Changes in motor unit recruitment strategy during pain alters force direction

Tucker, Kylie J. and Hodges, Paul W. (2010) Changes in motor unit recruitment strategy during pain alters force direction. European Journal of Pain, 14 9: 932-938. doi:10.1016/j.ejpain.2010.03.006

Author Tucker, Kylie J.
Hodges, Paul W.
Title Changes in motor unit recruitment strategy during pain alters force direction
Journal name European Journal of Pain   Check publisher's open access policy
ISSN 1090-3801
Publication date 2010-10
Sub-type Article (original research)
DOI 10.1016/j.ejpain.2010.03.006
Volume 14
Issue 9
Start page 932
End page 938
Total pages 7
Place of publication Kidlington, Oxford, U.K.
Publisher Elsevier
Collection year 2011
Language eng
Formatted abstract
Motor unit (MU) recruitment is altered (decreased discharge rate and cessation of discharge in some units, and recruitment of new units) in force-matched contractions during pain compared to contractions performed before pain. As MU’s within a motoneurone pool have different force direction properties we hypothesised that altered MU recruitment during experimental knee pain would change the force vector (total force (FT): amplitude and angle) generated by the quadriceps. Force was produced at two levels during 1 x 60-s and 3 x 10-s isometric contractions of knee extensors, and recorded by two force transducers at right angles. This enabled calculation of both FE (extension force) and FT. MU recruitment was recorded from the medial and lateral vastii with four fine-wire electrodes. Pain was induced by hypertonic saline injection in the infra-patella fat pad. Nine subjects matched FE and six subjects also matched both medial and lateral forces (FT) before and during pain. Changes in MU discharge pattern (decreased discharge rate (P < 0.001), complete cessation of firing, and recruitment of new units) during pain were associated with a ~5° change in absolute force angle. As force angle changed in both directions (left/right) for individual subjects with pain there was no change in average FT amplitude between conditions. When both medial and lateral forces were matched MU discharge rate decreased (P < 0.001) with pain, but, fewer units ceased firing or were newly recruited during pain. Change in motoneurone recruitment during pain alters direction of muscle force. This may be a strategy to avoid pain or protect the painful part.
© 2010 European Federation of International Association for the Study of Pain Chapters.
Published by Elsevier Ltd. All rights reserved.
Keyword Pain
Motor unit
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2011 Collection
School of Health and Rehabilitation Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 26 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 28 times in Scopus Article | Citations
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Created: Sun, 03 Oct 2010, 00:06:12 EST