portion of the peritoneum that underlies the diaphragm is innervated by the phrenic nerve, it could explain the shoulder tip pain. The parietal peritoneum traverses the entire abdominal wall, which could account for the widespread distribution of ETAP; the tension in the parietal peritoneum is increased with torso extension; children have a proportionally larger peritoneal surface compared to adults, which could explain the increased prevalence of ETAP in younger individuals; and pain arising from the parietal peritoneum relieves quickly on removal of the stimulus, similar to what is observed for ETAP when activity is ceased. After a meal, distention of the stomach could increase friction between the visceral and parietal layers of peritoneum, and sugary beverages could provoke ETAP due to slower emptying of the stomach. In fact, the fluid in the peritoneal cavity is highly responsive to osmotic gradients between it and its vascular supply. In the absence of a clear cause, any treatment techniques are uncertain. Typical strategies involve deep breathing and/or manual pressure on the affected area. Occurrence Side stitches occur in every level of athletes from school-aged children, weekend exercisers, or elite athletes, although they are more common in younger people. Activities that use upper body twists, like running, swimming, and horseback riding, report this affliction more often. Approximately two-thirds of runners will experience at least one episode of a stitch each year. See also Precordial catch syndrome References Further reading External links Abdominal pain Physical exercise