Vibratory and tactile sense of the fingers after working with sanders

Twenty-four volunteers worked four times in a laboratory under realistic conditions for 80 min with a relatively intensely vibrating plane-sander and a less intensely vibrating band-sander (each sander twice). Immediately before and after exposure, the left and right third finger was measured for vibratory sense with a 100 Hz rod-vibrameter and for width- and depth-sense by means of an apparatus modified after Carlson. The reproducibility of the parameters was poor: coefficients of intra-individual variation were 20 to 60%. After using the plane-sander the threshold of the width-sense in the right hand increased relative to the effect of the band-sander by 17% of the pre-exposure value; in the left hand no increase was found. The thresholds of the depth-sense and vibratory sense showed no change. The study suggests that brief vibration exposure below the ISO-guideline may cause some reduction of sensibility. One should be cautious in applying these tests. An exposure-free interval of at least several hours is recommended when studying chronic effects of vibration exposure.