The following reasons are common when sleeping at night: 1, it is possible that the lower extremities during the day to do a long time of physical exercise, or a long time of walking, resulting in the back of the calf muscles, fatigue and uncomfortable situation, the general rest 1-2 days symptoms will improve. 2, it is possible that the back of the calf muscles muscle strain, or muscle inflammation caused by the common lower extremities often do heavy physical labor or physical exercise. 3, may be neurological discomfort, such as lumbar disc herniation, lumbar spinal stenosis or lumbar spine slippage compression of the nerve roots of the lower limbs, which will also appear the calf muscle or skin, nerve sensory abnormalities and uncomfortable situation.