The left chest pain that occurs during running is commonly a neuropathic pain, commonly known as a bruit. The pain occurs when the respiratory muscles spasm and the sensory nerve endings within the respiratory muscles are stimulated. The most important respiratory muscles in the body are the intercostal muscles and the diaphragm. When the intercostal muscles spasm, pain occurs on both sides of the chest. When the diaphragm is in spasm, the pain is usually located bilaterally under the arch of the ribs. There are also some patients who have a history of hypertension and coronary heart disease, and have left chest pain after running, which can be relieved after rest, so they should be alert to the possibility of coronary heart disease, angina pectoris or heart attack.