Upper extremity muscular load during machine milking

Epidemiological studies have shown a high prevalence of wrist and hand diso rders associated with machine milking. The occurrence of tingling, numbness and reduced muscle strength indicates peripheral nerve involvement. This h as been confirmed by clinical examination revealing median nerve entrapment at the carpal tunnel and/or the elbow level. In a previous study, we showe d that machine milking implied high values of dorsiflexion and radial devia tion of the wrist, which may be associated with an increased risk of develo ping such conditions as carpal tunnel syndrom. To evaluate the impact of th e muscle tension on the nerve structures bilateral electromyographic record ings (EMG), of the biceps muscle and the flexor and extensor muscles of the forearm were performed in eleven healthy subjects milking both in a tradit ional and a more modern system. The peak loads for the flexor and extensor muscles were close to their maximum capacity which, in combination with pos itions and movements of the hand and forearm, might contribute to the devel opment of nerve injuries in addition to other tissue lesions such as tendin itis. Milking in the traditional tethering system was associated with highe r peak loads than milking in the more modern loose-housing system. On the o ther hand, the modern milking system, which had a considerably higher produ ctivity, implied higher "static" load and a lower relative duration of musc ular 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 th e basis for developing new techniques adapted to the demands of the work an d antropometrics of the female milkers in order to reduce the risk of injur ies in the upper extremity. (C) 2000 Elsevier Science B.V. All rights reser ved.