Electromyographical Recordings During Vibration

Surface or intramuscular electromyography (EMG) is used to record motor unit action potentials during skeletal muscle activation. The fidelity of the EMG parameters depends on numerous intrinsic and extrinsic factors summarized in this chapter. Additional motion artefacts due to vibration-induced high accelerations can influence the electronic properties of the EMG system and the electrode-skin interface. These accelerations can also excite the muscle spindles and modulate motor units’ activation by locking their firing rates to the vibration frequency via spinal and supraspinal pathways. Therefore, conventional filtering approaches are not appropriate for studying the effects of vibration on muscle activation. This chapter outlines some preventative measures to improve the signal-to-noise ratio during recording. An off-line data processing method combining high-pass filtering with full-wave rectification for discriminating the motor unit action potentials from motion artefacts is also presented. This method has been validated against intramuscular and simulated EMG recordings and allows the reliable study of vibration benefits for training and rehabilitation.