Documents Spielholz, Peregrin 2 results

The prevention of work-related musculoskeletal disorders has become a national priority in many countries. Increasingly, attempts are made to quantify those exposures that increase risk in order to set exposure limit values. This study used commonly employed field measurement methods and tools in order to perform an inter-method comparison between three primary methods of risk factor exposure assessment: self-report questionnaires, observational video analysis and direct measurement. Extreme posture duration, repetition, hand force (estimated from electromyography) and movement velocity were assessed for 18 subjects while performing each of three jobs processing tree seedlings. Results indicated that self-reports were the least precise assessment method, which consistently overestimated exposures for each of the measured risk factors. However, adjustment of the reports as psychophysical scales may increase agreement on a group level. Wrist flexion/extension duration and repetition were best measured by electrogoniometer. Electrogoniometric measures of wrist deviation duration and frequency were less precise than video analysis. Forearm rotation duration and repetition, grip force and velocity appeared to be best quantified by direct measurement as measured by electrogoniometer and electromyography (EMG) (as root-mean-square amplitude). The results highlight the fact that it is as important to consider and report estimated measurement error in order to reduce potential exposure misclassification in epidemiologic studies.

"This paper addresses the issue of quantifying forceful exertions of lifting, pushing/pulling, pinch and power griping with several commonly used methods (direct measurement, force-matching, ergonomist estimation based on observation and worker's self-report). The aims were to study differences of ergonomists in making decisions of collecting forceful exertion data, ability of the studied force quantification methods in detecting exposure differences between jobs, and relationships between measurements obtained by different methods. Seven hundred and thirty-three (733) subjects participated in the study, and 2482 forceful exertions were quantified with the selected force quantification methods. Results showed that the determination of whether a forceful exertion was considered important enough to be measured was very subjective. More objective criteria need to be developed. Although the different force quantification methods could detect exertion-level differences between different types of jobs, the sensitivity of detecting the difference varied. Direct measurement of lifting and pushing/pulling forces seems to be slightly more sensitive than ergonomists' estimates, and the force matching of grip forces may be more sensitive than workers' self-reports. Ergonomists estimations through observation seem to be a good alternative for measuring forceful exertions. Pearson correlation coefficients between force estimations obtained by the different methods were between 0.28 and 0.71. The degrees of the correlations between the different measurement methods varied. This indicates that the different methods might quantify different aspects of the forceful exertions. These methods may not necessarily be used interchangeably in job evaluation tools. Different weights and/or cut-points may need to be developed when different force quantification methods are used."