Besides the Rhomboids, Levator Scapula and Latissimus Dorsi, Trapezius is one of the broadest muscles of the back and is also the most superficial of all the neck, back and upper trunk muscles. Together with the semispinalis capitis muscles, it creates a wide column along the back section of the neck delivering upright posture support. Triangular and flat, and named for its diamond shape, the trapezius connects the ribs, scapulae, clavicles and spine.
Promoting active movement and good posture, the trapezius exists to steady the shoulders, shrug, tilt and turn the head and neck, and twist the arms. More specifically, this muscle works on the shoulder blade (the scapula) to retract, depress, elevate, and rotate, and also to support the arms. It is innervated (controlled) by the spinal accessory nerve.