Effects of acclimatization to cold baths on men's responses to whole-body cooling in air

Abstract

The purpose of this study was to investigate the thermoregulatory mechanisms underlying artificial acclimatization to cold and to compare them with those of naturally acclimatized men. Six white men were cooled, nude, in air at 10 degrees C for 2 h before and after they had been acclimatized by ten daily cold (15 degrees C) baths of 30-60 min followed by rapid rewarming in hot (38-42 degrees C) water, and again 4 months later after acclimatization had decayed. Six control subjects also underwent the same tests, providing an opportunity to discriminate between changes caused by the immersions and those caused by extraneous influences. Acclimatization significantly reduced heat production and heat loss (P < 0.05) but did not change heat debt. The reduced heat production was accompanied by reductions in shivering (P < 0.10) and in cold-induced muscle tenseness; no evidence of nonshivering thermogenesis or active brown fat was found. These findings are attributed to increased tissue insulation, mediated by an enhanced vascular response to cold that did not involve the cutaneous circulation and was probably located in skeletal muscle. Thermal sensation and discomfort did not change, although perceived strain tended to increase (P = 0.08). Acclimatization was accompanied by, but was unrelated to, slower cooling of the finger and toe. The main conclusions, and many specific findings, agree with those of two previous studies made by the same techniques in naturally acclimatized men wintering in Antarctica. Other significant findings included changes--in particular reduced thermoneutral rectal temperature and a delayed onset of shivering--that are commonly regarded as evidence of acclimatization but were in fact unrelated to it as they also occurred in the control group. They are attributed to extraneous influences, in particular the relaxation of heightened arousal ('first-time effects') found in the baseline tests.

Human Brown Adipose Tissue: What We Have Learned So Far

“…Because of findings in rodent models and observations of increased energy expenditure in response to b3-adrenergic agonists (32) and different responses to cold in lean versus obese humans (33), it was speculated that decreased BAT mass and activity might be implicated in the development of obesity and type 2 diabetes (34). At that time it was, however, not possible to unequivocally prove the metabolic activity in human adults (35)(36)(37).…”

Relationship between seasonal cold acclimatization and mtDNA haplogroup in Japanese

“…In short-term cold acclimatization studies during which subjects were exposed to cold stimulation in an artificial climate chamber with a room temperature of 5 °C or were immersed in cold water, the heat insulation capacity was reportedly enhanced by a reduction in blood flow following acclimatization associated with a decrease in thermogenesis, a delay in shivering, and a decrease in distal skin temperature [13,14]. In contrast, no changes were seen in core body temperature and mean skin temperature from cold acclimation after cold exposure in a 5 °C room for 2 hours per day for 11 days [15].…”

“…In addition to individual differences, this component may vary with the level of cold stimulation depending on factors such as exposure conditions and amount of clothing. Cold water immersion and other types of strong cold stimulation are often reported to result in a decrease in skin temperature and a decrease in thermogenesis [13,14], suggesting that the strength of the temperature environment may also affect the population in studies on seasonality because the strength of cold stimulation depends on their area of habitation.…”

The effect of repeated mild cold water immersions on the adaptation of the vasomotor responses

“…A habituation of metabolic response to cold is the most common adaptation after repeated cold water immersion (Golden and Tipton 1988;Budd et al 1993;Jansky et al 1996a;Rees et al 2002). Since the participants in the previous studies were repeatedly immersed in colder water (10-15°C) than the present study, they decreased their deep body temperature more and increased metabolic heat production much more than in this study.…”

“…In laboratory-based studies, habituation of the metabolic response to cold is the most common adaptation reported after repeated cold water immersions (Golden and Tipton 1988;Budd et al 1993;Jansky et al 1996a;Rees et al 2002). A relatively small number of studies have reported insulative adaptation after repeated cold immersions, including a significant decrease of skin temperature (Young et al 1986;Bittel 1987;Jansky et al 1996a, b) or increase in total peripheral resistance (O'Brien et al 2000) during cold exposure.…”