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This chapter reviews the incidence and severity of exercise-associated gastrointestinal symptoms (GIS) in sport, and defines exercise-induced gastrointestinal syndrome (EIGS) and the factors exacerbating this condition. It discusses the role of the gastrointestinal microbiota in EIGS. It outlines aspects of EIGS related to food intolerances, allergies and gastrointestinal disorders, along with a diagnostic pathway and recommended nutrition management. It provides guidance on applying a validated GIS assessment tool before, during and after exercise and includes recommendations for conducting a comprehensive gastrointestinal assessment. It also assesses prevention and management strategies for EIGS.


Reports of exercise-associated GIS vary greatly. This considerable variability is underpinned by a wide range of factors (e.g. type and duration of exercise, ambient temperature, training status, food intake, hydration). It appears that exercise stress ≥2 h at 60% VO2max is the threshold at which moderate or severe GIS develop (Costa et al. 2017b). In longer, ultra-endurance events, GIS are reported consistently in >60% of athletes (Costa et al. 2017b). Comparatively, ~10% of athletes participating in half- and full-marathon events reported GIS (ter Steege et al. 2008). Type of exercise is also a central factor influencing GIS. Pfeiffer et al. (2012) investigated GIS incidence and severity in a range of endurance events (e.g. marathon, triathlon, road cycling) and reported severe GIS in 4–32% of athletes across the different events, with the highest prevalence of symptoms in ultra-endurance triathlon. Running, compared to cycling and swimming, has repeatedly been linked with higher incidence and severity of GIS (Pfeiffer et al. 2012; ter Steege & Kolkman 2012). Upper GIS, particularly nausea and urge to regurgitate, appear to be the most commonly reported symptoms across a wide range of endurance events (ter Steege et al. 2012; ter Steege & Kolkman 2012; ter Steege et al. 2008; Costa et al. 2016; Pfeiffer et al. 2012; Snipe & Costa 2018a; Stuempfle & Hoffman 2015; Hoogervorst et al. 2019). Finally, ambient temperature, biological sex, and predisposition or history of GIS further influence risk and incidence rates of GIS (Costa et al. 2017b). Ambient temperatures ≥30°C are associated with greater incidence and severity of GIS (Costa et al. 2016), and increase in proportion to increasing ambient temperature (Snipe et al. 2018a; Snipe et al. 2018b). Some research suggests greater prevalence of GIS in females, which may be associated with frequency of functional gastrointestinal disorders (i.e. irritable bowel syndrome) and/or monthly hormonal alterations (Alonso et al. 2008; Costa et al. 2017a; Kim & Kim 2018; Lovell & Ford 2012; Snipe et al. 2018a). There appears to be an interplay between various factors underpinning the incidence and severity of GIS associated with exercise.


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