Electrical Impedance Myography for Evaluating Muscle Fatigue Induced by Neuromuscular Electrical Stimulation

Objectives: During Neuromuscular Electrical Stimulation (NMES), a real-time monitoring method is urgently needed to reduce the negative effect induced by muscle fatigue. Technology or Method: A novel method named electrical impedance myography (EIM) is proposed to evaluate muscle fatigue degree during NMES. The experiments were performed on the anterior tibialis muscle on several voluunteers. Two EIM parameters: impedance amplitude (|Z|) and phase (theta), were measured in real time, while applying six NMES parameter combinations. The mean power frequency (MPF) of the surface electromyography (sEMG) was selected for verification of the proposed method. Results: |Z| and theta of EIM signals decreased significantly after NMES (p < 0.05). They also both showed a linear downward trend during NMES, which was also observed in MPF of sEMG signals. At the measurement frequency of 20 kHz, steady-state fatigue was achieved when |Z| decreased to approximately 14% of the initial value. Clinical or Biological Impact: This study provides a method for monitoring muscle fatigue induced by NMES, which is beneficial to the application of NMES.