(a) a sole member (46) having upper and lower surfaces;

(b) an upper member (44) secured to said sole member to define a shoe having a foot-receiving chamber (40);

(c) a unitary insole member (2) removably inserted within said foot-receiving chamber, said sole member and said insole member having corresponding heel, arch, ball and toe portions, the portion of said chamber adjacent said insole ball portion having given internal width (w) and girth dimensions, said insole member being formed of a resilient cushioning material and including top and bottom surfaces, toe and heel edge portions, and inside and outside arch side edge portions;

(d) slip-resistant stabilizing means (20) arranged on the bottom surface of said insole member heel portion, said stabilizing means cooperating with the adjacent bottom surface of said foot-receiving chamber to prevent sliding displacement of said insole member heel portion relative to said shoe;

(e) contour means defined on the top surface of said insole member for positioning at least the heel and arch portions of the user's foot relative to said insole member, said contour means including a pair of curved side walls (2c) that extend upwardly from at least said heel and arch inside and outside side edge portions;

(f) means for varying the effective width and girth of said chamber ball portion, comprising;

(1) a width adjustment pad (12) arranged beneath the bottom surface of said insole member ball portion, and

(2) releasable connecting means (12a, 16) connecting said width adjustment pad with said insole member, said width adjustment pad having such a thickness (t) as to cause the bottom surface of said pad to protrude downwardly for engagement with the adjacent bottom surface of said chamber; and

(g) bellows means operable upon walking by the shoe's user to pump air between the outer and inner of said insole member inside arch portion, said bellows means comprising:

(1) a plurality of longitudinally-spaced transversely-extending continuous grooves (24) contained in the outer surface of said sole member inside arch portion, each of said grooves including a first portion extending horizontally transversely across the bottom surface of said insole member, and a second portion extending vertically upwardly within the outer surface of the adjacent inner arch side wall portion, thereby to define between said grooves a plurality of flexure ribs (26), respectively;

(2) said groove first and second portions having bottom walls containing a plurality of perforations (28) extending completely through said insole member, thereby to transmit air between the outer and inner surfaces of said insole member inside arch portion.