US Patent 7941938 Article of footwear with lightweight sole assembly

An article of footwear includes an upper and a sole assembly secured to the upper. The sole assembly includes a first portion having a lower ground engaging surface, an upper surface, and a recess formed in the upper surface. The upper surface of the first portion is in contact with the upper. A second portion is seated in the recess in the first portion and has an upper surface, with the upper surface of the second portion being in contact with the upper. The second portion comprises a foam material having a density less than 0.25 g/cm3.