US Patent 7340851 Shoe having an inflatable bladder

An article of footwear including a sole and an upper with an exterior and interior surface, and a bladder which comprises at least one of the exterior or interior surfaces. The bladder comprising sheets of polyurethane attached together via welding. The bladder includes a medial compartment and a lateral compartment attached to each other under the foot of the wearer. The article of footwear also includes a inflation mechanism for selectively introducing air to the chambers. The inflation mechanism is located under the foot of the wearer to be activated by the normal action of the wearer.