Clinician-accessible motor assessment with surface EMG: Key parameters and reliability

Despite the evident value of surface electromyography (EMG) in neurorehabilitation, its clinical use is limited. Researchers have developed many sophisticated EMG methods to test scientific hypotheses and address technical issues. However, there is a lack of simple and easily reproduced (i.e., clinician-accessible) procedures with available reference literature to support interpretation. To make EMG assessments accessible and interpretable for clinicians, we propose a template for surface EMG acquisition and data analysis using stereotyped movements and manual cursor placements. We apply our template by creating a simple protocol for measuring the root mean square (RMS) and mean frequency (MNF) of the EMG signal in active muscles during hand opening, wrist extension and flexion, and elbow flexion. In 36 healthy males and females, we assess interclass correlations (ICCs) to evaluate the relative inter-rater reliability of manual cursor placements, and the relative inter-session reliability of the MNF and RMS values. We also assess smallest detectible change (SDC) between assessments as a function of the number of contributing measurements (i.e., repetitions). Manual cursor placement exhibited excellent inter-rater reliability (ICC > 0.9) and inter-session reliability of MNF and RMS feature measurements was good (0.75 > ICC > 0.9) or excellent. As expected, SDCs decreased as movement repetitions increased. Compared to a single RMS measurement, taking the 14-repetition mean lowered SDC95 by 21 % for elbow flexion, 118 % for wrist extension, 66 % for wrist flexion and 15 % for hand opening. Compared to a single MNF value taking a 14-reepetion mean reduces the SDC95 by 3 Hz for elbow flextion, 4 Hz for wrist extension, 5 Hz for wrist flexion, and 4 Hz for hand opening. We demonstrate a clinician-accessible template for reliable EMG assessment, and an intuitive approach to interpreting changes in the obtained measurements. Designing protocols explicitly for broad use by clinicians will be necessary to advance clinical acceptance and integration of the modality into practice.