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Quantification of intrinsic and reflexive properties during multijoint arm posture
Erwin de Vlugt1, Alfred C Schouten, Frans C T van der Helm
1Biomechanical Engineering, Department of Mechanical Engineering, Delft University of Technology, Mekelweg 2, 2628CD Delft, South Holland, The Netherlands. e.devlugt@3me.tudelft.nl
Journal of Neuroscience Methods
|March 1, 2006
Summary
This study reveals how the nervous system controls muscle properties during arm posture. Reflexive feedback is key for shoulder muscles, with properties adjusted at the joint level, not the endpoint.
Area of Science:
- Biomechanics
- Neuroscience
- Human Motor Control
Background:
- Understanding muscle control is crucial for human movement.
- Previous studies focused on single joints, limiting insights into multi-joint coordination.
- The nervous system's role in adapting muscle properties remains incompletely understood.
Purpose of the Study:
- To estimate intrinsic and reflexive properties of single- and two-joint muscles around the shoulder, elbow, and wrist during posture maintenance.
- To investigate how the nervous system modifies these properties under varying conditions.
- To introduce a novel method for quantifying muscle property parameters.
Main Methods:
- Applied external force disturbances to the hand during posture maintenance tasks.
- Varied external damping, disturbance power, and arm configuration.
- Introduced a new identification method to quantify intrinsic, activation, and reflexive properties, including afferent feedback gains.
Main Results:
- Consistent estimates for reflex pathway gains were obtained.
- Shoulder muscles exhibited minimal intrinsic visco-elasticity but the largest reflexive feedback.
- Reflex gains remained consistent across different experimental conditions, unlike in single-joint studies.
Conclusions:
- Intrinsic and reflexive properties of two-joint muscles were greater than those of single-joint muscles.
- Mechanical properties are efficiently controlled at the joint level during multi-joint posture maintenance.
- Nervous system adaptation of reflex gains was not observed under the tested conditions for multi-joint tasks.
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