The most common causes of calf pain after running are calf muscle strain and microscopic tears in the calf muscle fibers. Calf muscle strain can usually be relieved in 1-3 days after resting, while small tears in the calf muscle caused by training can be relieved in 3-5 days after muscle stretching and resting, if the pain persists for 1 week without relief, it should be considered as medial and lateral gastrocnemius muscle head injury. Running requires repeated knee flexion and extension activities, and the gastrocnemius muscle will be strained when the front foot is on the ground and stretched backwards to complete the running action. If you rarely participate in physical exercise, the gastrocnemius muscle has very little tolerance, and once it exceeds the tolerance level, the medial and lateral heads of the gastrocnemius muscle can be injured, resulting in persistent pain in the lower leg. The examination method is as follows: straighten the knee joint, passive dorsiflexion of the ankle joint, the patient can feel the pain behind the calf is positive.