US Patent 7383647 Mechanical cushioning system for footwear

A midsole for footwear comprising a midsole element, which comprises a top plate, a bottom plate, and a plurality of strut members disposed between the top and bottom plates for supporting the top plate a distance away from the bottom plate. Adjacent strut members have a C shaped cross-section facing in the same direction. The midsole element may further comprise a heel cleft to increase the flexibility of the sole. In a preferred embodiment, the strut members on the medial side are arranged at an angle to the strut members on the lateral side of the sole. The directional design provides flexibility and stiffness anisotropically to the sole in the longitudinal and lateral directions of the sole respectively.