The use of flexible arm muscle synergies to perform an isometric stabilization task

Abstract Objective To evaluate if functional synergies are comprised of flexible combinations of a small number of ensembles of upper limb muscles to stabilize a particular performance variable during a force production task. Methods Electromyographic (EMG) signals of wrist, elbow and shoulder muscl...

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Bibliographic Details
Published in:Clinical neurophysiology 2007-03, Vol.118 (3), p.525-537
Main Authors: Krishnamoorthy, Vijaya, Scholz, John P, Latash, Mark L
Format: Article
Language:English
Subjects:
Adult
Arm - innervation
Arm - physiology
Balance
Biological and medical sciences
Electrodiagnosis. Electric activity recording
Electromyogram
Electromyography
Female
Fundamental and applied biological sciences. Psychology
Human
Humans
Investigative techniques, diagnostic techniques (general aspects)
Isometric Contraction - physiology
Male
Mathematics
Medical sciences
Movement - physiology
Muscle mode
Muscle synergy
Nervous system
Neurology
Posture - physiology
Principal component analysis
Psychomotor Performance
Striated muscle. Tendons
Task Performance and Analysis
Uncontrolled manifold
Variance
Vertebrates: osteoarticular system, musculoskeletal system
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Summary:Abstract Objective To evaluate if functional synergies are comprised of flexible combinations of a small number of ensembles of upper limb muscles to stabilize a particular performance variable during a force production task. Methods Electromyographic (EMG) signals of wrist, elbow and shoulder muscles were recorded. Linear combinations of indices of the integrated EMG of nine muscles (muscle modes or M-modes) and their relationship to changes in the moment of force produced by the right arm of subjects about the horizontal axis of a handle were first determined. Uncontrolled manifold (UCM) analysis was performed to determine the extent to which variance of the M-modes acted to produce a consistent change in the moment of force. Results Subjects exhibited three M-modes, two of which were ‘reciprocal’ while the third mode was considered a co-contraction mode. The three M-modes were found to be combined to form synergies that produced a consistent change in the moment of force across repetitive trials. Variance in the M-mode space that led to consistent changes in the moment of force across repetitions was significantly higher than variance that tended to produce inconsistent changes in the moment of force. Conclusions Flexible combinations of activations of ensembles of muscles are organized to stabilize the value of or produce consistent changes in the value of important performance variables. Significance The study of flexible muscle synergies in healthy individuals paves the way to understanding abnormal postural and movement patterns in individuals with neurological disorders.
ISSN:1388-2457
1872-8952
DOI:10.1016/j.clinph.2006.11.014