Factors influencing vibration sense thresholds used to assess occupational exposures to hand transmitted vibration.

Abstract

The effects of various conditions, including temporary threshold shifts (TTS) induced by exposure to vibration on vibration sense thresholds, have been investigated. The vibration sense thresholds of five subjects were measured on the middle fingertip of the left hand. A contactor with a diameter of 7 mm was surrounded by three alternative plates with holes of different sizes. The contact force was controlled at either 1 N, 2 N, or 3 N. For the TTS test, the left hand was exposed to vibration at 20 ms2 rms for five minutes. The frequencies of both the exposure to vibration and the vibration threshold test were in the range 16 Hz to 500 Hz. Using a surround around the contactor greatly reduced the vibration sense threshold at 16 Hz and 31-5 Hz but increased the threshold at 125 Hz, 250 Hz, and 500 Hz. An effect of contact force was seen only at the higher frequencies; larger contact forces led to lower thresholds at 125 Hz, 250 Hz, and 500 Hz. As temperature of the finger skin decreased, the vibration thresholds increased, with the changes at higher frequencies greater than those at lower frequencies. The TTS at 16 Hz and 31-5 Hz measured 0-5 minutes after exposure to vibration (TTS0.5) were highest after exposures to vibration at lower frequencies.The TTSO.5 at 63 Hz was similar after exposure to all frequencies. The TTSfr values at 125 Hz, 250 Hz, and 500 Hz were highest after exposures to vibration at 125 Hz and 250 Hz. It was apparent that the physiological characteristics of vibration sensation at low and high frequencies differed significantly. These find-

Equivalent comfort contours for vertical vibration of steering wheels: Effect of vibration magnitude, grip force, and hand position

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Frequency Weightings Based on Biodynamics of Fingers-Hand-Arm System

“…This suggests that the ISO weighting not only underestimates the high frequency effect but also overestimates the low frequency effect. The frequency dependency of the temporary threshold shift of the vibration sense at the fingertip suggests that the relative high value of the acute neurological effect is in the range of 63 to 500 Hz, with a peak effect at 100-250 Hz 37,38) . Vascular studies also found that the relatively stronger vibration effect on the digital blood flow was in the middle frequency range (30 to 500 Hz), with the strongest effect at 125 Hz 24,39) .…”

Short-term effect of hand-arm vibration exposure on tactile sensitivity and manual skill

“…They observed no difference in the performance of standard tasks before and after vibration exposure. Other studies have tried to quantify the short-term neurological effects, in particular the impairment of the vibration perception sense, without considering the potential interference with workplace safety (1,(11)(12)(13). The objective of the present research was to investigate whether the impairment of tactile sensitivity after exposure to vibration disturbs the motor control of precision handling, and, if so, whether it can result in an increased risk of injury during or after tasks involving the use of vibrating tools.…”