Gastrointestinal complaints are very common among endurance athletes and are one of the main causes of underperformance in endurance events. Runner Gastrointestinal tract (GIT) distress has two main factors:

• Diversion of blood flow from the GIT to the muscles: When exercising at high intensity, muscles need to be supplied by oxygen-enriched blood. As such, our body diverts blood flow away from our internal organs, like the gastrointestinal tract, and directs it to the exercising muscles instead. This leads to delay of GIT emptying.

• Dehydration: Dehydration leads to the aggravation of gastrointestinal complaints during exercise. Dehydration also leads to a delayed Gastro-intestinal emptying.

The combination of reduced blood flow and dehydration puts the colon under great pressure. This can result to symptoms such as stomach cramps, vomiting, nausea and bloating. However, appropriate nutritional choices can reduce the risk of gastrointestinal discomfort during exercise. Here are recommendations that may help you minimize the risk of experiencing GI problems during your race:

• Hydration strategy: Drink plenty of water and include electrolytes.
• Training with a nutrition strategy can improve tolerance and stomach comfort: Test and plan carefully your meals & snacks
• Stress management: In the months and weeks leading to your race practice the exact same warm-up before every workout. On race day, repeat the exact routine you used for every workout.
• Pre-race diet: Switch to low-fibre diet two to three days prior to race day.
• Eat at least 2 to 3 hours before the start of the race.
• Carefully choose sport drink: Avoid high fructose drinks. A combination glucose/fructose may be more appropriate to avoid GIT problems.
• Avoid the use of aspirin and NSAIDs drugs like ibuprofen: Recent research points to a strong correlation between non-steroidal anti- inflammatory drug use and vomiting during endurance events.

 
Prado De Oliveira,E., Burini,R.C., Jeukendruo,A., (2014) .Gastrointestinal Complaints During Exercise: Prevalence, Etiology, and Nutritional Recommendations. Sports Medicine. 44 ( 1), 79-85.
 
Van Wijck,K., Lenaerts,K., Van Bijnen, A., Boonen,B. Van Loon, L., , LUC J. C; Dejong,C., (2012) Aggravation of Exercise-induced intestinal injury by Ibuprofen in athletes. Medicine & science in Sports & Exercise. 44 (12) p 2257-2262.