You might be mid-run, hurrying to catch the bus, or pushing through a workout when a sudden pain appears in your side and forces you to slow down. This sharp, stabbing sensation, often called a side stitch, can come on without warning and be uncomfortable enough to stop you in your tracks.
If this has happened to you, it is completely natural to feel concerned or frustrated. The reassuring news is that stitch pain is common during physical activity and is usually harmless.
While it can feel intense in the moment, understanding why it happens and how to prevent it can help you stay active with greater confidence and fewer interruptions.
What is stitch pain?
That sudden sharp pain in the side of your abdomen is called exercise-related transient abdominal pain (ETAP), often referred to as a 'side stitch' or simply a 'stitch'. It is not an illness but a very common and harmless response to physical activity.
Even though it can feel worrying at the moment, a side stitch is usually just a muscle cramp affecting the muscles around your abdomen. It tends to show up during activities that involve repeated upper body movement, such as running, swimming, or horse riding.
What are the symptoms?
A side stitch usually causes pain on one side of the abdomen, most often the right.
It may feel like a dull ache, tightness, or cramp
It can also be sharp or stabbing, sometimes forcing you to slow down or stop
Some people are also surprised to feel pain at the tip of the shoulder joint. This happens because the phrenic nerve, which extends from your neck to your diaphragm, can sometimes send pain signals to the shoulder when it becomes irritated.
The pain is usually short-lived and often eases within a few minutes when you slow down, rest, or adjust your breathing or movement.
What causes a stitch?
Researchers are still learning exactly why side stitches happen, but they believe several factors in your body can trigger them. Your abdominal muscles, internal organs, and digestion may all play a role.
Irritation of the parietal peritoneum
Your abdominal cavity is lined by a thin membrane called the peritoneum, which includes two layers:
The parietal peritoneum, which lines the inside of your abdominal wall
The visceral peritoneum, which covers the internal organs
Normally, a small amount of fluid sits between these layers, helping everything move comfortably and smoothly. During intense exercise, especially if your stomach is full, increased friction between these layers may cause irritation, leading to pain.
Strain on the transverse abdominis
The transverse abdominis is a deep core muscle that helps stabilise your body and support breathing. During exercise, heavy or rapid breathing makes this muscle work harder.
If blood flow to the diaphragm or abdominal muscles cannot keep up with the increased demand, it may result in cramping or discomfort felt as a stitch.
Digestion and diet
What you eat or drink before exercise can make a real difference.
Certain choices can increase your chances of getting a stitch, especially if your body is still digesting:
High-fibre foods
Large meals
Carbonated drinks
These can make your stomach feel swollen or uncomfortable as you exercise. That pressure can strain the diaphragm and its supporting tissues, increasing the chance of developing a stitch while you are active.
Electrolyte imbalances
Like other muscle cramps, side stitches may also be linked to electrolyte loss.
When you sweat, you lose salts that help muscles contract and relax properly. If you do not replace them, especially during longer or harder workouts, the muscles can tighten suddenly and painfully (a spasm), which may trigger that sharp side pain.
While the cause is not always clear, understanding that this pain is common and usually harmless can help make it feel less alarming when it happens.
What to do when it strikes
Most side stitches resolve on their own with simple lifestyle adjustments. You don't usually need a doctor for ETAP, but knowing how to handle it can save your workout.
Here are a few steps you can take to manage the stitches:
Take slow, deep breaths to help your diaphragm relax and settle the pain.
Reduce your pace, especially if you move into high-intensity exercise (like HIIT cardio) too quickly, and walk until the discomfort fades
Raise the arm on the painful side and gently lean away to stretch the abdominal muscles and ease the cramp
Try gently massaging the sore area to help release the tension
Sip water or a sports drink to stay hydrated and maintain blood flow
Avoiding large amounts of fluids at once, as it can worsen the pain
Once the pain settles, you can usually ease back into your activity when your body feels ready. Listening to your body and making small adjustments along the way can help stop side stitches from interrupting your exercise next time.
