| The human metabolic rate(met)is one of the six main factors that affect the thermal comfort of the human body.It determines the comfort or fatigue degree of people exposed to the thermal environment,and is the prerequisite for calculating the human body’s thermal balance,physiological and psychological thermal response.However,the metabolic rate measurement method is complicated,the test equipment is expensive,and the data sources for the reference values given in the ISO and ASHRAE standards are European and North American populations,which have not been updated for a long time.Therefore,in view of the lack of metabolic rate data values that are characteristic of the Chinese population in the standard,and the efficient and convenient method of obtaining metabolic rate data,the research content of this article is the metabolic rate values and characteristics of the Chinese population under different activity levels.At the same time,we are also exploring the feasibility of thermal comfort field applications of wearable devices(sports accelerometers).In this paper,a portable wearable gas metabolism analyzer(Cosmed K5)was used to measure the performance of 111 Chinese people aged 20-69 who have been in indoor office for a long time under 18 activity conditions such as office activities,family activities,and walking activities.It turned out that the reference value of metabolic rate given in the thermal comfort standard is not equally applicable to the Chinese population.ISO and ASHRAE standard values tend to underestimate the metabolic rate of sitting activities and overestimating standing activities by about 0.1-0.2 met(10-20%);and ISO standards significantly underestimated the metabolic rate of walking activities by 0.2-0.4 met(7-17%),the ASHRAE standard underestimated by more than 20%.Analyzing the gender-age difference in metabolic rate,it was found that women’s metabolic rate was slightly lower than that of men by about 10%at moderate and high levels of activity,and the difference was significant(p<0.001);There was a significant age difference at 2-6km/h between 20-29 years old and 50-59,60-69 years old.Further study the method of obtaining on-site metabolic rate data,taking the measured metabolic rate in this article as the dependent variable,taking the subject’s personal information,heart rate,and accelerometer activity counts as the independent variables,and finally establishing the metabolic rate prediction equation through the stepwise regression method.Analysis and comparison of the results found that the heart rate prediction metabolic rate equation in ISO 8996 standard overestimateed the metabolic rate at the same heart rate level;the three-axis sports accelerometer can be applied to thermal comfort field research to predict the metabolic rate,which can improve the accuracy of the heart rate prediction equation to a certain extent,and the combined equation of the accelerometers for the hands,waist,and feet can reduce the prediction error to 10 %.In conclusion,this study measures the metabolic rate of people who have been in indoor office for a long time under different activity levels,which may have an important impact on the thermal comfort and energy efficiency of environmental design.The measured values of metabolic rate in the current study can be used to estimate the activity level and metabolic rate value of the Chinese population in laboratory and field studies,and will also contribute to the establishment of a metabolic rate database for the Chinese population in the future.At the same time,the exploration of field data acquisition methods for metabolic rate provides more possibilities for data acquisition of thermal comfort field research. |
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