Marianne Stål

Wrist positions and movements as possible risk factors during machine milking.

High prevalence of hand and wrist symptoms has been found in females working with machine milking. Therefore the aim of this study was to quantify the positions and movements of the wrist during machine milking, and to compare tethering and loose-housing systems with respect to this. Biaxial electrogoniometers and data loggers were used for recording flexion and deviation angles of both the right and left wrists in 11 healthy milkers. For each individual 25 min of representative work was recorded in each system. High values of dorsiflexion and radial deviation were found, which might induce an increased risk of carpal tunnel syndrome. Moreover, the velocity and repetitiveness were close to those values described in repetitive work with a high risk of elbow and hand disorders in the fish-processing industry and giro-form data entry work. According to our findings, the load on the upper extremities has increased with respect to dorsiflexed hand position and repetitiveness when milking in the modern loose-housing milking system. This is probably due to the change of the working position and/or the higher productivity (number of cows that milked per time unit) in the loose-housing system as compared to the old-fashioned tethering system. These negative effects on wrist positions and movements should be considered when building new milking systems.

Upper extremity muscular load during machine milking

Abstract 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.

Upper extremity nerve involvement in Swedish female machine milkers

Entrapment of the median nerve in the proximal forearm, the so-called pronator syndrome, is considered a rather rare condition but it is four times more common in women than in men. In this study, 23 of 30 female machine milkers with symptoms in the forearm and hand were clinically diagnosed as having the pronator syndrome. The diagnosis of median nerve involvement was based on the clinical history and on physical examination by a hand surgeon. All 23 milkers complained of aching in the volar part of the forearm and had a sensation of numbness, tingling, and decreased muscle strength in their hands, mostly in the hands which usually were statically loaded with heavy equipment. Objectively, all had an experience of tenderness over the pronator teres muscle. Furthermore, they showed reduced muscle strength, especially in the following muscles: pronator teres (PT), flexor carpi radialis (FCR), flexor pollicis longus (FPL), and flexor digitorum profundus II (FDP II). To validate the manual muscle testing, Mannerfeldts intrinsicmeter was used to quantify the clinically observed weakness. Eight of the 23 milkers with pronator syndrome were surgically released from neuropathy and were almost symptom-free at follow-up after six months. One patient had a slight sensation of numbness and had to be given surgical carpal tunnel release later on. The external exposure of the arm during the application of the milking cluster probably causes muscle and fascial tensions that induce compression of the nerve. Further studies are needed to establish the level of the internal exposure.

Ache, pain, and discomfort: the reward for working with many cows and sows?

Abstract The main purpose of the study was to investigate the prevalence of perceived symptoms of musculoskeletal disorders (MSD) among workers on large-scale dairy and pig farms in Sweden (herd size more than 300 cows and 450 sows) and to identify potential risk factors in the development of MSD. A study based on questionnaires was carried out among 42 workers on 10 large dairy farms and among 37 workers on 10 large pig farms in Southern Sweden during the autumn of 2002. Most importantly, the study showed that 86% of the dairy workers and 78% of the pig workers reported some kind of MSD during a period of 12 months prior to the study. The most frequently reported MSD among both the dairy and the pig workers were in the “upper extremities” (52% and 62%, respectively) especially in the shoulders and in “the back” (60% and 57%, respectively) especially in the lower back. Furthermore, being of short stature, doing repetitive work, working in awkward positions and being exposed to dust were significant risk factors in having MSD among the workers in this study. Thus, working with many cows and sows on large-scale farms in Sweden can be considered as a high risk job with regard to MSD.

The effect on workload by using a support arm in parlour milking

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 milkers 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.