The trapezius muscle is a flat, triangular muscle that covers the back of the
neck, shoulders and thorax. The upper and lower fibers are important to the
orientation of the shoulder blade (scapula). The upper part, acting alone,
elevates the shoulder and braces the shoulder girdle when a weight is carried.
The lower part draws the scapula downward. When both of the trapezius muscles
act together, the scapula can be brought toward the body and the head can draw