The trapezius muscle is a large, triangular muscle located in the upper back and neck. It originates from the occipital bone and the nuchal ligament of the skull, and inserts on the lateral third of the clavicle, the acromion, and the spine of the scapula. The primary function of the trapezius is to assist in the upward and downward rotation, as well as the adduction and abduction of the scapula. It also helps to stabilize the shoulder joint and maintain posture. The muscle is divided into three functional regions: the upper, middle, and lower trapezius.

The upper trapezius is responsible for the upward rotation and elevation of the scapula. This allows the shoulders to be shrugged upward, as well as allowing the head to be rotated and tilted.

The middle trapezius is responsible for the retraction and adduction of the scapula. This allows the shoulders to be drawn back and the scapula to be brought closer together.

The lower trapezius is responsible for the downward rotation and depression of the scapula. This allows the shoulders to be pulled down and the scapula to be lowered.

Together, the trapezius muscle helps to support the shoulder joint and maintain proper posture. It is commonly used in activities that involve pulling or rowing movements.

It is not necessary to use the trapezius muscle daily, as it will naturally be engaged during activities that involve movement of the shoulder and neck. However, incorporating specific exercises that target the trapezius can help to improve muscle strength and function.