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Job enlargement and mechanical exposure variability in cyclic assembly work

Moller, T; Mathiassen, Svend Erik LU ; Franzon, H and Kihlberg, S (2004) In Ergonomics 47(1). p.19-40
Abstract
Cyclic assembly work is known to imply a high risk for musculoskeletal disorders. To have operators rotate between work tasks is believed to be one way of decreasing this risk, since it is expected to increase variation in mechanical and psychological exposures (physical and mental loads). This assumption was investigated by assessing mechanical exposure variability in three assembly tasks in an electronics assembly plant, each on a separate workstation, as well as in a 'job enlargement' scenario combining all three stations. Five experienced operators worked for 1 h on each station. Data on upper trapezius and forearm extensor muscle activity were obtained by means of electromyography (EMG), and working postures of the head and upper arms... (More)
Cyclic assembly work is known to imply a high risk for musculoskeletal disorders. To have operators rotate between work tasks is believed to be one way of decreasing this risk, since it is expected to increase variation in mechanical and psychological exposures (physical and mental loads). This assumption was investigated by assessing mechanical exposure variability in three assembly tasks in an electronics assembly plant, each on a separate workstation, as well as in a 'job enlargement' scenario combining all three stations. Five experienced operators worked for 1 h on each station. Data on upper trapezius and forearm extensor muscle activity were obtained by means of electromyography (EMG), and working postures of the head and upper arms were assessed by inclinometry. The cycle-to-cycle variance of parameters representing the three exposure dimensions: level , frequency and duration was estimated using ANOVA algorithms for each workstation separately as well as for a balanced combination of all three. For a particular station, the variability of trapezius EMG activity levels relative to the mean was higher than for extensor EMG: between-cycles coefficients of variation (CV) about 0.15 and 0.10, respectively. A similar relationship between CV applied to the parameter describing frequency of EMG activity. Except for head inclination levels, the between-cycles CV was larger for posture parameters than for EMG. The between-cycles variance increased up to six fold in the job enlargement scenario, as compared to working at only one station. The difference in mean exposure between workstations was larger for trapezius EMG parameters than for forearm extensor EMG and postures, and hence the effect of job enlargement on exposure variability was more pronounced for the trapezius. For some stations, job enlargement even implied less cycle-to-cycle variability in forearm extensor EMG parameters than working at that station only. Whether the changes in exposure variability associated with job enlargement were sufficient to imply a decreased risk for musculoskeletal disorders is not known. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
physical load, neck-shoulder, inclinometry, electronics assembly, electromyography, arm posture, cycle time, repetitiveness
in
Ergonomics
volume
47
issue
1
pages
19 - 40
publisher
Taylor & Francis
external identifiers
  • wos:000186928900002
  • scopus:17544392386
ISSN
0014-0139
DOI
10.1080/0014013032000121651
language
English
LU publication?
yes
id
d15e6f0c-4fd8-4e81-ad79-1ce1caf4feae (old id 293912)
date added to LUP
2007-10-26 17:00:08
date last changed
2017-10-01 03:45:56
@article{d15e6f0c-4fd8-4e81-ad79-1ce1caf4feae,
  abstract     = {Cyclic assembly work is known to imply a high risk for musculoskeletal disorders. To have operators rotate between work tasks is believed to be one way of decreasing this risk, since it is expected to increase variation in mechanical and psychological exposures (physical and mental loads). This assumption was investigated by assessing mechanical exposure variability in three assembly tasks in an electronics assembly plant, each on a separate workstation, as well as in a 'job enlargement' scenario combining all three stations. Five experienced operators worked for 1 h on each station. Data on upper trapezius and forearm extensor muscle activity were obtained by means of electromyography (EMG), and working postures of the head and upper arms were assessed by inclinometry. The cycle-to-cycle variance of parameters representing the three exposure dimensions: level , frequency and duration was estimated using ANOVA algorithms for each workstation separately as well as for a balanced combination of all three. For a particular station, the variability of trapezius EMG activity levels relative to the mean was higher than for extensor EMG: between-cycles coefficients of variation (CV) about 0.15 and 0.10, respectively. A similar relationship between CV applied to the parameter describing frequency of EMG activity. Except for head inclination levels, the between-cycles CV was larger for posture parameters than for EMG. The between-cycles variance increased up to six fold in the job enlargement scenario, as compared to working at only one station. The difference in mean exposure between workstations was larger for trapezius EMG parameters than for forearm extensor EMG and postures, and hence the effect of job enlargement on exposure variability was more pronounced for the trapezius. For some stations, job enlargement even implied less cycle-to-cycle variability in forearm extensor EMG parameters than working at that station only. Whether the changes in exposure variability associated with job enlargement were sufficient to imply a decreased risk for musculoskeletal disorders is not known.},
  author       = {Moller, T and Mathiassen, Svend Erik and Franzon, H and Kihlberg, S},
  issn         = {0014-0139},
  keyword      = {physical load,neck-shoulder,inclinometry,electronics assembly,electromyography,arm posture,cycle time,repetitiveness},
  language     = {eng},
  number       = {1},
  pages        = {19--40},
  publisher    = {Taylor & Francis},
  series       = {Ergonomics},
  title        = {Job enlargement and mechanical exposure variability in cyclic assembly work},
  url          = {http://dx.doi.org/10.1080/0014013032000121651},
  volume       = {47},
  year         = {2004},
}