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.
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.
Schenk
Kai
K
School of Sports Medicine, University of Verona, Policlinico GB Rossi, 37134 Verona, Italy. kai.schenk@yahoo.com
Gatterer
Hannes
H
Ferrari
Marcello
M
Ferrari
Pietro
P
Cascio
Vincenzo Lo
VL
Burtscher
Martin
M
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
D012964:Sodium