The temporary, sharp abdominal pain experienced during exercise, commonly called a “stitch” or “side stitch,” is medically termed Exercise-Related Transient Abdominal Pain (ETAP). This condition is a frequent occurrence, especially among athletes involved in rhythmic activities like running and swimming; approximately 70% of runners report an episode within a year. Despite its prevalence, the precise physiological mechanism responsible for the pain remains a subject of ongoing debate among sports medicine professionals. The pain is transient, resolving quickly upon cessation of exercise, but its sudden onset significantly disrupts athletic performance.
Physical Characteristics of Exercise-Related Abdominal Pain
ETAP typically manifests as a localized pain that sufferers can pinpoint with a finger. The pain is most commonly felt along the costal border (the lower edge of the ribcage) and frequently occurs on the lateral aspects of the mid-abdomen. Although it can happen on either side, it is reported more often on the right side of the body.
The sensation varies based on severity. Less intense pain is described as a dull ache, cramping, or a pulling sensation. More severe episodes are characterized by a sharp, stabbing pain that forces the athlete to slow down or stop. The pain occasionally presents with referred pain to the shoulder tip, which suggests potential structures involved in its causation.
Leading Physiological Theories of Causation
Scientific hypotheses explaining ETAP focus on mechanical stress, irritation, or reduced blood flow to structures within the torso.
Diaphragmatic Ischemia
One long-standing theory attributes the pain to diaphragmatic ischemia. Intense exercise diverts blood flow away from the diaphragm muscle to the working limbs. This reduced blood supply leads to a temporary lack of oxygen, causing the diaphragm to cramp or spasm. Evidence supporting this includes the occasional shoulder tip pain, as the phrenic nerve that innervates the diaphragm refers pain to that specific location.
Visceral Ligament Stress
Another prominent theory involves mechanical stress on the visceral ligaments. These connective tissues suspend internal abdominal organs, such as the liver and stomach, from the diaphragm and abdominal wall. Repetitive, jarring movements inherent in activities like running create a downward tug on these organs, pulling on the ligaments. This constant tension, especially when organs are heavy from recent food or fluid intake, is thought to stretch and irritate the sensitive ligaments, causing localized pain.
Parietal Peritoneum Irritation
The theory currently receiving the most attention proposes that ETAP results from the irritation of the parietal peritoneum, the sensitive outer lining of the abdominal cavity. This membrane adheres to the abdominal wall and the underside of the diaphragm. Repetitive friction between the parietal peritoneum and the visceral peritoneum during high-impact, torso-moving exercise is thought to cause the sharp, localized pain. Its irritation offers the most comprehensive explanation for the localized nature of the stitch, aggravation by a full stomach, and referred shoulder pain.
External Factors That Increase Susceptibility
Several external behavioral factors increase an individual’s susceptibility to experiencing ETAP.
Pre-Exercise Intake
Consuming food or large volumes of fluid shortly before exercise is a significant trigger. A full stomach increases the mass and volume of abdominal contents, exacerbating the downward pull on visceral ligaments and increasing friction on the peritoneum during movement. Hypertonic beverages, such as fruit juices, sodas, and certain sports drinks, are particularly provocative. These high-concentration drinks delay stomach emptying and cause fluid shifts in the gut, which increases abdominal distension and irritation.
Posture and Warm-up
Poor posture, especially a slouched or hunched position, can compress the abdomen and restrict diaphragm movement, potentially contributing to the onset of a stitch. Beginning high-intensity exercise without an adequate warm-up also increases the risk of ETAP. A proper warm-up allows the body to gradually adapt to physical demands, preparing the core musculature and respiratory system. Conversely, a sudden onset of vigorous activity prematurely stresses the involved structures.
Immediate Strategies for Relief and Avoidance
Immediate relief can often be achieved by momentarily slowing down the activity or stopping completely.
Acute Relief Techniques
Focusing on deep, controlled breathing is helpful; take a deep breath in and force a slow, complete exhalation to stretch and relax the diaphragm. Applying gentle but firm pressure directly to the area of pain can alleviate acute discomfort. Stretching maneuvers also provide quick relief, such as bending forward slightly or stretching away from the painful side to ease tension on the abdominal structures. Once the pain subsides, resume activity at a lower intensity while maintaining an upright, extended posture to prevent recurrence.
Long-Term Prevention
For long-term avoidance, adjusting pre-exercise habits offers the most effective preventative measures. Individuals should avoid eating large meals or consuming sugary, hypertonic drinks for at least two hours before vigorous exercise. Maintaining a strong, supported core through targeted exercises helps stabilize the torso and minimizes excessive movement of abdominal contents. Always start exercise with a gradual warm-up and progressively increase intensity to help the body adapt to physical stress.