title: Comparison of thermoregulatory responses to heat between Malaysian and Japanese males during leg immersion.
abstract: The objective of this study was to investigate thermoregulatory responses to heat in tropical (Malaysian) and temperate (Japanese) natives, during 60 min of passive heating. Ten Japanese (mean ages: 20.8 ± 0.9 years) and ten Malaysian males (mean ages: 22.3 ± 1.6 years) with matched morphological characteristics and physical fitness participated in this study. Passive heating was induced through leg immersion in hot water (42°C) for 60 min under conditions of 28°C air temperature and 50% RH. Local sweat rate on the forehead and thigh were significantly lower in Malaysians during leg immersion, but no significant differences in total sweat rate were observed between Malaysians (86.3 ± 11.8 g m(-2) h(-1)) and Japanese (83.2 ± 6.4 g m(-2) h(-1)) after leg immersion. In addition, Malaysians displayed a smaller rise in rectal temperature (0.3 ± 0.1°C) than Japanese (0.7 ± 0.1°C) during leg immersion, with a greater increase in hand skin temperature. Skin blood flow was significantly lower on the forehead and forearm in Malaysians during leg immersion. No significant different in mean skin temperature during leg immersion was observed between the two groups. These findings indicated that regional differences in body sweating distribution might exist between Malaysians and Japanese during heat exposure, with more uniform distribution of local sweat rate over the whole body among tropical Malaysians. Altogether, Malaysians appear to display enhanced efficiency of thermal sweating and thermoregulatory responses in dissipating heat loss during heat loading. Thermoregulatory differences between tropical and temperate natives in this study can be interpreted as a result of heat adaptations to physiological function.
authors.affiliation: Department of Ergonomics, Faculty of Design, Kyushu University, Minami-ku, Fukuoka, Japan. titis09@gsd.design.kyushu-u.ac.jp
authors.forename: Titis
authors.initials: T
authors.lastname: Wijayanto
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Wakabayashi
authors.forename: Joo-Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Nobuko
authors.initials: N
authors.lastname: Hashiguchi
authors.forename: Mohamed
authors.initials: M
authors.lastname: Saat
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tochihara
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D044466:Asian People; D001833:Body Temperature Regulation / Q000502:physiology*; D002980:Climate; D018869:Heat-Shock Response / Q000502:physiology; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D007101:Immersion / Q000009:adverse effects* / Q000503:physiopathology*; D007564:Japan; D007866:Leg; D008296:Malaysia; D008297:Male; D013546:Sweating / Q000502:physiology; D014329:Tropical Climate / Q000009:adverse effects; D055815:Young Adult
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