What causes sharp pain under right breast under rib cage when running?

Pain under the: rib cage may be due to a collection of gas in the large intestine which curves under the rib cage on both sides of the abdomen...the "shaking" of running forces normal bowel gases to "collect" in those curves (eg on the left and more common side this is called "splenic flexure syndrome" This diagnosis is only made when other causes are ruled out so an in person visit to your PCP is indicated. Z