When exercising, a sie stitch (also called a side cramp, a side sticker or, more commonly in proper English, simply a 'stitch') is an intense stabbing pain under the lower edge of the ribcage. It is also referred to as exercise related transient abdominal pain (ETAP). This pain is caused by the internal organs (like the liver and stomach) pulling downwards on the diaphragm. It is therefore more likely to occur in sports involving up and down actions - like running, jumping and horse riding.