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[Value of heart rate as an optimum index in evaluating physical labor intensity].

Objective: To investigate the possibility of heart rate as an optimum index for evaluating physical labor intensity. Methods: From September to October, 2015, a total of 111 male young adults were selected as study subjects. A cycle ergometer was used for exercise at different intensities (20, 40, 60, 80, 100, 120, 140, 160, and 180 W) , and the exercise at each intensity lasted for 6 minutes. The subjects wore the K4b2 portable cardiopulmonary function testing instrument for the real-time monitoring of heart rate (HR) , pulmonary ventilation volume (Ve) , oxygen consumption (VO(2)) , and energy metabolic rate (E) . The origin software was used for correlation and regression analyses of HR, Ve, VO(2), and E collected at different intensities to establish Ve-HR, VO(2)-HR, and E-HR regression equations. Results: At different intensities, HR was positively correlated with Ve, VO(2), and E (r=0.8985, 0.8733, and 0.8973, all P<0.01) . There was a significant difference in the R(2) value of Ve-HR, VO(2)-HR, and E-HR regression equations (R(2)=0.8070, 0.7625, and 0.8049, all P <0.01) . The validation results showed that there was no significant difference between the calculated values and the measured ones (P>0.05) . Conclusion: HR can replace Ve, VO(2), and E and be used as an optimum index for evaluating physical labor intensity.