A sole having these characteristics is known, for example, from U.S. Pat. No. 1,895,660. The stiffening shank, termed an “arch support”, extends in this case from a backfoot part to the beginning of the adjacent midfoot part, and serves mainly to reinforce the footwear in the plantar arch area.
U.S. Pat. No. 6,785,986 describes a torsion stiffening shank which also extends in the plantar arch area, running diagonally relative to the longitudinal direction.
US20070107264 describes a stiffening shank for sports footwear in which a series of semi-rigid plates are connected to one another via locally weakened areas which form hinge systems. In this case also, the extension of the shank is mainly limited to the plantar arch.