Patients with muscle soreness in both thighs, in this case, generally have to consider a lot of exercise, fever, lumbar disc herniation and other causes, as follows: First, a lot of exercise: may be due to a lot of recent sports, such as long-distance walking, hiking, running, which will cause a lot of lactic acid to accumulate in the legs, and therefore will cause soreness and pain in the thighs. Secondly, fever: it may be caused by fever, because the basal metabolic rate in the body increases when the body is hot, which will make lactic acid glycolysis speed up, which will make lactic acid accumulate in the muscles and joints of the whole body, which will cause soreness in the muscles and joints of the whole body. When the body temperature drops, this soreness will disappear. Third, lumbar disc protrusion: when the protruding disc compresses the sciatic nerve, it will cause radioactive pain in both lower limbs, and sometimes it can manifest as pain in the back of the thighs.