Background: Alterations in the appearance and function of gastrointestinal mucosa are common after strenuous exercise. However, the duration of exercise required to alter the gastrointestinal mucosa has not been reported.
Hypothesis: We used 42 sled dogs to test the hypothesis that the magnitude of exercise-induced gastrointestinal mucosal dysfunction is related to exercise duration.
Animals: Six dogs served as conditioned controls, and the remaining dogs were randomly chosen for examination after 1-5 consecutive days of running at 100 miles/d.
Methods: Gastroduodenoscopy and measurement of gastric permeability were performed 24 hours after cessation of exercise. Intestinal protein loss (represented by fecal alpha-1 protease inhibitor concentration) was measured within 6 hours of cessation of exercise. Twelve of the 42 dogs were examined again after 5 months of detraining to determine the effect of training on gastrointestinal mucosal function.
Results: Exercise increased gastric permeability (P = .04) and endoscopic severity of gastric lesions (P < .0001), but neither variable was significantly affected by distance traveled. Acute exercise had no effect on intestinal protein loss. Untrained dogs had significantly lower fecal alpha-1 protease inhibitor concentrations compared with trained, unexercised dogs. Training had no effect on gastric permeability to sucrose or the endoscopic appearance of the stomach.
Conclusions and clinical importance: These data suggest that relatively modest exercise is required to increase intestinal protein loss, but more substantial exercise is required to cause alterations in the proximal gastrointestinal tract. However, none of these alterations appear to progress with increasing exercise duration.