A shoe having a toe region, a middle region, a heel region, and a multi-layer, multi-density midsole wherein an upper layer of the midsole has a bottom surface that has a longitudinal convexity and a longitudinal concavity, the longitudinal convexity typically occupying a substantial portion of the toe region or a substantial portion of the toe region and middle region, and the longitudinal concavity typically occupying a substantial portion of the heel region, the longitudinal convexity and the longitudinal concavity collectively contributing to simulating the effect, and imparting the fitness benefits, of walking on a sandy beach or on a giving or uneven surface regardless of the actual hardness of the surface.