The effect on workload by using a support arm in parlor milking
Department of Agricultural Biosystems and Technology, Swedish University of Agricultural Sciences, P.O. Box 88, Alnarp SE-23053, Sweden International Journal of Industrial Ergonomics
(Impact Factor: 1.07).
08/2003; 32(2):121-132. DOI: 10.1016/S0169-8141(03)00046-5
Swedish agriculture is currently undergoing radical changes with respect to the working environment. New production milking systems may alter the physical workload and thus have an effect on the development of musculoskeletal disorders. Earlier studies have shown that there is a manifest risk of suffering injury to the forearm, wrist and hand during machine milking especially during the attaching task (when holding the milking cluster in one hand while attaching the four teat-cups to the udder). High degrees of dorsiflexion and deviation of the wrist in combination with peak values of muscle activity in the forearm during milking might contribute injuries to the wrist and hand. Large-scale milk production increases the time spent performing the tasks involved. As a consequence, the cumulative engagement in extreme positions and rapid movements, and high level of muscular load on the upper extremities will also increase. The aim of this study was to investigate the impact of the workload on the milker's forearm, wrist and hands resulting from using the prototype of a device designed to facilitate the attaching task. The device is constructed as a support arm where the milking cluster is suspended in order to reduce the workload. The study was carried out in a loose-housing system where the cows come to be milked in a parlour. Eleven milkers participated in the study. The muscle activity in the biceps and the forearm flexors, as well as positions and movements of the wrists were measured by electromyography and electrogoniometry. The attaching task was measured both with and without the device. When the prototype was used only a minor decrease in the muscular load on the holding side was recorded. Surprisingly, the effect on the wrist positions and movements was small. This marginal effect could be due to the fact that all the milkers were used to milking without the support arm and despite the training period, they were unable to make full use of the device.Relevance to industryA prototype of a technical device (support arm) has been developed in order to reduce the workload on the upper extremities, especially on the wrist and hand. The effect on the workload has been evaluated by electromyography and electrogoniometry. The results have shown that by milking with the support arm, the muscle activity has diminished in the upper extremities. This might reduce the occurrence of the work-related musculoskeletal injuries found in earlier studies of milkers at work in a loose-housing system.
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