Back pain after running may be related to lactic acid accumulation, fasciitis, soft tissue injury and so on. 1. Lactic acid accumulation: if the patient runs for too long and with too much intensity, it can lead to the accumulation of a large amount of lactic acid in the dorsal muscles and other parts of the foot, which will make the patient suffer from pain in the dorsum of the foot after running. 2. Fasciitis: long-term running, mountain climbing, stair climbing and other activities can lead to chronic aseptic inflammation of the fascia and other tissues of the back of the foot, making patients experience pain in the back of the foot after running. 3. Soft tissue injury: when patients run with inadequate warm-up or sudden force, it can lead to muscle, ligament and other soft tissues due to tensile force and injury, so that the patients have pain in the back of the foot after running. Back pain after running can have many reasons, it is recommended to go to the hospital in a timely manner to improve the relevant examination for active intervention.