Tissue stiffness has become a hallmark of disease. Palpation is therefore part of the physical examination of a medical practitioner to assess the consistency of an organ or body part (soft/hard). However, the problem is that palpation can only assess shallow organs and that it is subjective. Shear wave elastography is a relatively new ultrasound-based technique that can measure tissue stiffness objectively based on the propagation speed of shear waves. These shear waves are generated inside the tissue of interest by applying a focused impulsive high-energy ultrasound beam. This pulse locally pushes tissue away from the probe and is the origin of the wave propagation. The link between shear wave propagation speed and tissue stiffness is straightforward in linear elastic materials. Soft biological tissue is however non-linear, anisotropic and viscoelastic, meaning that the measured shear wave propagation speed depends on the mechanical loading and time. Therefore, the main research question tackled within this thesis is whether we can use the shear wave propagation speed as measure of operational stiffness to reconstruct the stress-strain curve, while considering multiple loading states (see also fig. below).