Analysis of conduction velocity in the H pathway. Part 1. Methodology and results in normal subjects

An electrophysiological method is described for evaluating the conduction velocity in the different partial segments of the monosynaptic reflex pathway of the lower limbs in man. Using the latencies of M and H responses recorded from the soleus muscle elicited by stimulating the posterior tibial nerve at the popliteal fossa (pf) and the sciatic nerve at the upper thigh, the conduction velocities in the entire course (pf-to-spinal cord), in the proximal segment (upper thigh-to-spinal cord), and in the distal segment (pf-to-upper thigh) of the H circuit, were evaluated and expressed by mixed (sensory-motor) conduction indexes. The conduction distances were measured by using the Th11 spinal process as a reference point on the vertebral column. The conduction velocity of the 1a spindle afferent fibres and of the motor fibres was selectively determined in the pf-to-buttock segment. The results obtained in 50 healthy subjects are presented and the methodological problems related to the proposed technique are discussed.