Document Detail

Trunk extensor EMG-torque relationship.
MedLine Citation:
PMID:  3686232     Owner:  NLM     Status:  MEDLINE    
The integrated surface electromyogram (IEMG) of the lumbar erectores spinae and the torque generated were simultaneously recorded from 27 healthy subjects in the standing posture while they pulled isometrically against resistance provided by a harness around the shoulders. The IEMG-torque ratio (efficiency of electrical activity, or EEA) was used to characterize each subject. Individual recordings showed evidence of nonlinearity of the IEMG-torque relationship in that a statistically better fit to experimental recordings was obtained by using two straight lines with a breakpoint between them. However, with repeated testing, the gradients of these two lines were more variable than the slope of the single straight line fitted to the entire recording. The slope of the best fit line (EEA) was less for recordings made during torque decrease than for increasing-torque recordings. This also showed as a "hysteresis" pattern in the recordings. The coefficient of variability (within subjects) of the EEA was greater in day-to-day testing (24%) than with repeated pulls at the same testing session (14%). This was similar to variability of the maximum generated torque. About 25% of the variability between subjects was found to be due to anthropometric differences. The residual variability of the relationship would limit the accuracy of IEMG as a measure of muscular effort under changing torque conditions. However, the EEA may be useful for characterizing muscle performance, especially when maximum effort cannot be achieved.
I A Stokes; S Rush; M Moffroid; G B Johnson; L D Haugh
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Spine     Volume:  12     ISSN:  0362-2436     ISO Abbreviation:  Spine     Publication Date:  1987 Oct 
Date Detail:
Created Date:  1988-01-12     Completed Date:  1988-01-12     Revised Date:  2009-07-09    
Medline Journal Info:
Nlm Unique ID:  7610646     Medline TA:  Spine (Phila Pa 1976)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  770-6     Citation Subset:  IM    
Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington.
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MeSH Terms
Body Height
Body Weight
Electromyography / methods
Isometric Contraction
Lumbosacral Region / physiology
Muscles / physiology*

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