CYCLING PERFORMANCE TIPS

The Athlete and the GI Tract

by R. Rafoth MD
Sun Mountain Lodge - 1/2004



Introduction - What are the issues?

Let's look at some real life stories.

I. A quote from Derek Clayton - after his world record marathon run (Runner's World, 1977):

"Two hours later, the elation had worn off. I was urinating quite large clots of blood and I was vomiting black mucus and had a lot of black diarrhea. I don't think too many people can understand what I went through for the next 48 hours."

II. JAMA 1980:

A 24 year old medical student and long distance runner presented with a history of bloody diarrhea. He complained of three weeks of abdominal cramps after hard runs and 1 week of blood mixed with loose stools. He sought medical advice and his evaluation including a sigmoidoscopy, Ba Enema, and Upper GI/small bowel follow through were all negative. He continued his strenuous running schedule and his symptoms gradually disappeared. In the subsequent two years, he remained asymptomatic with the exception of occasional recurrent episodes of diffuse abdominal cramping, watery diarrhea, and rarely bloody diarrhea - almost always associated with particularly strenuous physical exertion such as a marathon run.

III. JAMA 1981:

A 17 y/o man ran competitively in short sprint events, and often had bouts of abdominal cramps during and after hard runs (both training and competition). After a particularly vigorous training session, he developed a dull, aching epigastric pain which then migrated to the RLQ and was associated with bloody diarrhea. When rebound and an elevated WBC developed, a tentative diagnosis of appendicitis was made and the patient went to laparotomy. A surgical diagnosis of Crohn's disease was made, but biopsies demonstrated only non specific colitis. The patient resumed running and has had no further abdominal symptoms.



These three stories raise several questions. And as I suspect many of you have had digestive tract symptoms during running or another athletic event, these may be questions that are personal as well.



It turns out that serious athletes often develop gastrointestinal (GI) symptoms and disorders during training and competition. GI symptoms are common in athletes at all performance levels, although they are more frequent and severe when the athlete is performing near their physical maximum, either in terms of %VO2max or the duration of a training or competition. The most common include lower GI symptoms of cramps and diarrhea, and the non specific upper GI symptom of nausea.

  1. During Triathlons, GI complaints are more common than musculoskeletal injuries.

  2. GI symptoms may limit an athlete's performance. They are not only distracting, but may lead to dropping out of the training session or competition.

  3. GI symptoms may suggest the presence of underlying GI disease.

  4. GI symptoms may limit oral intake, and as a consequence performance, during an event.

As we review the effects of exercise on the GI system the focus will be on the athlete who exercises, both in training and competition at >70% VO2 max, levels not likely to be reached by those involved in purely recreational exercise. However, for those weekend warriors who are not in the best of shape, it is not uncommon to reach 70% of their VO2 max, and as a result, they are at risk as well.




Next section - Normal Gastrointestinal Physiology


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