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Myosin heavy chain isoforms influence surface EMG parameters: a study of the trapezius muscle in cleaners with and without myalgia and in healthy teachers.

Larsson, Britt LU ; Andersen, Jesper L; Kadi, Fawzi; Björk, Jonas LU and Gerdle, Björn (2002) In European Journal of Applied Physiology1999-01-01+01:00 87(6). p.481-488
Abstract
The present study had two aims: (1) to investigate potential differences in proportion of myosin heavy chain isoforms in the trapezius muscle between female cleaners with and without trapezius myalgia and healthy teachers, and (2) to elucidate if myosin heavy chain composition and surface electromyogram (EMG) during an isokinetic endurance test of shoulder flexors are significantly related. The subjects were divided into three groups: (1) 25 female cleaners with diagnosed work-related trapezius myalgia; (2) 25 female cleaners without work-related trapezius myalgia; (3) a control group of 21 healthy female teachers who were not exposed to repetitive or static muscle work. All subjects performed a test involving150 forward flexions using an... (More)
The present study had two aims: (1) to investigate potential differences in proportion of myosin heavy chain isoforms in the trapezius muscle between female cleaners with and without trapezius myalgia and healthy teachers, and (2) to elucidate if myosin heavy chain composition and surface electromyogram (EMG) during an isokinetic endurance test of shoulder flexors are significantly related. The subjects were divided into three groups: (1) 25 female cleaners with diagnosed work-related trapezius myalgia; (2) 25 female cleaners without work-related trapezius myalgia; (3) a control group of 21 healthy female teachers who were not exposed to repetitive or static muscle work. All subjects performed a test involving150 forward flexions using an isokinetic dynamometer. During the test surface EMG was recorded from the trapezius muscle. Muscle samples were obtained from the descending part of the trapezius muscle. The fibre type area percentage based on ATPase staining and the proportions of different MHC isoforms as determined by gel electrophoresis. The trapezius was dominated by MHC I (71%), followed by MHC IIA (22-24%), and MHC IIX (5-7%); no significant differences between the three groups of subjects were found. The proportion of MHC I correlated negatively with MHC IIA ( r=-0.78; P<0.001) and MHC IIX ( r=-0.53; P<0.001). Significant correlations existed between the proportion of the MHC isoforms and the corresponding proportion of the fibre type area; 27-45% of the variance was explained. The multivariate analysis of the three groups of subjects revealed that MHC variables showed intercorrelations with EMG (both amplitude and frequency variables). However, the directions of the relationships differed among the three groups; the cleaners with myalgia and the teachers showed the greatest similarities in patterns. Intrinsic muscle properties appear to influence the frequency content of the EMG, which is in contrast to some of the theoretical models of the EMG. Our data could suggest that monotonous work such as professional cleaning can change the relationships between muscle structure and the frequency content of the EMG. (Less)
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author
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type
Contribution to journal
publication status
published
subject
in
European Journal of Applied Physiology1999-01-01+01:00
volume
87
issue
6
pages
481 - 488
publisher
Springer
external identifiers
  • pmid:12355186
  • wos:000178830700002
  • scopus:12244261622
ISSN
1439-6327
DOI
10.1007/s00421-002-0667-4
language
English
LU publication?
yes
id
36f02c1f-9bdc-49b0-aa05-460bf35b637a (old id 110846)
alternative location
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12355186&dopt=Abstract
date added to LUP
2007-07-12 09:35:48
date last changed
2017-07-02 03:33:55
@article{36f02c1f-9bdc-49b0-aa05-460bf35b637a,
  abstract     = {The present study had two aims: (1) to investigate potential differences in proportion of myosin heavy chain isoforms in the trapezius muscle between female cleaners with and without trapezius myalgia and healthy teachers, and (2) to elucidate if myosin heavy chain composition and surface electromyogram (EMG) during an isokinetic endurance test of shoulder flexors are significantly related. The subjects were divided into three groups: (1) 25 female cleaners with diagnosed work-related trapezius myalgia; (2) 25 female cleaners without work-related trapezius myalgia; (3) a control group of 21 healthy female teachers who were not exposed to repetitive or static muscle work. All subjects performed a test involving150 forward flexions using an isokinetic dynamometer. During the test surface EMG was recorded from the trapezius muscle. Muscle samples were obtained from the descending part of the trapezius muscle. The fibre type area percentage based on ATPase staining and the proportions of different MHC isoforms as determined by gel electrophoresis. The trapezius was dominated by MHC I (71%), followed by MHC IIA (22-24%), and MHC IIX (5-7%); no significant differences between the three groups of subjects were found. The proportion of MHC I correlated negatively with MHC IIA ( r=-0.78; P&lt;0.001) and MHC IIX ( r=-0.53; P&lt;0.001). Significant correlations existed between the proportion of the MHC isoforms and the corresponding proportion of the fibre type area; 27-45% of the variance was explained. The multivariate analysis of the three groups of subjects revealed that MHC variables showed intercorrelations with EMG (both amplitude and frequency variables). However, the directions of the relationships differed among the three groups; the cleaners with myalgia and the teachers showed the greatest similarities in patterns. Intrinsic muscle properties appear to influence the frequency content of the EMG, which is in contrast to some of the theoretical models of the EMG. Our data could suggest that monotonous work such as professional cleaning can change the relationships between muscle structure and the frequency content of the EMG.},
  author       = {Larsson, Britt and Andersen, Jesper L and Kadi, Fawzi and Björk, Jonas and Gerdle, Björn},
  issn         = {1439-6327},
  language     = {eng},
  number       = {6},
  pages        = {481--488},
  publisher    = {Springer},
  series       = {European Journal of Applied Physiology1999-01-01+01:00},
  title        = {Myosin heavy chain isoforms influence surface EMG parameters: a study of the trapezius muscle in cleaners with and without myalgia and in healthy teachers.},
  url          = {http://dx.doi.org/10.1007/s00421-002-0667-4},
  volume       = {87},
  year         = {2002},
}