The present invention provides a shoe having a multi-layer, multi-density midsole where the surfaces between midsole layers have one or more convexities and one or more concavities which collectively contribute 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.
1. A shoe having an upper, a midsole, and an outsole wherein said midsole comprises:
an upper layer and a lower layer wherein the lower layer has a bottom surface substantially adjacent to the outsole and a top surface substantially opposite the bottom surface of the lower layer, the lower layer being located substantially between the outsole and the upper layer, said upper layer having a bottom surface that substantially faces said top surface of said lower layer, said upper layer further having a heel region, said bottom surface of said upper layer further having at least a first convexity, a second convexity, and a first concavity, said first concavity occupying substantially all of said heel region of said bottom surface, and said upper layer and said lower layer each having a density wherein the density of the upper layer is denser than the density of the lower layer;
said upper layer further having a toe region and a middle region and at least a substantial portion of said first convexity is located in said toe region and at least a substantial portion of said second convexity is located in said middle region.
2. The shoe of claim 1 wherein the upper layer of the midsole has a density of between about 0.400 and about 0.500 grams per cubic centimeter, and the lower layer of the midsole has a density of between about 0.325 and about 0.419 grams per cubic centimeter.
3. The shoe of claim 1 wherein the lower layer of the midsole has a toe region, a middle region and a heel region and the lower layer is on average thicker in the heel region than it is in the toe region.
4. The shoe of claim 3 wherein the lower layer of the midsole is less than about 45 millimeters thick in said heel region and has an average thickness in said heel region of at least about 6.5 millimeters, and said lower layer is less than about 25 millimeters thick in said toe region and said middle region and has an average thickness in said toe region and said middle region of at least about 3 millimeters.
5. The shoe of claim 1 wherein the upper layer and lower layer of the midsole are molded together.
6. A shoe having an upper, a midsole, and an outsole wherein said midsole comprises:
an upper layer and a lower layer wherein the lower layer has a bottom surface substantially adjacent to the outsole and a top surface substantially opposite the bottom surface of the lower layer, the lower layer being located substantially between the outsole and the upper layer, said upper layer having a bottom surface that substantially faces said top surface of said lower layer, said upper layer further having a heel region, said bottom surface of said upper layer further having at least a first concavity and a second concavity, said second concavity occupying substantially all of said heel region of said bottom surface, and said upper layer and said lower layer each having a density wherein the density of the upper layer is denser than the density of the lower layer;
wherein said upper layer has a toe region and at least a portion of said first concavity is located in said toe region.
7. The shoe of claim 6 wherein the upper layer of the midsole has a density of between about 0.400 and about 0.500 grams per cubic centimeter, and the lower layer of the midsole has a density of between about 0.325 and about 0.419 grams per cubic centimeter.
8. The shoe of claim 6 wherein the lower layer of the midsole has a toe region, a middle region and a heel region and is on average thicker in the heel region than it is in the toe region.
9. The shoe of claim 6 wherein the upper layer and lower layer of the midsole are molded together.