In laboratory experiments, an evolution of the measured rock properties is often observed when the core undergoes cyclic solicitations. There is still a debate in order to define which value should be chosen, and basically the question is to define which value is intrinsic to the rock and which value should be considered as an artifact. Experiments have been performed on a reservoir sandstone and 9 loading cycles have been applied. It is shown that the sandstone behavior can be fully described using Biot's semi-linear poroelasticity. Within this theoretical framework, it is shown that cyclic loading leads to intrinsic values of the rock constitutive law.