Long-term training effects on masticatory muscles.

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Neuromuscular adaptations are well-studied in skeletal muscles for rehabilitation.
• The masticatory system's motor adaptation remains under-researched.
• Understanding jaw muscle adaptation is crucial for motor rehabilitation and understanding masticatory function.

Purpose of the Study:

• To evaluate and compare long-term training effects of different motor tasks on masseter and temporal muscles.
• To investigate the adaptability of the masticatory system to specific motor demands.
• To determine if complex coordination tasks induce greater adaptation than maximal voluntary clenching or chewing.

Main Methods:

• Electromyographic (EMG) responses of masseter and temporal muscles were recorded in 20 healthy subjects.
• Subjects performed unilateral/bilateral maximum voluntary tooth clenching, mandibular balancing under force-feedback, and unilateral chewing.
• Measurements were taken at baseline and at 2 and 10 weeks to assess long-term training effects.

Main Results:

• No significant training effects were observed for maximum biting (MB) tasks, except for transient avoidance behavior in one condition.
• Chewing tests showed no significant changes in muscle activity over the training period.
• Coordination tasks (CT) demonstrated robust, significant long-term adaptation, reducing EMG activity by ~20% at 2 weeks and ~40% at 10 weeks.

Conclusions:

• Masticatory muscles exhibit significant motor adaptation, particularly when engaged in demanding coordination tasks.
• The degree of adaptation is task-dependent, with complex coordination tasks yielding more pronounced effects than simpler tasks.
• Findings suggest potential for targeted motor training protocols to modulate masticatory muscle activity.