Physical workload on upper extremities in various operations during machine milking.

The aim of the study was to quantify the workload on the upper extremity for fundamental work tasks during machine milking. Eleven milkers working in a loose-housing system with a milking parlour participated in the study. Muscle activity for the biceps and the forearm flexors, as well as positions and movements of the wrists were simultaneously measured by electromyography and electrogoniometry while video-recording the work. The milking work was broken up in three main tasks "Drying (the cow's udder)", "Pre-milking (the first milk)" and "Attaching (the milking unit to the udder)" and three supplementary tasks. All three main tasks show high muscle load values and almost no time for rest. The highest load values for the biceps and flexor muscles were found during the tasks "Attaching, holding the milking unit" and "Drying", respectively. For 10% of the recording time, the milkers held active hands in 42 degrees dorsal flexion during the milking tasks "Pre-milking" and "Attaching" and in deviated positions exceeding 50% of their maximum values during "Attaching" and "Drying". The high muscle loads in combination with extreme positions and movements of the hand and forearm might contribute to the development of injuries among milkers. The result from the study aims to form a basis for technical improvements of the milking equipment to decrease the risk for arm wrist and hand disorders.