This invention is a full energy return shoe. It comprises various embodiments of a "full energy return" linkage attached to upper and lower sole plates along their full lengths. This linkage constrains relative motion of the upper and lower plates by limiting or eliminating relative tilting and by controlling or eliminating relative longitudinal motion. These constraints result in foot impact energy being stored in springs irregardless of whether the force acts on the front or rear of the sole. That is, both toe and heel impact energy are used or returned during toe-off. These spring are coupled to links or vertices of the linkage and are designed to achieve an optimal ground reaction force curve of the shoe on the ground - varying from linear to constant curves. Useful features include a push-off frame to allow heel lift and a flex-rigger to prevent sprained ankles.
