It took years for the medical community to learn what causes a side stitch in which a runner suddenly develops a sharp stabbing pain, usually in the right upper part of the belly just underneath the ribs. With continued running, the pain worsens, but it goes away as soon as you stop running.

Dr. Tim Noakes, a medical school professor from South Africa, offered the first reasonable explanation and successful treatment. Thick fibrous bands called ligaments extend downward from your diaphragm to hold your liver in place. When you run, your liver drops down at the same time that your diaphragm goes up from breathing out, stretching the ligaments to cause the pain.

Humans have a fixed pattern of breathing when they run. When you run slowly, you usually breathe out once for every four strides. When you run fast, you can breathe once for every two strides. When you breathe out, your diaphragm goes up, and at the same time, the force of your foot strike causes your liver to go down. Most people breathe out when their right foot hits the ground, so the cause of a side stitch during hard running is a stretching of the ligaments that hold the liver to the diaphragm on the right side. The cure is to relieve the stretching of the ligaments.

When you get a side stitch, stop running and press your hand deep into your liver to raise it up toward your diaphragm. At the same time, purse your lips tightly and blow out. Pushing the liver up stops stretching the ligaments. Breathing against pursed lips retards fully emptying your lungs and doesn’t let your diaphragm rise too high. The pain is relieved immediately and you can resume running as soon as the pain disappears. The pain usually will not go away unless you stop running long enough to raise your liver.

If You Get Frequent Side Stitches
• Breathe deeply when you run. The deeper you breathe, the more air you take in and the lower you push your diaphragm to decrease the stretching of the ligaments. Shallow breathing keeps the diaphragm in a high position to stretch the ligaments further.
• Breathe through pursed lips. This keeps your diaphragm high and allows you to relax your diaphragm.
• Try to breathe out when your left foot strikes the ground. Avoiding breathing on your right foot strikes will help to prevent maximum stretching of the ligaments when your diaphragm goes up as you breathe out.

Previous Theories About Side Stitches
We have learned that side stitches are not usually caused by:
• A liver swollen with blood during running. The liver has a very distensible capsule and it does not enlarge that much during exercise.
• Cramps in the belly muscles. The belly muscles are not held rigidly during a side stitch, and pushing on the belly muscles does not cause more pain.
• Lack of oxygen to the diaphragm. Blood flow to the diaphragm is not shut off by running.
• Trapped gas in the lungs. Gas does not get trapped in the lungs during exercise. Side stitches are rarely caused by intestinal gas. Pain caused by intestinal gas is relieved by passing the gas.
• Food in your stomach. Most runners have to eat during runs lasting longer than an hour. Eating does not cause discomfort unless you go so slowly that you spend more effort eating than running.

Constipation Can Cause Belly Discomfort
If your colon is empty when you run, it does not contract much during exercise. However, when you have stool in your colon, exercise can cause giant contractions of your colon which push stool towards the outside and can have catastrophic results. You will know that this is happening to you because you will feel these contractions in your lower belly and an urge to defecate. Always try to empty your colon before you exercise. If you are often constipated:
• Eat plenty of vegetables, fruits, whole grains and nuts. These are rich sources of fiber that keep food moving along your intestinal tract.
• Eat dried fruits such as dried apples, prunes and apricots. Dried skins of fruits contain lots of soluble fiber that binds to sugar in the fruit to prevent the absorption of these sugars in your upper intestinal tract. When soluble fiber reaches your colon, bacteria break it down to release the sugars so they are fermented immediately, drawing large amounts of fluid that dilates the colon and pushes stool toward the outside.
• Restrict constipating foods made from flour such as bakery products, pasta and many dry breakfast cereals.
• Try to have a bowel movement half an hour after you eat a meal to take advantage of the gastro-colic reflex. When food reaches your stomach, the stomach is stretched, sending a message along nerves from the stomach to cause the colon to contract and push foods forward. The longer stool remains in your colon, the drier and harder it becomes.