Observation Methods and Imaging Techniques. Assessments of physical exposure in repetitive work with focus on neck and upper extremities
Abstract: Observation methods and imaging techniques - assessments of physical exposure in repetitive work with focus on neck and upper extremities The aim of this thesis was to develop, establish and validate observation methods for exposure assessments in epidemiological studies of repetitive work. A second aim was to increase the quality of input data for biomechanical shoulder models, by reliability and validity studies of Magnetic Reso-nance Imaging (MRI) and Ultrasound Scanning (US). The first study, a review of existing observation methods, showed that criteria for work posture classification in observation methods were mostly based on practical experience, but that also scien-tific criteria based on biomechanics, EMG and to some extent epidemiology constituted the criteria. More standardised observation methods were considered desirable. In the next study a video-based observation method was developed for exposure assessments in an epidemiological follow-up study in 19 companies with repetitive work, the PRIM study (Project on Research and Intervention in Monotonous work). The observation method involved 43 variables re-presenting repetitiveness and level of exposure. Information on duration of exposure was obtained by means of a questionnaire. Based on work tasks, 103 exposure groups were formed, giving sufficient-ly large exposure contrasts between exposure groups and a sufficiently large homogeneity within groups for most of the variables studied. A large within-group variance in exposure to non-neutral shoulder postures may in future studies require individual assessment and/or the inclusion of groups with maximal contrast in exposure. In the third and fourth study data from the PRIM observation method were compared with direct measurements. Work postures and movements were studied during poultry processing by means of the PRIM observation method and goniometers and inclinometers. Differences between the methods were mainly due to different reference positions and measured variables. Force demands as studied by force registrations from the deboner knife and EMG corresponded well with observer-based peak force ratings used as a variable in the PRIM observation method. The same study revealed that new technology during deboning of poultry (mechanical instead of manual deboning) had only a marginal effect on the physical workload. In the fifth and sixth study imaging techniques were studied as techniques for quantifying muscle sizes and moment arms as input variables for biomechanical shoulder models used to quantify the in-ternal dose. MRI measurements of muscle sizes and moment arms of rotator cuff muscles were esti-mated to have a high reliability and validity. Data on muscle volumes, physiological cross-sectional areas and moment arms were added to the database of living healthy females representing the work-ing population. MRI values of muscle sizes and moment arms were reflected in the corresponding US values in m. supraspinatus and m. infraspinatus. US might thus be a valid alternative to MRI measurements, but further development and validation of the US technique are still required.
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