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Methods to Quantify Pharmacologically Induced Alterations in Motor Function in Human Incomplete SCI
Published on: April 18, 2011
Interaction between transient change in local muscle structure and segmented leg motor responses
Raymond K Y Chong1, Manh Cuong Do
1Department of Physical Therapy, Medical College of Georgia, CH-100, Augusta, GA 30912-0800, USA. rchong@pebbles.mcg.edu
Perceptual and Motor Skills
|October 9, 2002
Summary
A prolonged muscle stretch altered reflex responses to balance disturbances. Specifically, it reduced the amplitude of monosynaptic reflexes but not automatic reflexes, indicating greater supraspinal influence on automatic responses.
Area of Science:
- Neuroscience
- Human Physiology
- Biomechanics
Background:
- Muscle stretch reflexes are crucial for maintaining balance.
- The gastrocnemius muscle's response to support surface rotations involves both monosynaptic and automatic components.
- Local muscle fiber changes may influence reflex pathways.
Purpose of the Study:
- To investigate how a transient change in gastrocnemius muscle structure affects motor responses to support surface rotations.
- To differentiate the influence of local muscle events on monosynaptic versus automatic reflex components.
Main Methods:
- Healthy young subjects were divided into a prestretch group and a control group.
- The prestretch group's gastrocnemius muscle underwent a 2-minute isometric stretch before support surface rotations.
- Medial gastrocnemius and tibialis anterior muscle responses were analyzed for amplitude and onset latency.
Main Results:
- Prestretching significantly reduced the amplitude of the monosynaptic response in the medial gastrocnemius muscle.
- The automatic component of the medial gastrocnemius response was not significantly affected by prestretching.
- Tibialis anterior muscle response and response latencies remained unchanged.
Conclusions:
- The monosynaptic response (Ia afferent mediated) is more susceptible to local muscle changes than the automatic response (II afferent mediated).
- The automatic component of the muscle response to rotation likely involves greater supraspinal processing.
- Prolonged stretching primarily impacts spinal reflex pathways rather than higher brain center involvement in balance control.
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