Sole with removable insert

A sole for an article of footwear, comprising a mass of sole-forming material having provided therein a block of material functioning harmoniously with the remaining mass of soleforming material, said block having a pair of elongate side-by-side zig-zag shaped cavities extending transversely therethrough and having an open end, and a pair of user-selectable, removable elongate inserts having a zig-zag shape in end view complementary to the shape of said cavities and fitted snugly in said respective cavities, said inserts being slidable into and out of said cavities through said open end thereof, said inserts being made of a resilient plastics material having the ability to return to substantially to its pre-stressed condition after deflection, whereby said inserts for part of a compression spring system absorbing energy from a wearer on a downward stroke and subsequently returning such energy to the wearer.