The influence of biodynamic factors on the absorption of vibration energy in the human hand and arm.

Abstract

A possible basis for risk assessment for hand-transmitted vibration may be to determine the quantity of energy absorbed in the human hand and arm. In the present study the mechanical energy absorption in the hand-arm system has been measured on 10 healthy subjects during exposure to random vibration with constant velocity spectrum. In the study, the influence of various conditions, such as vibration direction (Xh, Yh, Zh), grip force (25-75 N), feed force (20-60 N), frequency weighted acceleration level (3, 6, 9, 12 m/s2) and hand and arm posture (5 flexions, 2 abductions) were studied. The outcome showed that the energy absorption in the human hand and arm depended mainly on the frequency and direction of the vibration stimuli. Higher vibration levels, as well as firmer hand grips and higher feed forces, resulted in a significantly higher absorption. As concerns the hand and arm posture the results show that the flexion had a significant contribution to the vibration absorption but the abduction had no influence on the quantity of absorbed energy. Furthermore, the influence of some of the studied variables had a non-linear effect on the absorption but also differed between different exposure directions. Moreover, it was concluded that the frequency-weighting routine in the international standard ISO 5349 do not reflect the energy absorbing properties of the human hand and arm.