Physiological Responses And Thermal Sensation In The Recovery Period After Extremely Cold Exposure

Climate extremes have become more frequent in recent years. Recovery to thermal neutral states is important for people who have to be exposed to cold outdoor built environment. This study aims to investigate physiological responses and thermal sensation during the recovery period after exposure to different degrees of cold environment. Twelve healthy males wearing uniform clothing were seated in a 24 degrees C room for 30 min before transferring to a cold climatic chamber for 30 min, after which they began recovery in a 24 degrees C room for 40 min. The temperature of the cold climatic chamber was set to -5 degrees C, -10 degrees C, and -15 degrees C, respectively. Most physiological parameters, including core temperature, local skin temperature, heart rate, blood pressure, respiratory rate, and overall thermal sensation, were recorded. After extremely cold exposure, heart rate decreased rapidly in the first 5 min of the recovery period, by as much as 14.69 bpm, and subsequently reached a steady state, which was significantly lower than the baseline value. Low temperature proved to be the main cause of the rapid drop in heart rate. Even though the duration of the recovery was longer than that of the exposure period, under the -10 degrees C and -15 degrees C conditions, blood pressure, heart rate and local skin temperature still could not return to baseline levels. Thermal sensation also showed an asymmetric phenomenon, similar to the thermal neutral environment. The results of this experiment can be used to provide recommendations for people with extremely cold exposure.