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Teeth clenching reduces arm abduction force.
Hajime Sato1, Tsutomu Kawano, Mitsuru Saito
1Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Experimental Brain Research
|April 2, 2014
Summary
Teeth clenching reduces arm abduction force during isometric contractions by inhibiting the deltoid muscle stretch reflex. This effect is velocity-dependent and suggests a neural inhibition mechanism.
Area of Science:
- Neuroscience
- Human Physiology
- Biomechanics
Background:
- Previous studies suggest teeth clenching reduces 90° arm abduction force.
- The physiological mechanisms behind this inhibitory effect remain unclear.
Purpose of the Study:
- To quantify the difference in arm abduction force under teeth clenching versus non-clenching conditions.
- To investigate the underlying physiological mechanisms, including the stretch reflex in the deltoid muscle.
Main Methods:
- Participants performed arm abduction against fast and slow ramp loads under both clenching and non-clenching conditions.
- Maximal isometric contraction force (MICF) and maximal eccentric contraction force (MECF) were measured.
- The stretch reflex of the deltoid muscle was examined during teeth clenching.
Main Results:
- Teeth clenching significantly reduced MICF, an effect amplified by faster load velocities.
- No significant difference in MECF was observed between clenching and non-clenching conditions.
- Teeth clenching inhibited the deltoid muscle stretch reflex.
Conclusions:
- Teeth clenching inhibits arm abduction force primarily during the isometric phase.
- The observed inhibition is likely mediated by a neural mechanism, specifically the depression of deltoid motoneurone recruitment via presynaptic inhibition of spindle afferent inputs.
- Fatigue is unlikely to be a factor in the observed force reduction.
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