The pain in the lower left corner of the running stomach may be caused by acute chest and rib pain, intestinal spasm, muscle strain and other reasons. 1. Acute chest and rib pain: when you don’t do the necessary preparatory movements before running, it may lead to spasm of intercostal muscles and diaphragm, which may cause pain in the lower left corner of the patient’s stomach and chest. 2. Intestinal spasm: when running, breathing with the mouth open makes a lot of cold air enter the gastrointestinal tract, which may also cause the symptoms of pain in the lower left corner of the stomach, and may be accompanied by abdominal distension, belching and other manifestations. 3. Muscle strain: when running is too strenuous and the exercise time is relatively long, it is likely to cause muscle strain in the lower left corner of the stomach, which can also cause the symptoms of running pain in the lower left corner of the stomach. Running pain in the lower left corner of the stomach may also be caused by other reasons, and it is recommended that the patient go to the hospital in time.