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Reducing the Risk for GI Problems during High-Intensity Endurance Training

March 18, 2014 by NCSF 1 comment

Clients who regularly compete in events from 5Ks to marathons and beyond will agree that steps must be taken to reduce the risk for gastrointestinal (GI) tract problems during both races and training sessions. It is well-known that long-duration endurance training can directly damage the GI tract and cause debilitating symptoms, especially when combined with inappropriate nutritional intake. Research indicates the 30-50% of endurance athletes experience some sort of GI issues related to their training. This value may be higher among recreational competitors who lack the training, nutritional expertise and guidance elite athletes often possess. Interestingly, GI issues appear to occur more frequently among women and individuals who run as opposed to those who cycle or swim. The latter may be directly due to the repeated jostling effect placed upon digestive tissues from the high-impact nature of running.

Frequently reported GI problems resulting from intense endurance training:

There are many potential causes for the above issues which can stem from physiological, mechanical or nutritional factors. High anxiety or stress often associated with competition can significantly reduce blood flow to the GI tract. This promotes hypoxia and increases the risk for direct damage to the colon. As it relates to mechanical causative factors, (1) the high-impact forces of repeated foot contacts during running have been shown to potentially cause intestinal bleeding and blood in the feces; (2) continuous jostling of the trunk and pelvis is thought to contribute to flatulence, diarrhea, and an urgency to defecate; (3) postural modifications such as leaning forward during cycling (or due to fatigue) can increase compressive forces upon the abdomen and GI tract; and (4) “swallowing” of air can cause moderate stomach distress. Nutritional causes of GI-related problems on the other hand are more controllable by the exercise participant. Potential causes include the ingestion of fiber, fat, protein or fructose during or immediately prior to training, dehydration, ingestion of fluid with a high osmolarity during training (e.g., fruit juice), and ingestion of dairy products before or during training/competition. In addition, it has been shown that consumption of allergenic foods such as wheat, eggs, chicken, shrimp, shellfish, nuts, fruits, and vegetables, followed by exercise may induce food-dependent exercise-induced anaphylaxis (FDEIAn). FDEIAn is separate from food allergies and is more likely triggered by high intensity and frequent exercise.

While also considering the above causes and risk factors, competitive or recreational endurance athletes should make note of the following research-based recommendations for preventing GI problems. Unfortunately, strict and precise guidelines are limited due to the fact that each individual’s physiology has an impact on how stress affects their digestive system as well as other factors.

Recommendations purported to reduce the risk for GI problems during high-intensity endurance training:

1 comment

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Matthew Potts
March 24, 2014, 09:44 AM
I'd recommend steering clear of metabolism-boosting foods prior to any endurance exercising. Foods with heat naturally stimulate the metabolism and therefore present GI problems once the exercising has started. Hi-fat foods pose problems to well-trained, low-fat practicing individuals. Diarrhea is the main symptom.

Matt's Personal Training
Minersville, PA