The causes of pain in the middle of both chests may be physical exertion, sternal lesions, upper gastrointestinal tract diseases, heart diseases, lung and mediastinal diseases. 1. Physical exertion: Physical exertion can cause lactic acid accumulation in the chest muscle tissues or muscle strains, resulting in hidden pain in the middle of the chest. 2. Sternum lesions: invasion of sternum by costochondritis, metastatic tumor of sternum, leukemia and other diseases can cause hidden pain in the middle of both chests. 3. Upper gastrointestinal system diseases: (1) Esophagitis and early esophageal cancer can appear as hidden pain behind the sternum, which is manifested as hidden pain right in the middle of two chests. (2) Gastroesophageal reflux disease and gastritis can present gastric acid reflux stimulation of esophageal mucosa, which may cause vague burning pain under the sternum. (3) Liver diseases, such as hepatitis and hepatocellular carcinoma, cause pain in the liver area, which can also extend and involve the chest, causing vague pain. 4. Heart diseases: angina pectoris, coronary heart disease, viral myocarditis, pericarditis, etc. because of myocardial ischemia, injury or inflammatory mediator stimulation of the pericardium can cause vague pain in the anterior region of the two chests in the middle. 5. Lung diseases: pleurisy, pneumonia, lung cancer and other diseases that stimulate the pleura or lung tissue can also cause vague pain in the middle of both chests. 6. Mediastinal diseases: thymoma, thymic carcinoma, lymphoma, thymic cysts and other diseases that cause masses to compress or invade the tissue behind the sternum can also cause vague pain in the middle of both chests. There are many causes of pain in the middle of both chests, among which there is no lack of high-risk diseases, and it is recommended to go to the hospital for further diagnosis and treatment after the appearance of related symptoms.