A new method to measure the distribution of motor conduction velocity in man.

A new method of measuring the distribution of conduction velocities in human motor fibers is described. In this method, a modification of Kimura's collision technique is combined with Hopf's technique. This enabled us to determine the collision end-point in Hopf's technique, from which the minimum velocity is derived. The size of the distorted compound muscle action potential (CMAP) measured with Hopf's technique is corrected using the CMAP size with the modified Kimura technique. This resolves the problem of CMAP distortion due to transient change in muscle conduction in Hopf's technique. In addition, a new equation to correct for the refractory period was developed. This can be applied even if there is stimulus spread. Using our method, one can clearly determine the maximum and minimum velocities. The former corresponds to the motor conduction velocity as measured by the conventional method.