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Side Stitches: What's the cause?


Every runner or sportsperson has been there, you’re running along, getting into your stride, loving life then suddenly you’re hit with a stabbing pain in the side of your abdomen.  This intense cramping/aching sensation is extremely common especially in runners; in fact around 70% of regular runners report experiencing stitches at least once a year.

So what’s the reason for this irritating pain in side? In scientific terms, a side stitch is referred to as “exercise-related transient abdominal pain” or “ETAP”.
The exact cause however remains unclear. Some physiologists have theorised there are several suggested causes:

  • Decreased Blood flow to the Diaphragm
  • Irritation of the parietal peritoneum.  Two layers of membrane (peritoneum) line the inside wall of the abdominal cavity. 
  • organs pulling on the ligaments that connect the gut to the diaphragm causing a Tugging of ligaments


Decreased Blood flow to the Diaphragm:

The Diaphragm is U-shaped muscle which is essential for breathing. As you inhale the diaphragm contracts and flattens allowing more air into the lungs. When you exhale the diaphragm relaxes and returns to its U-shape, forcing air out of the lungs. This theory suggests a reduction in blood flow (ischemia) to the diaphragm causes cramping leading to a stitch.

  • This theory would provide an explanation for why foods which are more difficult to digest increase the likelihood of experiencing a stitch. As these foods cause more blood to be directed to the stomach and therefore reduce the blood available to the diaphragm.
  • The decreased blood flow to the diaphragm would likely result in decreased ability or strength of inhalation. However, studies have found that the occurrence of side stitches have no significant effect on the strength of inhalation.


Irritation of the parietal peritoneum:

Two layers of membrane (peritoneum) line the inside wall of the abdominal cavity.  One layer covers the abdominal organs, the other layer (parietal peritoneum) attaches to the abdominal wall.  They are separated by lubricating fluid allowing the two surfaces to move against each.  Its thought that stitches occur when there’s friction between the abdominal contents and the parietal peritoneum.  This may be caused by a distended (full) stomach or a reduction in the lubricating fluid. 

The parietal peritoneum is also attached to the phrenic nerve, which refers pain to the shoulder tip region, which may explain the shoulder pain that has been described by some athletes. (AIS Sports Nutrition 2009)

  • This theory may help explain why eating and drinking is often a trigger for pain or a worsening of the condition.
  • A limitation of this theory is that it doesn’t explain why there would be a reduction in lubricating fluid. We are designed for movement, why would we therefore have such a design fault?


Tugging of ligaments:

Inside the abdomen the organs, muscles and bones are connected by ligaments. This theory suggests that the up and down motion during running causes the organs to move around creating stress on the diaphragm and this leads to the ligaments attached becoming irritated.

  • This theory would help explain why eating a meal before exercising often results in a stitch, as the food would cause the organs of the digestive system to become heavier and therefore tug with a greater force on the ligaments.
  • This theory however doesn’t explain why swimmers often experience stitches despite swimming not causing the same up and down tugging motion as running.



What is clear is there is no general consensus on the primary cause of stitches, only theories and whilst each of these theories has its strengths there are also limitations for each of them. It is possible that the actual cause of a stitch is more complex than these individual theories and may involve a combination of factors.


Preventing a Stitch

Richard Phillips

James McCormack

  • Don't consume foods which digest slowly such as large meals or high protein or fat snacks/meals within 2-4 hours of exercising.
  • Avoid concentrated fluids during exercise as these tend to empty more slowly from the stomach than water. Alternatively choose to drink water or a commercial sports drink such as GlycoSource.
  • Avoid taking on large volumes of fluids at one time. Take regular gulps which empty more rapidly from the stomach than large volumes or smaller sips.
  • Be aware of your breathing. Establish a breathing pattern rather than taking irregular breathes. Try breathing in time with your strides to help you get into a rhythm.
  • Do a thorough warm up prior to exercise


Treating a Stitch

  • Slow down
  • Take slow, deep Breathes
  • Stretch… raise the arm on the same side as the pain is and lean to the other side.
  • Try applying pressure to the area where the pain is and bend forward into the stitch. This appears to be the most effective immediate way to alleviate the pain from a stitch.


Suffer from Chronic Stitches?

If you regularly suffer from severe stitches, you should consider contacting a health professional to eliminate a more serious cause for your stitch.


This artiicle was written by Bobby Garlington & Danielle Davies. If you enjoyed this article visit our blog to read more of our nutritition & exercise content.


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