Cardiorespiratory and subjective strains during actuation of large hand wheels

Abstract

Large hand-wheel actuation has been studied mainly by its physical aspects and maximal strength capacities. The purpose of the present study was to evaluate the physiological strain of these activities, an area that has received little investigation in the past. Heart rate, oxygen consumption and subjective evaluation (Borg scale) were recorded on eight subjects over the course of six experimental sessions combining three hand-wheel positions (horizontal and vertical at subject elbow height and horizontal 70 cm from the floor) and two torque values (20 and 35 Nm). Each task lasted for 2 minutes and, by repetitive actuation resulted in 33 revolutions of a 40 cm diameter hand wheel. The results show that the position of the wheel has a small effect on the physiological strain. Despite the rather low-torque values studied, cardio-respiratory and subjective strains were high for the 35 Nm torque. Indeed, mean heart rate and oxygen consumption for the last 30 s of actuation were 149.7 bpm (SD = 9.4) and 1.858 l min-1 (SD = 0.179) for the 35 Nm torque setting and 130.4 bpm (SD = 6.3) and 1.476 l min-1 (SD = 0.128) for the 20 Nm torque setting. Rating of perceived exertion was 14.7 (SD = 1.2) and 11.3 (SD = 2.0) for the high- and low-torque conditions, respectively. These high strains were recorded in conditions which seem to be low with respect to both the standardization proposals currently being drawn up and to the maximum strength value proposed in the literature. Moreover, these values are for new valves; with ageing, the torque resistance of valves often rises due to wear and sediment deposition. The results of this study show that hand-wheel actuation in optimal laboratory conditions may induce high cardiorespiratory strains which are probably frequently encountered in real working situations. Relevance to industry: Quantification of physiological strains in hand-wheel actuation which is an infrequent but arduous task. Limitation of torque is proposed to prevent hazardous cardiac strains. © 2000 Elsevier Science B.V.