OPTIMUM HANDLE HEIGHT FOR A PUSH-PULL TYPE MANUALLY OPERATED DRYLAND WEEDER

A laboratory study was carried out at the Central Institute of Agricultural Engineering (CIAE), Bhopal to find out the optimum handle height for a push-pull type manually-operated dryland weeder from ergonomic considerations. Four handle heights, i.e. 0.6, 0.7, 0.8 and 0.9 of shoulder height (SH) were compared with eight subjects in a laboratory set-up which involved an application of 98 N horizontal push for operating the weeder. The observations made during the experiment were heart rate, ventilation rate, energy expenditure and rating of perceived exertion (RPE). The lowest heart rate and RPE were observed while working at 0.7 SH and lowest oxygen consumption at 0.8 SH. However, no significant differences were observed in physiological cost and perceived exertion between working with 0.7 and 0.8 SH handle height. Working at 0.9 SH produced the highest heart rate and oxygen consumption and subjects perceived the work as very hard. A handle height of 0.6 SH proved too low for the subjects resulting in increased muscle fatigue and higher heart rate as compared to 0.7 and 0.8 SH. Based on the results of this experiment, and the available anthropometric data of Indian workers, a handle height of 100 cm is recommended for the push-pull type manually-operated dryland weeder under study.