The conduction velocity of the ulnar nerve and the spinal reflex time measured by means of the H wave in average adults and athletes.

Abstract

An attempt was made to ascertain whether physical exercise might cause increase of the conduction velocity of the nerve fibers in young adults. Experiments were carried out on 32 university student athletes and 6 professional athletes with controls of 30 ordinary university students. The ages of these subjects ranged from 20 to 36 years. For the purpose of measuring the conduction velocity of the ulnar nerve, square wave stimulation of 0.5 msec. duration was applied to the ulnar nerve at the axilla, elbow and wrist, and evoked myograms were picked up from the hypothenar eminence muscles. The spinal reflex time was measured as the latency of the H wave which was recorded from the gastrocnemius muscle by stimulating the posterior tibial nerve at the popliteal fossa. Room temperature was carefully kept at 30°C during the experiments. (1) The average maximum conduction velocities of ulnar nerve fibers were 67.0±2.5 meters per second in the forearm and 67.6±2.6 meters per second in the upper arm in the control group and 66.5±2.3 meters per second in the forearm and 67.2±2.6 meters per second in the upper arm in the athletes group. It was noticeable that any significant differences were recognizable neither between the data of the forearm and upper arm in the two groups nor between those obtained in the athletes group and the control group. (2) No significant difference as to the spinal reflex time and the spinal reflex index was seen between the two groups, judging from the patterns of their distribution depicted in the graphs. The spinal reflex index is an index which corresponds to the mean conduction velocity of the impulse over the reflex arc. (3) Distinct individual differences in the maximum conduction velocity of ulnar nerve fibers were observed in both groups. However, no factor was found which might be related to the individual differences from the viewpoint of anthropometric measurements and skillfulness in sport. From these results, it may be said that no kind of physical exercise increases in the conduction velocity of the nerve fibers in young adults.