Sustained muscle tension as a risk factor for trapezius myalgia

Thirty female chocolate packers were included in a prospective study to relate trapezius muscle activity during work to the development of myalgia. Electromyographic (EMG) recordings and interviews on risk factors were performed at start of employment and every 10th week. The muscle activity was characterized by the averaged static and median level. Only data obtained before a possible development of severe symptoms of trapezius myalgia (patient) was used in the analysis. Seventeen of the subjects became patients within the first year of employment. Machine-stops occurred accidentally during work. At one task the stops induced a pause where the subjects passively waited for the machine to start. Twenty-one subjects experienced machine-stops of a sufficient duration to be evaluated for a potential “resting tension”. Future patients showed significantly higher “resting tension” compared to healthy controls.