title: Bioimpedance identifies body fluid loss after exercise in the heat: a pilot study with body cooling.
abstract: OBJECTIVE
  Assessment of post-exercise changes in hydration with bioimpedance (BI) is complicated by physiological adaptations that affect resistance (R) and reactance (Xc) values. This study investigated exercise-induced changes in R and Xc, independently and in bioelectrical impedance vector analysis, when factors such as increased skin temperature and blood flow and surface electrolyte accumulation are eliminated with a cold shower.
  
  
  METHODS
  Healthy males (n = 14, 24.1±1.7 yr; height (H): 182.4±5.6 cm, body mass: 72.3±6.3 kg) exercised for 1 hr at a self-rated intensity (15 BORG) in an environmental chamber (33°C and 50% relative humidity), then had a cold shower (15 min). Before the run BI, body mass, hematocrit and Posm were measured. After the shower body mass was measured; BI measurements were performed continuously every 20 minutes until R reached a stable level, then hematocrit and Posm were measured again.
  
  
  RESULTS
  Compared to pre-trial measurements body mass decreased after the run and Posm, Hct, R/H and Xc/H increased (p<0.05) with a corresponding lengthening of the impedance vector along the major axis of the tolerance ellipse (p<0.001). Changes in Posm were negatively related to changes in body mass (r = -0.564, p = 0.036) and changes in Xc/H (r = -0.577, p = 0.041).
  
  
  CONCLUSIONS
  Present findings showed that after a bout of exercise-induced dehydration followed by cold shower the impedance vector lengthened that indicates fluid loss. Additionally, BI values might be useful to evaluate fluid shifts between compartments as lower intracellular fluid loss (changed Xc/R) indicated greater Posm increase.
authors.affiliation: Department of Sport Science, University Innsbruck, Innsbruck, Austria.
authors.forename: Hannes
authors.initials: H
authors.lastname: Gatterer
authors.affiliation: Department of Sport Science, University Innsbruck, Innsbruck, Austria.
authors.forename: Kai
authors.initials: K
authors.lastname: Schenk
authors.affiliation: Department of Sport Science, University Innsbruck, Innsbruck, Austria.
authors.forename: Lisa
authors.initials: L
authors.lastname: Laninschegg
authors.affiliation: Department of Sport Science, University Innsbruck, Innsbruck, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Schlemmer
authors.affiliation: Department of Kinesiology and Public Health Education, University of North Dakota, Grand Forks, North Dakota, United States of America.
authors.forename: Henry
authors.initials: H
authors.lastname: Lukaski
authors.affiliation: Department of Sport Science, University Innsbruck, Innsbruck, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Burtscher
mesh_terms: D000328:Adult; D001826:Body Fluids / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology*; D003080:Cold Temperature; D003681:Dehydration; D017097:Electric Impedance; D015444:Exercise / Q000502:physiology*; D005500:Follow-Up Studies; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011379:Prognosis; D055815:Young Adult