title: Warming by immersion or exercise affects initial cooling rate during subsequent cold water immersion.
abstract: BACKGROUND
  We examined the effect of prior heating, by exercise and warm-water immersion, on core cooling rates in individuals rendered mildly hypothermic by immersion in cold water.
  
  
  METHODS
  There were seven male subjects who were randomly assigned to one of three groups: 1) seated rest for 15 min (control); 2) cycling ergometry for 15 min at 70% Vo2 peak (active warming); or 3) immersion in a circulated bath at 40 degrees C to an esophageal temperature (Tes) similar to that at the end of exercise (passive warming). Subjects were then immersed in 7 degrees C water to a Tes of 34.5 degrees C.
  
  
  RESULTS
  Initial Tes cooling rates (initial approximately 6 min cooling) differed significantly among the treatment conditions (0.074 +/- 0.045, 0.129 +/- 0.076, and 0.348 +/- 0.117 degrees C x min(-1) for control, active, and passive warming conditions, respectively); however, secondary cooling rates (rates following initial approximately 6 min cooling to the end of immersion) were not different between treatments (average of 0.102 +/- 0.085 degrees C x min(-1)). Overall Tes cooling rates during the full immersion period differed significantly and were 0.067 +/- 0.047, 0.085 +/- 0.045, and 0.209 +/- 0.131 degrees C x min(-1) for control, active, and passive warming, respectively.
  
  
  CONCLUSIONS
  These results suggest that prior warming by both active and, to a greater extent, passive warming, may predispose a person to greater heat loss and to experience a larger decline in core temperature when subsequently exposed to cold water. Thus, functional time and possibly survival time could be reduced when cold water immersion is preceded by whole-body passive warming, and to a lesser degree by active warming.
authors.affiliation: Faculty of Health Sciences, School of Human Kinetics, University of Ottawa, Ontario, Canada.
authors.forename: Chris G
authors.initials: CG
authors.lastname: Scott
authors.forename: Michel B
authors.initials: MB
authors.lastname: Ducharme
authors.forename: François
authors.initials: F
authors.lastname: Haman
authors.forename: Glen P
authors.initials: GP
authors.lastname: Kenny
mesh_terms: D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D004947:Esophagus / Q000502:physiology; D005080:Exercise Test; D006801:Humans; D007036:Hypothermia, Induced; D007101:Immersion; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D017694:Rewarming; D013997:Time Factors