Model of the supine human body and its reactions to external forces.

Mechanical impedance and vibration transmissibility measurements were conducted on supine humans using sinusoidal vibrations. The frequencies tested were 1-20 Hz with a constant acceleration amplitude of 0.3 G. The tests were repeated with 4.54 kg pure mass placed on each segment. Both results were used to calculate a multi-degree-of-freedom lumped parameter model. The nonlinear reactions of the body are revealed by comparing the model parameters under "no load" and "load" conditions. When the results are compared with impedance measurements conducted under sustained acceleration, it becomes obvious that the thorax, due to its anatomical design, reacts differently from the remaining body parts.