Analysis of intramuscular motor unit coherence in the tibialis anterior muscle as a tool for the assessment of robot-assisted rehabilitation

Robot-assisted rehabilitation has emerged as an advantageous tool in the recovery of patients suffering from abnormal motor conditions. The assessment of the electrophysiological behavior of the muscles involved in this rehabilitation process can provide important hints of the patient functional recovery. Such analysis has been commonly performed through the processing of bipolar surface electromyography (sEMG). Here we introduce recent techniques based on the acquisition of high-density electromyography (HD-sEMG) to be used as a tool for the assessment of robot-assisted rehabilitation. To that end, the activity of the tibialis anterior was measured during the performance of periodical ankle dorsiflexion with different frequencies and amplitudes. Intramuscular motor unit coherence was then computed showing peaks at the frequency of movement (delta band) but more interestingly at the beta band. These changes in amplitude and position of the coherence peaks may provide meaningful metrics for gait rehabilitation procedures where the muscle contraction is as well periodical and variable in strength and speed.