There are many reasons that lead to muscle pain in legs after walking, such as over-fatigue, muscle strain, lumbar disc herniation, deep vein thrombosis of the lower extremities, and so on. 1. Excessive fatigue: Long-term non-exercise, after participating in long-distance walking, will lead to fatigue of the leg muscles, and at the same time will produce a large amount of lactic acid accumulation in the muscles, thus triggering muscle pain in the legs. 2. Muscle strains: Exercising without warming up for the activity can lead to strains in muscles, ligaments and other soft tissues, thus causing muscle pain. 3. Lumbar disc herniation: when the nucleus pulposus in the lumbar intervertebral disc protrudes outward into the annulus fibrosus, it will compress the sciatic nerve, causing pain in the innervated area. Incorrect walking posture will strengthen the stimulation of compression and make the pain more obvious. 4. Lower extremity deep vein thrombosis: This disease affects the blood circulation of the legs, resulting in poor blood circulation in the lower extremities, reducing the amount of blood supplied to the muscles and making it easy to produce pain after walking. If pain occurs in the muscles of both legs after walking, it is recommended that the patient actively consult a doctor to clarify the cause of the disease after eliminating the physiological causes and under the guidance of the doctor.