Side stitches, medically known as Exercise-related Transient Abdominal Pain (ETAP), are a common nuisance for runners. This temporary, localized pain typically manifests as a sharp or stabbing sensation just below the ribs, most often on the right side of the abdomen. While the pain can also present as an aching or pulling sensation, it is almost exclusively associated with activities that involve repetitive torso movement, like running and horseback riding. Approximately 70% of runners report experiencing this pain at some point. Despite its frequent occurrence, ETAP is benign and self-limiting, meaning the pain resolves quickly once the activity stops.
The Leading Scientific Theories
The exact physiological cause of a side stitch remains an area of scientific investigation, but several leading theories attempt to explain the sudden onset of this abdominal pain.
Visceral Ligament Strain
The most widely accepted explanation involves traction or strain on the visceral ligaments, which are the supportive structures connecting the internal abdominal organs to the diaphragm. During running, the repetitive vertical motion of the torso causes these organs, particularly the liver on the right side, to pull down on the ligaments. This downward tugging action is amplified when the stomach is full, which increases the mass and weight of the organs, thereby heightening the stress placed on the attached ligaments. (4 sentences)
Parietal Peritoneum Irritation
A related theory centers on the irritation of the parietal peritoneum, the thin, sensitive membrane that lines the abdominal and pelvic cavities. Because this membrane is rich in nerve endings, friction or stretching caused by the organs shifting during high-impact exercise can trigger the localized, sharp pain. This theory is supported by the observation that some sufferers also experience shoulder tip pain, a phenomenon of referred pain. The phrenic nerve supplies the diaphragm and the peritoneum, suggesting a direct link between abdominal irritation and referred pain. (4 sentences)
Diaphragmatic Ischemia
Another contributing factor is diaphragmatic ischemia, where the breathing muscle experiences a temporary reduction in blood flow. When running intensity increases, the body prioritizes sending blood to the large working leg muscles, potentially diverting blood away from the diaphragm. This lack of oxygenated blood can cause the diaphragm to fatigue or spasm, leading to a cramp-like pain. Shallow or rapid chest breathing, common during intense exercise, may exacerbate this effect by not fully engaging the diaphragm. (4 sentences)
Immediate Relief Strategies
When a side stitch strikes mid-run, the first strategy is to reduce the intensity of your exercise, often by slowing down to a walk. This action decreases the impact and the vertical oscillation of the torso, reducing the stress on the visceral ligaments and the parietal peritoneum. Simultaneously, focus on changing your breathing pattern to address the potential diaphragmatic strain. (3 sentences)
Diaphragmatic Breathing
A technique involves deep, rhythmic diaphragmatic breathing, often called “belly breathing,” where you focus on expanding the abdomen rather than just the chest. As you breathe, exhale forcefully when the foot opposite the side of the stitch hits the ground. For example, if the pain is on your right side, exhale strongly as your left foot lands, which helps to pull the diaphragm upward and relieve the stress on the ligament. (3 sentences)
Pressure and Stretching
Applying direct physical pressure and stretching can also provide quick relief. Press two fingers firmly into the painful area just beneath the ribs while simultaneously bending forward slightly. Raise the arm on the side opposite the pain up and over your head, then gently lean your torso toward the side experiencing the stitch. Holding this stretch for 30 seconds can help elongate the torso muscles and stretch the diaphragm, which may help to release the cramp. (4 sentences)
Proven Prevention Techniques
Long-term prevention involves strategic pre-run habits and consistent training to fortify the body’s stabilizing structures.
Managing Intake
Timing your food and fluid intake is effective, as a heavy or full stomach increases the weight pulling on the visceral ligaments. Runners should avoid large meals or consuming high-fat, high-fiber foods, or hypertonic (sugary) drinks for at least one to two hours before a run. Small sips of water are better than gulping large volumes of fluid immediately before starting exercise. (3 sentences)
Core Strengthening
Strengthening the core muscles provides better stabilization for the torso, which limits the movement of internal organs and reduces the traction on the ligaments. Specific focus on the deeper abdominal muscles, such as the transversus abdominis, has been linked in studies to a lower incidence of ETAP. Exercises like planks and other anti-rotation movements can build strength to brace the trunk against the repetitive impact of running. (3 sentences)
Warm-up and Breathing
A proper warm-up and gradual increase in running intensity are preventative measures that allow the diaphragm and respiratory muscles to acclimate. Starting a run too fast can immediately force shallow, rapid breathing, which is a known trigger for stitches. Practicing an uneven breathing rhythm, such as inhaling for three steps and exhaling for two steps (a 3:2 pattern), can distribute the mechanical stress on the diaphragm. This technique ensures that the exhale does not always occur when the same foot strikes the ground, balancing the load across both sides of the torso. (4 sentences)