Changes in thermal homeostasis in humans due to repeated cold water immersions

Abstract

The purpose of this study was to monitor changes in body and skin temperatures, heat production, subjective shivering, cold sensation and body fat content in humans after intermittent cold water immersion. Repeated exposures of young sportsmen to cold water (head out, 14 degrees C, 1 h, 3 times per week for 4-6 weeks) induced changes in regulation of thermal homeostasis. "Cold acclimated" subjects exhibited an hypothermic type of adaptation. Central and peripheral body temperatures at rest and during cold immersion were lowered. The metabolic response to cold was delayed and subjective shivering was attenuated. The observed hypothermia was due to the shift of the threshold for induction of cold thermogenesis to lower body temperatures. "Cold acclimated" subjects also showed a lowered cold sensation. Because of the observed physiological changes, about 20% of the total heat production was saved during one cold water immersion of "cold acclimated" subjects. Maximal aerobic and anaerobic performances were not altered. No change in the thermosensitivity of the body temperature controller, as assessed from the unchanged slope of the relation between the deep body temperature and total heat production, was observed. Changes in cold sensation and regulation of cold thermogenesis were noticed first after four cold water immersions and persisted for at least 2 weeks after termination of the adaptation procedure. A trend towards a small increase in the body fat content was also observed. This finding, as well as the increased vasoconstriction, evidenced by the lowered skin temperature, indicate that slight changes in body insulation may also occur after "cold acclimation" in humans.

Thermoregulation in Winter Swimmers and Physiological Significance of Human Catecholamine Thermogenesis

“…Our experiments provide strong evidence that winter swimmers are adapted to cold by mechanisms inducing hypothermia. This is in agreement with our earlier observation (Jansk y et al 1996) that humans adapted to cold in the laboratory have lower resting body temperatures and basal metabolic rates and a lowered threshold for induction of cold thermogenesis. Adaptation via metabolic mechanisms is evident from the fact that adrenaline thermogenesis was markedly potentiated in winter swimmers (Lesn a et al 1999).…”

“…In general, our data complement earlier findings by Bruck et al (1976), McArdle et al (1984), Young et al (1986, Bittel (1987) and Golden & Tipton (1988) by showing that all three possible types of cold adaptation (hypothermic, metabolic and insulative) may occur in humans (Jansk y, 1998). Our findings also show that there are no qualitative differences in thermoregulatory adjustments between winter swimmers and young men adapted to cold by intermittent cold water immersion (Jansk y et al 1996).…”

Human Physiology in an Aquatic Environment

“…SNA increased but it did not appear to influence HR whereas it was associated with peripheral vasoconstriction (increased TPR) and a small increase in MAP (180).…”

“…These data suggest that in addition to physiological responses to WI per se, cold WI specifically, increases SNA (357). HOWI for one hour in 14 • C water increased SNA, as indicated by a fourfold increase in plasma NE, but not epinephrine or dopamine (180,181).…”

“…Repeated HOWIs in 15 • C for 1 h three times per week for 4 to 6 weeks has demonstrated that subjects had lower T c , presumably due to a delayed metabolic response and subjective shivering in acclimatized subjects, while they had less sensation to the cold. These changes suggest a slight increase in insulation due to acclimatization (180).…”