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Is what you see what you get?: Standard inclinometry of set upper arm elevation angles
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Research and Development, Gävleborg.
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2015 (English)In: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 47, 242-252 p.Article in journal (Refereed) Published
Description
Abstract [en]

Previous research suggests inclinometers (INC) underestimate upper arm elevation. This study was designed to quantify possible bias in occupationally relevant postures, and test whether INC performance could be improved using calibration. Participants were meticulously positioned in set arm flexion and abduction angles between 0 degrees and 150 degrees. Different subject-specific and group-level regression models comprising linear and quadratic components describing the relationship between set and INC-registered elevation were developed using subsets of data, and validated using additional data. INC measured arm elevation showed a downward bias, particularly above 600. INC data adjusted using the regression models were superior to unadjusted data; a subject-specific, two-point calibration based on measurements at 0 and 900 gave results closest to the 'true' set angles. Thus, inclinometer measured arm elevation data required calibration to arrive at 'true' elevation angles. Calibration to a common measurement scale should be considered when comparing arm elevation data collected using different methods.

Place, publisher, year, edition, pages
2015. Vol. 47, 242-252 p.
Keyword [en]
Measurement error, Observation, Working postures
National Category
Environmental Health and Occupational Health
Identifiers
URN: urn:nbn:se:uu:diva-245337DOI: 10.1016/j.apergo.2014.08.014ISI: 000347663600028PubMedID: 25479994OAI: oai:DiVA.org:uu-245337DiVA: diva2:792239
Available from: 2015-03-03 Created: 2015-02-26 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Bias and Precision in Biomechanical Exposure Assessment: Making the Most of our Methods
Open this publication in new window or tab >>Bias and Precision in Biomechanical Exposure Assessment: Making the Most of our Methods
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Insufficient exposure assessment is a suggested contributing factor to the current lack of clearly characterised relationships between occupational biomechanical risk factors and musculoskeletal disorders. Minimal attention has been paid to the potential bias of measurement tools from expected true values (i.e. accuracy) or between measurement tools, and empirical data on the magnitudes of variance contributed by methodological factors for measurement tool precision are lacking.

Aim: The aim of this thesis was to quantify aspects of bias and precision in three commonly employed biomechanical risk factor assessment tools - inclinometry, observation, and electromyography (EMG) - and provide recommendations guiding their use.

Methods: Upper arm elevation angles (UAEAs) were assessed using inclinometers (INC) and by computer-based posture-matching observation, and bias relative to true angles was calculated. Calibration models were developed for INC data, and their efficacy in correcting measurement bias was evaluated. The total variance of trapezius and erector spinae (ES) EMG recordings during cyclic occupational work was partitioned into biological and methodological sources, including the variance uniquely attributable to sub-maximal normalisation. Using algorithms to estimate the precision of a group mean, the efficacy of different trapezius EMG study designs was evaluated. Using precision criteria, the efficacy of different normalisation methods was assessed for ES EMG recordings.

Results and Discussion: Inclinometer measured UAEAs were biased from true angles, with increasing bias at higher angles. In contrast, computer based posture-matching observations were not biased from true angles.  Calibration models proved effective at minimizing INC data bias. The dispersion of estimates between- and within- observers at any given set angle underlined the importance of repeated observations when estimating UAEAs.  For EMG, a unique but relatively small component of the total variance was attributable to the methodological process of normalisation. Performing three repeats of the trapezius EMG normalisation task proved optimal at minimizing variance for one-day EMG studies, while two repeats sufficed for multi-day EMG studies. A prone normalisation task proved superior for maximizing normalised lumbar ES EMG precision.

Conclusion: Key aspects of measurement tool accuracy, bias between tools, and tool precision were quantified, and recommendations were made to guide future research study design.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 90 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1329
Keyword
measurement strategy, accuracy, inclinometry, electromyography, EMG, upper arm, shoulder, low back, lumbar, thoracic
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:uu:diva-314784 (URN)978-91-554-9902-0 (ISBN)
Public defence
2017-06-02, Krusenstjernasalen - Biblioteket, Högskolan i Gävle, Kungsbäcksvägen 47, 801 76, Gävle, 13:00 (English)
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Supervisors
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2009-1761
Available from: 2017-05-10 Created: 2017-04-07 Last updated: 2017-05-29

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