In this contribution, the performance of solid oxide fuel cells (SOFC) under high current density load cycles is studied by means of electrical measurements and material analyses. Our study is an important premise for the application of accelerated life testing (ALT) to SOFC single cells. In reliability engineering ALT is a well known method for rapid lifetime evaluation [Nelson, W., Accelerated Life Testing, 1990, John Wiley, New York]. Furthermore, our results are of particular interest for the (La,Sr)MnO3 -zirconia system. We find that during current treatment, a nanoporous domain containing lanthanum zirconate is formed at the cathode-electrolyte interface. The nanoporosity leads to an enhanced cathode performance while the formation of lanthanum zirconate degrades the mechanical stability of the interface.