LAUSR

Abstract Long-term heat acclimation in the tropics is a well-known positive response to cope with heat stress. A computational model of thermoregulatory responses from the population in the tropics has not yet been developed. This is partially because only a limited number of comparisons between the thermoregulation of people from different regions have been reported. Our group developed an integrated computational code of thermodynamics and thermoregulatory responses (blood flow and sweating rate) with anatomical human models. We explored parameters in the conventional formula of the thermoregulatory response model to consider the population from the tropics. A comparison of the computed core and local temperatures with those measured in previous studies suggests that the difference in thermoregulatory characteristics between populations from the tropical and temperate zones is mainly characterized by the difference in the countercurrent coefficient of blood, in addition to sweating rate. The estimated core temperature elevation in male adults from a tropical zone is 60% of the temperature of adults from temperate zones for low relative humidity. However, the difference becomes marginal for relatively high humidity, including the case for walking in an urban area of Tokyo, summer 2017, because the effect of the evaporative heat loss becomes marginal. The difference in thermoregulatory responses of people from tropical and temperate zones can be modeled by the core-to-limbs heat transfer and the sweating rate. The computational model developed here is useful to discuss the differences between heat-related illness and thermal comfort of the population in the tropical and temperate zones.