Investigation of the possibility of the use of heart rate as a human factor for thermal sensation models

According to the current thermal comfort theory, metabolic rate and clothing insulation are critical human factors that affect thermal sensation. Since heart rate is significantly correlated with human metabolic rate, it may undoubtedly be a potential parameter that directly (or indirectly) impacts the principle of thermal comfort. In addition, even though a few researchers have identified an insignificant relationship between heart rate and thermal conditions, many have reported heart rate variability at different thermal sensation levels based on the principle of thermoregulation. However, in spite of its potential as a thermal sensation effector, as well as an indicator, current thermal comfort models have focused mainly on several local body skin temperatures and the core body temperature without considering heart rate. Therefore, this research has relied on experiments with human subjects in two environmental chambers (each with a different thermal condition) to investigate and determine whether and how the heart rate during the same activity level is affected by warm and cold conditions. It also sought to determine how heart rate is related to thermal sensation, and whether the effect would vary depending on gender and body mass index. Results of this study revealed that the heart rate and the changes in rates that occurred between different activity levels showed a significant increase during warm conditions, with a 2.5 metabolic rate, especially in males and in body mass index groups higher than 22. A decent increase in the change rates was also found at 1.0 Met, as compared with 0.8 Met.