Propagation velocity measurement: autocorrelation technique applied to theelectromyogram

Muscle fibre conduction velocity is an important measurement in electrophys iology, both in the research laboratory and in clinical practice. It is usu ally measured by placing electrodes spaced at known distances and estimatin g the transit time of the action potential. The problem, common to all meth ods, is the estimation of this time delay. Several measurement procedures, in the time and frequency domains, have been proposed. Time-domain strategi es usually require two acquisition channels, whereas some frequency-domain methods can be implemented using a single one. The method described operate s in the time domain, making use of the autocorrelation function of the dif ference 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 voluntar y contraction, yielding an average of 3.58ms(-1) (SD=0.04 m s(-1)) and 3.37 m s(-1) (SD = 0.03 m s(-1)), respectively. Several tests showed that the p roposed method works properly with electromyogram records as short as 0.3s.