Hi
Pain in the stomach in runners is a very frequent problem. It may be due to the abdominal wall muscles ("stitch") or the gastrointestinal system.
Dehydration prior to running may lead to gastrointestinal complaints like belching, flatulence, nausea, vomiting, intestinal cramps, and stomachache.
Stitches are sharp pains like cramps that occur during exercise (particularly running), usually near the ribs, that may cause the runner to stop from running.