Propagation velocity measurement: Autocorrelation technique applied to the electromyogram

Abstract

Muscle fibre conduction velocity is an important measurement in electrophysiology, both in the research laboratory and in clinical practice. It is usually measured by placing electrodes spaced at known distances and estimating the transit time of the action potential. The problem, common to all methods, is the estimation of this time delay. Several measurement procedures, in the time and frequency domains, have been proposed. Time-domain strategies usually require two acquisition channels, whereas some frequency-domain methods can be implemented using a single one. The method described operates in the time domain, making use of the autocorrelation function of the difference signal obtained from two needle electrodes and only one acquisition channel. Experimental results were obtained from the electromyogram of two biceps muscles (two adult male subjects, nine records each) under voluntary contraction, yielding an average of 3.58 m s(-1) (SD=0.04 m s(-1)) and 3.37m s(-1) (SD=0.03 m s(-1)), respectively. Several tests showed that the proposed method works properly with electromyogram records as short as 0.3 s.

Methods for estimating muscle fibre conduction velocity from surface electromyographic signals

“…The presence of dips in the power spectrum of surface EMG signals detected by a bipolar electrode system has a counterpart in the temporal domain, that is in the autocorrelation function of the signal, indeed, it can be shown that the first dip introduced by a bipolar recording in the power spectrum approximately corresponds to the first minimum of the autocorrelation function of the signal (SPINELLI et al, 2001). SPINELLI et al (2001) proposed this method for estimating CV from invasive recordings, although the technique may fit surface recordings better.…”

“…SPINELLI et al (2001) proposed this method for estimating CV from invasive recordings, although the technique may fit surface recordings better. The method has the same problems related to the detection of spectral dips.…”

“…The method has the same problems related to the detection of spectral dips. Moreover, the correspondence between a spectral dip and the autocorrelation function minimum is only approximated (SPINELLI et al, 2001). …”

Arm EMG during abduction and adduction: hysteresis cycle

“…The surface electromyogram (EMG) is a rather ubiquitous tool used, for example, as a measure of muscular effort in traumatology, as an evaluation parameter in rehabilitation engineering, as the control input to myoelectric prostheses and as another diagnostic piece of information in myopathies many times faced in clinical medicine [1,2]. It can also be used to estimate the muscle action potential propagation velocity [3]. Its analysis permits a better knowledge of the muscle acti-vation sequence, either in lower or upper extremities, during predetermined voluntary movements.…”

Proposta e análise de indicadores eletromiográficos espectrais e temporais em protocolos dinâmicos com indução de fadiga muscular localizada

“…Nestes casos, as razões da proposição de tais técnicas eram, principalmente, o problema do uso de eletrodos monopolares ou bipolares para estimação da CV. Spinelli et al (2001) também abordam esta questão, porém, propondo um método baseado em autocorrelação. Solomonow et al (1990) (Solomonow et al, 1990).…”