Ergonomics evaluation of a lever-operated knapsack sprayer.

The lever-operated knapsack sprayer, a manually operated piece of equipment, is widely used by Indian farmers for the application of agricultural chemicals. The study reported here is an ergonomics evaluation of one model of this type of sprayer. Data on 18 body dimensions and the shape of the back were collected for 10 subjects and their relevance in sprayer design are discussed. During the operation of this sprayer, the mean heart rate, oxygen uptake and energy expenditure of the subjects were 94.6 beats/min, 0.454 1/min and 9.48 kJ/min, respectively. The mean overall discomfort ratings were 3.4, 5.0 and 5.7 (on 0-7 discomfort scale) and the mean body part discomfort scores were ,65.8, 93.8 and 89.1 (according to the technique described by Corlett and Bishop (1976)) at the end of first, second and third fill, respectively. The maximum discomfort was experienced at the left clavicle region, followed by lower back, neck, left thigh and right clavicle. The study indicated that though the workload in the spraying operation was within acceptable limits according to physiological criteria, there is a need to make improvements in the mounting of the sprayer on the operator's back to reduce the postural discomfort.