An application of a muscle model to study electromyographic signals

https://doi.org/10.1016/S0169-2607(02)00092-5Get rights and content

Abstract

A simulation program for research and teaching electromyography (EMG) has been developed. It has a great number of parameters that may be optionally changed in simulations of normal and diseased muscle. The simulator is user-friendly and fast and can actually be run without much help from the manual. It is easy to introduce new motor units (MU), to change MU and individual muscle fibre parameters, to insert an EMG electrode and to change its position. The model allows simulation of the most common pathological situations. The resulting signals are displayed in a conventional form. The generated EMG signals obtained with the three electrodes that have been used so far are reasonably similar to the signals obtained in real recordings. A few shortcomings in simulating, e.g. end plate zone and abnormal volume conduction characteristics do not seem to influence the principal results. The simulator can, therefore, be used in teaching and even for research.

Introduction

Single fibre action potentials have earlier been simulated as well as signals obtained from other types of EMG electrodes [1], [2]. These simulations have given important information about the generation of EMG signals. Often the signal processing has been very time consuming and it has not been possible to use these techniques as on line tools for research and teaching. With faster computers and with an improved line source model [3] it is now feasible to build an advanced user friendly simulator for these purposes.

The aim of the study is to construct a simulator of a muscle with its muscle fibres, motor end- plates and motor units (MU), and to simulate the generated signals obtained with different types of EMG electrodes.

Section snippets

Mathematical model of the single fibre action potential

Single muscle fibre action potentials can be simulated using different types of mathematical models. The first were either very complex, e.g. volume conductor models [4], or simpler but less accurate, e.g. the core conductor model and the tripole and dipole models [5]. As a trade-off between these two extremes, the line source model was developed [6], [7], modified [8], and later improved by introducing an antialiasing filter [3], see Fig. 1. With the improved model, it is possible to use a

Getting started

EMG Simulator is started from a shortcut or by double-clicking a file (*.cmg) associated with the program. When EMG Simulator starts from the start menu or the desktop an empty muscle is created. To add MUs click with the left mouse button in the magnified transversal muscle view (the left view). Specify parameters for the MU in the dialog box (Fig. 3) and click ‘OK’. The fibres in the MU will be distributed according to the given parameters with the clicked point as center point. If a MU with

Discussion

A model for research and teaching EMG has been developed. It has a great number of parameters that may be optionally changed in simulations of normal and diseased muscle.

Hardware and software specification

Pentium 166 MHz CPU and higher.

windows 95, 98, me, 2000, nt.

soundblaster 16 compatible soundcard.

RAM (64 MB) recommended (48 MB minimum).

Availability of the software

The software is a commercial product, EMG Simulator, and is distributed by Medtronic Functional Diagnostics A/D, Copenhagen, Denmark. E-mail: [email protected], http://www.mfd.medtronic.com.

Acknowledgements

The study was supported by the Swedish Medical Research Council, Grant 135 ES.

References (18)

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