Gastrointestinal Responses And Hydration Status In Mountain Ultramarathon Runners

Mountain ultramarathons impose unique and challenging physical demands on runners. Many courses are >162 km, include >7000 m of vertical ascent, and may take >24 hrs to complete. As a result, these events can have profound effect on hydration status and gastrointestinal (GI) distress. PURPOSE: To examine hydration status and GI responses during a 162 km mountain ultramarathon. METHODS: 17 experienced ultra-runners (13 M, 4F; 38.9 ± 7.1 yrs, 69.8 ± 17.8 kg, 172.9 ± 9.3 cm, 11.5 ± 13.0%bf) completed the Bear 100 (162 km, 7200 m of vertical gain) in northern Utah. Prior to the race runners completed surveys describing demographics and training history. Runners then completed a GI questionnaire to assess presence and severity of symptoms, provided a urine sample, and body composition immediately pre- and post-race. GI symptoms were divided into upper abdominal, lower abdominal, and systemic sections and scored on a 10-point scale (0 = no problems; 9 = worst it has ever been). A score of >4 was considered “serious”. Urine samples were analyzed for color (Ucol) and urine specific gravity (USG) was measured using refractometry. Ucol was rated using an 8-color scale urine hydration chart (1 = good; 8 = severe dehydration). Comparisons for body mass, urine color, and USG were made using a paired t-test (p < 0.05). RESULTS: Runners completed the race in 28.6 ± 3.8 hrs (23.2 to 34.9 hrs). GI complaints were reported by 60% (17.6% serious) of runners pre vs. 100% (100% serious) post-race. The most frequently reported pre-race symptoms (section; % experiencing symptom) included stomach pain/cramps (upper; 29.4%), urge to defecate (lower; 52.9%), and urge to urinate (systemic; 41.2%). Post-race symptoms included belching (upper; 94.1%), flatulence (lower; 76.5%), and fatigue/muscle soreness/weakness (systemic; 100%). Runners lost 1.8% of body mass (69.8 ± 17.8 kg to 68.6 ± 12.9 kg, p < 0.05) during the race. Ucol was darker (2.4 ± 1.5 to 7.0 ± 1.3, p < 0.05), and USG values higher (1.014 ± 0.008 to 1.023 ± 0.008, p < 0.05) post-race. CONCLUSION: Challenges inherent with running a 162 km mountain ultramarathon contribute to impaired hydration status and increased incidence of GI symptoms in runners. Recognition of these factors can provide insight into better management practices for athletes competing in similar events.