Trapezius muscle

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In human anatomy, the trapezius is a large superficial muscle on a person's back. It is innervated by the accessory nerve (Cranial Nerve 11) and the ventral rami of Cervical vertebrae 3 and 4, which also supplies the sternocleidomastoid muscle.

Actions

Because the fibers run in different directions, it has a variety of actions, including:

scapular elevation (shrugging up or lifting the shoulders)
scapular adduction (drawing the shoulder blades toward the midline)
scapular depression (pulling the shoulder blades down)

Different fibers control different actions:

The superior (upper) fibers elevate the scapula
the middle fibers retract it
The inferior (lower) fibers depress it
When the superior and inferior fibers act together, they superiorly (upwardly) rotate the scapula

Nomenclature

Trapezius gets its name from its trapezium-like shape when looking at both muscles at once: the corners being the neck, the two shoulders, and the thoracic vertebra, T12.

The word "spinotrapezius" refers to the human trapezius, although it is not commonly used in modern texts. In other mammals, it refers to a portion of the analogous muscle. See trapezius muscles (cat) for more details.

Anatomical details

It arises from the external occipital protuberance and the medial third of the superior nuchal line of the occipital bone, from the ligamentum nuchae, the spinous process of the seventh cervical, and the spinous processes of all the thoracic vertebræ, and from the corresponding portion of the supraspinal ligament.

From this origin:

the superior fibers proceed downward and lateralward. They are inserted into the posterior border of the lateral third of the clavicle.
the inferior fibers proceed upward and lateralward. They converge near the scapula, and end in an aponeurosis, which glides over the smooth triangular surface on the medial end of the spine, to be inserted into a tubercle at the apex of this smooth triangular surface.
the middle fibers proceed horizontally. They are inserted into the medial margin of the acromion, and into the superior lip of the posterior border of the spine of the scapula.

At its occipital origin, the Trapezius is connected to the bone by a thin fibrous lamina, firmly adherent to the skin.

At the middle it is connected to the spinous processes by a broad semi-elliptical aponeurosis, which reaches from the sixth cervical to the third thoracic vertebræ, and forms, with that of the opposite muscle, a tendinous ellipse.

The rest of the muscle arises by numerous short tendinous fibers.

The two Trapezius muscles together resemble a trapezium, or diamond-shaped quadrangle: two angles corresponding to the shoulders; a third to the occipital protuberance; and the fourth to the spinous process of the twelfth thoracic vertebra.

Variations

The attachments to the dorsal vertebrae are often reduced and the lower ones are often wanting; the occipital attachment is often wanting; separation between cervical and dorsal portions is frequent.

Extensive deficiencies and complete absence occur.

The clavicular insertion of this muscle varies in extent; it sometimes reaches as far as the middle of the clavicle, and occasionally may blend with the posterior edge of the Sternocleidomastoideus, or overlap it.

Exercise

The upper portion of the trapezius can be developed by elevating the shoulders. Common exercises for this movement are shoulder shrugs and upright rows. Middle fibers are developed by pulling shoulder blades together. Best exercises for this movement are rowing exercises and deadlifts. The lower part can be developed by drawing the shoulder blades downward while keeping the arms almost straight and stiff. This can be done in a pull-down station for example.

A person can feel the muscles of the superior trapezius become active by holding a weight in front of them in one hand, and with the other, touching the area between the shoulder and the neck. It is common for non-experienced gym users to focus mostly to the upper portion of the muscle, and thus forgetting the important middle part and creating muscle imbalances which can heavily affect posture and compromise shoulder health.

Barbell Shrug

Hold a barbell with both hands in front of you with your hands a little wider than shoulder width apart. Keep your feet at shoulder width. Stand straight up with the bar hanging at arms length. Droop shoulders down as much as possible to start. Raise your shoulders up as far as you can go. You can also rotate your shoulders as you go up, going in a semicircular motion from front to rear. Then slowly return to the starting position. Can also be done with dumbbells.

Barbell Shrug Behind The Back

Hold a barbell behind your back with your palms facing backwards. "Shrug" your shoulders upward as high as you can and squeeze it for a second. Then lower the bar all the way down as far as you can. To get the barbell into position, you can rest it on a power rack or bench and then pick it up from there. You can also do these with dumbbells.

Cable Shrugs

Grasp cable bar that is attached to the low pulley with a shoulder width or slightly wider overhand grip. Stand close to pulley. Elevate shoulders as high as possible. Lower and repeat.

-Machine Shoulder Shrug

This is a great way to work your traps and avoid having to hold dumbbells or barbells, which can be hard on your arms or wrists. Position yourself on the calf machine so that the shoulder pads are above your shoulders. Put your hands on your hips. Raise your shoulders up towards your ears and hold it for a full second. Slowly return to the starting position and repeat. You can change your shoulder position (bending over a little) to hit the traps from different angles.

Dumbbell Incline Shoulder Raise

Preparation:

Sit down on an incline bench with the dumbbells resting on your lower thigh. Kick the weights to your shoulders and lean back. Position the dumbbells above your shoulders with your elbows extended.

Execution

Raise your shoulders toward the dumbbells as high as possible. Lower shoulders to bench and repeat.

Dumbbell Shrug

Stand straight up with your feet at shoulder width. Hold two dumbbells with your arms hanging at your sides. Droop shoulders down as far as possible. Raise shoulders up as far as you can go. Then slowly return to the starting position. You can also rotate your shoulders by going up in a circular motion from front to rear and then back down. Can also be done holding a barbell instead.

Low Pulley Row To Neck

This is like a seated row but you use a rope handle and pull to your neck. Sit at a seated row station and grab the ends of the rope using a palms down grip. Sit with your knees slightly bent and your back straight. Your back should be almost completely vertical... do not lean back! Keeping your back in the same vertical position, pull the rope back and up to neck height. Your elbows should be out, away from your sides. Return slowly to the starting position. Ths targeted muscles are Biceps, Middle Back, Shoulders.

Smith Machine Shrug

Stand grasping Smith bar with shoulder width or slightly wider overhand grip. Disengage bar from the rack. Elevate shoulders as high as possible. Lower and repeat.

Smith Machine Upright Row

Same as the Upright Barbell Row but with a Smith Machine. The targeted muscles are Traps, Biceps, Shoulders.

Snatch Hang High Pull

These are just like the Power Clean except that you start from a hanging position and you do not catch it at the top. Check out the Power Clean for more info. The targeted muscles Traps, Worked: Biceps, Lower Back, Forearms, Hamstrings, Calves, Abdominals, Shoulders.

Standing Dumbbell Upright Row

Hold dumbbells, hanging, against your upper thighs. Keep dumbbells about 10 inches apart, thumbs facing in. Pull dumbbells straight up until nearly even with your chin. Keep your elbows up and out! Keep weights close to your body and slowly return to the starting position. Can also be done with a cable or barbell. The targeted muscles are Traps, Biceps, Shoulders.

Upright Barbell Row

Standing upright, grasp a barbell with your hands about shoulder width apart. Let the bar hang straight down in front of you. Keep your body and wrists straight. Pull the bar straight up towards your chin, keeping it close to your body. Concentrate on either pulling with your traps or the front of your shoulders, depending on what you want to work most. Lower slowly to the starting position. Don't cheat by leaning forward or backward. Don't swing! The targeted muscles are Traps, Biceps, and Shoulders.

Upright Cable Row

Standing upright, grasp a straight bar connected to a cable machine with your hands about shoulder width apart. Let the bar hang straight down in front of you. Keep your body and wrists straight. Pull the bar straight up towards your chin, keeping it close to your body. Concentrate on either pulling with your traps or the front of your shoulders, depending on what you want to work most. Lower slowly to the starting position. Don't cheat by leaning forward or backward. Don't swing! The targeted muscles are Traps, and Shoulders.

Additional images

Muscles of head and neck.
Occipital bone. Outer surface.
Left clavicle. Superior surface.
Left scapula. Dorsal surface.
Section of the neck at about the level of the sixth cervical vertebra.
Muscles of the neck. Anterior view.
Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.
The arteries of the face and scalp.
The triangles of the neck.
The nerves of the scalp, face, and side of neck.
Hypoglossal nerve, cervical plexus, and their branches.
Anterolateral view of head and neck.
Front view of neck.
Surface anatomy of the back.
The left side of the thorax.