This study deals with the experimental determination of heat sources in the crack tip vicinity of notched rubber specimens. The determination of heat source evolution at the stretched crack tip is an important issue to understand the physical mechanisms involved in the crack growth of such materials. Indeed, heat sources are a more relevant quantity than the temperature variations because the latter are influenced by the heat conduction as well as the heat exchanges with the outside of the specimen. Due to large deformations undergone by rubbery materials, a motion compensation technique has been developed in order to track material points at the surface of the specimen during the loading. For that purpose, during the experiments, the displacement and the temperature fields are measured by using both kinematic and infrared cameras. Measurements are then processed to associate a temperature and a strain level to each material point on the specimen surface. Then, the heat sources produced or absorbed by the material due to the deformation processes are derived from the corresponding temperature variation maps using the heat diffusion equation. The first results obtained by applying such a methodology open a new route in the study of crack growth in rubber.