What Causes a Side Stitch When Running?
Nothing kills the runner’s high faster than that sudden, sharp stab on your side. You’re crushing it on the road, or treadmill, focusing on your pace and form, and then you have to stop and clutch your side because of the sharp pains you feel. Slowing down to walk can feel really defeating and like your body is betraying you, especially if you’re training for a marathon and want to get a certain amount of miles in. Whether you get side stitches frequently or occasionally, learn about the causes behind this frustrating, workout-stopping pain.
Learning more about how to deal with injuries and running issues is one of the great features of having a running coach and community. Meet up with us for a run, or schedule a time to chat with Rachel at rachel@unstilllife.com, and learn more about coaching.
What Exactly Is a Side Stitch?
What we know as a side stitch is actually called Exercise-Related Transient Abdominal Pain (ETAP). It’s a localized pain that is usually felt on the right side of the mid-abdomen due to tension in the liver ligaments, but it can happen on the left side or both sides at the same time. The feeling can be anywhere from a dull ache or cramping feeling to a sharp, stabbing pain that makes it difficult to take a deep breath. Side stitches can happen to anyone, not just marathon runners, long distance runners, casual runners, or those jogging around the block. The pain is temporary, and subsides when you stop running and slow to a walk.
What Causes a Side Stitch When Running?
Despite decades of study, researchers and sports doctors still don’t agree on an exact cause of side stitches. Because the pain typically disappears soon after you stop running, it’s challenging for researchers to study it in real time. New research has suggested that a combination of factors, rather than just one cause side stitches. Here are four of those theories.
1. Irritation of the Abdominal Lining
Irritation of the abdominal lining (also known as friction on the peritoneum) is one of the top theories among researchers. Your abdomen is lined with a membrane called the peritoneum that has two layers: Parietal peritoneum and visceral peritoneum. A thin layer of lubricating fluid allows these membranes to slide effortlessly against each other, but when you’re running, your torso is constantly rotating and bouncing, and your core muscles are firing to keep you upright and steady. All this movement creates friction and stress in an area that’s usually unobstructed, so the theory is that friction between these layers causes irritation. If you’re dehydrated this reduces the lubrication, and if you’re running on a full stomach, this presses the layers together, both causing friction. When the irritation has reached its peak, the parietal peritoneum (which is very sensitive to pain) is what causes the sharp pain and has your brain screaming “stop running now!”
2. The Strain on Ligaments
For a long time, researchers thought the liver was what caused side stitches because it’s a large, heavy organ on your right side, connected to the diaphragm by ligaments. When you run and are bouncing up and down, this vertical motion causes the liver to drop while your diaphragm moves up to help you breathe. This theory suggests that when your body moves in opposite directions, it tugs on the ligaments connecting your liver to your diaphragm, causing them to stretch and produce pain. While this explains why you usually get a side stitch on your right side, it doesn’t explain why some people get stitches on their left side, or why swimmers⎯who don’t have the same vertical bounce, get them too.
3. Shallow Breathing and Diaphragm Ischemia
Ischemia is a medical term that means a shortage of blood flow and oxygen to a tissue. Your diaphragm is the primary muscle used for breathing, so when you’re running hard, your diaphragm has to work overtime. This theory suggests that as your lungs expand and your abdomen contracts, the pressure squeezes the blood vessels supplying the diaphragm, which reduces blood flow, depriving the muscle of oxygen and causing it to cramp. It is also theorized that if you aren’t rhythmic, deep belly breathing, this is a cause of side stitches.
4. Spine Issue
Research suggests that irritation of the thoracic (mid-back) spinal nerves can radiate pain to the abdomen, creating the sensation of a side stitch. In studies where researchers pressed on specific vertebrae in the spine of runners prone to stitches, they were able to reproduce the exact pain of the stitch. This suggests that poor running posture, specifically a hunched upper back could be pinching nerves that cause side stitch pain.
Why Are Some Runners More Prone to Side Stitches?
Anyone can get a side stitch, but certain habits are more likely to increase your risk.
- What time you eat and drink⎯Eating a heavy meal or drinking a beverage high in sugar or salt just before running is a common trigger for side stitches. The reason for this is the stomach distends, putting pressure on your abdominal lining.
- Fitness level⎯New runners are more susceptible to side stitches because it’s likely the core muscles haven’t been conditioned to stabilize the torso effectively yet.
- Warm-up⎯Skipping a proper warm-up can shock the respiratory system and muscles, causing irregular breathing patterns that lead to side stitches.
How Can You Prevent Side Stitches Before You Run?
To prevent side stitches, especially if you’re prone to them, practice these habits consistently during your workouts.
Strengthen Your Core
A strong core stabilizes your torso, reducing the internal movement that causes friction and ligament strain. Planks, bird dogs, bicycle crunches, mountain climbers, and dead bugs are excellent exercises for this. It’s also important to stretch your abs. .Learn how to do it in this blog post.
Focus On Your Posture
Picture a string gently pulling the crown of your head upward, helping you stand and run tall. Avoid hunching your shoulders or rounding your upper back. Good posture relieves pressure on the thoracic spine and allows your diaphragm to fully expand.
Time Your Meals
To help prevent side stitches, eat larger meals 2–3 hours before running to give your stomach time to digest and ease pressure on your diaphragm and abdominal ligaments. If you need a small snack closer to your run, choose easily digestible carbs like a banana or a small energy bar 30–60 minutes beforehand. Stay hydrated by sipping water throughout the day. Avoid drinks high in sugar or salt like fruit juice or sugary sports drinks right before running. Since digestion varies from person to person, experiment with timing and portions to see what works best for you.
Master Rhythmic Breathing
Focus on establishing a steady breathing rhythm. Consistent breaths help deliver oxygen to your diaphragm and prevent the shallow, irregular breathing that can trigger cramping. By strengthening your core, timing when you eat before a run, and learning to breathe rhythmically, this will all help keep side stitches away.
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