Use of heart rate monitor in assessing the net energy expenditure during motor-manual cutting

Abstract

Energy expenditure during labour constitutes one of the criteria used for assessing the laboriousness of timber harvesting. The major objective of this study was to point out the possibilities of defining work net energy expenditure (NEE) as related to the frequency of heart rate in the field exercise tests by changing posture and varied external work load. The scope of the study was restricted to the work of chainsaw operators performing hard physical labour during late thinning of fir and spruce on the middle mountain (Beskid Makowski, Beskid Śląski). The research involved dynamic work with elements of static load for which the NEE was investigated by means of heart rate as well as respiratory – indirect estimation of oxygen consumption as results of airflow measurement. The advantage of both methods is simplicity of application, the lack of necessity to perform additional analyses as time study and expected medium error. The conducted calculations pointed out to a strong linear correlation, where correlative coefficient was equal to 0.67. The conducted model analysis (including, among others: the normality, autocorrelation of residuals and identification of influential values) has confirmed its validity at the 10% statistical error. The obtained regression coefficient indicates a larger increase in value as compared to the available formulas with acceptable in practice standard error of prediction on 6.05 kJ/min level