Why Your Right Side Hurts When Running & How to Stop It

That sharp, grabbing pain under your right ribs during a run is almost certainly a side stitch, known in sports medicine as exercise-related transient abdominal pain, or ETAP. It is one of the most common complaints among runners: roughly 70 percent report experiencing it within the past year, and about one in five runners can expect it during any given event.¹ The right side is not just anecdotally the worst spot; survey data confirms it is the single most commonly affected area.

Why It Favors the Right Side

In a large survey of participants at the Sydney City to Surf community run, the right side of the abdomen was the most frequently reported location for a stitch, accounting for about 46 percent of all cases. The left side came in a distant second at roughly 23 percent.² So if your stitch reliably shows up on the right, you are in the majority.

The reason for this right-side bias is not definitively settled, but the anatomy of the area offers strong clues. Your liver, the heaviest internal organ, sits just under the right rib cage. When you run, the repetitive impact of footstrike sends vibrations upward through the torso, and the liver’s weight creates more downward tug on the ligaments and connective tissue on that side than on the left. The diaphragm, which anchors to the rib cage above, also attaches to ligaments that connect to the liver below, so the mechanical stress during each stride is asymmetric. Some researchers suspect this bouncing load is a contributing factor in why the right side is hit so much more often.

What Actually Causes a Side Stitch

Despite being such a universal experience, the exact mechanism behind ETAP is still debated. Several theories have competed for decades, and the honest answer is that more than one factor is probably at play.

The leading explanation involves irritation of the peritoneum, the double-layered membrane that lines the abdominal cavity and wraps around the internal organs. Normally the two layers slide smoothly against each other, lubricated by a thin film of fluid. During vigorous exercise, several things can disrupt that harmony: reduced blood flow to the area, increased friction from a full stomach pressing outward, or changes in the volume or composition of the lubricating fluid. When the layers catch or pull against each other, the result is localized, sometimes intense pain. This theory also neatly explains why the pain tends to be well-localized. In the Sydney study, 88 percent of sufferers described their stitch as a focused, pinpoint pain rather than a vague ache.²

Another explanation centers on the diaphragm itself. During hard running, the diaphragm works overtime to support rapid breathing while also absorbing the mechanical shock transmitted from below. If blood flow to the diaphragm is temporarily diverted toward working leg muscles, the resulting ischemia (reduced oxygen supply) could produce cramping. This theory was dominant for years and still gets repeated in many running guides, though the peritoneal-irritation model has gained more support recently because it better accounts for features like the stitch’s precise location and its connection to eating.

There is also a connection to referred pain in some cases. A severe stitch can trigger shoulder tip pain, which is the referred site from tissue innervated by the phrenic nerve.¹ If you have ever felt a stab under your right ribs that seemed to radiate into your shoulder, that nerve pathway is the likely explanation, and it further supports the idea that the peritoneum, not the diaphragm alone, is the primary pain source.

How Intensity Changes the Pain

The character of a side stitch changes depending on how bad it gets. When it is mild, people tend to describe it as a dull cramp, an ache, or a pulling sensation. Push through it or increase your pace, and the pain often sharpens into something stabbing.¹ The Sydney survey captured this nicely, with sufferers splitting fairly evenly among aching, sharp, and cramping descriptors.² That variability is why two runners can describe the same condition using completely different words and both be right.

The pain is also not a minor nuisance for many people. Among those who reported a stitch during the Sydney event, 42 percent said it was detrimental to their performance.² That is a meaningful chunk of runners whose race or training session was actively compromised. Dismissing a stitch as something you should just grit your teeth through ignores the fact that for many people it forces a genuine slowdown or stop.

Eating and Drinking Before a Run

One of the most consistent triggers for a side stitch is running on a stomach that is not empty enough. Large meals, fatty foods, and concentrated sugary drinks consumed too close to a run increase the volume and weight of the stomach contents, which sits right up against the peritoneum. The fuller your stomach, the more mechanical pressure it exerts during the jostling of a run, and the more likely those peritoneal layers are to become irritated.

Fluid intake matters too, but the picture is more nuanced than “don’t drink before running.” A study that had runners drink different fluids before treadmill running found that a stitch developed to a similar intensity regardless of which fluid was consumed during the first portion of exercise.³ In other words, the initial risk of getting a stitch was about the same whether you drank water, a sports drink, or anything else. The differences emerged later in the run, where one particular sports drink (a carbohydrate-electrolyte solution) saw stitch intensity decline to the level of drinking nothing at all, while other fluids kept the stitch going longer.

The practical takeaway is that what you drink may matter less for preventing the stitch from showing up and more for how quickly it resolves. Hypertonic or highly concentrated beverages, like fruit juice or soda, tend to empty from the stomach more slowly and are anecdotally some of the worst offenders. Sipping smaller amounts of a dilute sports drink is generally better tolerated than gulping a large volume of anything right before you head out.

Timing is the biggest controllable variable. Most experienced runners settle on a window of at least two hours between a full meal and a run, with lighter snacks tolerable closer to go time. If you are stitch-prone, even that lighter snack may need to be pushed back further. Everyone’s gut is a little different, so the specific window is something you discover through trial and error rather than from a universal rule.

How to Stop a Stitch Mid-Run

When a stitch hits, you have a few tools that tend to work, roughly in order of how disruptive they are to your run:

Slow down: Dropping your pace reduces the mechanical forces on your torso and gives the diaphragm and abdominal tissues a partial reprieve. For many mild stitches, easing off the intensity for 30 to 60 seconds is enough.
Deepen your breathing: Shift to slow, deep belly breaths, focusing on a full exhale. Shallow chest breathing tends to keep the diaphragm tense and high, while a deep exhale lets it relax downward and may relieve some of the traction on the peritoneal ligaments.
Press and bend: Press your fingers firmly into the painful spot and lean your torso slightly forward or toward the opposite side. This physically compresses the tissue and changes the angle of pull on the structures beneath your ribs. Many runners find this offers near-instant partial relief.
Coordinate exhaling with the opposite foot: If the stitch is on your right side, try exhaling each time your left foot strikes the ground. This shifts the timing of diaphragm contraction relative to the impact force, reducing the downward tug on the right side. It sounds awkward at first but becomes second nature surprisingly fast.
Walk: If nothing else is working, walk. A stitch almost always resolves within a few minutes of walking, and you can resume running once the pain fades. Pushing hard through a severe stitch rarely makes it go away faster and sometimes makes it worse.

These techniques are not guaranteed, and they tend to work better on moderate stitches than on the sharp, stabbing kind that stops you in your tracks. But most runners develop a personal toolkit from these options that gets them through the majority of episodes.

Prevention Strategies That Actually Help

Preventing stitches is more reliable than treating them on the fly. A few strategies have the best track record:

Building fitness gradually seems to be one of the strongest protective factors. Less experienced runners and those returning from a break are much more susceptible to ETAP. The Sydney data showed that runners got stitches at nearly double the rate of walkers during the same event.² This is not because running is inherently worse than walking; it reflects the higher mechanical forces involved. As your body adapts to those forces over weeks and months, stitch frequency tends to drop. Runners who have trained consistently for years report far fewer episodes than beginners, and many eventually stop getting them altogether.

Warming up properly also helps. Jumping straight into race pace or a hard tempo effort is a reliable way to provoke a stitch. A gradual warm-up of five to ten minutes at an easy pace gives your circulatory system time to redirect blood flow to the working muscles and your gut time to settle. This does not need to be elaborate; just avoid starting cold and fast.

Core strength training is often recommended by coaches and physiotherapists for stitch-prone runners. The logic is straightforward: a stronger core stabilizes the torso better during running, reducing the internal jostling that contributes to peritoneal irritation. There are no large controlled trials proving this works specifically for stitches, but the mechanism is plausible and the side benefits of a stronger core for running efficiency and injury prevention make it a worthwhile bet regardless.

Posture during running deserves mention too. Slouching or running with an exaggerated forward lean compresses the abdominal cavity and can increase the internal pressure on the peritoneum. Maintaining a tall, relaxed posture with a slight forward lean from the ankles, rather than from the waist, keeps the abdominal space open and may reduce your susceptibility.

Runners Versus Walkers and the Age Factor

A consistent finding across stitch research is that younger and less experienced exercisers get hit harder. Younger runners in their teens and twenties report stitches far more frequently than runners over 40, and the pain tends to be more intense in the younger group. This seems counterintuitive: shouldn’t a fitter body handle the stress better? But the trend likely reflects a combination of factors. Younger runners often push harder relative to their current fitness, are less attuned to pacing, and may have less conditioned abdominal connective tissue. As people age and accumulate years of running, their bodies seem to adapt in ways that make stitches less frequent and less severe.

The runner-versus-walker divide also holds important information. In the Sydney event, 30 percent of runners got a stitch compared to 16 percent of walkers.² Running produces greater vertical oscillation and ground reaction forces, which means more jostling of the abdominal contents with each stride. Walking, with its lower impact and more controlled gait, simply does not create the same mechanical environment. This is one reason why run-walk interval strategies often help newer runners avoid stitches during longer efforts.

When Right-Side Pain Is Not a Stitch

Most right-side pain during running is a garden-variety stitch, and the defining feature of ETAP is that it resolves quickly once you stop or slow down. Pain that persists well after exercise, gets worse over days, or is accompanied by other symptoms warrants attention.

Gallbladder problems can produce pain in the right upper abdomen that mimics a stitch but tends to be triggered by fatty meals rather than exercise specifically, and it usually does not fully resolve with rest the way a stitch does. Appendicitis, while it typically presents in the lower right abdomen rather than under the ribs, is another diagnosis people worry about. The distinguishing feature is that appendicitis pain progressively worsens over hours and is accompanied by nausea, fever, or tenderness that does not go away when you stop moving.

Musculoskeletal issues in the rib cage or abdominal wall can also masquerade as a recurring stitch. Nerve entrapment in the abdominal wall, for instance, causes localized pain that can flare with physical activity. A case report and review of ETAP in an elite triathlete noted that clinicians should consider differential diagnoses when the pain pattern is atypical or does not respond to the usual stitch-management strategies.⁴

A few red flags that should prompt a visit to a doctor rather than another attempt at breathing techniques:

Pain after stopping: A stitch resolves within minutes of resting. Pain that lingers for hours or into the next day is something else.
Fever or nausea: ETAP does not cause systemic symptoms. If you feel sick along with the pain, that points toward an abdominal or infectious cause.
Recurring in the same exact spot: A stitch can land in slightly different spots from run to run. Pain that is always precisely in the same location, especially if tender to the touch at rest, may involve the abdominal wall or an underlying organ.
Blood in urine or stool: Rarely associated with running-related gut stress in extreme endurance events, but always worth investigating.

Why Running Surfaces and Breathing Patterns Matter More Than You Think

One variable that runners rarely consider is how terrain affects stitch risk. Hard, flat surfaces like asphalt and concrete transmit more impact force up through the body than softer surfaces like trails or grass. That increased vibration load is the same mechanical factor implicated in the peritoneal irritation model. Runners who mostly train on roads and then find stitches less common on trails are not imagining it; the physics genuinely differ. This does not mean you need to abandon road running, but if you are chronically stitch-prone, mixing in softer surfaces for some of your runs may help.

Breathing patterns during running are another underappreciated factor. Most people naturally fall into a 2:2 breathing rhythm when running at moderate effort, inhaling for two footstrikes and exhaling for two. The problem with this pattern is that it consistently links the same phase of breathing to the same foot, so if you always start exhaling as your right foot hits the ground, the diaphragm is contracting and rising at the exact moment the right side absorbs impact. Switching to an odd-numbered rhythm, like 3:2 (inhaling for three steps, exhaling for two), alternates which foot lands during the exhale and distributes the mechanical stress more evenly across both sides. Elite runners tend to adopt these asymmetric patterns naturally, which may be part of why experienced runners report fewer stitches. Experimenting with your breathing cadence during easy runs is a low-cost strategy that can pay off during harder efforts.

1
PubMed Central. Exercise-Related Transient Abdominal Pain (ETAP)
2
PubMed. Epidemiology of exercise-related transient abdominal pain at the Sydney City to Surf community run
3
PubMed. Investigation of the side pain “stitch” induced by running after fluid ingestion
4
PubMed Central. Exercise related transient abdominal pain: a case report and review of the literature