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  • 1.
    Jackson, Jennie A
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper. Högskolan i Gävle, Avdelningen för arbets- och folkhälsovetenskap.
    Bias and Precision in Biomechanical Exposure Assessment: Making the Most of our Methods2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

    Delarbeten
    1. Is what you see what you get?: Standard inclinometry of set upper arm elevation angles
    Öppna denna publikation i ny flik eller fönster >>Is what you see what you get?: Standard inclinometry of set upper arm elevation angles
    Visa övriga...
    2015 (Engelska)Ingår i: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 47, s. 242-252Artikel i tidskrift (Refereegranskat) Published
    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.

    Nyckelord
    Measurement error, Observation, Working postures
    Nationell ämneskategori
    Arbetsmedicin och miljömedicin
    Identifikatorer
    urn:nbn:se:uu:diva-245337 (URN)10.1016/j.apergo.2014.08.014 (DOI)000347663600028 ()25479994 (PubMedID)
    Tillgänglig från: 2015-03-03 Skapad: 2015-02-26 Senast uppdaterad: 2018-01-11Bibliografiskt granskad
    2. Observer performance in estimating upper arm elevation angles under ideal viewing conditions when assisted by posture matching software
    Öppna denna publikation i ny flik eller fönster >>Observer performance in estimating upper arm elevation angles under ideal viewing conditions when assisted by posture matching software
    2016 (Engelska)Ingår i: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 55, s. 208-215Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Selecting a suitable body posture measurement method requires performance indices of candidate tools. Such data are lacking for observational assessments made at a high degree of resolution. The aim of this study was to determine the performance (bias and between- and within-observer variance) of novice observers estimating upper arm elevation postures assisted by posture matching software to the nearest degree from still images taken under ideal conditions. Estimates were minimally biased from true angles: the mean error across observers was less than 2. Variance between observers was minimal. Considerable variance within observers, however, underlined the risk of relying on single observations. Observers were more proficient at estimating 0 and 90 postures, and less proficient at 60. Thus, under ideal visual conditions observers, on average, proved proficient at high resolution posture estimates; further investigation is required to determine how non-optimal image conditions, as would be expected from occupational data, impact proficiency.

    Nyckelord
    Measurement error, Working postures, Observation
    Nationell ämneskategori
    Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi
    Identifikatorer
    urn:nbn:se:uu:diva-300293 (URN)10.1016/j.apergo.2016.01.012 (DOI)000374074600021 ()26995050 (PubMedID)
    Forskningsfinansiär
    Forte, Forskningsrådet för hälsa, arbetsliv och välfärd, 2009-1761
    Tillgänglig från: 2016-08-08 Skapad: 2016-08-08 Senast uppdaterad: 2017-11-28Bibliografiskt granskad
    3. Methodological variance associated with normalization of occupational upper trapezius EMG using sub-maximal reference contractions
    Öppna denna publikation i ny flik eller fönster >>Methodological variance associated with normalization of occupational upper trapezius EMG using sub-maximal reference contractions
    2009 (Engelska)Ingår i: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 19, nr 3, s. 416-427Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    OBJECTIVES: To quantify the variance introduced to trapezius electromyography (EMG) through normalization by sub-maximal reference voluntary exertions (RVE), and to investigate the effect of increased normalization efforts as compared to other changes in data collection strategy on the precision of occupational EMG estimates.

    METHODS: Women performed four RVE contractions followed by 30 min of light, cyclic assembly work on each of two days. Work cycle EMG was normalized to each of the RVE trials and seven exposure parameters calculated. The proportions of exposure variance attributable to subject, day within subject, and cycle and normalization trial within day were determined. Using this data, the effect on the precision of the exposure mean of altering the number of subjects, days, cycles and RVEs during data collection was simulated.

    RESULTS: For all exposure parameters a unique component of variance due to normalization was present, yet small: less than 4.4% of the total variance. The resource allocation simulations indicated that marginal improvements in the precision of a group exposure mean would occur above three RVE repeats for EMG collected on one day, or beyond two RVEs for EMG collected on two or more days.

    Nationell ämneskategori
    Arbetsmedicin och miljömedicin
    Identifikatorer
    urn:nbn:se:uu:diva-314744 (URN)10.1016/j.jelekin.2007.11.004 (DOI)18155593 (PubMedID)
    Tillgänglig från: 2017-02-06 Skapad: 2017-02-06 Senast uppdaterad: 2018-01-13Bibliografiskt granskad
    4. Precision based guidelines for sub-maximal normalisation task selection for trunk extensor EMG
    Öppna denna publikation i ny flik eller fönster >>Precision based guidelines for sub-maximal normalisation task selection for trunk extensor EMG
    2017 (Engelska)Ingår i: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 37, s. 41-51Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Aim: The object of this study was to quantify the contribution of sub-maximal normalisation to the overall variance of exposure parameters describing erector spinae (ES) activity, and to provide guidelines for task selection which minimize methodological variance. Methods: ES EMG was measured from three locations (T9, L1 and L5 levels) on fifteen men performing a manual materials handling task in the laboratory on three separate days. Four repeats of each of eleven sub-maximal normalisation tasks (eight static, three dynamic) were collected, work data were normalised to each task and repeat, and exposure parameters calculated. The unique contribution of normalisation to the overall variance was determined for each task and exposure parameter using variance component analyses. Normalisation tasks were scored according to their relative contributions to the overall variance and coefficients of variation.

    Results: A prone task, similar to the Biering-Sørensen test posture, was the most repeatable for all electrode locations and across all exposure parameters. Thoracic level normalisation typically showed poorer repeatability than lumbar normalisation.

    Discussion: We recommend that future ES EMG studies employing sub-maximal normalisation utilise said prone task. An alternate normalisation task specific to thoracic level ES muscles may be warranted.

    Nyckelord
    Exposure variability, variance components, low back, lumbar, erector spinae
    Nationell ämneskategori
    Arbetsmedicin och miljömedicin
    Identifikatorer
    urn:nbn:se:uu:diva-314783 (URN)10.1016/j.jelekin.2017.07.001 (DOI)000415646600007 ()28918109 (PubMedID)
    Forskningsfinansiär
    Forte, Forskningsrådet för hälsa, arbetsliv och välfärd, 2009-1761]
    Tillgänglig från: 2017-01-20 Skapad: 2017-02-06 Senast uppdaterad: 2018-02-27Bibliografiskt granskad
  • 2.
    Jackson, Jennie A
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper. Högskolan i Gävle, Avdelningen för arbets- och folkhälsovetenskap.
    Mathiassen, Svend Erik
    Högskolan i Gävle, Avdelningen för arbets- och folkhälsovetenskap.
    Callaghan, Jack
    University of Waterloo, Department of Kinesiology.
    Dempsey, Patrick
    National Institute for Occupational Safety and Health, Pittsburgh.
    Precision based guidelines for sub-maximal normalisation task selection for trunk extensor EMG2017Ingår i: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 37, s. 41-51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aim: The object of this study was to quantify the contribution of sub-maximal normalisation to the overall variance of exposure parameters describing erector spinae (ES) activity, and to provide guidelines for task selection which minimize methodological variance. Methods: ES EMG was measured from three locations (T9, L1 and L5 levels) on fifteen men performing a manual materials handling task in the laboratory on three separate days. Four repeats of each of eleven sub-maximal normalisation tasks (eight static, three dynamic) were collected, work data were normalised to each task and repeat, and exposure parameters calculated. The unique contribution of normalisation to the overall variance was determined for each task and exposure parameter using variance component analyses. Normalisation tasks were scored according to their relative contributions to the overall variance and coefficients of variation.

    Results: A prone task, similar to the Biering-Sørensen test posture, was the most repeatable for all electrode locations and across all exposure parameters. Thoracic level normalisation typically showed poorer repeatability than lumbar normalisation.

    Discussion: We recommend that future ES EMG studies employing sub-maximal normalisation utilise said prone task. An alternate normalisation task specific to thoracic level ES muscles may be warranted.

  • 3.
    Jackson, Jennie A
    et al.
    Centre for Musculoskeletal Research, University of Gävle, SE-80176 Gävle, Sweden.
    Mathiassen, Svend Erik
    University of Gävle.
    Dempsey, Patrick G
    Methodological variance associated with normalization of occupational upper trapezius EMG using sub-maximal reference contractions2009Ingår i: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 19, nr 3, s. 416-427Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    OBJECTIVES: To quantify the variance introduced to trapezius electromyography (EMG) through normalization by sub-maximal reference voluntary exertions (RVE), and to investigate the effect of increased normalization efforts as compared to other changes in data collection strategy on the precision of occupational EMG estimates.

    METHODS: Women performed four RVE contractions followed by 30 min of light, cyclic assembly work on each of two days. Work cycle EMG was normalized to each of the RVE trials and seven exposure parameters calculated. The proportions of exposure variance attributable to subject, day within subject, and cycle and normalization trial within day were determined. Using this data, the effect on the precision of the exposure mean of altering the number of subjects, days, cycles and RVEs during data collection was simulated.

    RESULTS: For all exposure parameters a unique component of variance due to normalization was present, yet small: less than 4.4% of the total variance. The resource allocation simulations indicated that marginal improvements in the precision of a group exposure mean would occur above three RVE repeats for EMG collected on one day, or beyond two RVEs for EMG collected on two or more days.

  • 4.
    Jackson, Jennie A.
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Arbets- och miljömedicin. Univ Gavle, Dept Occupat & Publ Hlth Sci, Ctr Musculoskeletal Res, SE-80176 Gavle, Sweden..
    Mathiassen, Svend Erik
    Univ Gavle, Dept Occupat & Publ Hlth Sci, Ctr Musculoskeletal Res, SE-80176 Gavle, Sweden..
    Liv, Per
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centrum för klinisk forskning, Gävleborg. Univ Gavle, Dept Occupat & Publ Hlth Sci, Ctr Musculoskeletal Res, SE-80176 Gavle, Sweden..
    Observer performance in estimating upper arm elevation angles under ideal viewing conditions when assisted by posture matching software2016Ingår i: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 55, s. 208-215Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Selecting a suitable body posture measurement method requires performance indices of candidate tools. Such data are lacking for observational assessments made at a high degree of resolution. The aim of this study was to determine the performance (bias and between- and within-observer variance) of novice observers estimating upper arm elevation postures assisted by posture matching software to the nearest degree from still images taken under ideal conditions. Estimates were minimally biased from true angles: the mean error across observers was less than 2. Variance between observers was minimal. Considerable variance within observers, however, underlined the risk of relying on single observations. Observers were more proficient at estimating 0 and 90 postures, and less proficient at 60. Thus, under ideal visual conditions observers, on average, proved proficient at high resolution posture estimates; further investigation is required to determine how non-optimal image conditions, as would be expected from occupational data, impact proficiency.

  • 5.
    Jackson, Jennie A
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper. Högskolan i Gävle, Avdelningen för arbets- och folkhälsovetenskap.
    Mathiassen, Svend Erik
    Högskolan i Gävle, Avdelningen för arbets- och folkhälsovetenskap.
    Srinivasan, Divya
    Grado Department of Industrial and Systems Engineering, Virginia Polytechnic Institute and State University.
    Identification of individual working styles in a long-cycle assembly task using kinematic and EMG variables2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Background.Increased motor variability while performing repetitive tasks has been suggested to decrease the risk of developing musculoskeletal disorders. However, support for this positive effect is lacking outside of short, simple, highly controlled tasks. It is also currently unknown whether or not existing motor variability metrics are viable for characterising occupational tasks. The purpose of this study was to assess motor variability during a long-cycle simulated occupational task. Using metrics previously validated for short-cycle tasks, this study aimed to determine the extent to which: (1) individuals dif-fered in motor variability with respect to kinematics and/or EMG activation; (2) individual motor variability was consistent across days; and (3) kinematics and EMG motor variability were correlated.

    Methods.Following a stringent, three-day training regime, 15 females proved sufficiently proficient to participate. On two occasions, participants performed 36 cycles of an assembly task (combining gross and fine motor skills) at 110 MTM pacing (51 s per cycle). For each cycle, multiple upper arm kinematic and trapezius EMG summary mean and SD variables were calculated; for each variable, the variability across the 36 cycles was assessed. The relative size of variability across individuals, and the consistency of each individual’s motor behaviour across days were assessed using kinematic and EMG vari-ables. The correlation between kinematic and EMG variables was also assessed.

    Results.Distinct individual behaviours were observed across days: some participants were clearly more consistent in their motor behaviour than others. Further, a high correlation was found between some kinematic and muscle activation variables.

    Discussion. Using previously validated upper arm assessment metrics, we were able to differentiate between individuals performing a long-cycle assembly task based on their degree of motor variability. Given the nature of our study task, we believe the metrics that we found to be successful at identifying individual behaviours could be used for assessing field tasks.

  • 6. Jackson, Jennie A.
    et al.
    Mathiassen, Svend Erik
    Wahlstrom, Jens
    Liv, Per
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centrum för klinisk forskning, Gävleborg.
    Forsman, Mikael
    Is what you see what you get?: Standard inclinometry of set upper arm elevation angles2015Ingår i: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 47, s. 242-252Artikel i tidskrift (Refereegranskat)
    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.

1 - 6 av 6
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