I often get asked about the cause of the “stitch” pain many people suffer from when running. No-one is entrirely sure of the cause or if there are multiple causes, but a recent study has helped define it.
Sports Injury Bulletin: Stitch pain article.
It appears that most people get a stitch on their right side, around the height of the upper abdomen. That’s where my stitch pain occurs (very rarely) and I don’t remember ever having a stitch on the opposite side. I think that I’ve also had pain in my right shoulder at the same time, suggesting to me that my diaphragm is involved. They linked eating a large amount of food within the 2 hours before exercise to the stitch, which also fits my history as I rarely eat much before running. If I do I often feel generally awful.