Runner’s trots is the common term for exercise-induced gastrointestinal syndrome (EIGS), describing digestive distress that occurs during or immediately following a run. Symptoms often include diarrhea, abdominal cramping, and an urgent need for a bowel movement. This condition is common among endurance athletes, but it is not one you must simply endure. Careful adjustments to your diet, hydration, and training routine can significantly reduce or eliminate the problem by addressing the relationship between running’s physical demands and your body’s digestive function.
Pre-Run Fueling Strategy
The food consumed in the hours before a run is a primary trigger for digestive upset. The final meal or snack, ideally eaten one to four hours before your run, should focus on easily digestible carbohydrates. This timing allows for partial digestion and gastric emptying before the physical stress of running begins.
Significantly reduce your intake of high-fiber foods, such as whole grains and raw vegetables, in the 24 hours leading up to a long run or race. Fiber remains in the digestive tract longer and can exacerbate bowel urgency. High-fat and excessive protein foods should also be limited because they slow the stomach’s emptying process, causing food to sit uncomfortably in the gut.
Concentrated sugar sources, like gels or high-sugar sports drinks, should be avoided immediately before the start. A high concentration of carbohydrates can draw excess water into the intestine, leading to fluid imbalance and diarrhea. Instead, opt for simple, low-residue carbohydrates like white rice, white toast, or a banana as your final solid food source.
Hydration and Electrolyte Balance
Proper fluid intake is a major factor in preventing runner’s trots. Dehydration causes or worsens GI distress because decreased blood volume slows the rate at which the stomach empties. This delayed gastric emptying means food and fluids sit longer in the gut, increasing the likelihood of discomfort.
Maintaining a proper baseline hydration level throughout the days leading up to a run is more impactful than drinking a large amount right before the start. For runs lasting longer than an hour or in hot conditions, incorporate electrolytes. Sodium and potassium are crucial for maintaining fluid absorption efficiency and preventing hyponatremia, a dangerous dip in blood sodium levels.
Avoid over-consuming plain water too quickly during a run, as this disrupts the body’s balance of salts and water. Highly concentrated carbohydrate drinks should also be avoided mid-run as they can pull water into the intestines. Instead, sip small amounts of a sports drink containing a balanced electrolyte mix regularly throughout the effort.
Training Adjustments and Intensity Management
The physical act of running places unique stress on the digestive system through two main mechanisms: blood flow diversion and mechanical jarring. During high-intensity running, the body prioritizes sending blood to the working muscles and the skin for cooling, diverting blood flow away from the gut. This reduced blood flow to the intestines, known as splanchnic ischemia, irritates the intestinal lining, leading to impaired absorption and distress.
Managing your running intensity is an effective way to mitigate this issue. Sustained high-intensity effort exacerbates blood diversion, so incorporating strategic walk breaks or running at a lower, more sustainable pace can prevent symptoms. The repetitive up-and-down motion of running also mechanically jostles the internal organs, which can directly stimulate bowel movements. Wearing clothing that is not overly tight around the abdomen may help, as excessive compression can constrict blood flow and worsen symptoms.
A progressive approach to “gut training” can help the digestive system adapt to fueling during exercise. This involves intentionally practicing the consumption of fluids and carbohydrates, such as gels or chews, during training runs to teach the stomach to tolerate them at race intensity. Pre-race anxiety and stress can trigger GI symptoms due to the release of stress hormones like adrenaline, which increases colonic motor activity. Employing mental strategies to manage pre-race nerves can therefore provide a physical benefit for your digestive comfort.
Acute Management and When to See a Doctor
If symptoms of runner’s trots begin during a run, the first acute strategy is to immediately slow your pace. Reducing the intensity lessens the blood flow diversion and mechanical jarring, offering the digestive system a chance to calm down. Taking a few sips of an electrolyte-containing fluid or a salt capsule, if available, can help address any sudden fluid imbalance contributing to the distress.
Over-the-counter anti-diarrheal medications, such as loperamide, can be used for acute management, but they should only be taken after testing them during a non-race training run to understand your body’s reaction. Never try a new medication on race day. These medications should be used cautiously and only after consulting with a healthcare provider.
You should seek immediate medical consultation if you notice specific red flags, as these may indicate a more serious condition than typical runner’s trots. These indicators include the presence of blood in your stool, persistent nausea or vomiting, or severe abdominal pain that does not resolve after stopping the run. Chronic symptoms that do not improve despite consistent application of preventative measures also warrant a visit to a sports medicine physician to rule out underlying conditions like irritable bowel syndrome or ischemic colitis.