Summary:
Intermittent exposures to cold (15 head out immersions into 14 °C water, for 1 h, within 3 weeks) induce
physiological changes leading to the restriction of heat loss from the body, due to hypothermia and vasoconstriction.
These adaptational changes may save more than 25 % of energy during 1 hour cold test. Insulative
adaptation due to increased amount of the subcutaneous fat is less prominent.Winter swimmers show similar
mechanisms of cold adaptationn as humans adapted by intermittent cold exposures in the laboratory. Additionally,
winter swimmers exert a greater capacity of nonshivering thermogenesis than nonadapted controls.Thus,
adaptation of humans to cold involves hypothermic, metabolic and insulative mechanisms. Time courses of
development of individual mechanisms of adaptation differ. Intermittent local cold exposures (20 immersions of
legs into 12 °C water, for 45 min, within 4 weeks lower sympathetic tone and induce redistribution of cardiac
output, in order to ensure preferential warming of central parts of the body. Basal metabolism and cold induced
thermogenesis are increased, but the threshold for induction of cold thermogenesis is not influenced. In contrast
to changes induced by repeated whole body immersions, these changes may not ensure greater resistance to the
cold stress.
Key words:
human adaptation to cold, nonshivering thermogenesis, cardiovascular changes
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