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Mandibular Jaw Movement and Masticatory Muscle Activity during Dynamic Trunk Exercise
Daisuke Sugihara1, Misao Kawara1, Hiroshi Suzuki1
1Division of Oral Function and Rehabilitation, Department of Oral Health Science, Nihon University School of Dentistry at Matsudo, 870-1 Sakaecho, Nishi-2, Matsudo, Chiba 271-8587, Japan.
Dentistry Journal
|December 5, 2020
Summary
During strenuous exercise like deadlifts, the jaw (mandible) shifts to a unique braced position. Both jaw-opening and jaw-closing muscles contract simultaneously to stabilize it, a process termed bracing.
Area of Science:
- Biomechanics
- Exercise Physiology
- Dental Science
Background:
- Understanding jaw function during physical exertion is crucial.
- Current knowledge lacks a unified explanation for mandibular fixation during exercise.
Purpose of the Study:
- To investigate mandibular displacement and masticatory muscle activity during dynamic trunk exercise.
- To test the hypothesis that the mandible adopts a non-maximal intercuspal position and is stabilized by co-contracting muscles during forceful exertion.
Main Methods:
- Simultaneous recording of jaw movements and masticatory muscle electromyography.
- Analysis during a deadlift exercise in 24 healthy adult males.
- Categorization of the deadlift into Ready, Pull, and Down phases.
Main Results:
- The mandibular incisal point significantly moved posteroinferiorly during the Pull phase of the deadlift.
- Masticatory muscles (temporalis, masseter, digastric) exhibited simultaneous and significant activation.
- Muscle activity persisted during the Down phase, indicating sustained mandibular bracing.
Conclusions:
- Dynamic trunk force exertion causes mandibular displacement to a posteroinferior, open-mouth position.
- Simultaneous activation of mouth-opening and closing muscles stabilizes the mandible via bracing.
- This study elucidates a novel mechanism of mandibular fixation during intense physical activity.
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