PMID- 20378379
OWN - NLM
STAT- MEDLINE
DCOM- 20110620
LR  - 20220318
IS  - 1532-2149 (Electronic)
IS  - 1090-3801 (Linking)
VI  - 14
IP  - 9
DP  - 2010 Oct
TI  - Changes in motor unit recruitment strategy during pain alters force direction.
PG  - 932-8
LID - 10.1016/j.ejpain.2010.03.006 [doi]
AB  - 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 (F(T)): 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 F(E) (extension force) and 
      F(T). 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 F(E) and six subjects also matched 
      both medial and lateral forces (F(T)) 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  approximately 5 degrees  
      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 
      F(T) 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.
CI  - Copyright (c) 2010 European Federation of International Association for the Study 
      of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
FAU - Tucker, Kylie J
AU  - Tucker KJ
AD  - The University of Queensland, NHMRC Centre of Clinical Research Excellence in 
      Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, 
      Australia. k.tucker1@uq.edu.au
FAU - Hodges, Paul W
AU  - Hodges PW
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20100407
PL  - England
TA  - Eur J Pain
JT  - European journal of pain (London, England)
JID - 9801774
SB  - IM
MH  - Adult
MH  - Female
MH  - Humans
MH  - Male
MH  - Muscle Contraction/*physiology
MH  - Muscle Fibers, Skeletal/*physiology
MH  - Muscle Strength/*physiology
MH  - Muscle Weakness/etiology/*physiopathology
MH  - Muscle, Skeletal/innervation/*physiopathology
MH  - Neuromuscular Junction/*physiopathology
MH  - Pain/*complications/*physiopathology
MH  - Young Adult
EDAT- 2010/04/10 06:00
MHDA- 2011/06/21 06:00
CRDT- 2010/04/10 06:00
PHST- 2009/11/24 00:00 [received]
PHST- 2010/02/22 00:00 [revised]
PHST- 2010/03/13 00:00 [accepted]
PHST- 2010/04/10 06:00 [entrez]
PHST- 2010/04/10 06:00 [pubmed]
PHST- 2011/06/21 06:00 [medline]
AID - S1090-3801(10)00055-8 [pii]
AID - 10.1016/j.ejpain.2010.03.006 [doi]
PST - ppublish
SO  - Eur J Pain. 2010 Oct;14(9):932-8. doi: 10.1016/j.ejpain.2010.03.006. Epub 2010 
      Apr 7.