A. Fiorito et al., ANALOG AND DIGITAL INSTRUMENTS FOR NONINVASIVE ESTIMATION OF MUSCLE-FIBER CONDUCTION-VELOCITY, Medical & biological engineering & computing, 32(5), 1994, pp. 521-529
Analogue and digital instruments for non-invasive on-live measurement
of muscle fibre conduction velocity (CV) have been designed, built and
compared using test signals and real myo-electric signals. Their inpu
ts consist of two-single-differential or double-differential myo-elect
ric signals, obtained using a three- or four-contact surface electrode
system. The analogue device computes CV by tracking the lag of the ze
ro-crossing of the cross-correlation between the first signal and the
derivative of the second. The digital device computes the peak of the
cross-correlation function between the two signals by sampling them at
50 KHz for 20 ms (or longer, up to 320 ms), computing CV in about 30
ms (or longer, up to about 670 ms) and resuming sampling. Both devices
allow estimation of CV during either voluntary or electrically elicit
ed contractions and include a stimulation stage and a signal condition
er with artefact suppression features. Both devices provide analogue a
nd numerical outputs and allow interfacing with analogue and digital i
nstrumentation. They can be used in clinical or in research environmen
ts for easy and quick identification of appropriate electrode location
s and/or for monitoring CV during sustained voluntary or electrically
elicited contractions. The digital version is more versatile and requi
res no adjustments; it provides an estimate based on intermittent read
ing of the signals and is more sensitive to noise and momentary CV flu
ctuations.