A Simplified Analysis of Real-time Monitoring of Muscle Contraction during Dynamic Exercise Using an MMG/EMG Hybrid Transducer System

Abstract

To evaluate muscle function accurately, it is necessary to simultaneously measure electromyogram (EMG) and mechanomyogram (MMG). We have developed an MMG/EMG hybrid transducer system that can simultaneously measure displacement-MMG (dMMG) and EMG, and reported that the dMMG and EMG measurements reflect muscle strength during dynamic exercise. The analysis of dMMG and EMG in our previous studies only calculated the total power spectrum obtained from discrete Fourier transform (DFT). Using this method of analysis, however, it is difficult to present information on muscle contraction in real time during exercise because of high computational cost due to huge amount of computation by DFT. In the present study, we propose a simplified method to evaluate muscle contraction during dynamic exercise by directly processing dMMG and EMG in the time domain. We adapted the dMMG/EMG data during recumbent bicycle pedaling obtained in our previous study to perform time-domain analysis. The novel time-domain analysis yielded equivalent results as those of previous analysis, and reflected muscle contraction during dynamic exercise. In addition, because dMMG and EMG by the proposed analysis increased with load increase during prolonged pedaling, it may be suitable for real-time monitoring of muscle function. The proposed method not only accurately measures muscle function during dynamic exercise in real time but also has a significantly lower computational cost.