In order to show how surface deformations may be taken into account in the modeling of static surface forces measurements, we present a simple model which qualitatively describes the behavior of elastic surfaces submitted to an oscillatory force field like solvation forces. We also show that the correct thermodynamic description for the experimental system (including the force measuring spring) is easily deduced from the isostrain (fixed grips) description. We briefly point out that the dynamic description of these systems is much more intricate.