title: Bike Transalp 2008: liquid intake and its effect on the body's fluid homeostasis in the course of a multistage, cross-country, MTB marathon race in the central Alps.
abstract: OBJECTIVE
  To investigate the drinking behavior of the participants in a multi-day mountain bike (MTB) cross-country competition, to monitor its effect on the body's fluid compartments and body mass, and to evaluate the prevalence of exercise-associated dysnatremia.
  
  
  METHODS
  Descriptive field study.
  
  
  METHODS
  The Jeantex Bike Transalp Competition 2008 (8 stages; 665.40 km; 21 691 m height).
  
  
  METHODS
  Twenty-five male, amateur MTB cyclists.
  
  
  METHODS
  Reported fluid intake during the race, air temperature.
  
  
  METHODS
  Changes in body mass and body composition from pre to post race and throughout the competition week, serum sodium concentration at finish line of stages 5 and 6.
  
  
  RESULTS
  Mean (+ or - SD) hourly fluid intake during the race correlated with air temperature (r = 0.868, P < .05) and ranged between 494 + or - 191 mL/h and 754 + or - 254 mL/h. In absence of exercise-induced hyponatremia (EAH) cases, we report 5 and 4 cases of asymptomatic post-race hypernatremia, on days 5 and 6, respectively. When related to race time and body mass, the liquid intake during the race (in mL x kg(-1) x h(-1)) correlated with post-race serum sodium concentration (stage 5: r = -0.463, P < .05, n = 24; stage 6: r = -0.589, P < .01, n = 23); no correlation was found between the change in body mass from pre to post race and serum sodium concentration at finish line.
  
  
  CONCLUSIONS
  Ad libitum fluid consumption during competition was spontaneously adjusted to the unsettled weather conditions in the course of the 2008 "Bike Transalp." The inverse linear relationship between hourly fluid intake and post-race serum sodium concentrations suggests underdrinking to be one contributing factor to the high reported incidence of hypernatremia in the absence of EAH. Experimental studies are requested to confirm this hypothesis and to further examine the pathogenesis of exercise-associated dysnatremia. In this setting, body mass monitoring was not an accurate instrument to control body fluid homeostasis.
authors.affiliation: School of Sports Medicine, University of Verona, Policlinico GB Rossi, 37134 Verona, Italy. kai.schenk@yahoo.com
authors.forename: Kai
authors.initials: K
authors.lastname: Schenk
authors.forename: Hannes
authors.initials: H
authors.lastname: Gatterer
authors.forename: Marcello
authors.initials: M
authors.lastname: Ferrari
authors.forename: Pietro
authors.initials: P
authors.lastname: Ferrari
authors.forename: Vincenzo Lo
authors.initials: VL
authors.lastname: Cascio
authors.forename: Martin
authors.initials: M
authors.lastname: Burtscher
mesh_terms: D000328:Adult; D001317:Austria / Q000453:epidemiology; D001642:Bicycling / Q000502:physiology*; D001823:Body Composition; D015992:Body Mass Index; D003163:Competitive Behavior; D004327:Drinking Behavior; D004435:Eating; D017079:Exercise Tolerance; D006706:Homeostasis; D006801:Humans; D006955:Hypernatremia / Q000453:epidemiology / Q000209:etiology*; D007010:Hyponatremia / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D016014:Linear Models; D008297:Male; D012307:Risk Factors; D012964:Sodium / Q000097:blood; D013223:Statistics as Topic; D013997:Time Factors; D014870:Water Loss, Insensible; D014882:Water-Electrolyte Balance; D055815:Young Adult
chemical_list: D012964:Sodium