Physiological Responses during Operation of a Rotary Power Tiller

Abstract

A study was carried out at Central Institute of Agricultural Engineering, Bhopal, India to measure heart rate and oxygen consumption rate of six male operators during rotatilling and rotapuddling operations by a 6·7 kW rotary power tiller. Another set of experiments was conducted to measure the physiological responses while the operators walked alone on a puddled field. Physiological responses were measured under actual field conditions using an ambulatory metabolic measurement system. The data were collected at three levels of forward speed obtained in three low-speed gears at about three-quarters of the rated engine speed (1500 min −1). Physiological responses during rotatilling and rotapuddling operations varied linearly with forward speed. During the rotatilling operation, the mean values of heart rate and oxygen consumption rate were 97, 103 and 110 beats min −1 and 0·48, 0·58 and 0·63 l min −1 at forward speeds 0·30, 0·47 and 0·63 m s −1, respectively. The corresponding values during rotapuddling operation were 101, 109 and 119 beats min −1 and 0·56, 0·70 and 0·86 l min −1. Mean values of heart rate and oxygen consumption rate while the operators walked alone on puddled field were 99, 105 and 112 beats min −1 and 0·54, 0·63 and 0·75 l min −1 at the above forward speeds. The mean values for human energy expenditure were 10·02, 12·11 and 13·15 kJ min −1 during rotatilling, 11·69, 14·62 and 17·96 kJ min −1 during rotapuddling and 11·28, 13·15 and 15·66 kJ min −1 during walking alone on puddled field at the forward speeds of 0·30, 0·47 and 0·63 m s −1, respectively. The study indicated that rotapuddling involved higher energy expenditure to an extent of 17–37% as compared with rotatilling for the above range of forward speeds. Walking alone on the puddled field was observed as a very strenuous activity, which required about 87–96% of total energy expenditure during the rotapuddling operation. Overall discomfort ratings on a 10-point visual analogue discomfort scale for 15 min work duration were 1·5, 2·6 and 4·1 during rotatilling, 3·3, 4·7 and 6·0 during rotapuddling and 3·4, 4·8 and 5·7 during walking alone on the puddled field at forward speeds 0·30, 0·47 and 0·63 m s −1, respectively. Considering the physiological responses and the overall discomfort rating data as well as work output of man–machine system, it is recommended to operate the power tiller at a forward speed of 0·63 m s −1 during rotatilling operation and at a speed of 0·47 m s −1 during rotapuddling operation.