Is a side stitch dangerous?

Exercise-related transient abdominal pain is benign and resolves when you stop. Pain that continues after exercise, or comes with fever or vomiting, is a different thing and needs assessment.

Why is it always the same side?

The right side is more commonly reported, and the usual explanation involves the liver's position and the mechanics of the peritoneum on that side. It is a pattern rather than a rule.

Does breathing technique prevent it?

A longer exhale and alternating which foot you exhale on help, and so does running tall. The single biggest preventive is not drinking or eating much in the two hours before you run.

A side stitch when running: what causes it and how to clear it mid-run

Two kilometres in, a stabbing point just under the ribs on the right, worse every time you breathe in. You slow down, press it, and it eases — and comes back at the same point next time.

Do this now

Clear it without stopping

1 minute

Slow the pace — do not stop dead.
Breathe out hard and long through pursed lips, emptying more than usual, and press your fingers firmly into the painful spot as you do.
Change which foot you exhale on. If you have been breathing out on the right foot strike, switch to the left.
Straighten up and lengthen the torso rather than bending toward the pain.
Five or six breaths like that. Then rebuild pace gradually with the exhale staying long.

Run it with a timer

What it probably is

Exercise-related transient abdominal pain is the formal name. The best-supported explanation is irritation of the parietal peritoneum — the lining of the abdominal cavity — as the two surfaces rub during the movement of running, rather than the older diaphragm-cramp theory. It fits the evidence better: the pain is often felt at the shoulder tip as well, which follows the peritoneum's nerve supply, and it is strongly associated with drinking before exercise.

The two strongest triggers

Fluid and food in the stomach shortly before running, especially high-sugar or hypertonic drinks, and being less well trained or newly increasing intensity. In surveys of runners and swimmers those are the most consistent associations. Shallow, fast breathing makes it worse by reducing diaphragmatic movement and leaving the torso braced.

Why forced exhalation and pressure work

A long forced exhale moves the diaphragm through a larger range and briefly increases intra-abdominal pressure, and direct pressure on the site plus lengthening the torso alters the mechanics at the irritated surface. Switching the foot you exhale on changes the timing of the impact relative to the breath, which matters because most runners unconsciously synchronise exhalation with the same foot every stride.

What changes it, over a week

Before running
No large drink or meal in the two hours before. Test it: this alone resolves it for a large share of runners.
During
Breathe out longer than in, and deliberately alternate which foot you exhale on every few minutes.
Build gradually
Side stitch tracks unaccustomed intensity. Raise pace or distance by no more than about ten percent a week.
Core and posture
Run tall. Trunk strength and an upright posture both reduce recurrence, and slumping forward increases it.

When this is not a breathing pattern

See a clinician — promptly, and before assuming any of this applies to you — if any of these describe you:

Pain that persists after you stop running, or that wakes you at night
Pain with vomiting, fever, or tenderness when pressed at rest
Chest pain, or pain radiating to the jaw or arm during exertion — stop and seek assessment
Pain with blood in urine or stool
Sudden severe abdominal pain — emergency assessment

This page is education, not medical advice, and no part of it is a diagnosis. Full disclaimer.

Questions people ask

Is a side stitch dangerous?: Exercise-related transient abdominal pain is benign and resolves when you stop. Pain that continues after exercise, or comes with fever or vomiting, is a different thing and needs assessment.
Why is it always the same side?: The right side is more commonly reported, and the usual explanation involves the liver's position and the mechanics of the peritoneum on that side. It is a pattern rather than a rule.
Does breathing technique prevent it?: A longer exhale and alternating which foot you exhale on help, and so does running tall. The single biggest preventive is not drinking or eating much in the two hours before you run.

What this page is built on

— Morton & Callister, 2015, Sports Medicine — exercise-related transient abdominal pain: a narrative review
— Morton & Callister, 2010, Medicine & Science in Sports & Exercise — fluid ingestion and the incidence of ETAP
— Traditional: the long-standing runner's remedy of forced exhalation with pressure on the site, which the peritoneal model now explains

Named by author and year. The DOIs live in the journal.

Put a number on it

Most of what is on this page tracks one measurement: the Control Pause. It takes sixty seconds, needs no account, and it is the thing that tells you whether any of this is working.