A stitch, also known as exercise-related transient abdominal pain (ETAP), is a localized pain felt on one side of the abdomen that many people experience from time to time when running or performing activities that require considerable torso movement. The pain can be mild, similar to cramping and aching, or severe, described as sharp and stabbing. The exact cause of a stitch is not yet conclusively determined, but some theories suggest that it could be due to diaphragm spasms, a decrease in blood flow to the diaphragm, or the stretching of ligaments between the diaphragm and some organs. To prevent a stitch from happening, it is recommended to avoid large meals or extra fluid before running, enhance your core, start slowly and gradually increase your pace, and properly warm up before exercising.