Frequent calf cramps are caused by the following reasons: 1, the calves are stimulated by the cold environment, for example, the winter night temperature is relatively low, the quilt is too thin or sleep with bare legs and feet. 2, too fatigue, insufficient rest time or too long rest can cause the accumulation of local acidic metabolites in the calves. For example, prolonged walking or exercise, so that the legs are overworked or not enough rest and sleep can accumulate lactic acid. If the sleep time is too long blood circulation will slow down, and will accumulate carbon dioxide, can cause muscle spasm.3, blood calcium levels are too low, increasing muscle pressure and often produce spasm.4, no good sleep position, such as sleeping flat for a long time, so that the quilt pressed on the feet or sleeping on the back of the feet for a long time, so that the back of the feet pressed on the bed for a long time, forcing the muscles of the calf in a long time of absolute relaxation, resulting in muscle contracture. resulting in passive muscle contracture.