Stitches Hurt
Who hasn't felt it? The dreaded side stitch! The pain is usually on the right side under the ribs, sometimes up to the right shoulder, but it can be felt anywhere in the abdomen. It occurs often in runners but also occurs in other sports such as swimming, biking and horse riding. Indeed, it can even be reproduced in a few people with thoracic kyphosis (hunched upper back) by spine manipulation.
Simple observation reveals the problem to be more common with vigorous & prolonged exertion, especially if poorly conditioned, overweight or exercising soon after eating. Some have related it to breathing patterns related to footfall and a few even attributed it to chest wall muscle trigger points.
Recognizing more then one etiology, "side stitch" has now acquired the more impressive name, Exercise related Transient Abdominal Pain (ETAP).
It's no fun! Runners have tried many things to relieve the pain. Aerobic conditioning, abdominal muscle strengthening, good upright posture, weight loss and avoiding eating before running all do have benefits. So do "tricks" such as bending slightly at the waist while pressing your fist under the right side of the ribs and lifting. Some people find belly breathing and coordinating their breathing with foot strike (avoiding exhaling when the right foot hits the ground) also helps but trigger point pressure seems to have little success.
Knowing the cause is always more likely to lead to to an effective treatment. Since we're not talking about a cure for cancer here, research data has not been pouring in, but the subject has piqued the interest of a few scientists in recent years. They studied pain generators in the area making a rather logical assumption that something in or around the diaphragm was involved.
For those who have forgotten their anatomy, the diaphragm is a thick, flat muscular plate separating the chest and abdominal cavities. It's nerve supply is the phrenic nerve whose branches can produce referred shoulder pain. Diaphragm contraction, combined with external chest wall muscles connected to the ribs, move air in and out of the lungs.
The abdominal contents are partially suspended from the diaphragm by bands (visceral ligaments) and the biggest "hanging, solid hunk" is the liver on the right side (where pain is most common).
Two theories are proposed about the diaphragm:
- Lack of oxygen (ischemia) resulted in spasm and pain
- Traction/jerking caused spasm and pain
The fact that ETAP can occur at low exertion level (horse riding) unlikely to cause a shortage of oxygen is against ischemia as a cause.
Having more abdominal fat (weight) and food (slightly more weight) would increase the traction lending more weight (pun intended) to theory #2.
Lifting up on the liver and teaching breathing technique to reduce this traction/jerking also seems to confirm #2.
OK, looked like the diaphragm jerking theory has a lot going for it, but wait a minute. What about those swimmers? Bikers? Horse riders? Not a lot of jolting or jerking going on there.
And why does the relatively small amount of food (not that much weight) before exercise cause problems. Some have blamed gas in the bowel with colon spasm (which can cause severe pain), but it's a different pain and easy to recognize.
So, evidence against a solely diaphragmatic origin of ETAP include the high prevalence of the complaint among horse riders, an activity characteristically not of high respiratory demand, as well as the distribution of the pain as low in the abdomen as the iliac and hypogastric regions. Further, it has been shown that spirometry (lung function) measures remain unchanged during an episode of ETAP. The variability in the site of the pain is similarly inconsistent with the visceral ligament theory as is the observation of the pain when swimming, which lacks the torso "jolting" pivotal to the theory.
These observations have led to the development of an alternative explanation for the ailment by Dr Morton in Australia. He proposes one theory to explain how this occurs in different sports.
He argues that characteristics of ETAP are consistent with irritation of the parietal peritoneum (the thin membrane lining the abdominal cavity and its organs). The parietal peritoneum is sensitive to any torso movement when irritated, and as it extends throughout the abdomen it can give rise to well localized pain in various sites. Further, the subdiaphragmatic portion of the parietal peritoneum is supplied by branches of the phrenic nerve, which can account for the observation of shoulder tip pain in association with ETAP.
Morton proposes that movement/jolting causes peritoneal friction which leads to pain. Friction could be the result of increased pressure on the tissue, as in the case of a bowel being distended by food or drink, or as a consequence of changes in the volume or properties of the lubricating fluid contained within the peritoneal cavity. Some of this lubricating fluid is drawn up and away by surface tension as the diaphragm moves up with deep breathing.
Abdominal content compression and friction can occur with both trunk flexion (biking and horse riding) and extension (swimming).
Other observations are that ingesting energy dense, hypertonic fluids are more provocative of ETAP than isotonic and hypotonic beverages. They "suck" liquid out of the peritoneal cavity into the bowel, distending it leading to more friction.
There may be a small group where ETAP is spine related but for the majority it appears irritation of the extremely sensitive peritoneal lining is the cause.
It's nice to know why, but the real question is how do we prevent it?The key is reducing friction/movement/compression of the sensitive abdominal peritoneum rather then the diaphragm itself.
How?
Lose abdominal weight, strengthen the abdominal muscles, belly breathing, coordinate breathing and foot strike, don't eat before running, maintain an upright posture avoiding abdominal compression or extension and avoid hypertonic oral fluids .
Turns out most of the treatment has been right all along, but for the wrong reason. :-)