Analysis of phasic and tonic electromyographic signal characteristics: Electromyographic synthesis and comparison of novel morphological and linear-envelope approaches

Belavý, Daniel L.; Mehnert, Andrew; Wilson, Stephen; Richardson, Carolyn A.

doi:10.1016/j.jelekin.2007.02.018

« Previous Next »Journal of Electromyography and Kinesiology
Volume 19, Issue 1 , Pages 10-21, February 2009

Analysis of phasic and tonic electromyographic signal characteristics: Electromyographic synthesis and comparison of novel morphological and linear-envelope approaches

Daniel L. Belavý
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane QLD 4072, Australia
- School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane QLD 4072, Australia
- Corresponding author. Address: Zentrum für Muskel- und Knochenforschung, Charité Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany. Tel.: +49 178 979 5006; fax: +49 30 8441 5817.
Andrew Mehnert
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane QLD 4072, Australia
Stephen Wilson
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane QLD 4072, Australia
Carolyn A. Richardson
- School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane QLD 4072, Australia

Received 28 March 2006; received in revised form 4 September 2006; accepted 22 February 2007. published online 15 July 2007.

Abstract

The pattern of tonic and phasic components in an EMG signal reflects the underlying behaviour of the central nervous system (CNS) in controlling the musculature. One avenue for gaining a better understanding of this behaviour is to seek a quantitative characterisation of these phasic and tonic components. We propose that these signal characteristics can range between unvarying, tonic and intermittent, phasic activation through a continuum of EMG amplitude modulation. In this paper, we present two new algorithms for quantifying amplitude modulation: a linear-envelope approach, and a mathematical morphology approach. In addition we present an algorithm for synthesising EMG signals with known amplitude modulation. The efficacy of the synthesis algorithm is demonstrated using real EMG data. We present an evaluation and comparison of the two algorithms for quantifying amplitude modulation based on synthetic data generated by the proposed synthesis algorithm. The results demonstrate that the EMG synthesis parameters represent 91.9% and 96.2% of the variance of linear-envelopes extracted from lumbo-pelvic muscle EMG signals collected from subjects performing a repetitive-movement task. This depended, however, on the muscle and movement-speed considered (F=4.02, p<0.001). Coefficients of determination between input and output amplitude modulation variables were used to quantify the accuracy of the linear-envelope and morphological signal processing algorithms. The linear-envelope algorithm exhibited higher coefficients of determination than the most accurate morphological approach (and hence greater accuracy, T=8.16, p<0.001). Similarly, the standard deviation of the coefficients of determination was 1.691 times smaller (p<0.001). This signal processing algorithm represents a novel tool for the quantification of amplitude modulation in continuous EMG signals and can be used in the study of CNS motor control of the musculature in repetitive-movement tasks.