There are two main reasons for the soreness and weakness in the legs: first, a slight strain of the leg muscles, which can lead to the formation of local sterile inflammatory lesions, in which the inflammatory metabolites will stimulate the muscles, causing muscle tension, and stimulate the peripheral nerves around the soreness and weakness. Second, due to the leg muscles and surrounding soft tissues, strain and cold, after the formation of inflammatory lesions, in the cold state of blood circulation slowed down, the accumulation of inflammatory metabolites, and due to the slowdown of blood circulation, the blood supply to the muscles and surrounding soft tissues gradually decreased, will lead to the leg muscles present a soreness and weakness. Usually, after applying heat and keeping warm, the symptoms will be significantly relieved.