GI (or gastrointestinal) issues are no fun. GI issues are one of the most commonly blamed reasons for underperforming on race day. In some cases, gut related issues can result in athletes not finishing the event.
Many athletes have come to me expressing great frustration and discomfort from nausea, bloating, gas, bloody diarrhea, loose stools, cramping, stomach pain, abdominal distention or vomiting during training and competition. While these complaints can have a negative effect on performance, they have an even bigger impact on physical and mental health.
Thankfully, several research studies have discussed the reasons why endurance athletes are at great risk for GI issues. There is also good research discussing how to mitigate these issues during exercise - especially in the heat, at high intensity or during long duration.
Reduced blood flow to the intestines during exercise is one of the main contributors to GI symptoms. These issues are only exacerbated when the body is dehydrated. Because blood is diverted from the gut and to the working muscles, the lack of blood flow in the gut slows gastric emptying. As a result, the delivery of nutrients and fluids to the muscles gets delayed and may cause gut discomfort (and a lot of other uncomfortable side effects). Reduced blood flow to the intestines may also contribute to increased permeability of the gut wall, which may trigger an inflammatory response resulting in GI distress.
Because the consumption, digestion and absorption of calories, carbohydrates, electrolytes and fluids are all important components of the training adaptation process and the ability to perform well on event day, minimizing the risk for GI issues is critical.
The takeaway: The gut is an extremely adaptable organ. Don't wait until race week (or race day) to figure out your fueling strategy. Training your stomach is just as important as training your muscles.
