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Peripherally induced and anticipating elevator muscle activity during simulated chewing in humans
F A Ottenhoff1, A van der Bilt, H W van der Glas
1Department of Oral Pathophysiology, Faculty of Medicine, University of Utrecht, The Netherlands.
Journal of Neurophysiology
|January 1, 1992
Summary
The jaw muscles quickly adapt to changes in food resistance during chewing. Additional muscle activity (AMA) adjusts within two cycles when encountering or no longer encountering resistance.
Area of Science:
- Neuromuscular control
- Biomechanics of mastication
Background:
- Chewing requires minimal muscle activity for jaw movement but significant additional muscle activity (AMA) to overcome food resistance.
- Understanding the neuromuscular control of AMA is crucial for masticatory function.
Purpose of the Study:
- To investigate the neuromuscular control of additional muscle activity (AMA) during chewing with varying food resistance.
- To determine the adaptation rate of jaw muscles to the presence or absence of food resistance.
Main Methods:
- Subjects performed rhythmic jaw open-close movements synchronized with a metronome.
- External force simulated food resistance during closing movements, alternating unexpectedly with no-force cycles.
- Jaw movement and surface electromyography (EMG) of masseter, temporalis, and digastric muscles were recorded.
Main Results:
- Jaw movement trajectories adapted within two cycles after transitions between force and no-force conditions.
- In the first cycle with force, AMA onset was 129 ms after force onset.
- In subsequent cycles with force, AMA began 70 ms before force onset, increasing steeply after its start. In the first cycle without force, AMA started 69 ms before the expected force onset but was significantly reduced.
Conclusions:
- Jaw muscles demonstrate rapid adaptation to changes in mechanical load during chewing.
- The neuromuscular system adjusts predictive and reactive muscle activity to altered food resistance within two chewing cycles.