The sternocleidomastoid (SCM) muscle is a long, thin muscle that runs from the sternum (breastbone) and clavicle (collarbone) to the mastoid process, which is a bony protrusion at the base of the skull. The muscle has two heads, one on each side of the neck, and it is responsible for several important functions in the neck and head.
The sternocleidomastoid muscle is responsible for turning the head from side to side, as well as tilting the head forward and backward. It also helps to lift the head and shoulders when you are lying on your back. Additionally, the SCM muscle is involved in breathing, as it can help to open the airway by pulling the larynx (voice box) upward.
The sternocleidomastoid muscle is a common site for muscle spasms and tension, which can cause pain and discomfort in the neck and head. Stretching and massaging the muscle can help to relieve tension and improve range of motion in the neck. In some cases, physical therapy may be recommended to help manage muscle tension and improve neck function.