| Fire rescue operations are often carried out under complex and extreme conditions,so the personal protective equipment of firefighters is very important.The fire-retardant and waterproof materials used on the surface of fire-fighting boots,and the anti piercing steel plates placed in the toe and sole of fire-fighting boots,while playing a protective role,prevent the escape of the heat and the sweat generated by human feet,and increase the rigidity and weight of fire-fighting boots.The weight-bearing brought by fire helmet,fire-fighting protective clothing,respirator and other equipment may increase the pressure of firefighter’s feet,at the same time,lead to the increase of metabolic heat production and sweating of human body,and further affect the thermal and wet comfort of feet.In order to meet the protection requirements,protective equipment such as fire boots may damage the comfort of feet.Therefore,this paper will consider the effect of fire boots and equipment load on foot pressure comfort and hot and wet comfort in different sports modes and stages,comprehensively analyze the quantitative indexes of subjective and objective evaluation of human foot comfort,and study its impact on human foot comfort.For the evaluation of foot pressure comfort,this paper uses a self-made pressure acquisition system to measure and collect the real-time pressure of seven areas of human foot under different experimental conditions,including P1(the upper surface of the thumb),P2(the upper surface of the little toe),P3(the inner side of the widest part of the foot),P4(the outer side of the widest part of the foot),P5(the upper surface of the highest arch of the foot),P6(the turning point of the connection between the dorsum of the foot and the lower leg),P7(the back of the heel).Subjective questionnaire was used to collect the examinees’ subjective evaluation of stress comfort in the first,middle and last three stages of exercise.By using the methods of variance analysis and correlation analysis,combined with the data of three-dimensional scanning of human foot shape and the measurement and calculation results of the space size in shoes,this paper discusses the influence of shoes,equipment load and exercise mode on the pressure comfort of human foot and the relationship between subjective and objective evaluation.Through analysis,it is found that the shoe factor has a significant impact on the objective pressure measurement value of the foot.The average pressure of P3,P4 and P5 areas without other external factors when wearing training shoes,and P2,P3 and P4 areas under the condition of simulated fire fighting operation are greater than that of fire boots.The weight-bearing factors had no significant effect on the subjective and objective evaluation of foot pressure comfort.The subjective and objective evaluation of foot pressure comfort was significantly influenced by the exercise mode.The mean pressure of P3 and P4 was significantly higher than that of walking when standing still.In the middle stage of exercise without other external factors,the score of P7 in standing was significantly higher than that in walking.In addition,the correlation between subjective and objective evaluation of foot pressure comfort is weak.For the evaluation of thermal and wet comfort of human feet,iButton temperature and humidity recorder and infrared thermal imager are used to collect the micro environment temperature and humidity changes in the front,middle and back areas of the insole area under different experimental conditions,as well as the temperature index of the human foot surface.Subjective questionnaire was used to collect the subjective evaluation of feet ’thermal and wet comfort.Using the methods of variance analysis and correlation analysis,combined with the indexes of the thermal resistance,the moisture resistance,the moisture permeability of the upper composite fabric,the moisture absorption of the inner layer fabric of the fire boots and the training shoes measured by the warm body dummy,the moisture permeability tester and the capillary effect tester,etc.,the influence of shoe and boot,equipment load and exercise mode on the thermal and wet comfort of human feet and the relationship between subjective and objective evaluation are analyzed.The results show that the shoe factor has a great influence on the micro environment humidity in the shoes.The humidity in the later stage of the simulated fire-fighting operation is about 14% higher than that in the training shoes.In addition,the shoe factor also has a significant influence on the micro environment temperature and subjective humidity feeling in the shoes.The micro environment temperature and humidity,the distribution of foot surface temperature and the subjective evaluation of foot thermal and humidity comfort are significantly affected by load-bearing factors.The micro environment temperature in shoes with load can be higher than 0.6℃ ~ 1℃ without load.The sports mode has significant influence on the temperature and humidity inside the shoes,the temperature distribution of the foot surface and the subjective thermal and humidity comfort evaluation.The micro environment temperature and foot surface temperature in walking mode were higher than that in standing mode,and the micro environment humidity in walking mode was lower than that in standing mode.In addition,there is a positive correlation between the subjective and objective evaluation indexes of temperature comfort,but the correlation between the subjective and objective evaluation of humidity comfort is not obvious,which may be related to the mechanism of human perception of humidity.Through the correlation analysis and the establishment of regression equation between the subjective evaluation of the foot comprehensive comfort and the subjective and objective evaluation of the pressure and heat and humidity in each area of the foot,it is found that to improve the comprehensive comfort of the foot,the stress comfort in the rear area of the heel,the temperature comfort in the front area of the foot and the pressure comfort in the upper surface area of the little toe should be improved.To sum up,footwear,weight-bearing and sports mode all have certain impact on foot comfort.Shoe factors mainly affect the foot pressure comfort and humidity comfort;weight-bearing factors mainly have a significant impact on the foot thermal and wet comfort;sports mode has a significant impact on the foot pressure and thermal and wet comfort.The subjective evaluation of the whole foot comfort is mainly related to the subjective evaluation of foot pressure,thermal and wet comfort and the micro environment temperature in the shoes,among them,the pressure comfort in the rear area of the heel,the temperature comfort in the front area and the pressure comfort in the upper part of the little toe have a great influence on the subjective evaluation of the whole foot comfort. |
