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Published on: August 23, 2022
Premovement electromyographic silent period and α-motoneuron excitability
1Laboratory of Applied Physiology, The Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606, Japan.
Summary
Premovement silence (PMS) in electromyography (EMG) signals is linked to enhanced rapid force development during ballistic movements. This phenomenon may involve presynaptic inhibition and disfacilitation of spinal motoneurons.
Area of Science:
- Neurophysiology
- Motor Control
- Biomechanics
Background:
- Electromyography (EMG) signal silence, termed premovement silence (PMS), precedes ballistic movements.
- The underlying neurophysiological mechanisms of PMS and its relation to force production remain incompletely understood.
Purpose of the Study:
- To investigate the neurophysiological mechanisms of PMS preceding ballistic ankle plantar flexion.
- To determine the relationship between PMS and the maximal rate of force development.
- To explore the role of spinal α-motoneuron excitability during PMS.
Main Methods:
- Recorded EMG from agonist (LG, SO) and antagonist (TA) muscles, and force during rapid plantar flexion in 10 healthy volunteers.
- Utilized H-reflex analysis to assess spinal α-motoneuron pool excitability throughout movement execution.
- Compared subjects with and without clear PMS regarding force development and H-reflex modulation.
Main Results:
- Subjects with clear PMS exhibited a significantly greater maximal rate of force development (dF/dt).
- A significant decrease in H-reflex amplitude occurred ~40 ms before PMS, preceding force development by ~50-60 ms.
- Decreased H-reflex gain, alongside maintained surface EMG and motor unit activity changes, suggests presynaptic inhibition and/or disfacilitation during PMS.
Conclusions:
- PMS is associated with enhanced rapid force development, potentially via optimal motor unit synchrony.
- Presynaptic inhibition and/or disfacilitation are key mechanisms contributing to PMS during ballistic movements.
- Understanding PMS provides insights into motor control strategies for rapid, forceful actions.
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