FUNDAMENTAL PROBLEMS ON CLINICAL APPLICATION OF THE H-WAVE : Part I. Fluctuation of the H-wave

Electrical stimulation of the human tibial nerve at the popliteal fossa evokes two kinds of action potentials : the M-wave and the H-wave in the calf muscle. The M-wave has a short response time and is derived from an impulse descending through the efferent nerve. The H-wave has a long response time and is derived from a reflex impulse monosynaptically transmitted through the afferent nerve which originates from muscle spindle. As the stimulus strength applied to the nerve is increased, gradually the H-wave appears first and gets larger, then the M-wave appears. By further increasing the stimulus strength, the H-wave decreases in its amplitude while the M-wave gets larger and finally the H-wave disappears. Although the stimulus strength is strictly defined and repeatedly applied the effect of each stimulus is not always constant, and the amplitude of the H-wave fluctuates. The greatest H-wave which is not accompanied by the M-wave is least variable. After measurement of such H-wave in succession, it is found that the distribution curve of the amplitude of the H-wave is in accord with the normal distribution. The mean value, the standard deviation and then the variation coefficient were calculated. In 36 normal cases, the average of the variation coefficient was 7.31. Patients were classified in three groups according to the grade of tendon reflex regardless of clinical entities, then the variation coefficient was calculated in each group. In 37 cases, the reflex activities were accelerated and the variation coefficient was 4.71 on an average. In 22 cases, the reflex activities were normal and the variation coefficient averaged 9.14. In 15 cases, the reflex 'activities were reduced and the coefficient was 14.07 on an average. It is concluded that the fluctuation of the H-wave is small in the group of the accelerated reflex activity and large in the group of the reduced reflex activity.