A gastrointestinal disorder that affects runners, especially just before a competition. It is characterized by a mild, but inconvenient diarrhoea (commonly called ‘runner's trots’) and nausea. Exercise-induced diarrhoea is not confined to runners: activity of any kind is usually associated with increased secretion of sympathetic hormones (e.g. adrenaline) that increases gut motility. However, mild diarrhoea during or after competition appears to be more frequent in runners than other athletes, indicating that there are predisposing factors specific to that activity. Perhaps the bouncing movements performed during running increases mechanical mixing in the gut, increasing motility. Other predisposing factors to diarrhoea include a mild intolerance to milk products or a sensitivity to some other factor (e.g. fructose). Eating a low-fibre diet for 24–48 h before competition will reduce the risk of diarrhoea. If diarrhoea occurs, it is important to ensure that fluids are replaced to prevent dehydration (see water replacement).
Subjects: Sports and Exercise Medicine.