Relations between shoulder/neck disorders and EMG zero crossing shifts in female assembly workers using the test contraction method.

Pain and discomfort in the shoulder/neck region is a serious problem amongst workers in many categories of assembly work. It has been suggested that these disorders are related to local muscular fatigue. In this study 14 female assembly workers were studied. Several of these women had occupational shoulder/neck disorders of various degrees. The method (FTC), applied during work, involved short test contractions every ten minutes during which EMG from m. trapezius and m. infraspinatus bilaterally was recorded. The EMG was analysed using the zero crossing technique. The subjects filled in a standard questionnaire concerning their muscular shoulder/neck disorders. It is shown that subjects reporting disorders have more pronounced EMG alterations than those without disorders.

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