An ideal combination of characteristics for an elastic support surface would be resistance that also adjusts to the magnitude of compressive forces . The support surface should have a high enough compression resistance to fully support the load (prevent bottoming-out) without providing too high a reactive force (memory) to keep interface pressure low. Over time and with extended use, foam degrades and loses its stiffness. This decreased ability results in higher interface pressures. Krouskop estimates that in approximately three years, the mattress wears out and the compressive forces are transferred to the underlying supporting structure used to support the foam . In other words, the mattress "bottoms out".

Foam is limited in its capability to immerse and envelop by its stiffness and thickness. Soft foams will envelop better than stiffer foams, but will necessarily be thicker to avoid bottoming out. Foam seat cushions are frequently contoured to improve their performance. Pre-contouring the seat cushion to provide a better match between the buttocks and the cushion increases the contact area thus reducing average pressure; pre-contouring also increases immersion and envelopment properties thus decreasing pressure peaks (Sprigle, 1990; Brienza, 1996; Brienza, 1998).