Midsole Structure for a Shoe

A midsole structure of a shoe includes an upper midsole, a lower midsole disposed below the upper midsole, and a wavy sheet interposed between the upper midsole and the lower midsole. The wavy sheet has a wavy shape at its medial and lateral side edge portions and a planar area at its central portion. The lower surface of the upper midsole and the upper surface of the lower midsole have wavy shapes that correspond to the wavy shape of the wavy sheet at their medial and lateral side edge portions and have a planar area that corresponds to the planar area of the wavy sheet at their central portions. The lower surface of the upper midsole and the upper surface of the lower midsole have a plurality of recesses that are disposed in the longitudinal direction at their central portions.