Assessing the effect of surface stiffness on performance doeis not directly limited to the function measurement. Arampatzis et al. () found that energy rates are greater on a soft -sprung surface than on a hard one. Although the results of this study showed surfaces stiffness does not affect the mechanical energy of ankle and knee joints, but this is not the case for peak power. After familccustoniarzityng to the surface, peankle peankle power at the positive phase on the surface with lowest stiffness (300 kN/m) and knee peak knee power at the negative phase on 300 and 400 kN/m surfaces decrease. This result is in accordance to Sanders and Allen (26), [[who found that reducing the energy absorbed by the subject during the negative phase and through an increase of the energy transmitted to the sprung surface.]] REVISE