A photovoltaic stack comprising at least two p.sup.+ i n.sup.+ cells in optical series, said cells separated by a transparent ohmic contact layer(s), provides a long optical path for the absorption of photons while preserving the advantageous field-enhanced minority carrier collection arrangement characteristic of p.sup.+ i n.sup.+ cells.

A forward recovery foot support system for any shoe but primarily for running and jogging shoes. The system includes a base conforming generally to the contour of a human foot, a first ray extension attached to the base and extending substantially only under the first proximal phalanx of the foot, a fifth ray extension attached to the base and extending substantially only under the fifth proximal phalanx of the foot, and a heel post attached to the base and extending substantially only under the heel bone and providing added elevation at the most lateral aspect of the heel bone to compensate for the natural inversion of 2.degree.-3.degree. that is present in most persons' heels. This support can be designed as an insert independent of a conventional shoe sole or may be incorporated into the sole of a shoe.

A sole for an athletic shoe, such as a cleated soccer or football shoe, comprises a thin, unitary member formed of flexible material. The member has a contour or configuration which renders the flexible material substantially rigid at the arch and heel portions of the sole. This provides substantial support to the arch of the foot. Cleats may extend from the toe and heel portions of the lower surface of the sole member.

A foot or fifth toe support for any shoe but primarily for running and jogging shoes, consisting of a flat, flexible and resilient member located below the fifth proximal phalanx from the metatarsal-phalanx joint to the proximal phalanx neck. This support lies independently on the upper surface of a conventional shoe sole or it may be an extension of a semi-rigid orthotic device contoured and dimensioned to cradle the sole and heel to a line across the foot near the distal ends of the metatarsal bones.

A lightweight, flexible gymnastic shoe is disclosed. The shoe includes an upper formed of a lightweight synthetic fabric. A relatively broad closure strap has a first end fixed to a medial inside surface of the upper in the area of the arch and a second free end for detachable attachment to the medial outside of the upper. A hook and pile fastener selectively fastens the second end of the closure strap to the upper. A sole is attached to an outer bottom surface of the upper, and is formed of a relatively thin resilient material located only below the toe, ball and heel areas. A liner is located inside the upper and extends along substantially the entire length of the inside top surface of the upper. The liner is formed of a relatively low density cushioning material. A metatarsal pad is located along the liner only in the area of the first and second metatarsal heads of a wearer's foot, and a heel pad is located along the liner in the heel area. The pads are formed of a shock-absorbing material different from and having a higher density than the material of the liner. An arch support is formed of a built up area of material positioned below the medial arch area.