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Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task

Mathiassen, Svend Erik LU ; Moller, T and Forsman, M (2003) In Ergonomics 46(8). p.800-824
Abstract
Data on exposure variability is an important remedy for designing and interpreting studies of occupational ergonomics. The present study aimed at retrieving the within- and between-subjects variance of several mechanical exposure parameters in a repeated, short-cycle task. Seven experienced operators repeatedly secured joints using two types of hand-held nutrunners. The joints were placed in three different locations on a rack, simulating automotive assembly. Bilateral muscle activity from the upper trapezius and the lower arm extensors, as well as head and upper arm inclination was continuously monitored. Exposure levels and their variance components were assessed in several data subsets using ANOVA. The results were interpreted in terms... (More)
Data on exposure variability is an important remedy for designing and interpreting studies of occupational ergonomics. The present study aimed at retrieving the within- and between-subjects variance of several mechanical exposure parameters in a repeated, short-cycle task. Seven experienced operators repeatedly secured joints using two types of hand-held nutrunners. The joints were placed in three different locations on a rack, simulating automotive assembly. Bilateral muscle activity from the upper trapezius and the lower arm extensors, as well as head and upper arm inclination was continuously monitored. Exposure levels and their variance components were assessed in several data subsets using ANOVA. The results were interpreted in terms of statistical precision and power, and discussed as markers of important ergonomic qualities. A substantial exposure variability was found within and between subjects in all joint locations and for both tools. For mixed work across tools and locations, the necessary number of subjects to arrive at a group mean exposure with 95% confidence limits corresponding to +/- 10% of the mean ranged between 8 and 158, with posture recordings tending to require smaller populations than muscle activity recordings. Within-subject variance increased 2- to 37-fold, depending on exposure parameter, when work was 'enlarged' from securings with a specified location and tool to a mix of all locations and tools. Systematic differences between subjects in variability and responsiveness to 'work enlargement' indicated individualized motor control strategies. The results illustrate the importance of exposure variability data to the design of proper measurement strategies. They also suggest that the sizes of exposure variability per se can be interpreted as operational indices of what is thought to be important ergonomic risk indicators, such as the 'sameness' of repeated operations and the allowance for flexible working techniques. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
study design, statistical power, shoulder, neck, inclinometry, tools, hand-held, exposure variability, electromyography, arm, assembly work
in
Ergonomics
volume
46
issue
8
pages
800 - 824
publisher
Taylor & Francis
external identifiers
  • wos:000182886900003
  • pmid:12745980
  • scopus:0038053146
ISSN
0014-0139
DOI
language
English
LU publication?
yes
id
ab46fbb9-9c35-4e20-b339-a744deb75157 (old id 310956)
date added to LUP
2007-09-18 08:22:40
date last changed
2018-06-03 03:43:21
@article{ab46fbb9-9c35-4e20-b339-a744deb75157,
  abstract     = {Data on exposure variability is an important remedy for designing and interpreting studies of occupational ergonomics. The present study aimed at retrieving the within- and between-subjects variance of several mechanical exposure parameters in a repeated, short-cycle task. Seven experienced operators repeatedly secured joints using two types of hand-held nutrunners. The joints were placed in three different locations on a rack, simulating automotive assembly. Bilateral muscle activity from the upper trapezius and the lower arm extensors, as well as head and upper arm inclination was continuously monitored. Exposure levels and their variance components were assessed in several data subsets using ANOVA. The results were interpreted in terms of statistical precision and power, and discussed as markers of important ergonomic qualities. A substantial exposure variability was found within and between subjects in all joint locations and for both tools. For mixed work across tools and locations, the necessary number of subjects to arrive at a group mean exposure with 95% confidence limits corresponding to +/- 10% of the mean ranged between 8 and 158, with posture recordings tending to require smaller populations than muscle activity recordings. Within-subject variance increased 2- to 37-fold, depending on exposure parameter, when work was 'enlarged' from securings with a specified location and tool to a mix of all locations and tools. Systematic differences between subjects in variability and responsiveness to 'work enlargement' indicated individualized motor control strategies. The results illustrate the importance of exposure variability data to the design of proper measurement strategies. They also suggest that the sizes of exposure variability per se can be interpreted as operational indices of what is thought to be important ergonomic risk indicators, such as the 'sameness' of repeated operations and the allowance for flexible working techniques.},
  author       = {Mathiassen, Svend Erik and Moller, T and Forsman, M},
  issn         = {0014-0139},
  keyword      = {study design,statistical power,shoulder,neck,inclinometry,tools,hand-held,exposure variability,electromyography,arm,assembly work},
  language     = {eng},
  number       = {8},
  pages        = {800--824},
  publisher    = {Taylor & Francis},
  series       = {Ergonomics},
  title        = {Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task},
  url          = {http://dx.doi.org/},
  volume       = {46},
  year         = {2003},
}