Abstract
Introduction: While the thermal sensitivity of specific body parts has been well-studied, less attention has been given to whole-body sensitivity to ambient temperature. A pioneering study by Battistel et al. (2023) addressed this gap by investigating thermal perception in a fully immersive environment (24 ± 1 °C) using the climate chambers of terraXcube (Eurac Research). Their findings revealed increased sensitivity when the whole body was exposed to temperature changes, with a Just Noticeable Difference (JND) of 0.38 °C, lower than values observed for isolated regions. This finding raises further questions about how thermal sensitivity may vary under more extreme conditions.
Objective. This study examined whole-body thermal sensitivity under mild (cool: 18 ± 1 °C; warm: 28 ± 1 °C) and extreme (cold: 8 ± 2 °C; hot: 38 ± 2 °C) ambient temperatures. Since ambient temperature affects heat exchange and activates thermoregulatory processes, we hypothesized that thermal sensitivity would be modulated by the body’s physiological state, reflected by skin temperature (ST) and core temperature (CT). Specifically, we expected that internal thermoregulation would override perceptual sensitivity to external changes, reducing discrimination under extreme conditions.
Material and Methods. Participants were asked to report whether a target chamber was warmer or colder than a reference chamber. 26 participants (50% female) were tested in the mild condition, while 25 (48% female) in the extreme condition. Skin temperature and sweating were monitored using cutaneous sensors, tympanic temperature, heart rate, and respiratory rate were also recorded.
Results. Thermal sensitivity declined under extreme temperatures, with higher JNDs in cold (0.94 °C) and hot (0.76 °C) conditions compared to cool (0.39 °C) and warm (0.45 °C). To explore physiological influences, we examined core and skin temperatures, discrepancy between ST recorded at four body regions (chest, arm, thigh, calf), and sweating level. Despite extreme conditions caused substantial physiological variations (mean cool ST: 29,3 °C; mean cold ST: 25.3 °C; mean warm ST: 31.6 °C; mean hot ST: 34.7 °C), none of these factors correlated significantly with thermal sensitivity.
Discussion. Although the body exhibited clear physiological responses to different temperatures, these changes did not explain the decline in sensitivity. We speculate that the decline may be due to the sensitivity limits of cutaneous thermoreceptors. At extreme temperatures approaching pain thresholds (8 ± 2 °C and 38 ± 2 °C), noxious receptor activity may dominate, reducing perceptual accuracy.
Conclusion. These findings highlight the need for further research on the neural and physiological underpinnings and how thermal sensations are integrated across different body regions.