Comparison of heat dissipation response between Malaysian and Japanese males during exercise in humid heat stress

Abstract

This study investigated the differences in heat dissipation response to intense heat stress during exercise in hot and humid environments between tropical and temperate indigenes with matched physical characteristics. Ten Japanese (JP) and ten Malaysian (MY) males participated in this study. Subjects performed exercise for 60 min at 55% peak oxygen uptake in 32°C air with 70% relative humidity, followed by 30 min recovery. The increase in rectal temperature (T(re)) was smaller in MY during exercise compared to JP. The local sweat rate and total body mass loss were similar in both groups. Both skin blood flow and mean skin temperature was lower in MY compared to JP. A significantly greater increase in hand skin temperature was observed in MY during exercise, which is attributable to heat loss due to the greater surface area to mass ratio and large number of arteriovenous anastomoses. Also, the smaller increase in T(re) in MY may be explained by the presence of a significantly greater core-skin temperature gradient in MY than JP. The thermal gradient is also a major factor in increasing the convective heat transfer from core to skin as well as skin blood flow. It is concluded that the greater core-skin temperature gradient observed in MY is responsible for the smaller increase in T(re).

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

“…The present study consisted of the following three experimental protocols: resting (Experiment 1), passive heating by legs immersion (Experiment 2 in Wijayanto et al 2011) and active heating by the cycle ergometer exercise (Experiment 3 in Wakabayashi et al 2011). Each subject participated all in the following four experiments ( _ VO 2 peak test, Experiments 1, 2, and 3) on 4 separate days.…”

“…The identical categorical scales for the measurement of subjective responses as Experiment 1 were provided every 10 min. More details on Experiment 3 were demonstrated in Wakabayashi et al (2011).…”

“…The DT re were -0.23 ± 0.06°C and -0.09 ± 0.05°C for Japanese and Malaysians, respectively at rest; 0.66 ± 0.06°C and 0.31 ± 0.07°C (passive heating); 1.24 ± 0.09°C and 0.79 ± 0.04°C (the active heating). The time courses of T re during passive and active heating were presented in Wijayanto et al (2011) and Wakabayashi et al (2011), respectively.…”

Calculating Workplace WBGT from Meteorological Data: A Tool for Climate Change Assessment

“…Increased heat exposure raises the core body temperature of the human body. While some increase in core temperature above 37°C is acceptable, an increase beyond 39°C creates health risks 8) , which vary from person to person, depending on ethnic group, age, gender, the duration of high heat exposure, and the degree of acclimatization 11) . The International Standard for heat stress uses WBGT to recommend work-rest limits for work in hot environments 2) in order to ensure that average core body temperatures of worker populations does not exceed 38°C.…”

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.…”