Tinker Hatfield was one of the early wear testers of the Air Force 1 prototypes, and he fondly remembered the steel shank years later. Placed beneath the Air bag, it added spring to every step, serving as a primitive energy return system. Unfortunately the shank wasn't used in the production model due to liability concerns, and the concept of a stiff plate in a basketball sneaker wouldn't be revived until 1995 - in Hatfield's Air Jordan XI.