Importance

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Abstract

Athletic and other footwear has an upper and also an insole, a midsole and an outsole in successive layers. The midsole may be made from a flexible material (e.g. polyurethane or EUA) and may be shaped to conform to the shapes of the insole and the outsole. A cavity in the midsole at a forefoot position extends from the top surface to a position near the bottom surface of the midsole. The cavity may extend downwardly and rearwardly at an angle of approximately 10.degree.-45.degree., preferably approximately 15.degree. to the horizontal. The cavity may be undercut to provide a recess at the bottom of the cavity. A spring disposed in the cavity may have a slightly concave configuration in the cavity. The spring may have a flat configuration at the opposite ends of the spring in the longitudinal direction. The spring may be made from a fabric material woven with a warp and a fill and impregnated with a resin material. The spring may extend rearwardly past the cavity to a position substantially flush with the top surface of the midsole. The cavity and the spring may be disposed to provide the spring with potential energy having components in the upward and forward directions when the wearer's foot is disposed on the ground. When the wearer's foot is lifted from the ground, the potential energy in the spring is released to facilitate the movement of the foot upwardly and forwardly. The spring provides a dynamic response, durability, strength and adequate flex in the forefoot.

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First Claim