The Relationship between Jaw Imbalance and Arm Strength Loss through Fractal Analysis of Surface EMG Signals

It has been thought that imbalance in the jaws can cause loss in arm strength. In this study, EMG will be used to determine the EMG–Force relationship of the jaw, neck and arms muscles. This will give us useful insights on the arms strength loss due to the biomechanical effects of the imbalance in the jaw mechanism. Three male subjects (average age: 20.67±2.89 years old) participated in this investigation. The subject were asked to stand with their arms and legs extended in frontal plan in such a way that the ratio subject intra-feet distance/ subject height equal 0.25. The experimental protocol consisted of two paradigms that (1) From the initial position (0 mm, 5 kg), external loading weight was added incrementally (6kg, 7kg) until the subject can hold the weight in 10 seconds. Check EMG signal quality and data storage; (2) Perform variation in spacer thickness from 2mm to 3mm and execute step 1 for each variation. Myoelectric signals of the masseter, trapezoid, deltoid and brachiodiolis muscles were measured. Higuchi fractal dimension was used to analyze the complexity of surface EMG signal of these four muscles. The results showed that (1) The activities of arm muscles varied according to the applied pull-down force; (2) The masseter, trapezoid and deltoid muscles displayed the greatest amount of activity in this study. There was also a significant difference in the fractal dimension values of the surface EMG signal before and after the loss of arm strength.