Ethnic differences in thermoregulatory responses during resting, passive and active heating: application of Werner’s adaptation model

Abstract

For the coherent understanding of heat acclimatization in tropical natives, we compared ethnic differences between tropical and temperate natives during resting, passive and active heating conditions. Experimental protocols included: (1) a resting condition (an air temperature of 28°C with 50% RH), (2) a passive heating condition (28°C with 50% RH; leg immersion in a hot tub at a water temperature of 42°C), and (3) an active heating condition (32°C with 70% RH; a bicycle exercise). Morphologically and physically matched tropical natives (ten Malaysian males, MY) and temperate natives (ten Japanese males, JP) participated in all three trials. The results saw that: tropical natives had a higher resting rectal temperature and lower hand and foot temperatures at rest, smaller rise of rectal temperature and greater temperature rise in bodily extremities, and a lower sensation of thirst during passive and active heating than the matched temperate natives. It is suggested that tropical natives' homeostasis during heating is effectively controlled with the improved stability in internal body temperature and the increased capability of vascular circulation in extremities, with a lower thirst sensation. The enhanced stability of internal body temperature and the extended thermoregulatory capability of vascular circulation in the extremities of tropical natives can be interpreted as an interactive change to accomplish a thermal dynamic equilibrium in hot environments. These heat adaptive traits were explained by Wilder's law of initial value and Werner's process and controller adaptation model.

Cognitive performance during passive heat exposure in Japanese males and tropical Asian males from Southeast Asian living in Japan

“…All the subjects in both groups were all right-handed and had normal or corrected-to-normal visual acuity. Heat acclimatization status of the subjects in TR group was confirmed from the physiological responses during heat exposure in this study, that is they showed a smaller increase of rectal temperature ( T re ) and a small amount of total sweat rate () during heat exposure, that are commonly observed in tropical natives [18–23, 25, 26]. Therefore, subjects in TR group in this study could be considered as heat-acclimatized subjects.…”

“…First, we observed that subjects in tropical group showed a higher rectal temperature during control condition, a smaller increase of rectal temperature, and a less amount of total sweat rate during heat exposure than Japanese. A higher resting core temperature, a small increase of core temperature, and a less amount of total sweat rate during heat exposure are considered as the physiological adaptation feature of heat acclimatization reported in the previous studies [21–23, 25]. These adaptation features to tolerate heat stress become advantages for tropical subjects in this study to deal with performance decrement during heat exposure; that is, the tropical subjects in this study could maintain mental arithmetic test performance, while it was not observed in Japanese.…”

“…In terms of physiological adaptation, long-term heat-acclimatized individuals are reportedly to have smaller rises in core temperature during heat exposure [20–22] and an advantage in body fluid regulation [20], in which they indicate the ability to deal with stress from any given heat exposure [23, 24]. Although several studies have been investigating the acclimatization state of an individual during heat exposure, none of the authors specifying heat acclimatization (natural adaptation) or heat acclimation (artificial adaptation) level of their subjects in examining heat exposure effects on cognitive performance.…”

Comparison of the Physical Properties of Showers that the Satisfaction of Shower Feeling among Users in Three Asian Countries

“…There is previous research relating to this where it has been reported that there are differences between races when it comes to human body temperature adjustment response [20,21]. For example, when exposed to heat, rectal temperatures for Malays, who live in tropical regions, do not rise as easily as the Japanese, who live in mesodermal climates, and because there is a large rise in temperature of the extremities for the Malays, they have a greater ability to effectively stabilize their internal body temperature, giving them abilities appropriate for tropical climates [22,23]. The average temperature in Japan (Fukuoka Prefecture) is 17.0 °C [24], a temperate zone, while Taipei, Taiwan has an average temperature of 23.0 °C [25], a subtropical zone, while Hanoi, Vietnam has an average temperature of 24 °C [26], a tropical zone.…”

The use of language to express thermal sensation suggests heat acclimatization by Indonesian people

“…Heat acclimatization is triggered as a response to a variety of complex environmental factors in hot climates. Over the past half century, a number of studies on heat acclimatization have been reported in terms of physiological adaptation (Lee et al, 2011b;Saat and Tochihara, 2008;Taylor, 2006;Wakabayashi et al, 2011;. Though heat acclimatization in psycho-physiological traits has been a relatively neglected area of research, several interesting studies have been conducted.…”