The relationship between the imbalance of the jaw and the loss of arm strength

Abstract

It has been reported that imbalance in the jaw can cause loss in arm strength. In

the process of understanding whether the origin of this phenomenon is muscular, neurological or neuromuscular, we investigated the electrical activities of muscles as well as the hemodynamic of the brain using the Electromyography (EMG) and functional Near-infrared spectroscopy (f-NIRS), respectively. The results from these measurements will allow us to establish the relationship between bite and arm strength according to the muscle and brain activities. EMG and f-NIRS were administered to 10 healthy female subjects as each subject was asked to perform three different tasks: bite on the firm spacer using one side of the jaw, apply pull-down force on the contralateral arm and combine those two tasks. For EMG measurements, four different muscles – masseter muscles, deltoid muscles, bicep muscles and trapezoid muscles – were involved. Integrated EMG (iEMG) and fractal dimension were used to analyze the results. The iEMG showed the intensity of muscle activities decreased when the degree of jaw imbalance increased (spacer thickness increased). In addition, the tendency of fractal dimension decreased for all muscles. This finding indicates that muscle fatigue and the decrease in muscle contraction level leads to the loss of arm strength. The results from the f-NIRS measurement also help to demonstrate the changing of concentration of OxyHemoglobin of motor cortex in controlling the activities of jaw and arm muscles. Keywords – Jaw imbalance, arm strength, Electromyography (EMG), Functional Near- infrared Spectroscopy (f-NIRS), Higuchi fractal dimension.