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rdf:type |
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lifeskim:mentions |
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pubmed:issue |
Pt 2
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pubmed:dateCreated |
2003-10-16
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pubmed:abstractText |
The activity pattern of low-threshold human trapezius motor units was examined in response to brief, voluntary increases in contraction amplitude ('EMG pulse') superimposed on a constant contraction at 4-7 % of the surface electromyographic (EMG) response at maximal voluntary contraction (4-7 % EMGmax). EMG pulses at 15-20 % EMGmax were superimposed every minute on contractions of 5, 10, or 30 min duration. A quadrifilar fine-wire electrode recorded single motor unit activity and a surface electrode recorded simultaneously the surface EMG signal. Low-threshold motor units recruited at the start of the contraction were observed to stop firing while motor units of higher recruitment threshold stayed active. Derecruitment of a motor unit coincided with the end of an EMG pulse. The lowest-threshold motor units showed only brief silent periods. Some motor units with recruitment threshold up to 5 % EMGmax higher than the constant contraction level were recruited during an EMG pulse and kept firing throughout the contraction. Following an EMG pulse, there was a marked reduction in motor unit firing rates upon return of the surface EMG signal to the constant contraction level, outlasting the EMG pulse by 4 s on average. The reduction in firing rates may serve as a trigger to induce derecruitment. We speculate that the silent periods following derecruitment may be due to deactivation of non-inactivating inward current ('plateau potentials'). The firing behaviour of trapezius motor units in these experiments may thus illustrate a mechanism and a control strategy to reduce fatigue of motor units with sustained activity patterns.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-10096844,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-1018273,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-10400978,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-10501799,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-10747207,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-11160531,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-11219764,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-11287499,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-11351010,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-11698507,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-11744225,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-11929906,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-12071492,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-12205139,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-13969854,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-2358878,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-2750539,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-3267153,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-4135549,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-499395,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-6204844,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-7084949,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-7143247,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-7279310,
http://linkedlifedata.com/resource/pubmed/commentcorrection/14561844-9772258
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:status |
MEDLINE
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pubmed:month |
Oct
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pubmed:issn |
0022-3751
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:day |
15
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pubmed:volume |
552
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
645-56
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:14561844-Adult,
pubmed-meshheading:14561844-Electromyography,
pubmed-meshheading:14561844-Electrophysiology,
pubmed-meshheading:14561844-Female,
pubmed-meshheading:14561844-Humans,
pubmed-meshheading:14561844-Male,
pubmed-meshheading:14561844-Middle Aged,
pubmed-meshheading:14561844-Motor Neurons,
pubmed-meshheading:14561844-Muscle, Skeletal,
pubmed-meshheading:14561844-Muscle Contraction,
pubmed-meshheading:14561844-Muscle Fatigue,
pubmed-meshheading:14561844-Muscle Fibers, Skeletal,
pubmed-meshheading:14561844-Recruitment, Neurophysiological
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pubmed:year |
2003
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pubmed:articleTitle |
Motor unit recruitment and derecruitment induced by brief increase in contraction amplitude of the human trapezius muscle.
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pubmed:affiliation |
Department of Industrial Economics and Technology Management, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
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pubmed:publicationType |
Journal Article,
Clinical Trial,
Research Support, Non-U.S. Gov't
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