Back pain after running is generally considered to be caused by incorrect running posture, chronic lumbar muscle strain, acute lumbar muscle injury and lumbar spine disease. 1. Incorrect running posture: If the running posture is incorrect, during the process of running, the muscles of the lumbar back and abdomen are in a state of relaxation, and the core stability is not strong, which will increase the lumbar load, and you will have back pain after running. 2. Chronic lumbar muscle strain: If you have lumbar fasciitis or lumbar muscle strain, you will suffer from back pain if you exert yourself too much and pull the lumbar muscles during running. 3. Acute lumbar muscle injury: If you run too long and too fast, it will easily lead to acute injury of lumbar muscle or fascia, which will also lead to back pain after running. 4. Lumbar spine disease: If you suffer from lumbar spine disease, such as lumbar intervertebral disc herniation, lumbar intervertebral stenosis, etc., it will usually press on the lumbar nerves to cause lumbar pain, and the lumbar pain will be aggravated after running. If you have back pain after running, you must pay attention to rest and avoid strenuous exercise. If the back pain can not be relieved after rest, it is recommended to go to the orthopedic department of the regular hospital as soon as possible to improve the X-ray, CT examination, etc., to find the cause of the disease and timely treatment.