Sore legs, weakness and feeling tired may be caused by overwork, hypokalemia, lumbar disc herniation and so on. 1. Over-exertion: It may be caused by strenuous exercise, long-term weight-bearing and other reasons. Patients may suffer from poor blood circulation in the legs and accumulation of large amount of lactic acid in the muscles, which may lead to symptoms such as leg pain, lumbago and fatigue. 2. Hypokalemia: Insufficient intake of potassium and excessive loss of body fluids may lead to a decrease in the concentration of potassium in the serum, resulting in hypokalemia and causing periodic paralysis. Symptoms such as numbness, soreness and weakness of limbs may occur. 3. Lumbar intervertebral disc herniation: it may be caused by trauma, lumbar intervertebral disc degeneration and other reasons. The herniated lumbar intervertebral disc can compress the nerves of the lower limbs, causing abnormal sensation in the lower limbs, thus causing the above phenomena. It is recommended that patients with sore legs, weakness and tiredness should go to the hospital in time, and follow the doctor’s instructions after clarifying the cause of the disease, so as to avoid delaying the condition.