Upper arm elevation and repetitive shoulder movements: a general population job exposure matrix based on expert ratings and technical measurements

Objectives We recently constructed a general population job exposure matrix (JEM), The Shoulder JEM, based on expert ratings. The overall aim of this study was to convert expert-rated job exposures for upper arm elevation and repetitive shoulder movements to measurement scales. Methods The Shoulder JEM covers all Danish occupational titles, divided into 172 job groups. For 36 of these job groups, we obtained technical measurements (inclinometry) of upper arm elevation and repetitive shoulder movements. To validate the expert-rated job exposures against the measured job exposures, we used Spearman rank correlations and the explained variance (R-adj(2)) according to linear regression analyses (36 job groups). We used the linear regression equations to convert the expert-rated job exposures for all 172 job groups into predicted measured job exposures. Bland-Altman analyses were used to assess the agreement between the predicted and measured job exposures. Results The Spearman rank correlations were 0.63 for upper arm elevation and 0.64 for repetitive shoulder movements. The expert-rated job exposures explained 64% and 41% of the variance of the measured job exposures, respectively. The corresponding calibration equations were y=0.5% time+0.16xexpert rating and y=27 degrees/s+0.47xexpert rating. The mean differences between predicted and measured job exposures were zero due to calibration; the 95% limits of agreement were +/- 2.9% time for upper arm elevation >90 degrees and +/- 33 degrees/s for repetitive shoulder movements. Conclusions The updated Shoulder JEM can be used to present exposure-response relationships on measurement scales.