Abstract Global warming induces a dramatic elevation of heat-related morbidity and mortality worldwide. Individual variation of heat stress vulnerability depends on various factors such as age, gender, living area and conditions, health status, and individual innate characteristics. Sasang typology is a unique form of Korean traditional medicine, which is based on the hypothesis that constitution-specific traits of an individual determine the particular distinctive tendency in various aspects, including responses to the external environment. Recent scientific evidence shows that Sasang types differ in body composition, metabolic profile, susceptibility to certain disease patterns, and perspiration. This review aims to interpret these findings under the context of heat balance consisting of heat production ( H prod), heat loss ( H loss), and heat load ( H load). Based on the published data, at a given body mass, the TaeEum type tended to have a lower H prod at rest and at the exhaustion state, which may indicate the lower metabolic efficiency of this type. Meanwhile, the surface-to-mass ratio and heat capacity of the TaeEum type appear to be lower, implying a lower heat dissipation capacity and heat storage tolerance. Thus, because of these characteristics, the TaeEum type seems to be more vulnerable to heat stress than the other constitutions. Differences in temperature regulation across constitutional types should be taken into account in daily physical activity, health management, and medical research. Keywords heat balance ; Sasang medicine ; temperature load ; thermoregulation prs.rt("abs_end"); 1. Introduction Over the past several decades, climate change has become an emerging global threat to our planet and has induced a remarkable increase in morbidity and mortality by affecting the human health. According to an estimation by the World Health Organization, between 2030 and 2050, climate change may cause approximately 38,000 heat stress-related deaths annually. 1 It has been demonstrated that some populations are at a higher risk of heat-related illness and damage than others. Elderly persons and children are most vulnerable to heat stress 2 , 3 and 4 due to degeneration and immaturity in heat acclimation, respectively. Physical and mental illnesses also affect how the body responses to heat stress. Those who suffer from obesity, diabetes, hypertension, cardiovascular, and/or respiratory diseases have a higher incidence of heat-related disorders than healthy individuals of the same age and gender. 4 Although population-based factors related to heat stress have been reported, far too little attention has been paid to physiological traits as determinants of heat stress vulnerability. Investigation on the impact of physiology traits on health could be dated back to the ancient time, with the “Four Humor” theory of Hippocrates and Galen 5 in the West and constitution-based medicine, Ayurveda, in the East. 6 Recently, there has been an emerging interest in body type and constitution-based approach in the fields of individualized and tailored medicine. The somatotype theory of Sheldon 7 and Sasang constitutional medicine of Lee 8 have been investigated thoroughly. Among these four available constitution-based approaches, Sasang constitutional medicine appeared to be a well-structured theory that provided not only a type classification, but also a comprehensive theory related to medical practice. According to Sasang constitutional medicine, human beings can be classified into four constitutional types: the Taeyang, TaeEum (TE), SoEum (SE), and SoYang (SY) types. Scientific evidence revealed that these four body types have distinct genetic bases 9 , 10 and 11 and differ in physical appearance, 12 and 13 body composition, 14 temperament traits, 15 hormonal regulations, 16 and 17 and vulnerability to particular diseases patterns. 18 , 19 and 20 In terms of thermoregulation, a few investigations suggested constitution-specific traits in skin structure, 21 and 22 sweating capacity, 21 and 23 and energy expenditure profile. 24 The current review aims to describe the constitution-specific characteristics of Sasang types in heat stress regulation capacity and discuss the factors need to be taken into account in the studies of thermoregulation in Sasang typology. 2. Thermoregulatory response at rest and during exercise Under basal condition (e.g., resting, thermoneutral, and fasting states), energy consumed for maintaining basal functional activities and body core temperature is the so-called basal metabolic rate (BMR). To some extent, BMR refers to the resting energy expenditure (REE), energy expenditure measured at the resting state. 25 Most of the energy consumed under basal con
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