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But there was something about me that was broken, unhealthy, unfit. Some called it allergies, some called it asthma, some just called it being out of shape. But no matter what we called it, no one knew how to fix it.

Novak Djokovic, 14-time Grand Slam winner, Serve to Win, 2013

The gut is not an athletic organ. During exercise, blood is directed away from the splanchnic vessels and to the exercising muscles. The gut therefore becomes relatively ischaemic causing many of the gastrointestinal symptoms associated with exercise. These symptoms may be divided into those relating to the upper gut and those relating to the lower gut (Table 12.1). Bleeding is another important clinical presentation, as discussed below.

Physiological changes that alter gastrointestinal function during exercise include reduced blood flow to the abdominal viscera, gastrointestinal hormone change and alterations to gastric emptying rates alongside intestinal motility. Vigorous diaphragmatic movements, abdominal contractions and intestinal jarring can all cause mechanically induced abdominal symptoms.1

Table 12.1Gastrointestinal symptoms associated with exercise

Although the incidence of gastrointestinal symptoms is increased with exercise, the presence of symptoms in an athlete should not automatically be assumed to be solely related to exercise. Athletes as well as non-athletes suffer from common conditions such as hiatus hernia and peptic ulceration, inflammatory bowel disease, polyps and cancer. Physical activity confers a 25% reduction in colon cancer risk.2 Clinical judgment is required to appreciate when these conditions must be considered in the athlete with gastrointestinal symptoms.

A summary of the management of common gastrointestinal symptoms is shown in Table 12.2.

Table 12.2Treatment of common gastrointestinal problems


Heartburn, reflux, nausea, vomiting and upper abdominal pain are the most common upper gastrointestinal (GI) tract symptoms related to exercise. Upper GI symptoms can affect anywhere from 30 to 70% of athletes.3, 4 Gastrooesophageal reflux is a common complaint among athletes and can even cause asthma-like symptoms.5 Twenty per cent of patients with established reflux consider exercise to be the major contributor to their symptoms.

The mechanism by which exercise causes reflux is ...

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