title: Activation deficit correlates with weakness in chronic stroke: evidence from evoked and voluntary EMG recordings.
abstract: OBJECTIVE
  To use evoked (M-wave) and voluntary (during maximal voluntary contraction (MVC)) EMG recordings to estimate the voluntary activation level in chronic stroke.
  
  
  METHODS
  Nine chronic hemiparetic stroke subjects participated in the experiment. M-wave (EMGM-wave) and MVC (EMGMVC) EMG values of the biceps brachii muscles were recorded.
  
  
  RESULTS
  Peak torque was significantly smaller on the impaired than non-impaired side. EMGM-wave was also significantly smaller on the impaired than non-impaired side. However, the normalized EMGM-wave/TorqueMVC ratio was not significantly different between two sides. In contrast, both absolute EMGMVC and normalized EMGMVC/TorqueMVC were smaller on the impaired than non-impaired side. The voluntary activation level, EMGMVC/M-wave, was also smaller on the impaired than non-impaired side. The voluntary activation level on the impaired side was highly correlated with weakness (R=0.72), but very low (R=0.32) on the non-impaired side.
  
  
  CONCLUSIONS
  Collectively, our findings suggest that both peripheral and central factors contribute to post-stroke weakness, but activation deficit correlates most closely with weakness as estimated from maximum voluntary torque generation.
  
  
  CONCLUSIONS
  These findings serve to highlight the potential benefit from high-intensity exercises to enhance central activation for facilitation of motor recovery.
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Neurorehabilitation Research Laboratory, TIRR Memorial Hermann Hospital, Houston, TX 77030, United States. Electronic address: sheng.li@uth.tmc.edu.
authors.forename: Sheng
authors.initials: S
authors.lastname: Li
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, United States.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Neurorehabilitation Research Laboratory, TIRR Memorial Hermann Hospital, Houston, TX 77030, United States.
authors.forename: Minal
authors.initials: M
authors.lastname: Bhadane
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Biomedical Engineering Program, University of Science and Technology of China, Hefei, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, United States.
authors.forename: W Zev
authors.initials: WZ
authors.lastname: Rymer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001132:Arm / Q000503:physiopathology; D002908:Chronic Disease; D004576:Electromyography / Q000379:methods*; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000175:diagnosis* / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology*
keywords: EMG; M-wave; Stroke; Voluntary activation; Weakness
references.citation: J Neuroeng Rehabil. 2013 Jan 21;10:1
references.pmid: 23336711
references.citation: Physiol Meas. 2013 Mar;34(3):315-24
references.pmid: 23399865
references.citation: Physiol Meas. 2011 Oct;32(10):1591-603
references.pmid: 21878708
references.citation: Muscle Nerve. 2013 Dec;48(6):971-6
references.pmid: 23494851
references.citation: Am J Phys Med Rehabil. 2012 May;91(5):393-400
references.pmid: 22357133
references.citation: Clin Neurophysiol. 2005 Jul;116(7):1566-70
references.pmid: 15905127
references.citation: J Appl Physiol (1985). 2010 Nov;109(5):1337-46
references.pmid: 20724561
references.citation: Am J Phys Med Rehabil. 2009 Apr;88(4):286-91
references.pmid: 19190483
references.citation: J Appl Physiol (1985). 2009 Jul;107(1):355-7; discussion 357-8
references.pmid: 19567806
references.citation: Sensors (Basel). 2010;10(1):796-807
references.pmid: 22315569
references.citation: Arch Phys Med Rehabil. 2006 Sep;87(9):1262-9
references.pmid: 16935065
references.citation: Muscle Nerve. 2000 Mar;23(3):376-84
references.pmid: 10679714
references.citation: Muscle Nerve. 2013 Jul;48(1):85-92
references.pmid: 23605647
references.citation: Eur J Appl Physiol. 2011 Dec;111(12):3041-9
references.pmid: 21455614
references.citation: Clin Biomech (Bristol, Avon). 2012 Mar;27(3):268-72
references.pmid: 22033224
references.citation: J Neuroeng Rehabil. 2005 Dec 06;2:33
references.pmid: 16332261
references.citation: Exp Brain Res. 2011 Oct;214(2):303-15
references.pmid: 21847644
references.citation: Muscle Nerve. 1998 Mar;21(3):318-28
references.pmid: 9486860
references.citation: Exp Brain Res. 2013 Mar;225(1):93-104
references.pmid: 23196803
references.citation: Clin Neurophysiol. 2008 Nov;119(11):2555-8
references.pmid: 18809353
references.citation: Muscle Nerve. 2005 May;31(5):535-51
references.pmid: 15714510
references.citation: Clin Neurophysiol. 2009 Aug;120(8):1539-42
references.pmid: 19564129
references.citation: Muscle Nerve. 1997 Sep;20(9):1187-90
references.pmid: 9270679
references.citation: Nat Rev Neurol. 2013 Dec;9(12):698-707
references.pmid: 24217509
references.citation: NeuroRehabilitation. 2014;34(2):381-9
references.pmid: 24419021
references.citation: Sports Med. 2004;34(4):253-67
references.pmid: 15049717
references.citation: Motor Control. 2013 Jul;17(3):283-97
references.pmid: 23761424