Document Detail

Electromyography tension and frequency spectrum analysis of some masticatory muscles at rest, isotonic and isometric contractions.
MedLine Citation:
PMID:  10546079     Owner:  NLM     Status:  MEDLINE    
On a population of 52 subjects surface electromyographic recordings of temporals and masseters, simultaneously with mandible dynamic of closure and clenching, were performed, in order to study tension and frequency behaviour in three postural conditions: rest, isotonic and isometric contractions. Frequency was studied using the median resulting from FFT calculation, and a new computing method, which presents the proportion of frequencies making up the whole EMG signal, by steps of 50 Hz. Tension was calculated as well. The results permit us to draw the following conclusions: 1. a period of EMG silence was present in 51 of 52 subjects at mandible closure (SPA--Silent Period Area); 2. SPA onset was before teeth contact (22.5 msec., during the motion of the mandible), while its end was after closure (10.2 msec., during motionless phase of clenching). This allowed to use the SPA as a tool to clearly distinguish isotonic from isometric contraction; 3. the comparison of tension and frequency, expressed as median, showed that at rest a muscle presents low frequency and low tension. In active contraction both increase their values. Nevertheless, in active contraction, while no differences were found in frequency behaviour, tension showed a difference: although higher than at rest, isotonic contraction presented lower values than during isometric contraction; 4. the study performed by the new program showed that the low frequency at rest was due to the high proportion (30-40%) of frequencies of less than 50 Hz, while the increase at function was due to the parallel increase of frequencies comprised between 100 and 250 Hz. Because it is known that muscles are composed of fibers at low frequency and at high frequency of discharge, which play different functional roles, the last finding suggests that the mathematical analysis of the spectrum of frequencies, could provide a functional-histological image of the muscle.
L Bazzotti
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Electromyography and clinical neurophysiology     Volume:  39     ISSN:  0301-150X     ISO Abbreviation:  Electromyogr Clin Neurophysiol     Publication Date:    1999 Oct-Dec
Date Detail:
Created Date:  1999-12-10     Completed Date:  1999-12-10     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0327533     Medline TA:  Electromyogr Clin Neurophysiol     Country:  BELGIUM    
Other Details:
Languages:  eng     Pagination:  421-34     Citation Subset:  IM    
Department of Dentistry, C.H.U. University of Liège.
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MeSH Terms
Bite Force
Fourier Analysis
Isometric Contraction / physiology*
Masseter Muscle / innervation
Masticatory Muscles / innervation*
Middle Aged
Motor Neurons / physiology
Reference Values
Signal Processing, Computer-Assisted*
Temporal Muscle / innervation

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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