Evaluation of work-rest schedules during operation of a rotary power tiller

Abstract

The operation of a power tiller involves walking behind the machine on a tilled or puddle land continuously for hours. Physical efforts required for the operation of the machine combined with exposure to varying degrees of solar radiation, dusty environment, monotonous nature of the job and the severe hand vibrations cause a lot of stress on the operator resulting in physiological and psychological fatigue after the daylong operation. To reduce the time-integrated workload on the operator, administration of a suitable work-rest schedule seems to be a feasible solution. An experiment was therefore, conducted with five subjects to study the influence of four work-rest schedules on physical workload during power tiller operation. Computerized heart rate monitor was used for continuous recording of heart rate data throughout the working day. Psychophysical measurement technique was used to quantify the overall discomfort as well as body part discomfort. The study indicated that the work-rest schedules did influence the physiological and postural workload as evidenced by the differences in working heart rate and postural discomfort. On the basis of the physiological and psychophysical results of the study it was concluded that duration of work bouts during rotatilling operation by power tiller should not exceed 75 min otherwise the operators may develop symptoms of physiological fatigue which may subsequently result in accidents and injury. Work schedules having smaller work bouts involved lower cardiac cost but subjectively felt more fatiguing on the basis of leg discomfort and upper arm discomfort. Rest pauses of 10 min duration were found insufficient for getting recovered from the fatigue developed during the previous work bout. To avoid excessive postural discomfort the minimum duration of rest pauses should be of 15 min. The duration of the lunch break should be more than 45 min and it should preferably be scheduled during the periods of maximum ambient temperature i.e. between 13:00–14:00 h. Relevance to industry An appropriate work-rest schedule for power tiller operation may serve as a guideline for making safety standards and norms for power tiller operation and in similar circumstances in other industries.