You’re halfway through a run, feeling good, and then it hits , a sharp, stabbing pain just below your ribs that makes every breath hurt. You slow down, press your hand against your side, and wonder what you did wrong. The answer might surprise you: that pain probably has nothing to do with your muscles.
A side stitch, officially called exercise-related transient abdominal pain (ETAP), affects about 70% of runners at some point. It’s one of those universal experiences that nobody really talks about in running forums, yet almost everyone who exercises has felt it. And for years, even doctors didn’t fully understand what was happening.
What You’ll Learn
- Why the pain appears on one side more than the other
- Which foods and drinks trigger stitches most often
- Real-time fixes that work in under 30 seconds
- Long-term training adjustments to prevent them entirely
The Leading Theory: Your Diaphragm Isn’t the Problem
For decades, people blamed the diaphragm , that dome-shaped muscle under your lungs that controls breathing. The old thinking went like this: during exercise, your diaphragm gets tired and cramps up, causing pain. Makes sense, right?
Wrong. Research published in the journal Sports Medicine found that the diaphragm theory doesn’t hold up. The pain actually comes from the peritoneum, a thin membrane that lines your abdominal cavity and wraps around your organs.
Think of the peritoneum as a double layer of tissue with a tiny bit of fluid between the layers. When you’re running, your organs bounce around inside your abdomen. That jostling creates friction between the two layers of the peritoneum, especially where it attaches to the abdominal wall. The result? Sharp, localized pain that gets worse with each impact.
Why It Hurts More on the Right Side
About 75% of side stitches happen on the right side. Your liver sits on the right side of your abdomen and weighs about three pounds. Every time your right foot hits the ground while running, your liver drops down. If this happens while you’re exhaling (when your diaphragm moves up), you get a pulling sensation on the peritoneum that attaches to your liver and diaphragm.
The left side can hurt too, but your spleen (the left-side equivalent) is smaller and causes less tugging.
What Makes Stitches More Likely
Not everyone gets side stitches with the same frequency. A 2015 study of 965 participants found clear patterns in who experiences them most often.
Timing Your Meals
Eating within two hours before running increases your risk significantly. But it’s not just about having food in your stomach , it’s about what you ate. High-sugar drinks and fatty foods are the worst offenders because they slow digestion and increase the weight pulling on your peritoneum.
A study in the Journal of Science and Medicine in Sport tracked runners who drank different beverages before exercise. Those who consumed concentrated fruit juice or sports drinks with high sugar content reported stitches 3.5 times more often than runners who drank water or nothing at all.
Your body doesn’t know you’re trying to set a personal record , it just knows you asked it to digest a meal and sprint at the same time.
Poor Core Strength and Posture
Runners with weaker core muscles get stitches more frequently. When your core can’t stabilize your torso properly, your organs move around more during each stride. That extra movement means more friction on the peritoneum.
Hunching forward while running makes it worse. That compressed position reduces the space in your abdomen and increases pressure on the peritoneum’s attachment points.
Breathing Patterns
Shallow chest breathing contributes to stitches. When you breathe only into your upper chest, you’re using your diaphragm less efficiently, which affects the pressure dynamics in your abdomen. Runners who breathe deeply into their belly report fewer stitches overall.
How to Stop a Stitch While Running
When a stitch hits mid-run, you don’t want theories , you want relief. Here’s what actually works, based on both research and what competitive runners have figured out through trial and error.
The Immediate Fix
Stop running and bend forward at the waist while taking slow, deep breaths. Press your fingers firmly into the painful spot and hold for 10-15 seconds. This pressure seems to interrupt the pain signals and calm the irritated peritoneum.
If you don’t want to stop completely, slow to a walk and raise your arm on the affected side straight up over your head. Stretch that side by leaning slightly away from the pain. This stretching technique worked for 83% of runners in a small University of Newcastle study.
The Breathing Reset
Change your breathing pattern deliberately. If you normally exhale when your right foot hits the ground, switch to exhaling on your left-foot strike. This simple change redistributes the forces pulling on your peritoneum.
Try this: breathe in for three steps, out for two. The uneven pattern prevents you from always exhaling on the same foot strike.
One marathon runner described it as “arguing with your lungs until they agree to a new rhythm.”
Long-Term Prevention Strategies
If you’re getting stitches regularly, something about your routine needs adjustment. The good news is that most runners can eliminate stitches almost entirely with some basic changes.
Adjust Your Pre-Run Timing
Wait at least 2-3 hours after eating a full meal before running. If you need energy closer to your workout, stick to easily digestible carbs in small amounts , half a banana or a few crackers work for most people.
Avoid these within three hours of running:
- Fruit juice or sugary sports drinks
- High-fiber foods like beans or whole grain bread
- Fatty foods like nuts or cheese
- Dairy products, which some people digest slowly
Build Your Core
A stronger core means less organ bouncing. Focus on exercises that build deep core stability, not just surface abs. Planks, dead bugs, and bird dogs all help stabilize your torso during running.
Research from the British Journal of Sports Medicine found that runners who did 15 minutes of core work three times per week reduced side stitch frequency by about 60% over eight weeks.
Work on Your Running Form
Stand tall when you run. Imagine a string pulling the top of your head toward the sky. Keep your shoulders back and down, not hunched forward. This posture gives your organs more room and reduces pressure on the peritoneum.
Shorter, quicker strides can also help. Overstriding creates more impact force with each step, which increases the bouncing that causes friction.
When to Worry
Side stitches are annoying but harmless. However, if you’re experiencing severe pain that doesn’t fit the typical stitch pattern, pay attention. Pain that persists after you stop exercising, pain accompanied by nausea or vomiting, or pain that feels different from your usual stitches might signal something else.
Conditions like appendicitis, gallbladder issues, or muscle strains can sometimes be mistaken for exercise-related pain. If the pain lasts more than a few hours after your workout or keeps coming back in the same spot regardless of what you eat or how you breathe, talk to a doctor.
The Bottom Line
Side stitches aren’t a sign that you’re out of shape or doing something terribly wrong. They’re a mechanical problem with a mechanical solution. The friction between layers of your peritoneum causes the pain, and reducing that friction through better timing, stronger core muscles, and smarter breathing patterns solves it.
Most runners find that stitches become less frequent as they build fitness and learn what eating schedule works for their body. If you’re just starting out and getting stitches often, that’s normal , your body is still figuring out this whole running thing.
Give yourself three hours between meals and runs, work on standing tall, and practice belly breathing. Those three changes alone will probably eliminate 80% of your stitches. The rest is just fine-tuning.