You're running at a fast clip and suddenly you feel a dull ache underneath your ribs on your right side. The pain worsens as you keep running and disappears when you stop. A side stitch is caused by stretching the ligaments that extend from your diaphragm to hold up your liver.
Humans breathe out once every two steps.
More than 70 percent of humans breath out when their left foot hits the ground, while 30 percent breathe out when their right foot hits the ground. Those who breathe out when their right foot hits the ground are the ones most likely to suffer side stitches because the force of the right foot strike causes the liver to go down and stretch when their diaphragm goes up as you breathe out. When you get a side stitch, stop running immediately, reach your fingers into the right side of your belly and push your liver up. And breathe out with you lips pursed at the same time. Then you can resume running without feeling any pain.