A sole assembly for an article of footwear comprises a sole having a heel region and a ball region. A first multi-turn wave spring disposed within the sole comprises an upper turn and a lower turn. The upper turn is in pivotal contact with the lower turn to define a first side and an opposing second...http://www.google.co.uk/patents/US6886274?utm_source=gb-gplus-sharePatent US6886274 - Spring cushioned shoe
