Resilience for mattresses refers normally refers to elasticity. It is measured by the "ball-rebound"-test (ASTM D3574). In this test, a steel ball is dropped off from a certain height on the material and the rebound is then measured in percentage compared to the predetermined height. The resilience or elasticity of regular Polyurethane (PU) foams is between 40% and 50%. High Resilience (HR) polyurethane foams have an elasticity of 50% to 60% and latex foams of 60% to 70%. Slow recovery foams have zero elasticity!