VIBRATION EFFECTS ON HAND-ARM-SYSTEM

Abstract

Electromyogram on the forearm flexor and extensor was observed with surface electrodes under conditions of experiments in which a subject was asked to grip a handle on a vibration table and was given vibration. In these experiments, factors concerning vibration exposure time, vibration amplitude, vibration frequency (30, 60, 125 and 250 Hz), gripping force, handle diameter and room temperature were examined by using the orthogonal array table in the experimental design method. It was found out that low frequency components of the electromyogram on the forearm flexor and the forearm extensor were significantly intensified with increase of the levels of vibration magnitude, gripping force, handle diameter and exposure time. Change of room temperature (22° or 10°C) did not affected the electromyogram.The relation between the increase of low frequency components of the electro-myogram on the forearm and sensation response for holding a weight was studied to establish the evaluation scale of the low frequency component. Using this scale, the emotional response to the vibration impressed during gripping of the handle was estimated and improvement of operating conditions of vibrating tools with regard to these factors was suggested on the basis of muscle fatigue.