Abstract
The object of this study was to evaluate the effect of the silent period (SP) when the thenar muscle strength (TMS) was increased under the constant stimulation voltage (SV) and when the SV was increased under the constant TMS.
Fifteen males and one female (mean age 24.8 ± 6.1 years) volunteers were served as subjects in this study. SP was obtained by stimulating the median nerve at the wrist and recording the electromyogram of the thenar muscle. During the measurements, the hand was rigidly stabilized on the plastic holder in flexion and opposition of the dominant thumb. The proximal phalanx of the thumb was suspended vertically between ergometer and cuff for control of the TMS. The electrical stimulation parameters had a duration of 0.5 ms, frequency of 0.5 Hz with jntensity of 60 to 210 V. Data was collected by digitization of the analogical signal and storage by electromyograph unit. The duration of SP was measured during increasing the TMS under the constant SV, and measured during increasing the SV under the constant TMS.
The following results were obtained ;
(1) The duration of SP was reduced below 90% in most subjects when the TMS was increased under the constant SV.
(2) The duration of SP was prolonged above 1.1 times when the SV was increased under the constant TMS.
(3) The duration of SP (100〜120 ms.) in this study was in good accord with that of the previous studies by others.
These data suggest that reduction or prolongation of the duration of SP may be associated with thener muscular tones, length and others.
