Optimal conditions for the measurement of muscle fibre conduction velocity using surface electrode arrays

Three factors influencing the accuracy of the muscle fibre conduction velocity estimates were studied. They were the recording position, the interelectrode distance and the misalignment of the electrode with respect to the muscle fibres. Experiments were performed on the biceps muscle of a normal subject. Bipolar recordings were made simultaneously from a linear electrode array consisting of 13 contacts. The accuracy of the conduction velocity was evaluated by the cross-correlation method. When the recording site was close to the innervation zone, the peak values of the cross-correlation function decreased and the estimates of the time delays became unreliable. High correlations were obtained when the interelectrode distance was small. Furthermore, the misalignment between electrode axis and muscle fibre axis led to overestimation of muscle fibre conduction velocity, but this effect was less if wider electrodes were used.