The Impacts Of Cold Environment On Foot Thermal Sensation And Human Physiological Indexes

Thermal comfort is one of people's physiological needs,people rely on temperature regulation system to maintain thermal comfort.Clothes are usually needed to help keeping thermal balance of human body,especially under the cold environment.At present,the passive thermal mode,the traditional mode of keeping warm by increasing the thermal resistance of clothes,has been unable to meet people's needs of more functional and comfortable clothes.While the thermal wear by the active thermal mode is favored by consumers.In a addiction,foot care is closely linked with health and human performance.However,the foot skin temperature is susceptible to external factors,then affects the human's thermal comfort.Therefore,this article from the point of view of foot thermal comfort,the foot skin thermal threshold and related physiological indexes were measured and explored,for the purpose of providing recommendations for the properly design the footwear in cold environment.Based on the physiologic theory of human thermal comfort,three physiological indexes related to human thermal comfort such as skin temperature,blood flow and metabolism were selected.Ten healthy female college students participated experiment as subjects,the influence of the physiological indexes were investigated while the ambient temperature decreased from 20°C to 5°C.With the decrease of the ambient temperature,the heat production and energy metabolism increased,in order to maintain the body core temperature.Meanwhile the limbs peripheral skin temperature decreased as well as the skin surface blood flow.Skin temperature is within a certain range adjusted by controlling the blood flow,blood flow is close to zero while the temperature is getting low.With the decrease of ambient temperature,the skin temperature of instep decreased gradually from the tiptoe to anterior ankle region.To a great extent,the local thermal sensation will affect the whole body thermal comfort.The decrease of peripheral skin temperature have negative effects on the thermal comfort,thus keeping warm of the limbs peripheral will be necessary in order to enhance the thermal comfort.The foot skin was subdivided into 11 parts,the thermal threshold,the reaction time and the temperature sensory difference of each region were measured at 28°C by temperature sensory analyzer.The statistical analysis showed that there was no significant difference in the thermal thresholds between separate parts,while significant differences exist in the reaction time and temperature sensory difference.Meanwhile,the reaction time is significantly correlated with the temperature difference.Besides,the sensory response time of cold sensation was shorter than that of thermal sensation,and the absolute value of cold sensation temperature difference was less than the thermal sensation,indicating that the subjects were more sensitive to cold stimulation and responded more quickly.Among them,plantar heel part of the lowest sensitivity to temperature stimulation,inside part of the instep of the highest sensitivity to temperature stimulation.In addition,the influence those there indexes in the cold environment at 10°C was also investigated.In the cold environment,the absolute value of temperature sensory reaction time and temperature differences were increased in all parts.The increased value of the plantar part was more than that of the other parts of the dorsal,this could be considered that the plantar part of foot was more cold tolerant than the dorsal part.The sensitivity of thermal sensation will affect the thermal comfort,which could be evaluated by the temperature sensory difference.Therefore,the temperature sensory difference index was chosen for further analysis.First,the difference and correlation of the temperature sensory difference in different parts were analyzed.Then the main parts which affecting the whole foot temperature sensation were explored through factor analysis.Based on the researches above,the appropriate site of heating and keep warm were suggested,which providing recommendations for optimizing the design of footwear.