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Force and Position Control in Humans - The Role of Augmented Feedback
Published on: June 19, 2016
Evidence for positive force feedback during involuntary aftercontractions
Amy Parkinson1, Martin McDonagh
1Applied Physiology Research Group, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham , UK. m.j.mcdonagh@bham.ac.uk
Experimental Brain Research
|January 20, 2006
Summary
Muscle aftercontractions in the deltoid muscle are influenced by arm loading. Increased loading leads to a linear rise in EMG amplitude, suggesting positive load feedback mechanisms in automatic postural control.
Area of Science:
- Neuroscience
- Human Motor Control
- Biomechanics
Background:
- Involuntary muscle aftercontractions offer insights into automatic postural control.
- Previous studies linked deltoid aftercontraction strength to body inclination.
- The role of gravitational arm loading in this response was unclear.
Purpose of the Study:
- To investigate the effect of varying arm loading on deltoid muscle aftercontractions.
- To determine if gravitational load, not just body inclination, influences aftercontraction strength.
- To explore the underlying mechanisms, specifically positive load feedback.
Main Methods:
- Subjects performed voluntary contractions followed by involuntary aftercontractions.
- Arm loading was manipulated using a counter-lever apparatus (0%, 25%, 50%, 75%, 100% of normal weight).
- Electromyography (EMG) amplitude of the deltoid aftercontraction was measured with head stationary.
Main Results:
- EMG amplitude of deltoid aftercontractions showed a linear dependence on arm loading.
- Aftercontraction EMG amplitude at 100% load was 2.7 times greater than at 0% load.
- This suggests gravitational load is a key factor, not solely body inclination.
Conclusions:
- Automatic postural control of the upper limb is significantly influenced by positive load feedback.
- The deltoid muscle's involuntary response is modulated by the mechanical load it experiences.
- Findings contribute to understanding sensorimotor control in humans and animals.
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