  We study the role of the superconducting proximity effect on the
electron-phonon energy exchange in diffusive normal metals (N) attached to
superconductors (S). The proximity effect modifies the spectral response of the
normal metal, in particular the local density of states. This leads to a
weakening of the electron-phonon energy relaxation. We show that the effect is
easily observable with modern thermometry methods, and predict that it can be
tuned in structures connected to multiple superconductors by adjusting the
phase difference between superconducting order parameters at the two NS
interfaces.
