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Mechanical impedance of the sitting human body in single-axis compared to multi-axis whole-body vibration exposure
1National Institute of Working Life, Technical Risk Factors, PO Box 7654, S-907 13, Umeå, Sweden. patrick.holmlund@niwl.se
Objective:
The study was aimed to investigate the mechanical impedance of the sitting human body and to compare data obtained in laboratory single-axis investigations with multi-axis data from in vehicle measurements.
Design:
The experiments were performed in a laboratory for single-axis measurements. The multi-axis exposure was generated with an eight-seat minibus where the rear seats had been replaced with a rigid one. The subjects in the multi-axis experiment all participated in the single-axis experiments.
Background:
There are quite a few investigations in the literature describing the human response to single-axis exposure. The response from the human body can be expected to be affected by multi-axis input in a different way than from a single-axis exposure. The present knowledge of the effect of multiple axis exposure is very limited.
Methods:
The measurements were performed using a specially designed force and accelerometer plate. This plate was placed between the subject and the hard seat.
Results:
Outcome shows a clear difference between mechanical impedance for multi-axis exposure compared to single-axis. This is especially clear in the x-direction where the difference is very large.
Conclusions:
The conclusion is that it seems unlikely that single-axis mechanical impedance data can be directly transferred to a multi-axis environment. This is due to the force cross-talk between different directions.