. "4. Effects of Excercise and Heat on Gastrointestinal Function." Nutritional Needs in Hot Environments: Applications for Military Personnel in Field Operations. Washington, DC: The National Academies Press, 1993.
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Nutritional Needs in Hot Environments: Applications for Military Personnel in Field Operations
Do GI symptoms and morphological changes associated with exercise-heat stress persist or do they subside quickly without functional impairment?
One of the first and most dramatic accounts of GI distress came from Derek Clayton (Benyo and Clayton, 1979) after he ran the marathon in 2:08:33.6. He commented:
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.
Table 4-1 lists the common GI symptoms experienced by runners, although these have also been observed in other athletes (Eichner, 1989).
TABLE 4-1 Gastrointestinal Disturbances Associated with Long-Distance Running
They are most often observed with overtraining, dehydration, and the use of aspirin. Another contributing factor may be high ascorbic acid intake (Sharman, 1982). These GI symptoms may be reduced by treatment with cimetidine (Baska et al., 1990) or consumption of an elemental diet (Bounous et al., 1967).
IMPORTANCE OF GI MANIFESTATIONS WITH EXERCISE-HEAT STRESS
Severe heat exposure simulates hemorrhage and intestinal ischemia because blood pools in the cutaneous capacitance vessels, central blood volume and splanchnic blood flow decline, and mean arterial pressure falls because increased heart rate cannot fully compensate for a declining stroke volume that causes cardiac output to fall. Hemorrhage and intestinal ischemia