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- Heiden, Marina, 1974-, et al.
(författare)
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Cost-efficient assessment of variation in arm posture during paper mill work
- 2016
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Konferensbidrag (refereegranskat)abstract
- Background. Arm posture is a recognized risk factor for occupational upper extremity musculoskeletal disorders and thus often assessed in research and practice. Posture assessment methods differ in cost, feasibility and, perhaps, bias. An attractive approach could be to build statistical models for predicting results of expensive direct measurements of arm posture from cheaper or more accessible data, and apply them to large samples in which only the latter data are available. We aimed to build and assess the performance of such prediction models in a random sample of paper mill workers.Methods. 28 workers were recruited to the study, and their upper arm postures were measured during three full work shifts using inclinometers. Simultaneously, the workers were video filmed, and their arm posture and gross body posture were assessed by observing the video afterwards. Models for predicting the inclinometer-assessed duration (proportion of time) and frequency (number/min) of periods spent in neutral right arm posture (<20°) were fitted using subject and observer as random factors, measured shift (1, 2 or 3) as fixed factor, and either observed time in neutral right arm angle or observed gross body posture as predictor.Results. For the proportion of time spent in neutral arm posture, the best performance was achieved by using observed gross body posture as predictor (explained variance: R2=26%; standard error: SE=9.8). For the frequency of periods spent in neutral arm posture, the corresponding model fit was R2=60% and SE=5.6. Bootstrap resample validation of the latter model showed an expected performance in other samples of R2=59-60% and SE=5.5-5.6 (5th-95th percentile).Discussion. Surprisingly, we found that observed gross body posture was a better predictor of variation in arm posture than observed arm angles. The findings suggest that arm posture during paper mill work can be cost-efficiently assessed using simple observations.
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| 3. |
- Trask, Catherine, 1979-, et al.
(författare)
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EMG estimated mean, peak, and cumulative spinal compression of workers in five heavy industries
- 2010
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Ingår i: International Journal of Industrial Ergonomics. - : Elsevier BV. - 0169-8141 .- 1872-8219. ; 40:4, s. 448-454
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this study was to explore the use of compression-normalized electromyography (CNEMG) to estimate mean, peak, and cumulative loading of the low back in workers of five heavy industries using and to compare the estimates to the NIOSH guidelines. Full-shift (5.5 to 10.3 hours) EMG measurements were collected from 105 workers and transformed into units of low back compressive force (Newtons). The mean, peak, and cumulative CNEMG as well as the percentage of work time spent above 3400 N and 6800 N thresholds were calculated. Mean CNEMG (sd) was 1564 N (796), peak was 2721 (1545), and cumulative was 38 MN.sec (22). Mean time spent above the NIOSH threshold of 3400 N was on average 6.3% of shift, while mean time spent above the 6400 N threshold was around 1%. CNEMG allowed the feasible investigation of tasks and jobs that would be virtually impossible with more advanced biomechanical methods and represents a more objective measure of exposure than observation or self-report. CNEMG is a relatively new method with methodological limitations, however, CNEMG's strength may be as an objective, relative measure of exposure in studies where low back EMG is collected in a relatively systematic and structured manner.
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| 4. |
- Trask, Catherine, 1979-, et al.
(författare)
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Observer variability in posture assessment from video recordings : the effect of partly visible periods
- 2017
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Ingår i: Applied Ergonomics. - : Elsevier BV. - 0003-6870 .- 1872-9126. ; 60, s. 275-281
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Tidskriftsartikel (refereegranskat)abstract
- Observers rank partly visible postures on video frames differently than fully visible postures, but it’s not clear if this is due to differences in observer perception. This study investigated the effect of posture visibility on between-observer variability in assessments of trunk and arm posture. Trained observers assessed trunk and arm postures from video recordings of 84 pulp mill shifts using a work sampling approach; postures were also categorized as ‘fully’ or ‘partly’ visible. Between-worker, between-day, and between-observer variance components and corresponding confidence intervals were calculated. Although no consistent gradient was seen for the right upper arm, trunk posture showed smaller between-observer variance when all observers rated a posture as fully visible. This suggests that, partly- visible data, especially when observers disagree as to the level of visibility, introduces more between-observer variability when compared to fully visible data. Some previously-identified differences in daily posture summaries may be related to this phenomenon.
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| 5. |
- Trask, Catherine, 1979-, et al.
(författare)
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Optimising sampling strategies: components of low-back EMG variability in five heavy industries
- 2010
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Ingår i: Occupational and Environmental Medicine. - : BMJ. - 1351-0711 .- 1470-7926. ; 67:12, s. 853-860
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Tidskriftsartikel (refereegranskat)abstract
- Background Direct/ measurement of work activities iscostly, so researchers need to distribute resourcesefficiently to elucidate the relationships betweenexposures and back injury.Methods This study used data from full-shiftelectromyography (EMG; N¼133) to develop threeexposure metrics: mean, 90th percentile and cumulativeEMG. For each metric, the components of variance werecalculated between- and within-subject, and betweengroupfor four different grouping schemes: grouping byindustry (construction, forestry, transportation,warehousing and wood products), by company, by job andby quintiles based on exposures ranked by jobs withinindustries. Attenuation and precision of simulatedexposureeresponse relationships were calculated for eachgrouping scheme to determine efficient sampling strategies.Results As expected, grouping based on exposurequintiles had the highest between-group variances andlowest attenuation, demonstrating the lowest possibleattenuation with this data.Conclusion There is potential for grouping schemes toreduce attenuation, but precision losses should beconsidered and whenever possible empirical data shouldbe employed to select potential exposure groupingschemes.
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| 6. |
- Trask, Catherine, 1979-, et al.
(författare)
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Using observation and self-report to predict mean, 90th percentile, and cumulative low back muscle activity in heavy industry workers
- 2010
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 54:5, s. 595-606
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Tidskriftsartikel (refereegranskat)abstract
- Occupational injury research depends on the ability to accurately assess workplace exposures for large numbers of workers. This study used mixed modeling to identify observed and self-reported predictors of mean, 90th percentile, and cumulative low back muscle activity to help researchers efficiently assess physical exposures in epidemiological studies. Full-shift low back electromyography (EMG) was measured for 133 worker-days in heavy industry. Additionally, full-shift, 1-min interval work-sampling observations and post-shift interviews assessed exposure to work tasks, trunk postures, and manual materials handling. Data were also collected on demographic and job variables. Regression models using observed variables predicted 31-47% of the variability in the EMG activity measures, while self-reported variables predicted 21-36%. Observation-based models performed better than self-report-based models and may provide an alternative to direct measurement of back injury risk factors.
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| 7. |
- Trask, Catherine, 1979-, et al.
(författare)
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Variance components of observed postural exposure - the effect of partly visible periods
- 2016
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Konferensbidrag (refereegranskat)abstract
- Background. Previous studies have shown that video-based observation of postures that are only partly visible leads to different daily summary values than when postures are fully visible. However, the source of these differences is unclear. The purpose of this study was to estimate the between-observer variance of trunk and arm posture estimates (relative to within- and between-worker variance), and to investigate the effect of visibility on this observer variability of trunk and arm postural exposure estimates.Methods. Video recordings were made of 28 pulp mill workers for three full shifts each. Trunk and arm postures were then estimated by trained observers using a work sampling approach; posture images were also assessed as being “fully” or “partly” visible. REML techniques were used to estimate the between-worker, between-day and betweenobserver components of variance at different visibility levels; Wald-based confidence intervals and p-values were used to determine sources of variation.Results. Estimates of partly visible postures (as agreed upon by all observers) were lower than fully visible postures. However, more than 90% of trunk observations and 85% of arm observations did not have full agreement on visibility between observers. Right upper arm posture showed smaller between-observer variance when all observers rated a posture to be fully visible, as compared to all observers agreeing it was only partly visible. This suggests partly visible data introduces more methodological (i.e. between-observer) variability when compared to fully visible data. However, no significant differences in between-observer variability were found for the trunk, suggesting that other factors explain the reported differences in estimated postures between fully and partly visible data in this case.Discussion. Future studies involving concurrent direct measurement would determine whether there is a true difference in posture between partly visible and fully visible periods, or whether the difference between fully and partly visible periods are related to observer performance.
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| 8. |
- Wahlström, Jens, et al.
(författare)
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Full-Shift Trunk and Upper Arm Postures and Movements Among Aircraft Baggage Handlers
- 2016
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 60:8, s. 977-90
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The present study assessed full-shift trunk and upper arm postural exposure amplitudes, frequencies, and durations among Swedish airport baggage handlers and aimed to determine whether exposures differ between workers at the ramp (loading and unloading aircraft) and baggage sorting areas.METHODS: Trunk and upper arm postures were measured using inclinometers during three full work shifts on each of 27 male baggage handlers working at a large Swedish airport. Sixteen of the baggage handlers worked on the ramp and 11 in the sorting area. Variables summarizing postures and movements were calculated, and mean values and variance components between subjects and within subject (between days) were estimated using restricted maximum likelihood algorithms in a one-way random effect model.RESULTS: In total, data from 79 full shifts (651h) were collected with a mean recording time of 495min per shift (range 319-632). On average, baggage handlers worked with the right and left arm elevated >60° for 6.4% and 6.3% of the total workday, respectively. The 90th percentile trunk forward projection (FP) was 34.1°, and the 50th percentile trunk movement velocity was 8° s(-1). For most trunk (FP) and upper arm exposure variables, between-subject variability was considerable, suggesting that the flight baggage handlers were not a homogeneously exposed group. A notable between-days variability pointed to the contents of the job differing on different days. Peak exposures (>90°) were higher for ramp workers than for sorting area workers (trunk 0.6% ramp versus 0.3% sorting; right arm 1.3% ramp versus 0.7% sorting).CONCLUSIONS: Trunk and upper arm postures and movements among flight baggage handlers measured by inclinometry were similar to those found in other jobs comprising manual material handling, known to be associated with increased risks for musculoskeletal disorders. The results showed that full-shift trunk (FP) and, to some extent, peak arm exposures were higher for ramp workers compared with sorting workers.
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