Why do I get side stitches when I run?

The stitch is one of running's universal experiences - a sharp, stabbing pain just under the ribs, usually on the right, that arrives mid-run and forces you to slow to a walk. Here is the honest science: despite being one of the most common exercise complaints, its exact cause is not settled. The leading explanations are irritation of the diaphragm or the ligaments suspending it (jolted with every stride while working hard to breathe), reduced blood flow to the diaphragm during hard effort, and pressure from a stomach still busy with a recent meal pulling on those same attachments. The triggers are consistent enough to act on: eating a large or fatty meal within a couple of hours of running, drinking a lot right before, shallow upper-chest breathing, weak core endurance, and going out too fast. The in-run fix, which works for most people: slow to a walk, breathe deeply and slowly with your belly, press your fingers firmly into the tender spot while exhaling fully, and stretch the side by raising the arm on the stitch side and leaning gently away. Prevention: leave 2 to 3 hours after a big meal before running, warm up gradually rather than sprinting off the doorstep, and train deep belly breathing at an easy pace before adding speed. One line worth drawing: stitch pain should vanish within minutes of stopping - pain that stays after you stop, sits in the chest, or comes with breathlessness or dizziness is a different problem and deserves medical advice. Pymander is a free AI doctor, 24/7 by text, that can help you troubleshoot.