A cramp is an involuntary, short-term persistent, intense muscle spasm that produces a series of symptoms such as pain and dysfunction of that group of muscles. There are several common causes of cramps: first, persistent muscle contractions, which do not relax the muscles and produce persistent muscle contraction tension leading to spasms. Common causes include prolonged overload activities, and strenuous exercise. The second, the physical and chemical environment of the body changes, resulting in persistent muscle spasm, such as calcium deficiency. The third, cold, because of cold local muscle vasoconstriction, resulting in less blood supply, resulting in muscle contraction or diastole, metabolites can not be timely discharge or degradation, resulting in muscle cramps. The total occurrence of cramps should pay attention to brake rest, reduce excessive workload and exercise, as well as pay attention to the warmth of the limbs. If the symptoms are not relieved in the short term, you need to go to the hospital in time for consultation.