If you feel the stitching in the right or left side while running or fast walking, know this: it's a pain in the capsule of the liver (if the pain in the right side) or spleen (if the tunic is in the left side).
And does this pain that's why. In the rest of the blood is not circulating in the blood stream, and is in reserve ("reserve"), while the majority of the circulating blood is in the thoracic and abdominal cavities. During physical activity the body is a redistribution of blood flow in favor of the working muscles. But if the muscles begin to work immediately, vegetative functions, which provide their work (breathing and circulation), required for the work for a few minutes. If we begin to move quickly without prior warm-up, the blood from the reserve enters the bloodstream, but it does not have time to quickly flowing out from the abdominal cavity. Liver and spleen are engorged with blood, increase in size and begin to put pressure on their capsules. And capsules have pain receptors - they give a signal in the form of a pricking pain.
To avoid this, before running must perform warm-up and do not forget about the gradual approach of the training is to prevent over-voltage when running.
If the pain has appeared, then you need to reduce the load to reduce the running speed or even go for a walk) and take a few deep breaths. Deep breathing allows you to accelerate the outflow of blood from the internal organs (including liver and spleen) and to normalize the blood circulation. Still useful as deeply as possible to suck in your gut. So you spend a massage of the liver - when the retraction of the abdomen, the diaphragm presses the liver to the spine and squirts from her blood. When the hyperextension of the capsule of the liver or spleen will stop the pain goes away.
Pain in right side may receive and if you start running immediately after eating. The cause of the pain is the same - the hyperextension of the capsule of the liver. Because the liver is involved in the digestion of food, and if the food has entered the digestive tract, blood vessels dilate; enhanced bile ducts - they begin in the intestinal bile.
To avoid pain in this case is very simple: you need to start training no earlier than 2-3 hours after eating. And don't drink too much water during exercise.