This experimental study aimed at acquiring detailed data about the human transmission behaviour as a basis for an improved estimation of the strain, induced by whole body vibration (wbv). Four male subjects were exposed to verti-cal sinusoidal wbv (2-12 Hz;​ 1.5 and 3.0 ms^-2 RMS). The steady state force re-sponse was measured at the input interface, and accelerations were registered at the seat, head, shoulder, and upper trunk. Transmissibilities and apparent mass as quotients of RMS-values were determined. In addition, the corresponding quotients of peak values, as well as their accompanying phase angles were calculated separately for maximum acceleration or minimal acceleration, and for the extreme values of apparent mass in relation to the body mass.

The resonance frequencies were lower at higher intensity levels. Near the resonance of the whole body, the quotients for maximum accelerations were significantly higher than those for minimal accelerations, and the shapes of time histories of the output deviated clearly from those of the sinusoidal input.

The results speak in favour of a pronounced nonlinearity of human biodynamics even at low acceleration levels, the system properties depending on the input pa-rameters. These factssuggest a higher strain of biological structures than that predicted by RMS-values assuming linearity.