Introduction

The technical term for a stitch is Exercise-related Transient Abdominal Pain (EATP), and although a significant amount of research has been carried out over the last 2 decades, the exact cause is still unknown.

Summary

• Getting a "stitch" is one of the most common complaints amongst runners
• The range of pain levels associated with a stitch can vary between mild (2/10) and severe (9/10), often reaching a level high enough to interrupt a running session and sometimes end it completely
• A number of possible causes exist but the exact cause is still unknown
• The list of causes in this article represents the most well-known and most-likely causes based on recent research

Read The Article

Many runners have experienced a stitch at some point in their running life. In fact, in a study of 965 athletes by Morton and Callister¹ (439 of which were runners), it was found that nearly 70% had experienced a stitch within the previous 12 months.

In this article, I will try to break down what are believed to be the most likely causes of a stitch (EATP).  There are also a number of other known problems that can result in similar symptoms but are not actually EATP but are equally painful.  I will cover these in a future blog post.

If you’re reading this then you’re probably already aware of the symptoms of a stitch, but I will run through them here first as a quick reminder.

Symptoms of a Stitch (EATP)

In most cases, individual runners experience a stitch in a very similar location each time it occurs. However, not everyone experiences it in the same place. The right and left sides at about the height of the belly button (umbilicus) are where the majority of runners report pain, but it can also be lower, higher, or closer to the middle.

The words most often used to describe the pain are stabbing, sharp, aching, cramping or pulling. The severity of the pain also varies quite considerably, with some runners reporting that it is so painful they are unable to continue running.

Often, the more severe the pain, the longer it takes to subside once the activity is stopped.

What Causes A Stitch?

The cause of EATP is unknown but there are a number of popular theories, each of which has its own factors that could provoke the symptoms.  The most popular theories are:

Muscle Cramp of the Diaphragm (Diaphragmatic Ischemia)

Believed to be caused by the redirection of blood from the diaphragm (the main muscle used for breathing) to the gut for digestion, this theory fits with the often reported involvement of eating and drinking prior to exercise, along with the additional strain on the diaphragm due to increased breathing with the intensity of the exercise.

This theory appears to be unlikely as the pain is often much lower than the diaphragm. Also, studies have also shown that the body is likely to redirect blood to the respiratory muscles during exercise rather than away from them (as a survival instinct). Another study showed that following a large meal there was no change in the movement of the diaphragm of runners who were experiencing a stitch.

Stress on Internal Connections Between Organs and Diaphragm (Visceral ligament stress)

The jolting effect, on the ligaments between the abdominal organs and the diaphragm, from running is another possibility, but the pain associated with this is often along the midline of the abdomen and reported as a dull pain. This doesn’t really fit with the typical experience of a stitch but the stitch pain could be explained by referred pain from the ligaments.

Further research² has been carried out that supports this theory but the evidence is inconclusive.

Muscle Cramp

Cramping of the respiratory muscles (e.g. the diaphragm) is another theory that often gets suggested, but research that measured the muscle activity (through EMG) in the area of the stitch showed no changes in the muscle during the stitch compared to after the pain had subsided. Measurement of lung function (through spirometry) also showed no changes to support the cramping theory.

Irritation Between Internal Layers of Protective Linings (Parietal peritoneum irritation)

The abdominal organs are lined with the layer of tissue (known as the visceral peritoneum), and the abdominal wall and pelvic cavity is lined with another layer of tissue (known as the parietal peritoneum). The space between these two layers is filled with fluid to try and stop the friction between the two surfaces.

A study by Morton and Callister¹ in 2000, found that problems (exertional peritonitis) caused by friction between these layers, explains many of the symptoms and experiences of a stitch. Symptoms and experiences such as:

• The range of locations where the pain is experienced
• The highly localised and sharp pain
• How a large meal could distend the stomach and increase friction between the two surfaces
• Differences in the effect of different fluids used to hydrate, as these will affect the friction between the surface
• The parietal peritoneum is sensitive to movement when irritated
• The change in intensity of the pain is associated with a change in intensity of running as this would be consistent with an increase in friction

Referred Pain from the Spine (Thoracic facet referral)

Problems in the thoracic region of the spine may be a factor in runners experiencing a stitch. The thoracic spine runs from the base of the neck down below the shoulder blades and is an area that I often see causing problems for runners. Nerves from the thoracic regions of the spine run into various parts of the abdomen which would be consistent with the areas reported as painful with a stitch.

Analysis of runners who experienced a stitch found that in over 80% of cases, manipulation of the thoracic spine either recreated the stitch pain or induced pain radiating towards the area. The research is not yet conclusive, but does suggest that the involvement of the thoracic spine should at least be considered when treating a stitch.

This limited evidence, along with my own experience of thoracic spine dysfunction in runners further supports the work I typically do with runners to increase mobility and function in the thoracic spine whilst also working on technique changes that allow the spine to work effectively when running.

Tightness or Problems with Psoas major and/or Quadratus lumborum

Ligaments from the diaphragm run over and attach to various parts of the psoas major and quadratus lumborum muscles. These are deep stabilising muscles that support the lumbar spine and pelvis, and flexion of the hip joint. They are heavily utilised in running.

It is possible to expect that the increased activation of these muscles through an intense activity could result in the pain associated with a stitch through their connection to the diaphragm, particularly if there is any tightness or dysfunction in these muscles.

I didn't want to share EVERYTHING in this one blog article as it would become too overwhelming.  So in the interest of trying to keep the information I share in these posts both comprehensive and concise, I have broken the topic down into a series of articles that will be published over the coming weeks.

Next week I will be looking at some of the common causes of stitch-like pain that have different and clear diagnoses.

What has been your experience with getting and managing a stitch?  Are you one of the 70% of runners who have experienced one in the last year?  Let me know in the comments down below, I always enjoy hearing about the experiences of other runners...

Until next time, happy running and bye for now 👋🏻

Coach Barrie

BE Fit Coach

References

¹ Morton DP, Callister R. Characteristics and etiology of exercise-related transient abdominal pain. Med Sci Sports Exerc. 2000 Feb;32(2):432-8. doi: 10.1097/00005768-200002000-00026. PMID: 10694128.

² Plunkett BT, Hopkins WG. Investigation of the side pain "stitch" induced by running after fluid ingestion. Medicine and Science in Sports and Exercise. 1999 Aug;31(8):1169-1175. DOI: 10.1097/00005768-199908000-00014. PMID: 10449020.

Related Posts

How to confidently use your Garmin to track running sessions

6 Great Reasons You Shouldn’t Skip Easy Runs

Runners, how do you push your body when your mind says "NO!"?

Are You Self-Sabotaging Your Running?

5 Signs Lack Of Sleep Could Be Sabotaging Your Running

7 Core Pillars of Running - Hint: It's Not Just About Getting The Miles In!

How can BE Fit Coach help you?

We have a range of services that can ensure you are training optimally for you! We are all individuals, with unique and sometimes challenging lives, so choose a training solution that works with you, for you.

At BE Fit Coach, we are constantly working on developing new programs and courses. If you'd like to ensure you are kept up-to-date then I recommend joining our email list (below) as that is where all new announcements are made first!