The main causes of weakness and weakness of the feet are excessive sports, disorders of water-electrolyte balance, lumbar spine or cervical spine problems, as follows: 1. Excessive sports: For example, a lot of sports during the day can cause a large accumulation of lactic acid in the joints and muscles, which can lead to joint weakness and weakness at night. 2. Disorders of water-electrolyte balance: Especially when the potassium is low, weakness of the limbs can occur. When this occurs, it is important to go to the hospital for a blood electrolyte test. If hypokalemia is found, make sure to actively replenish potassium to correct the blood potassium to normal levels so that the weakness of the legs can be completely improved. 3, lumbar or cervical spine problems: For example, when cervical spondylosis compresses the cervical medulla, it will cause weakness of the legs and unstable walking. And when there is lumbar spinal stenosis, it will also cause weakness in walking and intermittent claudication in the lower limbs.