Comparative analysis of methods for determining the metabolic rate in order to provide a balance between man and the environment

Abstract The incorrect determination of metabolic rate can be linked to discrepancies between the model of the PMV (Predicted Mean Vote) and real thermal sensation collected in field studies. Aiming to improve the correlation of the PMV model and the real thermal sensation, this work established new values for the metabolic rate: one way being called “calculated” using Newton's Method and the other called "measured" using a metabolic analyzer. Welder's activities were evaluated, through the measurements of environmental and personal variables. New values of metabolic rate were determined for this activity. The values found for the calculated form and the measured one were, respectively, 178.63 and 145.46 W/m 2 , different from the range provided by the table of ISO 8996 (2004) for this activity (75–125 W/m 2 ). In order to verify which of the values of the metabolic rate was closer to the real thermal sensation of PMV, a linear regression was made between the PMV and the real thermal sensation in three ways: S × PMV tabulated ( R 2  = 0.1749), S × PMV calculated (R ² = 0.7481) and S × PMV measured ( R 2  = 0.7854). It was found that the values measured by the instrument gave a higher coefficient of determination which was chosen for the correction of the table. The correction of the table provides a value of M predicted , that is a value of metabolic rate that corrects the values provided by the tables of ISO 8996 (2004) , by means of a correction coefficient. For the welder's activities in a metal-mechanics industry, tabulated values can be multiplied by the correction coefficient 1.4648 in order to minimize inaccuracies. The PMV predicted , obtained through the M predicted , when related to the actual thermal sensation, provides a coefficient of determination of 0.7511, thereby improving the model of the PMV. Relevance to Industry By knowing the metabolic demands of a determined activity makes it possible for employers not only to plan their activities in a way that metabolic rates do not generate excess heat to workers but also to provide them with work clothes and instruments that are appropriate for the generated heat.

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