GI training

GI training refers to purposeful practice of consuming carbohydrate-rich beverages and foods during exercise to condition the digestive system to tolerate them. Athletes aim to reduce gastrointestinal distress while improving energy delivery during long-duration events.

Explanation

Carbohydrate intake is vital during endurance activities to maintain blood glucose and delay fatigue. Yet many runners and cyclists experience stomach cramps, bloating, or diarrhea when taking in large volumes of sports drink or gels. The digestive system can adapt if gradually exposed to carbohydrate and fluid during training. GI training teaches the stomach to empty more quickly and increases the intestine’s ability to absorb sugars. Repeated exposure also upregulates transporters such as SGLT1 and GLUT5 that move glucose and fructose from the intestine into the bloodstream. Athletes typically start by sipping a low-concentration drink during shorter sessions and slowly increase the volume or concentration over several weeks. Consistency is important; practicing consumption under race-like intensity helps the body learn to manage the fluid and carbohydrate load. Adequate hydration and sodium intake support absorption and reduce gastrointestinal upset.

Practical steps for adapting the gut

Begin with small carbohydrate doses, such as 30 grams per hour, and divide them into sips or small bites throughout training sessions. Over time increase to 60–90 grams per hour, using combinations of glucose and fructose to utilize multiple transport pathways. Try different sports drink formulations and temperature settings to find what sits best. Incorporate some sessions at race pace to test the stomach’s tolerance under stress. Avoid high-fiber and high-fat meals before training, as these slow gastric emptying. Pay attention to individual signals; if cramps or nausea arise, reduce intake and progress more slowly. Keeping track of fluid intake relative to sweat rate also helps maintain proper hydration and minimize GI symptoms.

Most people can develop greater tolerance with consistent practice. Regular GI training is an effective strategy for endurance athletes to improve tolerance to carbohydrate intake and optimize performance. By gradually increasing intake and monitoring personal responses, athletes can develop a fueling plan that supports energy needs without upsetting their stomach.

Related Terms: carbohydrate loading, carbohydrate oxidation, hydration strategy, gastric emptying, gut adaptation