ARM AND TRUNK POSTURE DURING WORK IN RELATION TO SHOULDER AND NECK PAIN AND TRAPEZIUS ACTIVITY

Objective. To investigate work technique in relation to work-related s houlder and neck pain (SNP) and upper trapezius muscle activity. Desig n. A matched pair, case-control field study of female employees with a nd without SNP. Background. It has proved difficult to distinguish sub jects with SNP from those without by vocational electromyographic reco rdings from the upper trapezius muscle. Other potential risk indicator s include psychosocial factors and work technique. This study focuses on the latter. Methods. Manual (14 pairs) and office workers (24 pairs ) were recorded during a 30-min work period. Simultaneous recordings o f upper trapezius activity by surface electromyography and arm and upp er back postures by inclinometers were analysed. Results. Cases and co ntrols were not differentiated on the basis of arm elevation or of tru nk posture in the sagittal plane. No significant correlations were fou nd between variables averaging the muscle activity and the arm elevati on over the recording period. Statistically significant correlations w ere, however, found between these variables when analysing recordings at high time resolution (0.2 s) and adjusting for the delay in arm ele vation relative to the upper trapezius muscle activity (r = 0.43, manu al group; r = 0.32, office group). Conclusions. Factors other than arm elevation probably contribute more significantly to the load in the u pper trapezius muscle, and to the development of work-related SNP in w ork situations with moderate arm elevation.