title: Fluid intake and gastrointestinal problems in runners competing in a 25-km race and a marathon.
abstract: A group of 114 previously untrained subjects, 31 females and 83 males, was followed for 18 months while training for a marathon. Forty-four of the subjects completed a survey regarding fluid intakes and gastrointestinal (GI) disturbances during competition for both their first 25-km race (run after 1 year of training) and their first marathon. GI problems were common. Among the individuals surveyed, 25% had GI complaints in the 25-km race. In the marathon, 52% complained of GI distress. In general, fluid consumption was low (25 km means = 109 ml; marathon w = 577 ml). Body weight losses in the marathon were substantial (w = 3.2%, BW; range 1.5%-6.2%) indicating sweat losses greater than fluid replacement. These losses were greater in men than in women (men w = 3.4% BW; women w = 2.6% BW). GI complaints were not associated with larger drink intakes. In contrast, dehydration above a certain limit appears to increase the frequency of GI disorders. In the marathon, 80% of the runners who lost greater than 4% BW had GI problems. It is possible that reduced blood flow to the GI region is compromised via the exercise itself as well as by a reduced blood volume, which may disrupt normal secretion/absorption of the digestive tract. It may also be that a rising core body temperature, associated with decreased sweating at high levels of dehydration, may be related to GI dysfunction.
authors.affiliation: Dept. of Human Biology, University of Limburg, Maastricht, The Netherlands.
authors.forename: N J
authors.initials: NJ
authors.lastname: Rehrer
authors.forename: G M
authors.initials: GM
authors.lastname: Janssen
authors.forename: F
authors.initials: F
authors.lastname: Brouns
authors.forename: W H
authors.initials: WH
authors.lastname: Saris
mesh_terms: D000328:Adult; D003681:Dehydration / Q000209:etiology; D004068:Digestive System Physiological Phenomena; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012420:Running; D012737:Sex Factors; D013035:Spasm / Q000209:etiology; D013997:Time Factors; D014882:Water-Electrolyte Balance