

The upper trapezius elevates the scapula and is active during neck movements, load carrying, and shoulder elevation. In cases of overactivity, emphasis should be placed on control and relaxation, not strength alone.

Dumbbell shoulder shrugs

Starting position: Stand with dumbbells in each hand, arms relaxed at the sides.

Execution: Elevate the shoulders straight upward toward the ears with control, without elbow flexion.

Tempo: 2 seconds up – 3 seconds down.

Tip: Avoid shoulder rolling. Maintain a long, relaxed neck.

Progression: Resistance bands or cable machines may be used for constant tension.

Isometric elevation against resistance

Performed by actively pressing the shoulders upward against a static load (e.g. holding weights or pushing against a wall).

Useful in weakness following accessory nerve injury and for improving neuromuscular signaling.

Middle trapezius – retraction and stability

The middle trapezius draws the scapulae toward the spine and plays a key role in postural control and shoulder mechanics.

Prone horizontal abduction (T-exercise)

Starting position: Lie prone with the arms abducted to 90° (T-position), thumbs pointing upward.

Execution: Lift the arms while actively drawing the shoulder blades together.

Focus: Keep the forehead supported to avoid neck compensation.

Tip: Minimize upper trapezius activation – movement should originate from the scapula.

Row exercises with emphasis on retraction

Execution: Perform rowing movements (cable, TRX, or dumbbells) with deliberate scapular squeeze at end range.

Control: Hold the end position for 2–3 seconds.

Clinical benefit: Enhances neuromuscular control and postural endurance.

Lower trapezius – depression and upward rotation

The lower trapezius is frequently underactive, particularly in individuals with scapular dyskinesis or forward shoulder posture.

Wall slides with upward rotation

Start: Stand against a wall with arms at 90° (cactus position), elbows and hands in contact with the wall.

Movement: Slowly slide the arms upward while actively drawing the shoulder blades

downward and medially.

Purpose: Activate lower trapezius and serratus anterior simultaneously.

Common error: Excessive upper trapezius activation or loss of wall contact.

Y-exercise on bench or mat

Position: Lie prone on a bench with arms in a Y-formation (30–45° from the head).

Execution: Lift the arms upward and slightly backward while depressing and retracting the scapulae.

Variation: May be performed with resistance bands or suspension systems for increased proprioceptive demand.

Research: EMG studies demonstrate high lower trapezius activation with minimal upper trapezius involvement.

Relaxation and control

For many patients, trapezius rehabilitation is as much about reducing overactivity as strengthening weakness, particularly in the upper fibers.

Relaxation exercise – shoulder drop with breathing

Starting position: Sit or stand with upright posture.

Execution: Inhale deeply while elevating the shoulders. During exhalation, allow the shoulders to drop heavily and consciously release tension.

Repetition: Perform 5–10 repetitions, especially during neck or shoulder tension.

Neuromuscular control training using a mirror

Purpose: Improve body awareness and activation of the middle and lower trapezius.

Execution: Perform gentle retraction and depression movements while visually correcting motion patterns.

Summary

The trapezius plays a fundamental role in normal shoulder function. When this muscle becomes dysfunctional – whether through weakness, overactivity, or nerve involvement – the entire scapulothoracic system is affected. This often results in pain, reduced function, and compensatory strategies that may perpetuate or worsen the condition over time.

Sources:

• Palastanga, N., Field, D., & Soames, R. (1989). Anatomy and human movement: Structure and function. Oxford, England (6th edition): Churchill Livingstone.

• Standring, S. (2016). Gray's Anatomy: The anatomical basis of clinical practice (41st ed.). Edinburgh: Elsevier Churchill Livingstone.

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.