Temporary threshold shift of vibratory sensation after clasping a vibrating handle.

The temporary threshold shift of vibratory sensation (TTSv) at 125 Hz after clasping a vibrating handle was investigated in relationship to four influencing factors: discrete frequency and acceleration of the vibration exposed to, the grip in clasping a handle and the time after exposure. Clasping the vibrating handle resulted in significantly larger TTSv than shown in clasping a non-vibrating handle. The TTSv after exposure to the 250 Hz vibration was significantly the largest in all frequencies at equal acceleration. The TTSv recovered exponentially as time elapsed after exposure. The TTSv also increased proportionally to the power of acceleration at each frequency and grip force. The larger grip force resulted in a significantly larger TTSv. A general form of regression equation of TTSv involving the four factors was established. The prediction equations obtained confirmed that a frequency around 200 Hz induced the largest TTSv among vibrations with equal acceleration and around 240 Hz among vibrations with equal velocity.