title: Physical fitness influences water turnover and body water changes during trekking.
abstract: OBJECTIVE
  This study was performed to assess water turnover and changes of body water during a trekking tour at moderate altitude.
  
  
  METHODS
  Fifteen healthy normally trained adults participated in a 7-d backpack trek tour in the Swiss Alps (total walking distance: 120.5 km; cumulated altitude difference: 6990 m (uphill) and 7550 m downhill; lowest point: 1285 m; highest point: 3317 m). Total body water and water turnover were measured using deuterium dilution and elimination (oral load of 0.33 g 99.8% D2O per kg body weight, overnight equilibration period, pre- and postdose saliva samples immediately before and after sleep, analysis of D2O concentrations in saliva using Fourier-transform infrared spectroscopy, CV < 1%). Physical training state was assessed after the tour using the lactate-exercise intensity relationship obtained by performing 50-W increments every 3 min on a cycle ergometer.
  
  
  RESULTS
  Body water decreased from the evening of day 0 to the evening of day 4 (from 45.3 +/- 7.3 L to 43.4 +/- 7.6 L, P < 0.05), and did not significantly decrease (43.5 +/- 7.9 L) until the evening of day 5 (maximum of trekking exercise intensity). Mean daily water turnover was 5.7 +/- 1.8 L x d(-1) corresponding to 78.7 +/- 17.5 mL x kg(-1) x d(-1). Body water changes and water turnover were significantly related to the exercise intensity obtained at the lactate threshold as well as at the level of 4 mM lactate.
  
  
  CONCLUSIONS
  This correlation may be in part explained by differing glycogen content of muscle tissue.
authors.affiliation: Division of Neonatology, University Women's Hospital, Bern, Switzerland. fusch@rz.uni-greifswald.de
authors.forename: C
authors.initials: C
authors.lastname: Fusch
authors.forename: W
authors.initials: W
authors.lastname: Gfrörer
authors.forename: H H
authors.initials: HH
authors.lastname: Dickhuth
authors.forename: H
authors.initials: H
authors.lastname: Moeller
mesh_terms: D000328:Adult; D000531:Altitude; D001823:Body Composition; D005260:Female; D006801:Humans; D019344:Lactic Acid / Q000097:blood / Q000378:metabolism; D008297:Male; D010807:Physical Endurance / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D014882:Water-Electrolyte Balance
chemical_list: D019344:Lactic Acid