Dooley Noted: 1/9/15
The trapezius muscle is a fascinating muscle that assists with spinal movement and stability, as well as shoulder movement.
This muscle gets its name from its trapezoid appearance. It originates from the skull, extending it’s length to the last thoracic (midback) vertebrae.
It heads laterally to insert on the spiny, posterior part of the scapula (shoulder blade) and its peak-like acromion, as well as the clavicle (collarbone).
The muscle is considered to be a limb muscle that moves the shoulder and neck, with little ability to move the midback. Through its fascial connections, it absolutely stabilizes spinal movement in primarily the sagittal (front to back) plane.
The muscle is a powerful extensor.
Trapezius is the only muscle of the limb to be innervated by a cranial nerve – but it’s not innervated by the brainstem.
Ventral rami (motor and sensory nerves) from C1-C5 actually exit the spine and ascend to enter the skull, just to once again exit the skull and hit the motor end plates. This is where these rami innervate trapezius and the sternockeidomastoid (SCM).
So, trapezius is innervated by the upper neck. Low level joint compressions in this area lead to increased facilitation of the muscle’s upper fibers.
We earned that neck curve first when we started trying to hold our heads up after birth.
And many of us are still using our necks to dominate movement.
Holding up our heads was one of our first great achievements. We are programmed to seek stability and movement here.
The upper trapezius has the function of scapular elevation and upward rotation, as well as neck lateral flexion and extension . Just imagine yourself shrugging and you’ll see the actions of upper trapezius.
The upper trapezius is in a force couple with lower trapezius and serratus anterior’s lower fibers for the powerful action of upward scapular rotation.
But when the neck is compressed or upper trapezius is overused, it disturbs this smooth force couple motion.
Since upper trapezius attaches to the clavicle and acromion, it also disturbs acromioclavicular (AC) joint movement. This joint permits overhead movement.
So, the same muscle that facilitates overhead movement can actually prevent it when the muscle is overused!
If the upper trapezius is allowed to dominate movement, then shoulder biomechanics are altered significantly. Shoulder instabilities soon follow.
So, most shoulder problems start as neck problems. Remember: it’s the upper trapezius that attaches to the neck and skull.
If you are focusing on shoulder mechanics with no regards to the neck, you are missing the boat.
Assess the neck.
Then, assess the force couple of upper/lower trapezius with serratus anterior.
Start here, then branch out to other shoulder prime movers, like pectoralis and latissimus.
And don’t forget your stabilizers, like rotator cuff muscles.
But don’t skip the neck and spine. In fact, I encourage you to start there.
If your client gets fussy that you’re not addressing the “shoulder,” show the anatomy and explain upper trapezius and its attachments, as well as its innervation from the neck.
As always, it’s your call.
– Dr. Kathy Dooley