The following reasons are common: 1, overwork: daytime work is too tired or participate in strenuous exercise, can lead to double lower limb muscle overwork, muscle fatigue, at the same time, there is a large amount of lactic acid inside the muscle accumulation, can also cause the clinical symptoms of weakness, and even can not walk normally. Through massage, hot compresses and elevation of the affected limbs, the clinical symptoms can be relieved.2. Lumbar diseases: severe lumbar spinal stenosis or lumbar disc herniation can stimulate and compress the nerves of the lower extremities, resulting in the loss of innervation of the muscles of the lower extremities, which will also manifest in the clinical symptom of weakness of the legs, accompanied by lumbar pain and lumbar spine activity restriction. CT or MRI examination can find the specific degree of lumbar spine lesions. 3, calcium deficiency or osteoporosis: calcium deficiency or osteoporosis can lead to generalized pain in many bones, lower limb weakness, should be serum calcium ion test and bone mineral density test to rule out. Sleeping legs appear sore and weak, must be early diagnosis, early treatment, to avoid serious consequences such as muscle atrophy of both lower limbs, to avoid affecting the normal life and work.