Absorption of Mechanical Energy in the Skin of the Human Hand While Exposed to Vibrations

When using a vibratory hand-held tool, all mechanical energy entering the hand and arm has to be transmitted through, or absorbed by, the glabrous skin in contact with the handle. Early signs of an incipient vibration injury are often neurological and/or vascular disturbances located in the skin of the palm, such as a reduction in tactile sensibility or episodes of finger blanching. The aim of this investigation was to study the absorption of mechanical energy in the glabrous skin of the human hand while exposed to vibations from five different types of hand-held tools (die grinder, chipping hammer, wrench, nibbler, angle grinder). The influence of various experimental factors such as static load (1–3 N/cm2), five test points, type of tools were studied on five subjects. The frequency weighted value of the acceleration level, according to the guidelines given in the International Standard ISO 5349, was however held constant througout the study, ca 3.1 m/s2rms. The results show that the static load and the type of tool have a great influence on the quantity of energy absorbed. The highest and lowest quantity of energy absorbed was found for the die and angle grinder, respectively. Futhermore, it was found that, the higher the static load the higher the absorption of vibration energy. In contrast, small and insignificant differences were found between different testpoints and between subjects.