Firing patterns of low-threshold trapezius motor units in feedback-controlled contractions and vocational motor activities

The study aimed to examine firing patterns of low-threshold trapezius motor units, with attention given to motor unit recruitment threshold. Different motor tasks were explored: shoulder elevation, arm movement in typing, and the motor response to mental stress. Contraction amplitudes in the range f...

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Bibliographic Details
Published in:Experimental brain research 2004-10, Vol.158 (4), p.465-473
Main Authors: WESTAD, C, MORK, P. J, WESTGAARD, R. H
Format: Article
Language:English
Subjects:
Action Potentials - physiology
Adult
Analysis of Variance
Biological and medical sciences
Feedback
Feedback - physiology
Female
Fundamental and applied biological sciences. Psychology
Humans
Male
Middle Aged
Motor Activity - physiology
Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration
Muscle Contraction - physiology
Muscle function
Muscle, Skeletal - physiology
Shoulder
Vertebrates: nervous system and sense organs
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Summary:The study aimed to examine firing patterns of low-threshold trapezius motor units, with attention given to motor unit recruitment threshold. Different motor tasks were explored: shoulder elevation, arm movement in typing, and the motor response to mental stress. Contraction amplitudes in the range from 1 to 10% of the surface electromyographic (SEMG) signal at maximal voluntary contraction (1-10% EMGmax) were studied, representing the range of trapezius muscle activity commonly observed in daily living. Single motor unit activity was recorded by a quadrifilar fine-wire electrode. A surface electrode simultaneously recorded the SEMG signal. Low-threshold motor units showed a small increase in mean firing rate, from 10.5 to 12.5 pulses per second ( p
ISSN:0014-4819
1432-1106
DOI:10.1007/s00221-004-1925-y