A complete description of the core collapse supernova mechanism requires an appropriate treatment of both the hydrodynamics and the microphysics. We study the influence of a nuclear physics input, namely the temperature dependence of the nucleon effective mass in nuclei induced by the in-medium effects, in the core collapse of a massive star. Methods. We present here the first implementation of this nuclear input in a hydrodynamical one-dimensional simulation. The simulations are performed with a spherically symmetric Newtonian model, with neutrino transport treated in the multi-group flux-limited diffusion approximation. Results. The inclusion of the temperature dependence of the in-medium nucleon mass has an impact on the equation of state of the system and reduces the deleptonisation during the collapse. This results in a non-negligible effect on the shock wave energetics. The shock wave is formed more outwards, and in the first few milliseconds after bounce the shock front has propagated further out.