What is this sharp twinge of pain just below the rib cage usually on the right? It is called a "side stitch" or "exercise related transient abdominal pain" (ETAP); and until recently there was no clear and universally explanation for the cause of this annoying cramp. Although not considered a true sports injury, it has been estimated that 70% of regular runners suffered from a side stitch in the last 12 months, that's a big pain in the gut!

Some researchers believe that the side stitch is caused by stretching the ligaments that extend from the diaphragm to the internal organs, particularly the liver. The jarring motion of running while breathing in and out tends to stretch these ligaments. Runners tend to exhale every two or four steps, more frequently when trying to get back into shape. The majority of people exhale as the left foot hits the ground, but some people exhale when the right foot hits the ground. It is this group who seem more prone to get side stitches.

There is greater force on the liver (which is on the right side just below the rib cage) when exhaling while the right foot hits the ground. So, just as the liver is dropping down the diaphragm raises for the exhalation. It is believed this repeated stretching leads to spasms in the diaphragm and this spasm causes your pain. Seems like a good explanation to me, much better than my old coach's explanation, "because you are an out-of-shape wimp!" Other less accepted theories have included: diaphragmatic ischemia, imbalances of the thoracic spine, and irritation of the parietal peritoneum. Whatever the internal cause, there are some simple veteran runners tips that may help avoid or at least diminish this pain.

How do you stop a Side Stitch?

A good way to stop a side stitch is to stop running and place your hand into the right side of your belly pushing upward to lift the liver slightly. Inhale and exhale evenly as you push up.

Can you prevent a Side Stitch?

To prevent a side stitch, take even, deep breaths while running. Shallow breathing tends to increase the risk of cramping because the diaphragm is always slightly raised and never lowers far enough to allow the ligaments to relax. When this happens the diaphragm becomes stressed and a spasm or "stitch" is more likely. This is why they happen more often when runners are trying to get back into shape after a layoff.

Ten other tips to alleviate or avoid the pain of a side stitch include:

1. Improve your cardiovascular fitness.

2. Warm up properly before you run. Yes, that 5 minute warm-up walk again....

3. Strengthen your core muscles (lower back, abdominal and oblique muscles).

4. Avoid too much, too soon, too fast syndrome (my daughter's problem).

5. Avoid eating one to two hours before a workout. Having food in your stomach during a workout may increase cramping by creating more force on the ligaments.

6. Stretching may relieve and even prevent a cramp. Raise your right arm straight up and lean toward the left. Hold for 30 seconds, release and relax, and then stretch the other side.

7. Slow down your pace until pain lessens, or walk it out.

8. Breathe deeper to stretch the diaphragm when you feel a cramp coming on. Then, breathe slowly out of your mouth with pursed lips; this tends to relax the diaphragm.

9. Drink before exercise; dehydration can increase muscle cramps. An electrolyte sports drink may be even more helpful than just plain water. Avoid any carbonated beverages one to two hours prior to running.

10. Massage or put firm pressure on the area with pain. Bend forward and relax to stretch the diaphragm and ease the pain.

If you continue to experience pain, seek medical attention. A side stitch that lasts more than a few minutes could be early signs of appendicitis (or just simply annoying constipation). Pain radiating into your shoulder, chest or back may even be heart-related.

For most runners, a side-stitch is just a signal to slow down and relax! In my family, it gives my daughter an excuse to skip the end of a grueling workout! Maybe she is the smarter one?!