The mechanical characterization of body support materials is presented. After an introduction of extra-corporal and intra-corporal body support devices (Sect. 4.1), the mechanical description of polymeric soft foam material on the microstructure and macrostructure level is introduced, (Sect. 4.2). Details regarding the experimental approach, as well as the material parameter identification to continuum mechanical description of the steady state (equilibrium) elasticity, (Sects. 22.214.171.124 and 126.96.36.199), are shown. The characterisation and modelling of polymeric soft foam viscoelastic material behaviour based on material equations of nonlinear hyperelasticity and linear viscoelasticity at finite strain is presented, (Sects. 188.8.131.52 and 184.108.40.206). Automotive and aircraft seat material characterization is demonstrated, (Sect. 4.2.2).