Citation

Lundstrom R, Burstrom L. Int. J. Ind. Ergonomics 1989; 3(3): 235-242.

Copyright

(Copyright © 1989, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The mechanical impedance of the human hand-arm system was measured within the frequency range of 20-1500 Hz. A handle, specially designed for such measurements, was used. The studies were carried out on eight healthy male subjects during different experimental conditions defined by three different hard-arm postures, hand grip forces (25-75 N) adopted by the subjects, the amplitude (27-53 mm/ srms; 1.4-2.8 g at 80 Hz) and direction of the vibration stimuli. The outcome shows that the mechanical impedance of the hand-arm system depends on the frequency of the vibration stimuli. Above 200 Hz, the impedance, in general, increases quite rapidly, from about 150 Ns/m up to about 500 Ns/m at 1500 Hz, with the frequency. At lower frequencies, however, various shapes of the impedance curves were found which were most pronounced between different hand-arm postures. For the transverse direction, the impedance increased from about 50 Ns/m at 20 Hz to maximum about 100 Hz followed by a slight decrease. For the proximal-distal direction the impedance decreased from about 150 Ns/m at 20 Hz to minimum at about 100 Hz. More firm hand grips, as well, as higher vibration levels, resulted in higher impedance magnitudes for frequencies above about 100 Hz. Remarkably enough, for lower frequencies an almost opposite relationship was found. Furthermore, the results indicate a non-linear relationship between mechanical impedence and the studied experimental variables. Therefore, prior to setting up future standards, the mechanical properties of the hand-arm system should be taken into careful consideration.