Upper extremity muscular load during machine milking

Epidemiological studies have shown a high prevalence of wrist and hand disorders associated with machine milking. The occurrence of tingling, numbness and reduced muscle strength indicates peripheral nerve involvement. This has been confirmed by clinical examination revealing median nerve entrapment at the carpal tunnel and/or the elbow level. In a previous study, we showed that machine milking implied high values of dorsiflexion and radial deviation of the wrist, which may be associated with an increased risk of developing such conditions as carpal tunnel syndrom. To evaluate the impact of the muscle tension on the nerve structures bilateral electromyographic recordings (EMG), of the biceps muscle and the flexor and extensor muscles of the forearm were performed in eleven healthy subjects milking both in a traditional and a more modern system. The peak loads for the flexor and extensor muscles were close to their maximum capacity which, in combination with positions and movements of the hand and forearm, might contribute to the development of nerve injuries in addition to other tissue lesions such as tendinitis. Milking in the traditional tethering system was associated with higher peak loads than milking in the more modern loose-housing system. On the other hand, the modern milking system, which had a considerably higher productivity, implied higher static load and a lower relative duration of muscular rest, as compared to the traditional system. Relevance to industry. Electromyography (EMG) was used to assess the muscular load during milking in two different milking systems. The results of this study will provide the basis for developing new techniques adapted to the demands of the work and antropometrics of the female milkers in order to reduce the risk of injuries in the upper extremity. (C) 2000 Elsevier Science B.V. All rights reserved.