Risk of shoulder tendinitis in relation to shoulder loads in monotonous repetitive work.

BACKGROUND Few studies relate the occurrence of shoulder disorders to quantified ergonomic exposures. This study evaluates the hypothesis that shoulder loads in repetitive work might contribute to the occurrence of shoulder tendinitis. METHODS This is a cross-sectional study of 1961 workers in repetitive work and 782 referents. Shoulder loads were quantified at task level and measures of exposures were assigned based on task distribution. Symptoms in combination with clinical criteria defined shoulder tendinitis. RESULTS The prevalence of shoulder tendinitis was higher among exposed workers (adjusted OR 3.1, 95% CI 1.3-3). Neither frequency of movements (ranging 1-36/min) nor lack of micro-pauses in shoulder flexion (ranging 0-100% of cyclus time) was related to disease prevalence. Increasing force requirements (categorized as light = 1, somewhat hard = 2, hard = 3 or very hard = 4) increased risk slightly (OR 1.6, 95% CI 1.0-2.6 per unit). CONCLUSIONS The results indicate that workers with repetitive tasks have increased risk of shoulder tendinitis, which partially can be attributed to force requirements.