Side Aches
Over the years I have had people ask me “what causes side aches and how can I get rid of them”? Usually I tell them the cause isn’t well known but the thought is that the pain is related to the structures that hold the abdominal organs in place (visceral ligaments) or it is related to the diaphragm – possibly a muscle spasm.
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 kid that the three candy bars he had eaten before running may not have been helpful.

I found myself not being satisfied with these answers and decided to search the medical journals to see if any research has been conducted on side aches.
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 seventeen studies published on ETAP that I could find, ten were published by 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, “W hat causes side aches? ” According to Dr. Morton side aches are most likely an “ irritation of the parietal peritoneum … perhaps exacerbated by friction. ” 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 should not strain the ligaments that support the abdominal organs..
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.
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 painful spot 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.
The Side Ache Solution is a recently developed eBook designed to eliminate side aches. It is based on research conducted on nearly a thousand young runners. For more information on this program visit SideAcheSolution.com

Bryan Whitesides MPT, OCS ( Bryan is a physical therapist and has been running for over 25 years. He is now old enough that he rarely experiences side aches.)
References:
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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.
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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.
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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
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