The Physiological Society Human adaptations to cold stress Andrew J. Young Search PubMed for AJ Young US Army Research Institute of Environmental Medicine, Natick, MA, USA Chronic or repeated cold exposures can induce thermoregulatory habituation, acclimatization or acclimation in humans. Comparing adaptations exhibited by persons naturally exposed to cold over the course of their normal lifestyle with adaptations induced in human volunteers exposed to cold in different controlled experiments provides insights regarding biological determinants for which of these develops.
Habituation is characterized by diminished physiological responses to cold.
Blunted shivering and cold-induced vasoconstriction, hallmarks of habituation observed in circumpolar residents and persons whose occupations require frequent intermittent cold exposure, may be advantageous by conserving body energy stores and allowing warmer skin temperatures to be maintained during cold exposure. However, the reduced heat production and facilitated heat loss can compromise maintenance of thermal balance, resulting in a more pronounced fall in body core temperature in adapted compared with non-adapted persons. Thus the blunted thermogenic response to cold, i.e. shivering habituation, may develop extremely rapidly after only a few cold exposures. In contrast, acclimatization and acclimation are characterized by more pronounced physiological responses to cold exposure. Cold acclimatization, which develops in response to natural environmental changes, and its analogue, cold acclimation, which develops in response to experimental exposure to artificial conditions, both show two different patterns.