The scalene or trapezius muscle (posterior scalene muscle) is one of the muscles that are part of the lateral muscle group of the human neck. Normally, the lower trapezius muscle is invisible to our eyes, but this group of muscles plays an important role in maintaining the correct position of the neck and head. This muscle is located behind the collarbone and connects to the first rib of the sternum. It is responsible for the movement of the head and neck, and is also involved in maintaining posture when lifting and moving objects. The main function of this muscle is to lift the shoulder up and, accordingly, tighten the collarbone. This protects the larynx and thyroid gland, which ensures safe swallowing and breathing. The muscles of this muscle are triceps. They form a triangle that ends at the corner of the shoulder blade, similar in shape to a rounded rectangle. It consists of the deltoid, teres major and teres minor muscles. Unlike most upper back muscles, the posterior scalene muscle is not supplied with blood and relies on other muscles for its blood supply. The anterior part of the muscle is supplied by the anterior scalene muscle, and the posterior part by the posterior interscalene muscle. The muscle also receives power from a muscle known as the musculus dorsi minor. During movement, the muscle is subjected to intense stress. This leads to fatigue and poor blood supply, which can lead to sports injuries and chronic diseases. In addition, prolonged stress on the trapezius muscle can lead to an imbalance of blood circulation in the neck and chest, which adversely affects a person’s mental state and can cause sleep problems