Publication

Interindividual variability of human thermoregulation: Toward personalized ergonomics of the indoor thermal environment

Dolaana Khovalyg
2022
Journal paper
Abstract

Objective The study was undertaken to show the magnitude of interindividual differences in energy expenditure (i.e., heat production) under normal living conditions with the aim of providing physiological evidence to support the advancement of a personalized thermal conditioning approach. Methods Three sets of experimental protocols with six participants were conducted at neutral and mild cold temperatures. Energy expenditure, local skin temperatures, and core body temperature were measured continuously, while cognitive performance and thermal sensation were surveyed intermittently. The protocols were designed to study the effects of several normal day activities, low-level physical activity and eating a meal, on metabolic and physiological parameters. Results Large interindividual differences among the subjects were demonstrated using non-normalized data by design. The resting metabolic rate difference was 58%, the percentage change in energy expenditure during standing compared to sitting was up to 31%, and the difference in mechanical work efficiency between the least and the most efficient individual was 39.1%. Energy expenditure increase due to the meal effect was 11.2% to 23.3% at neutral and 9.9% to 33.9% at mild cold temperatures across individuals. Conclusions Large interindividual differences in metabolic rate under typical everyday living and office activities suggest facilitating personalized thermal conditioning instead of providing uniform temperature. Therefore, it is necessary to find noninvasive markers that can be easily measured and used as surrogates for human heat production to individualize the climate control of buildings.

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Ontological neighbourhood
Related concepts (38)
Basal metabolic rate
Basal metabolic rate (BMR) is the rate of energy expenditure per unit time by endothermic animals at rest. It is reported in energy units per unit time ranging from watt (joule/second) to ml O2/min or joule per hour per kg body mass J/(h·kg). Proper measurement requires a strict set of criteria to be met. These criteria include being in a physically and psychologically undisturbed state and being in a thermally neutral environment while in the post-absorptive state (i.e., not actively digesting food).
Thermal comfort
Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation (ANSI/ASHRAE Standard 55). The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat.
Human body temperature
Normal human body-temperature (normothermia, euthermia) is the typical temperature range found in humans. The normal human body temperature range is typically stated as . Human body temperature varies. It depends on sex, age, time of day, exertion level, health status (such as illness and menstruation), what part of the body the measurement is taken at, state of consciousness (waking, sleeping, sedated), and emotions. Body temperature is kept in the normal range by a homeostatic function known as thermoregulation, in which adjustment of temperature is triggered by the central nervous system.
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