A vehicle seat comprises three layers of polymer foams, the upper and lower layers being polyurethane and the center layer being polyethylene. The thicknesses and deformation characteristics of the layers of foam are optimized for a given overall seat thickness range so as to interact with an injury model correlating the deformation characteristics of the human spine such that deformation and hence injury to the spine, occasioned by the impacting of the rider's upper torso upon the seat, will be minimized. A procedure of evaluating a seat in order that the deformation characteristics of the seat may be optimized is set forth.
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