Over the years I have had people ask me “What causes side aches (or stitches) and how can I get rid of them? ” Although the cause isn’t well known, most doctors think that the pain is related to the structures that hold the abdominal organs in place (visceral ligaments) or that the pain is related to the diaphragm, possibly a muscle cramp. When asked how to get rid of the side ache, I would shrug my shoulders and say, "Keep trying to run. It should get better." Or, "Avoid running with a full stomach." I did tell one high school cross-country runner that the three candy bars he had eaten before running may not have been the best choice. As I repeated these answers I began think there must be some better information available so I decided to search the Internet and the medical journals.

The Information on the Internet basically repeated what I had been telling people. However, one popular sports medicine doctor stated that 30% of runners breathe out as they strike with their right foot and that this causes the ligaments that support the liver to be “ stretched and hurt ” (I couldn't find any research that verifies this claim). He advocated breathing out as your left foot hits the ground to avoid a side ache, and to cure the side ache he suggests putting your fingers into the right side of your belly to push your liver up. I actually tried the breathing with the left foot strike on my next run. I think I would become schizophrenic if I stuck with this program, but I have had some luck with applying pressure to the sore area.

When I searched the medical journals I came across the work of Doctor Darren Morton at the Avondale Centre for Exercise Science in Australia . He has been doing research on side aches, or exercise related transient abdominal pain (ETAP), for the past six years. Of the sixteen studies published on ETAP that I could find, nine were published Dr. Morton. The Doctor is determined to find out more about this extremely common condition, which he states nearly 60% of runners have experienced. The following summarizes some of Dr. Morton ’ s findings.

• Side aches are more common in younger people, decreasing in frequency and severity with age.
• People who train more days per week tend to have fewer side aches.
• Runners are ten times more likely to experience side aches than cyclists.
• Runners are twice as likely to experience a side ache on the right side as the left side.
• Running, endurance horse riding, and swimming have the highest reported occurrence of side aches.
• People with postures that are more rounded through the mid back are more likely to experience side aches.
• When pressure is applied to the mid back after a side ache many people feel their symptoms return.
• Weight and gender do not appear to have an effect on the incidence of side aches.
• Drinking fruit juice or a high calorie, electrolyte sports drink before or during exercise is more likely to result in a side ache for those who are more susceptible.
• Participants in a 14 km run who ate a “large mass of food” 1-2 hr before the event were more likely to experience a side ache. However, the “nutritional content” of the meal did not influence the likely hood of experiencing a side ache.

Aside from Dr. Morton’s research, I came across two interesting case reports. These cases are rare, and I mention them primarily to demonstrate that the runners’ symptoms developed from restrictions in the abdomen. One case told about an elite runner that was experiencing severe abdominal pain when he ran. He was diagnosed with a condition where a portion of the diaphragm (arcuate ligament) was compressing an artery (celiac axis). Surgeons freed the artery, and this procedure eliminated the side aches. In the other case, the runner had been born with tissue that was binding his gallbladder to his abdominal wall. Surgeons removed his gallbladder and the tissue. The runner was then able to return to running without pain.

Now, back to the original question, “What causes side aches? ” The parietal peritoneum is the outer lining of your abdomen, if you could reach beneath your abdominal muscles, you would be touching the peritoneum. Dr. Morton makes an argument that side aches are not related to the diaphragm because breathing capacity is not lowered during a side ache, and horse back riding has a high incidence of side aches although breathing is not vigorous. He also argues against the theory that the pain arises from the ligaments that support the abdominal organs because swimmers frequently experience side aches, and swimming does not strain the ligaments.

So, when your training partner asks why you are doubled over in the middle of a run, you can intelligently tell them how irritated your parietal peritoneum is. Perhaps repeating the phrase “ parietal peritoneum ” ten times, quickly, will alleviate the pain, or at least distract you for long enough to regain your composure.

Unfortunately, there is very little research on how to prevent or relieve a side ache. Much of the information on the Internet is based on the theory that side aches are caused by a “ pinched diaphragm ” or a “ muscle cramp of the diaphragm, ” which according to Dr. Morton may not be the underlying cause. Based on Dr. Morton ’ s research we can make some suggestions.

• Run more regularly.
• Don ’ t eat a large meal 1-2 hours prior to a run.
• Avoid fruit or high carbohydrate / electrolyte drinks prior to or during a run (try diluting a drink like Gatorade in half).
• For those of you who have a more rounded posture in the mid back, performing stretches to improve your posture may be helpful.
• Anticipate fewer side aches with each birthday (one of the few benefits of aging).

In addition to Dr. Morton's findings I have had some relief with the following strategies.

• Slowing the pace or briefly walking.
• Reaching overhead and leaning to the opposite side to stretch the stitch.
• Applying moderate pressure to the stitch for about ten seconds.
• When I have run hard through a side ache, I experienced a remnant of the pain for two or three days afterwards, which may not be worth it if you are just doing a workout.

Hopefully, with a better understanding of side aches, researchers can provide us with improved methods to prevent and relieve this condition. But, until then keep running!

To share your remedies (or failures) for side aches, please visit the forum for side aches at injuredrunner.com. I will create a list of the most successful remedies from respondents and attach them to this article.

Bryan Whitesides MPT, OCS ( Bryan is a physical therapist and has been running for over 20 years. He is now old enough that he rarely experiences side aches.)

References:

Desmond CP, Roberts SK. Exercise-related transient abdominal pain a s a manifestation of the median arcuate ligament syndrome. Scand J Gastroenterol 2004 Dec;39(12):1310-3.

Dimeo FC, Peters J, Guderian H. Abdominal pain in long distance runners: case report and analysis of the literature. Br J Sports Med 2004 Oct;38(5):E24.

Koistinen PO, Janhonen P, Lehotola J, et al. Gastrointestinal symptoms during endurance running. Scand J Med Sci Sports 1991;1:232-4.

Morton DP, Aragon-Vargus LF, Callister R. Effect of ingested fluid composition on the experience of exercise-related transient abdominal pain. Proceedings of the Australian Conference of Science and Medicine in sport. Perth, October. ACT: Sports Medicine Australia, 2001:63.

Morton DP, Aune T, Callister R. Influence of body type and posture on the experience of ‘stitch’ [abstract]. Fifth International Olympic Committee World Congress on Sports Sciences: book of abstracts, Sydney, October, 1999, ACT: Sports Medicine Australia, 1999:226.

Morton DP, Aune T. Role of the thoracic spine in the experience of exercise-related transient abdominal pain. Proceedings of the Australian Conference of Scince and Medicine in Sport. Perth, October. ACT: Sports Medicine Australia, 2001:80.

Morton DP, Callister R. Electromyography and spirometry measurements during ‘stitch’[Abstract]. Fifth International Olympic committee World Congress on Sports Sciences: book of abstracts Sydney, October, 1999. ACT: Sprots Medicine Australia, 1999;226.

Morton DP, Callister R. Characteristics and etiology of exercise-related transient abdominal pain. Med Sci Sports Exerc. 2000;32:432-8.

Morton DP, Callister R. Factors influencing exercise-related transient abdominal pain. Med Sci Sports Exerc. 2002;34:745-9.

Morton DP, Richards D, Callister R. Epidemiology of ‘stitch’ at a community run/walk event. Med Sci Sports Exerc.1999;35:S262.

Morton DP, Richards D, Callister R. Epidemiology of exercise-related transient abdominal pain at the Sydney City to Surf community run. J Sci Med Sport 2005 Jun;8(2):152-62.

Rehrer NJ, Brouns F, Beckers EJ, et al. Physiological changes and gastrointestinal symptoms as a result of ultra-endurance running. Eur J Appl Physiol 1992;64:1-8

Shi X. Gastrointestinal discomfort during intermittent high-intensity exercise: effect of carbohydrate – electrolyte beverage. Int J Sport Nutr Exerc Metab. 2004 Dec;14(6):673-83.