Most of us will have experienced a stitch at some point during our lives. The nagging pain in your stomach, side or shoulder can often taint a good training session or race, but what causes a stitch and what can we do to get rid of them? 

We've asked Sports Physiologist and running coach, Ben Cox, to shed some light on the matter... 

What is a stitch?

Most people who run have probably had a ‘stitch’ at one point or another. I remember getting loads as a kid, but maybe that’s just because I was always trying to outrun one of my older brothers, so my 'fight or flight' response probably imprinted that burning pain in my side deeper into my memory. 

Being afflicted with 'The Stitch' is something we grow up with and accept. If we’re lucky, it only affects us occasionally and some extremely fortunate people won’t have a clue what I’m talking about. 

Some people can be more affected than others and, more often than not, the stitch hits us on race day. Studies have shown that in a single running event, between 17% - 27% of entrants can suffer with a stitch. 

Image Credit: ©

I’m surprised at those percentages as the existence of stitches seem to be something we just accept and we rarely question its origin. 

As with many of these things, the people that do know about the stitch, don’t call it the stitch, they call it something else so us Muggles don’t catch on.

In the scientific world it's known as Exercise-Related Transient Abdominal Pain, or ETAP for short. The first real studies into ETAP started around the late 1920’s and have only ramped up in the last 15 years - I guess because the results were not seen to be that commercially important.

ETAP is explained as being a pain that's most commonly localised to the lateral aspects of the mid-abdomen, but it can occur anywhere in the abdomen. 

There are some circumstances where ETAP can present in the shoulder but this is purported to be a pain referral from the phrenic nerve. 

This explains an athlete trying to tell me once - “I don’t know how to explain it but it feels like my heart is going to burst out my shoulder”. 

What causes a stitch?

In severe manifestations, ETAP can be sharp, stabbing and unbearable, whereas in lesser presentations it manifests as a cramping or dull aching pain. It's suggested that ETAP is made worse if intense exercise is undertaken too soon after eating food. 

There are many theories proposed for the root causes of ETAP, including:

  • Ischemia (inadequate blood flow) of the diaphragm
  • Stress on the supportive visceral ligaments that attach the abdominal organs to the diaphragm
  • Gastrointestinal ischemia or distension
  • Cramping of the abdominal musculature
  • Ischemic pain resulting from compression of the celiac artery 
  • Aggravation of the spinal nerves
  • Irritation of the parietal peritoneum

Recent studies into ETAP have suggested that the presentation of pain in individual athletes is fairly uniform and this carries across different sports. 

This is fairly significant as it seems that ‘The Stitch’ is a single physiological condition, rather than a range of ailments within the region of the abdomen.

Whilst I mentioned earlier that the pain can present anywhere in the abdomen region and in some cases in the shoulder, it's thought that the pain is definitive and 'pinpointed' rather than wandering around a localised area. 

It's reported that ETAP is a condition for the young and that incidences diminish with age. I’m sceptical of that one as I think the reduced activity of some people who get older skews that data. In addition, maybe we get wise to the things that cause ETAP and take preventative measures as we grow older.

Are stitches more prevalent in runners?

Whilst ETAP is reported across all sports, it's more prevalent in running.  Swimming elicits moderate numbers of incidents, whilst cycling presents lower incidences of ETAP. 

An explanation for this is that ETAP is more prevalent in sports that require the athlete to repetitively rotate the torso whilst extended and elongated, and especially whilst undergoing vertical or longitudinal movement. Ground impact forces and the repetition are also implicated.

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The act of running meets all of these criteria, whereas swimming doesn't have the ground force impact and cycling has low incidences of torso rotation and ground impact, which perhaps explains why incidences in these sports are moderate.

Ingestion of food and drink prior to exercise are closely linked to ETAP too. 

It's suggested that volume of food to bodyweight consumed prior to exercise is more of a precursor than the make-up of the food (i.e. carbs, fat, protein, fibre). 

Additionally, the time between eating and exercise is closely related to incidence of ETAP, with one study suggesting 30 out of 35 participants elicited ETAP when exercising straight after a meal. 

Maybe not surprisingly, fluids were quite predictable in their effects on ETAP with high-carb / hypertonic (higher concentration than blood) beverages seeming to elicit ETAP much more easily.

Again, maybe not such a surprise is that exercise intensity is linked to ETAP, with higher intensities resulting in a greater response.

In studies between runners and walkers, the runners are approximately 3.5 times more likely to report ETAP than the walkers. Is this due to the intensity of the exercise or the way that velocity changes a required action? As we move from walk to run, we elicit more ground action force and with speed comes further rotation, therefore I would suggest that the action is more relevant in this case.

As previously mentioned, there are many suggested physiological routes to ETAP. Morton and Callister (2014) believe that irritation of the parietal peritoneum is the most likely (see further reading).

The parietal peritoneum is the outer layer of the peritoneum that adheres to the abdomen wall and underside of the diaphragm. The peritoneum itself is the lining of the abdominal cavity which wraps around the internal organs providing them with support.

It's suggested that sharp localised pain can be elicited by aggravation of the part of the parietal peritoneum that adheres to the abdomen wall. 

Another contributing factor and reinforcing agent for the parietal peritoneum case is that the fluid filling the peritoneal cavity is constantly in flux, and is also derived from blood flow to the abdominal gastrointestinal organs which is decreased during physical activity. In addition, the fluid in the peritoneal cavity can be negatively effected by consuming hypertonic fluids.

How hydration can help prevent a stitch

It's thought that maintaining blood plasma volume via optimal hydration may help this reduction in blood flow and go some way to preventing ETAP. 

For those who suffer chronically with a stitch, you may want to try preloading with PH 1500 before your next event or big training session if you haven't tried it before. 

In addition, the fluid in the peritoneal cavity can be negatively affected by consuming hypertonic fluids so sticking to hypotonic options might be a better option - for more on the differences between isotonic, hypertonic and hypotonic drinks, check out this blog.

Image Credit: ©

How to get rid of a stitch

So, how do we get rid of The Stitch? In short, you slow down or you stop.

There are a number of other methods we can employ to prevent getting ETAP, including restriction of food during the 2-4 hours prior to exercise and limitation of bulk fluids.

Know your own body. Work out how much time you need to leave between food ingestion and exercise, and work out your own hydration strategy and needs. There will be some trial and error required. 

It's suggested that techniques to restrict rotational movement of the torso whilst running can be beneficial and for athletes who suffer from the condition regularly a restrictive waist compression may assist. 

Within these realms we now enter back to the good old core of trunk strength and conditioning.

I would suggest that if you want to limit incidences of ETAP then a strong core and attention to the obliques and laterals would be very beneficial. 

There are conflicts over whether one should deep breath or shallow breath when afflicted with ETAP, so I would suggest trying both. Horses for courses.

Further reading