Document Detail

The dynamic response of the cat ankle joint during load-moving contractions.
MedLine Citation:
PMID:  7729837     Owner:  NLM     Status:  MEDLINE    
The dynamic response of the cat's ankle joint during load-moving activation of the medial gastrocnemius was determined. Sinusoidal-input oscillations of ankle plantar flexion were performed by the muscle at frequencies ranging from 0.4 to 5 Hz against a 10-N load acting via a cable through a pulley with a 2 cm radius. This was followed by sinusoidal muscle length changes against the same load while excluding the joint. The frequency responses of the two conditions were compared and decomposed in terms of their relative phase and gain, and best-fit pole-zero models to yield the dynamic model of the joint isolated from the muscle properties. The muscle displacement transfer function M(j omega) was characterized as two sets of double poles at 2.1 and 3.2 Hz, with a pair of zeros at 0.92 and 20 Hz, and pure time delay of 8 mS. The joint model J(j omega) was obtained by adding a pole at 5 Hz and a zero at 13 Hz. It was concluded that the ankle joint acts as a lag system, introducing significant increase in the phase lag between stimulus input and mechanical output without affecting the frequency-dependent attenuation of gain. Average harmonic distortion was less than 5% in all cases. This particular finding reveals that, despite its inherently nonlinear mechanical characteristics, the joint introduces no degradation in the simplified linear behavior of the muscle-joint system. This model is useful in the design of systems employing electrical stimulation to restore movement to limbs paralyzed by spinal cord injury or stroke.(ABSTRACT TRUNCATED AT 250 WORDS)
B H Zhou; R V Baratta; M Solomonow; R D D'Ambrosia
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  IEEE transactions on bio-medical engineering     Volume:  42     ISSN:  0018-9294     ISO Abbreviation:  IEEE Trans Biomed Eng     Publication Date:  1995 Apr 
Date Detail:
Created Date:  1995-06-01     Completed Date:  1995-06-01     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0012737     Medline TA:  IEEE Trans Biomed Eng     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  386-93     Citation Subset:  IM; S    
Department of Orthopaedic Surgery, Louisiana State University Medical Center, New Orleans 70112, USA.
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MeSH Terms
Ankle Joint / physiology*
Electric Stimulation / methods
Linear Models
Models, Neurological
Muscle Contraction / physiology*
Muscle, Skeletal / physiology*
Weight-Bearing / physiology

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

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