title: Is what you see what you get? Standard inclinometry of set upper arm elevation angles.
abstract: 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° and 150°. 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 60°. INC data adjusted using the regression models were superior to unadjusted data; a subject-specific, two-point calibration based on measurements at 0° and 90° 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.
authors.affiliation: Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, SE-80176 Gävle, Sweden. Electronic address: jennie.jackson@hig.se.
authors.forename: Jennie A
authors.initials: JA
authors.lastname: Jackson
authors.affiliation: Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, SE-80176 Gävle, Sweden. Electronic address: svenderik.mathiassen@hig.se.
authors.forename: Svend Erik
authors.initials: SE
authors.lastname: Mathiassen
authors.affiliation: Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, SE-80176 Gävle, Sweden; Department of Public Health & Clinical Medicine, Occupational and Environmental Medicine, Umeå University, SE-901 85 Umeå, Sweden. Electronic address: jens.wahlstrom@envmed.umu.se.
authors.forename: Jens
authors.initials: J
authors.lastname: Wahlström
authors.affiliation: Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, SE-80176 Gävle, Sweden; Centre for Research and Development, Uppsala University/County Council of Gävleborg, SE-801 88 Gävle, Sweden. Electronic address: per.liv@lg.se.
authors.forename: Per
authors.initials: P
authors.lastname: Liv
authors.affiliation: Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, SE-80176 Gävle, Sweden; Institute of Environmental Medicine, Karolinska Institutet, SE-171 77 Stockholm, Sweden. Electronic address: mikael.forsman@ki.se.
authors.forename: Mikael
authors.initials: M
authors.lastname: Forsman
mesh_terms: D000328:Adult; D053587:Arthrometry, Articular / Q000295:instrumentation*; D015982:Bias; D001696:Biomechanical Phenomena; D002138:Calibration; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016272:Occupational Health; D011187:Posture; D012785:Shoulder Joint / Q000502:physiology*; D034941:Upper Extremity / Q000502:physiology*
keywords: Measurement error; Observation; Working postures