Legs are always cramping at night for three main reasons: First, because the activity is often greater during the day, the lactic acid and inflammatory metabolites produced locally, are metabolized in a more timely manner, but at night rest state blood circulation slows down, local metabolites appear to increase and accumulate, in the legs are prone to induce the promotion of the situation. Second, the night is cooler, which will lead to muscle tissue becomes more tense, blood circulation will also appear to slow down and decline. As a result, it leads to the accumulation of metabolic products, and leg cramps are induced under muscle tension. Thirdly, there is a trigger for leg cramps at night, that is, when lying down, if the quilt covered is too thick and heavy, it will cause the ankle joint to show the state of plantar flexion, and after a long time, it is also easy to induce leg cramps.