The relationship between masseter force and masseter electromyogram during mastication in the monkey Macaca...

Area of Science:

• Biomechanics
• Neuroscience
• Physiology

Background:

• Understanding the relationship between muscle electrical activity and force production is crucial for studying mastication.
• Electromyography (EMG) is a common method for assessing muscle activation, but its correlation with actual muscle force requires precise quantification.

Purpose of the Study:

• To investigate the correlation between electromyograms (EMG) of the masseter muscle and estimated relative muscle force during mastication in adult monkeys.
• To compare the efficacy of surface versus fine-wire EMG electrodes in predicting masseter muscle force.

Main Methods:

• Recorded electromyograms (EMG) from superficial and deep masseter muscles using surface and fine-wire electrodes in five adult monkeys.
• Measured relative masseter force by surface bone strain on the zygomatic arch using strain gauges.
• Utilized multiple step-wise regression to analyze the relationship between EMG activity and muscle force.

Main Results:

• Peak EMG values explained a significant portion of the variation in peak relative masseter force (R² values up to 0.96).
• Surface EMG electrodes generally provided more information about overall relative muscle force compared to fine-wire electrodes.
• Surface EMG typically preceded muscle force by approximately 22 ms at peak activity, with latency decreasing during the power stroke.

Conclusions:

• Surface EMG recordings are a reliable indicator of masseter muscle force during mastication.
• The timing relationship between EMG and muscle force provides insights into the neuromuscular control of chewing.