Warming by immersion or exercise affects initial cooling rate during subsequent cold water immersion

Aviat Space Environ Med. 2004 Nov;75(11):956-63.


Introduction: 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.

Discussion: 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.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Body Temperature / physiology*
  • Esophagus / physiology
  • Exercise Test*
  • Humans
  • Hypothermia, Induced*
  • Immersion*
  • Male
  • Oxygen Consumption / physiology
  • Rewarming*
  • Time Factors