How humans adapt to hot climates learned from the recent research on tropical indigenes
Abstract This review mainly aimed to introduce the findings of research projects comparing the responses of tropical and temperate indigenes to heat. From a questionnaire survey on thermal sensation and comfort of Indonesians and Japanese, we found that the thermal descriptor “cool” in tropical indi...
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| Format: | Article |
| Language: | English |
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BMC
2022-07-01
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| Series: | Journal of Physiological Anthropology |
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| Online Access: | https://doi.org/10.1186/s40101-022-00302-3 |
| _version_ | 1811293850211188736 |
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| author | Yutaka Tochihara Hitoshi Wakabayashi Joo-Young Lee Titis Wijayanto Nobuko Hashiguchi Mohamed Saat |
| author_facet | Yutaka Tochihara Hitoshi Wakabayashi Joo-Young Lee Titis Wijayanto Nobuko Hashiguchi Mohamed Saat |
| author_sort | Yutaka Tochihara |
| collection | DOAJ |
| description | Abstract This review mainly aimed to introduce the findings of research projects comparing the responses of tropical and temperate indigenes to heat. From a questionnaire survey on thermal sensation and comfort of Indonesians and Japanese, we found that the thermal descriptor “cool” in tropical indigenes connotes a thermally comfortable feeling, suggesting that linguistic heat acclimatization exists on a cognitive level. Ten male students born and raised in Malaysia were invited to Fukuoka, Japan, and compared their responses with 10 Japanese male students with matched physical fitness and morphological characteristics. Cutaneous thermal sensitivity: The sensitivities were measured at 28 °C. The forehead warm sensitivity was significantly blunted in Malaysians. The less sensitivity to the warmth of tropical indigenes is advantageous in respect to withstanding heat stress with less discomfort and a greater ability to work in hot climates. Passive heat stress: Thermoregulatory responses, especially sweating, were investigated, during the lower leg hot bathing (42 °C for 60 min). The rectal temperature at rest was higher in Malaysians and increased smaller during immersion. There was no significant difference in the total amount of sweating between the two groups, while the local sweating on the forehead and thighs was lesser in Malaysians, suggesting distribution of sweating was different from Japanese. Exercise: Malaysian showed a significantly smaller increase in their rectal temperature during 55% maximal exercise for 60 min in heat (32 °C 70% relative humidity), even with a similar sweating and skin blood flow response in Japanese. The better heat tolerance in Malaysians could be explained by the greater convective heat transfer from the body core to the skin due to the greater core-to-skin temperature gradient. In addition, when they were hydrated, Malaysian participants showed better body fluid regulation with smaller reduction in plasma volume at the end of the exercise compared to the non-hydrated condition, whereas Japanese showed no difference between hydration conditions. We further investigated the de-acclimatization of heat adaptation by longitudinal observation on the heat tolerance of international students who had moved from tropical areas to Fukuoka for several years. |
| first_indexed | 2024-04-13T05:07:40Z |
| format | Article |
| id | doaj.art-ddd44aae4f6d4209be84bc1033f6d357 |
| institution | Directory Open Access Journal |
| issn | 1880-6805 |
| language | English |
| last_indexed | 2024-04-13T05:07:40Z |
| publishDate | 2022-07-01 |
| publisher | BMC |
| record_format | Article |
| series | Journal of Physiological Anthropology |
| spelling | doaj.art-ddd44aae4f6d4209be84bc1033f6d3572022-12-22T03:01:07ZengBMCJournal of Physiological Anthropology1880-68052022-07-0141111610.1186/s40101-022-00302-3How humans adapt to hot climates learned from the recent research on tropical indigenesYutaka Tochihara0Hitoshi Wakabayashi1Joo-Young Lee2Titis Wijayanto3Nobuko Hashiguchi4Mohamed Saat5Department of Human Science, Faculty of Design, Kyushu UniversityLaboratory of Environmental Ergonomics, Faculty of Engineering, Hokkaido UniversityDepartment of Textiles, Merchandising and Fashion Design, College of Human Ecology, Seoul National UniversityLaboratory of Ergonomics, Department of Mechanical and Industrial Engineering, Faculty of Engineering, Universitas Gadjah MadaDepartment of Health Science, Faculty of Medicine, Kyushu UniversitySchool of Medical Sciences, Health Campus, Universiti Sains MalaysiaAbstract This review mainly aimed to introduce the findings of research projects comparing the responses of tropical and temperate indigenes to heat. From a questionnaire survey on thermal sensation and comfort of Indonesians and Japanese, we found that the thermal descriptor “cool” in tropical indigenes connotes a thermally comfortable feeling, suggesting that linguistic heat acclimatization exists on a cognitive level. Ten male students born and raised in Malaysia were invited to Fukuoka, Japan, and compared their responses with 10 Japanese male students with matched physical fitness and morphological characteristics. Cutaneous thermal sensitivity: The sensitivities were measured at 28 °C. The forehead warm sensitivity was significantly blunted in Malaysians. The less sensitivity to the warmth of tropical indigenes is advantageous in respect to withstanding heat stress with less discomfort and a greater ability to work in hot climates. Passive heat stress: Thermoregulatory responses, especially sweating, were investigated, during the lower leg hot bathing (42 °C for 60 min). The rectal temperature at rest was higher in Malaysians and increased smaller during immersion. There was no significant difference in the total amount of sweating between the two groups, while the local sweating on the forehead and thighs was lesser in Malaysians, suggesting distribution of sweating was different from Japanese. Exercise: Malaysian showed a significantly smaller increase in their rectal temperature during 55% maximal exercise for 60 min in heat (32 °C 70% relative humidity), even with a similar sweating and skin blood flow response in Japanese. The better heat tolerance in Malaysians could be explained by the greater convective heat transfer from the body core to the skin due to the greater core-to-skin temperature gradient. In addition, when they were hydrated, Malaysian participants showed better body fluid regulation with smaller reduction in plasma volume at the end of the exercise compared to the non-hydrated condition, whereas Japanese showed no difference between hydration conditions. We further investigated the de-acclimatization of heat adaptation by longitudinal observation on the heat tolerance of international students who had moved from tropical areas to Fukuoka for several years.https://doi.org/10.1186/s40101-022-00302-3Human heat adaptationTropical and temperate indigenesThermal sensationCutaneous thermal sensitivityDecay of acclimatizationCognitive function |
| spellingShingle | Yutaka Tochihara Hitoshi Wakabayashi Joo-Young Lee Titis Wijayanto Nobuko Hashiguchi Mohamed Saat How humans adapt to hot climates learned from the recent research on tropical indigenes Journal of Physiological Anthropology Human heat adaptation Tropical and temperate indigenes Thermal sensation Cutaneous thermal sensitivity Decay of acclimatization Cognitive function |
| title | How humans adapt to hot climates learned from the recent research on tropical indigenes |
| title_full | How humans adapt to hot climates learned from the recent research on tropical indigenes |
| title_fullStr | How humans adapt to hot climates learned from the recent research on tropical indigenes |
| title_full_unstemmed | How humans adapt to hot climates learned from the recent research on tropical indigenes |
| title_short | How humans adapt to hot climates learned from the recent research on tropical indigenes |
| title_sort | how humans adapt to hot climates learned from the recent research on tropical indigenes |
| topic | Human heat adaptation Tropical and temperate indigenes Thermal sensation Cutaneous thermal sensitivity Decay of acclimatization Cognitive function |
| url | https://doi.org/10.1186/s40101-022-00302-3 |
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