# Metabolic Rate Measuring with Indirect Calorimetry for Thermal Comfort Evaluation
## 4 Conclusions  
In this study, the MET and HR are measured and compared in various environments. The predictive equations for MET based on walking speed and HR are developed, respectively. In addition, their applications in thermal comfort are investigated. The main conclusions are as follows:  
1. The environments have little impact on MET, except the MET of 6 km/h walking in the hot environment, which is about 10 W/m\({}^{2}\) higher than that in the cold and warm environments (\(p\) = 0.006 and \(p\) < 0.01). On the contrary, the HR of all activities in the cool environment is significantly lower at 3-7 ppm than that in the other environments (\(p\) < 0.05).
2. The linear, exponential, and quadratic polynomial relationships between walking speed and MET are fitted. Compared to most research, there are higher intercepts and lower slopes of linear predictive equations in this study. That means that the values of MET at low activity are higher than others, and the values of MET at high activity are lower in this study. In addition, the linear relationship can better represent the relevance between MET and walking speed than the exponential and quadratic polynomial relationships.
3. The linear relationships between HR and MET at the cool and the other environments are fitted, respectively: MET = 3.67 \(\times\) HR \(-\) 195.56 and MET = 3.80 \(\times\) HR \(-\) 218.90. The slope and intercept of the latter are higher than the former, although the R\({}^{2}\) of them is equivalent (0.77 and 0.76). It indicates that the RM in the cool environment is lower than the others.  
Figure 14: Linear relationship between HR and TSV.  
* The TSV and PMV from various sources of MET at sitting and 2 km/h and 4 km/h walking are collected and compared. The TSV always rises following the increase in activity intensity, and the environment becomes warm. For the sitting activity, a slight difference from the MET could cause a significant difference in PMV, which leads to a PMV that may be above, below, or close to the TSV. For the 2 km/h walking activity, five kinds of PMV are close to TSV. On the contrary, for the 4 km/h walking activity, the PMV is always higher than the TSV.  
Conceptualization, R.J., X.L., H.Z., T.Y., and W.Z.; Project Administration, H.Z.; Supervision, T.Y.; Writing--Review and Editing, R.J., X.L., and W.Z. All authors have read and agreed to the published version of the manuscript.  
This work is supported by the Science and Technology Research and Development Program of China State Railway Group Co., Ltd. (No. L2021G011) and the National Engineering Research Center for Digital Construction and Evaluation of Urban Rail Transit.  
The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of Tianjin University (protocol code: TJUE-2024-338 and date of approval: 31 March 2023).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in this study.  
The data presented in this study are available on request from the corresponding author.  
The authors declare that this study received funding from Science and Technology Research and Development Program of China State Railway Group Co., Ltd. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.