The sternocleidomastoid muscle is a very important muscle in the superficial layer of the neck, yet it is a muscle that is often overlooked. The reason it is called the biggest sleeper of neck pain is that injuries to this muscle can cause neck and even head pain, but this muscle never shows pain, so it is rarely or not treated enough. In modern life, basically no one’s sternocleidomastoid muscle is painless to palpation, so it is a big question of which muscle or sides to deal with when a person has neck pain. The sternocleidomastoid muscle is the most superficial muscle in the neck and is called sternocleidomastoid because it starts at the temporalis mastoid and is divided into two muscle bundles, one ending at the sternum, called the sternocleidomastoid bundle (medial, diagonal and more superficial); and one ending at the upper edge of the anterior surface of the medial 1/3 of the clavicle, called the clavicular bundle (lateral and deeper). According to its starting point we can find: the sternocleidomastoid muscle is the longest bundle of muscle fibers when the head is kept in an upright position, and whether we tilt our head, head down or side flexion our sternocleidomastoid muscle is in a shortened state, while modern people read books, read computers, and play with cell phones are basically in a low state for a long time, when the posterior cervical muscle group is elongated and the anterior cervical muscle group is shortened. At the same time, the sternocleidomastoid muscle is also shortened, and the sternocleidomastoid muscle in a shortened state for a long time will naturally shorten habitually, which will lead to a series of symptoms caused by damage to the sternocleidomastoid muscle. When a patient comes in with what we call “upper cross – round shoulder hunchback head lead” and tells us that he has pain at the back of his neck, should we deal with his anterior or posterior cervical muscles. Traditionally, we think that we should push where the pain is, and after treatment, the patient will tell us that he is much better, but in a few days, the patient will come back and tell us that the pain has started again, so we keep treating the patient, and we keep receiving thanks from the patient. In fact, we can think about it, we keep dealing with the stretched muscles, the pain will be temporarily relieved, but the real cause of the disease is the shortening of the anterior neck muscles, the more the posterior neck muscles are relaxed, the more the anterior neck muscles will be tense. So if we keep dealing with the posterior cervical muscles, we are treating the disease and causing the disease at the same time. The real way should be to deal with the muscles in the front of the neck and on both sides of the neck, and the back of the neck is also something that should be dealt with if there is muscle damage. Functions of the sternocleidomastoid muscle: Bilateral simultaneous contraction: 1. flexes the neck and pulls the head forward to bring the chin closer to the chest; 2. can control hyperextension of the neck; 3. acts with the superior trapezius to help stabilize the head in space during speech and chewing; 4. can assist the respiratory muscles to inhale when the head is extended; 5. is also involved in swallowing movements, so many patients with clinical swallowing disorders should not only be treated The sternocleidomastoid muscle should also be dealt with; 6. The sternocleidomastoid muscle helps with spatial orientation, weight perception, and motor coordination. Unilateral contraction: 1. is ipsilateral lateral flexion and contralateral rotation of the neck; 2. acts together with the trapezius muscle so that the ear can touch the shoulder in a downward direction. Symptoms resulting from injury to the sternocleidomastoid muscle: can cause different autonomic phenomena as well as proprioceptive disturbances. The pain radiates to the top of the skull, occipital region, cheeks, orbits, and reaches the neck. Patients often feel headache in the forehead and ear pain, and tinnitus is also associated with it. Pediatric tilt neck, postural vertigo, headaches experienced early in the morning after getting drunk, and spinal cord piercing headaches are all associated with sternocleidomastoid muscle injury. If the sternocleidomastoid muscle is too tight, it can trap the collateral nerve that passes through it and cause mild paralysis of the trapezius muscle.