Lack of energy, weakness and tiredness of legs may be physiological reasons or pathological reasons, such as varicose veins of the lower limbs, thrombosis of the lower limbs, lumbar spinal stenosis and so on. 1. Physiological reasons: if the patient performs high-intensity sports, stands for a long time or maintains the same posture, the muscle tissues of the legs will experience twitching and other phenomena, so the legs will feel weak and tired. 2. Pathological reasons (1) Varicose veins of the lower limbs: congenital weakness of superficial vein wall or valve closure will lead to venous expansion, proximal vein valves of the branch of atresia incomplete, so that the blood flow backward, destroying the distal valves and the formation of varicose veins, the blood flow is not smooth, which will lead to the tiredness of the legs. (2) Lower extremity thrombus: the solid mass of blood condensed in blood vessels is thrombus, and the formation of thrombus will lead to bruising of lower extremities, which will lead to swelling of lower extremities and symptoms of fatigue and tiredness. (3) Lumbar spinal stenosis: Lumbar spinal stenosis can compress the nerves that innervate the legs, which may lead to atrophy of the muscles of the lower limbs, resulting in weakness and fatigue. Tiredness may also be caused by lumbar disc herniation, overwork, etc. If the symptoms of tiredness persist and are not relieved, you need to consult a doctor in time.