Development of Displacement-MMG and EMGHybrid Transducer

摘要

The mechanomyogram (MMG) is the vibration associated with muscle contraction. When both the electromyogram (EMG) and the MMG are measured simultaneously, muscle contraction can be evaluated correctly. Though a piezoelectric accelerometer is generally used for the measurement of MMG. the measured portion or posture should be fixed securely, because body movement causes a large artifact. The authors have already developed a small-sized MMG transducer that can easily measure a displacement MMG by applying a small, lightweight photo-reflector. In this study, we have developed a wireless MMG transducer with EMG electrodes (50×15×10 mm, 3.5g including two electrodes without a logger module). A new reflector (7×4×2.5 mm) and a simplified electronic circuit realized downsizing, and a wireless transmission module was newly added to the transducer. The reflector included an infrared emitter (950 nm) and a daylight blocking filter. MMG/EMG signals were connected to a logger module (40×2×55 mm, 35g including the battery), and they were sampled at 500 Hz and transmitted at 2.4 GHz. Using this transducer, experiments involving twitch contraction, voluntary isometric contraction and tetanic contraction were performed, and their results were similar to the conventional reports.