The main reasons for the stiff neck in the morning are twofold: 1, the pillow is not suitable when sleeping at night, such as the pillow is too high or too low, resulting in the normal physiological curvature of the cervical spine can not be maintained, there will be cervical spine parts of the muscles, tendons, ligaments and other soft tissues, strain, the formation of inflammatory lesions, inflammatory metabolites will stimulate the surrounding muscles, which will lead to muscle tension, so that the muscle becomes more tense. As a result, stiffness will occur. 2, because at night, the location of the neck is cooled, because after being cooled will lead to a slowing of blood circulation, and the muscles will become tense. In addition, the small blood vessels that travel through it will also contract, leading to a decrease in blood supply to the muscles from the small arteries, a decrease in the state of nutrition, and a restriction in venous return, which will lead to a further accumulation of inflammatory metabolites, leading to more pronounced stimulation of the muscles and muscle stiffness.