Effect of heavy exercise on gastrointestinal transit in endurance athletes

Abstract

Background and aims. Disturbances in transit of the gastrointestinal (GI) tract have been proposed to be involved in the etiology of the GI symptoms in heavy exercise. However, the results are conflicting. In the present study, we investigated the effect of heavy exercise on GI transit in well-trained athletes. Methods. Fifteen healthy well-trained athletes underwent measurement of gastric emptying, small bowel transit and colonic transit with radiopaque markers during a resting week and during a week with heavy training. GI symptoms, bowel habits, food intake and exercise performed were registered. Results. Small bowel transit was accelerated during the training period compared with the resting period (3.7 (2.6–12.3) h vs. 6.9 (4.2–17.2) h, p = 0.04). Segmental colonic transit in the descending colon was significantly accelerated during exercise compared with rest (0.1 (0–0.4) h vs. 0.4 (0.1–0.7) h, p = 0.03). Gastric emptying did not change during exercise compared with resting (2.4 (0.7–4.6) h vs. 1.8 (0.9–3.3) h, p = 0.16). Stool frequency increased significantly during the week with heavy exercise compared with the week without training (1.5 (1.2–1.8) stools/day vs. 1.3 (1.0–1.7) stools/day, p = 0.02). Stool consistency according to Bristol Stool Form Scale tended to be looser during the training period compared with the resting period (4.2 (3.7–4.5) vs. 3.9 (3.0–4.3), p = 0.08). Conclusion. Heavy exercise affects transit in the GI tract, which might be involved in the generation of GI symptoms and altered stool frequency/consistency in endurance athletes.

Key Words::

• Exercise
• gastrointestinal symptoms
• gastrointestinal transit
• stool consistency
• stool frequency

Acknowledgements

The authors would like to thank the orienteers for participating in the study. We would also like to thank Mrs Gisela Ringström, Mrs Pia Agerforz, Mrs Annette Lindh and Mrs Jessica Fennander for excellent technical support. This study was supported by the Swedish Medical Research Council (grant 13409) and by the faculty of Medicine, University of Göteborg.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.