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 side of the multi-turn wave
spring. Compression of the first side causes expansion pressure on the second side
and compression of the second side causes expansion pressure on the first side
to provide cushioning and energy return responsive to a rolling footstrike.
