title: No case of exercise-associated hyponatraemia in top male ultra-endurance cyclists: the 'Swiss Cycling Marathon'.
abstract: The prevalence of exercise-associated hyponatraemia (EAH) has been investigated in endurance athletes such as runners and Ironman triathletes, but not in ultra-endurance road cyclists. We assessed fluid intake and changes in body mass, urine specific gravity and plasma sodium concentration ([Na(+)]) in 65 ultra-endurance road cyclists in a 720-km ultra-cycling marathon, the 'Swiss Cycling Marathon'. The cyclists lost 1.5 (1.7)% body mass (P < 0.01). No athlete developed EAH. Fluid intake was associated with the change in plasma [Na(+)] (r = -0.32, P < 0.05) and the change in body mass (r = -0.30, P < 0.05). The change in plasma [Na(+)] was related to post-race plasma [Na(+)] (r = 0.63, P < 0.0001). To conclude, ad libitum fluid intake in ultra-endurance cyclists in a single-stage ultra-endurance road cycling race showed no case of EAH. Future studies regarding drinking behaviour in different ultra-endurance disciplines might give insights into why the prevalence of EAH is different in the different disciplines.
authors.affiliation: Institute of General Practice and for Health Services Research, University of Zurich, Zurich, Switzerland.
authors.forename: Christoph Alexander
authors.initials: CA
authors.lastname: Rüst
authors.forename: Beat
authors.initials: B
authors.lastname: Knechtle
authors.forename: Patrizia
authors.initials: P
authors.lastname: Knechtle
authors.forename: Thomas
authors.initials: T
authors.lastname: Rosemann
mesh_terms: D001642:Bicycling; D006801:Humans; D007010:Hyponatremia / Q000453:epidemiology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance; D015995:Prevalence; D013557:Switzerland / Q000453:epidemiology; D014882:Water-Electrolyte Balance