The trapezius muscle is much more than meets the eye. Far from just being the muscle located above the shoulders, the trapezius actually extends over a large portion of your back. When well-developed, it resembles the hood of a cobra. The trapezius is divided into three parts: the upper, middle, and lower fibers, each with similar but distinct functions.

Upper Fibers

When the trapezius muscle comes into discussion, the upper fibers are often the first to come to mind. This portion of the trapezius originates from the occipital bone (the bone at the bottom of the skull) and inserts into the outer part of the clavicle. Functionally, the upper trapezius has several roles including scapular retraction (pulling your shoulder blades back), scapular elevation (raising the shoulder blades), upward rotation of the scapula (when the shoulder blades twist upwards), and neck extension (looking upwards). In essence, the upper fibers are involved in almost all movements of the shoulder blades.

Middle Fibers

The middle, or medial, fibers of the trapezius originate from the vertebrae and insert into the scapula. The primary function of the middle trapezius is scapular retraction.

Lower Fibers

The lower fibers are the most overlooked part of the trapezius. When fully developed, the lower fibers contribute to the cobra hood appearance mentioned above. These fibers originate from the spinal column and insert into the scapula. The lower fibers are responsible for scapular depression (pushing the shoulder blades downward), adduction of the scapula (bringing the shoulder blades closer together), and, in conjunction with the upper fibers, assist in the upward rotation of the scapula.