Muscle load and fatigue of film rolling workers

Effects of locally concentrated loading by repetitive upper limb operations on the musculature were studied in female workers of ages 19--33 rolling photographic film. They repeated rolling and capping of a 35 mm film every 2.5--5 sec during the whole day shift which had a 60 min lunch recess and two 10 min rests. Increase of dull-drowsy symptoms and shoulder complaints was dominant after work, stiff shoulders complaints being divided into 41.6% for prework and 78.7% for postwork. It was characteristic for these workers to have the trapezius muscle showed continuous electromyographic activities in sustaining arms. The average level of the contraction was estimated at about 10--30% of the maximum contraction. Eighty-four per cent of those studied had tenderness at the ascending part of the trapezius, while the same tenderness was found in only 48% of female office workers of the same firm. The operators having low tenderness threshold of 0.6 kg/cm2 or less had stiff shoulders more frequently as well as lower levels of back muscle and upper arm abduction forces than those having no tenderness. It is thus likely that habitual shoulder muscle fatigue is due to repetitive tasks that results in localized tenderness and possibly in occupational hazards.