The sudden, sharp abdominal pain that often forces a runner to stop or slow down is a common and frustrating experience. This temporary discomfort is scientifically known as Exercise-Related Transient Abdominal Pain (ETAP). ETAP affects a large majority of runners and athletes involved in repetitive torso movement, with approximately 70% reporting an episode within a single year. While the pain is harmless and fleeting, it remains a performance-limiting complaint during physical activity.
Understanding the Pain and Terminology
A side stitch is a localized sensation ranging from a dull ache to a sharp, stabbing pain. The pain most frequently occurs along the lower edge of the ribcage, commonly on the right side of the abdomen.
The medical term is Exercise-Related Transient Abdominal Pain (ETAP), describing temporary, exercise-induced pain in the abdominal area. In some instances, the pain may also be felt at the tip of the shoulder, known as referred pain. This shoulder pain results from the phrenic nerve, which innervates the diaphragm and refers sensation to that area.
Primary Theories Explaining Side Stitch Causes
The precise biological cause of the side stitch is not definitively proven, but current research points to a few leading hypotheses related to running mechanics and digestion.
Parietal Peritoneum Irritation
The most widely accepted theory involves the irritation of the parietal peritoneum, the thin membrane lining the abdominal and pelvic cavities. Repetitive torso movement and the jarring motion of running may cause friction and tension on this membrane, leading to localized pain.
Visceral Ligament Stress
This theory focuses on stress on the visceral ligaments, connective tissues that anchor internal organs (like the stomach and liver) to the diaphragm. The constant up-and-down motion of running pulls on these ligaments, especially when the stomach is full, creating tension and subsequent pain. This explains why consuming large volumes of food or fluid too close to exercise increases the likelihood of a stitch.
Diaphragm Spasm or Ischemia
The third hypothesis centers on the diaphragm muscle itself, suggesting a muscular spasm or ischemia (a temporary lack of blood flow). Shallow, rapid breathing patterns, common during intense running, can overwork the diaphragm, leading to fatigue and cramping. Digestion also requires blood flow to the gastrointestinal tract, which may momentarily divert blood away from the diaphragm, potentially triggering the cramp.
Immediate Actions to Stop a Side Stitch
When a side stitch strikes mid-run, immediately slow your pace or stop momentarily to reduce the vertical impact on your torso. Reducing the jarring motion allows abdominal structures to settle and decreases stress on the diaphragm and ligaments. This pause often prevents the pain from escalating.
A change in breathing technique can help relieve the spasm by targeting the diaphragm. Focus on taking long, deep breaths that expand the abdomen, avoiding shallow, chest-level breaths. Exhale forcefully through pursed lips when the foot opposite the side of the pain hits the ground; this helps stretch the diaphragm and release the cramp.
Applying manual pressure directly to the area of pain can also provide immediate relief. Gently press inward and slightly upward with your fingers or palm on the stitch while simultaneously exhaling. Another effective maneuver is performing a side stretch by raising the arm on the affected side overhead and bending the torso away from the pain.
Long-Term Strategies for Prevention
Adjusting pre-run nutrition and hydration timing is an effective preventive measure. Avoid consuming large quantities of food or highly concentrated, sugary beverages within one to two hours of starting your run. These items require significant digestive effort, which can exacerbate visceral ligament stress by increasing stomach mass and diverting blood flow.
Training your breathing is another strategy, emphasizing diaphragmatic or “belly” breathing during exercise. Deep, controlled inhalations and exhalations ensure the diaphragm is fully engaged. This helps prevent the shallow breathing patterns that lead to muscle fatigue. Practicing this technique consistently helps establish a natural running rhythm.
Developing stronger core musculature provides better support for the torso and helps stabilize the spine during running impact. Runners with stronger abdominal muscles, particularly the deep transversus abdominis, report less pain from ETAP. Incorporating exercises like planks and bird dogs can reduce strain on the visceral ligaments and the peritoneum. Always begin your run with a proper warm-up, gradually increasing intensity to prepare the body for the demands of the activity.