Thermal sensation and physiological responses in non-uniform bathing thermal environment: A comparative study on 25-, 52-, and 71-year-old participants

Abstract

A non-uniform thermal environment significantly affects human physiological responses and even harms health. Specifically, a non-uniform bathing thermal environment is particularly deadly for older adults. Although each body part's arterial blood flow changes in the bathing thermal environment, little research has been conducted on the physiological responses of participants of different ages. Herein, we conducted a series of bathing experiments on three healthy participants aged 25, 52, and 71. The aim of these experiments to elucidate and analyze the thermal sensations and physiological responses of the participants in a non-uniform bathing thermal environment (i.e., the upper body was exposed to air, whereas the lower body was immersed in hot bathwater). We found that the non-uniform thermal environment greatly influenced a variety of physiological parameters and increased the participants' heart rates and blood flow. The youngest participant (i.e., the 25-year-old) and oldest participant (i.e., the 71-year-old) had the fastest and slowest perception of thermal sensation, respectively. The physiological responses changed significantly with the perception of thermal sensation change for the three participants. Unlike the other two participants, the oldest participant had decreased blood pressure and slowly increased thermal sensation. In addition, the oldest participant in a short bathing time had minor thermal health risks than younger participants due to exhibiting the slowest thermal response. However, older adults may experience greater thermal health risks due to their relatively slow thermal response in long-time and high-temperature bathing environments.