This International Standard describes the range of idealized values of the driving-point mechanical impedance, apparent mass and seat-to-head transmissibility modulus and phase applicable to seated individuals subjected to z-axis sinusoidal or broad-band random vibration under specific experimental conditions. Additionally, a human body model is provided to satisfy the range of idealized values defined for driving-point mechanical impedance/apparent mass and seat-to-head transmissibility. This model is further used to compute values of driving-point mechanical impedance and apparent mass for fixed body masses which are recommended to be used as test loads in current standards defining laboratory seat testing methodologies. Alternatively, mathematical expressions in the form of transfer functions are provided to approximate the weighted mean (target) values defined for all three biodynamic response functions.