fig1 a - c illustrate , in frontal plane cross sections in the heel area , the applicant &# 39 ; s concept of the theoretically ideal stability plane applied to shoe soles . fig1 a - 1c illustrate clearly the principle of natural deformation as it applies to the applicant &# 39 ; s design , even though design diagrams like those preceding ( and in his previous applications already referenced ) are normally shown in an ideal state , without any functional deformation , obviously to show their exact shape for proper construction . that natural structural shape , with its contour paralleling the foot , enables the shoe sole to deform naturally like the foot . in the applicant &# 39 ; s invention , the natural deformation feature creates such an important functional advantage it will be illustrated and discussed here fully . note in the figures that even when the shoe sole shape is deformed , the constant shoe sole thickness in the frontal plane feature of the invention is maintained . fig1 a shows a fully contoured shoe sole design that follows the natural contour of all of the foot sole , the bottom as well as the sides . the fully contoured shoe sole assumes that the resulting slightly rounded bottom when unloaded will deform under load as shown in fig1 b and flatten just as the human foot bottom is slightly round unloaded but flattens under load . therefore , the shoe sole material must be of such composition as to allow the natural deformation following that of the foot . the design applies particularly to the heel , but to the rest of the shoe sole as well . by providing the closes match to the natural shape of the foot , the fully contoured design allows the foot to function as naturally as possible . under load , fig1 a would deform by flattening to look essentially like fig1 b . fig1 a and 1b show in frontal plane cross section the essential concept underlying this invention , the theoretically ideal stability plane which is also theoretically ideal for efficient natural motion of all kinds , including running , jogging or walking . for any given individual , the theoretically ideal stability plane 51 is determined , first , by the desired shoe sole thickness ( s ) in a frontal plane cross section , and , second , by the natural shape of the individual &# 39 ; s foot surface 29 . for the case shown in fig1 b , the theoretically ideal stability plane for any particular individual ( or size average of individuals ) is determined , first , by the given frontal plane cross section shoe sole thickness ( s ); second , by the natural shape of the individual &# 39 ; s foot ; and , third , by the front plane cross section width of the individual &# 39 ; s load - bearing footprint which is defined as the supper surface of the shoe sole that is in physical contact with the supports the human foot sole . fig1 b shows the same fully contoured design when upright , under normal load ( body weight ) and therefore deformed naturally in a manner very closely paralleling the natural deformation under the same load of the foot . an almost identical portion of the foot sole that is flattened in deformation is also flatten in deformation in the shoe sole . fig1 c shows the same design when tilted outward 20 degrees laterally , the normal barefoot limit ; with virtually equal accuracy it shows the opposite foot tilted 20 degrees inward , in fairly severe pronation . as shown , the deformation of the shoe sole 28 again very closely parallels that of the foot , even as it tilts . just as the area of foot contact is almost as great when tilted 20 degrees , the flattened area of the deformed shoe sole is also nearly the same as when upright . consequently , the barefoot fully supported structurally and its natural stability is maintained undiminished , regardless of shoe tilt . in marked contrast , a conventional shoe , shown in fig3 makes contact with the ground with only its relatively sharp edge when tilted and is therefore inherently unstable . the capability to deform naturally is a design feature of the applicant &# 39 ; s naturally contoured shoe sole designs , whether fully contoured or contoured only at the sides , though the fully contoured design is most optimal and is the most natural , general case , as note in the reference sep . 2 , 1988 , application , assuming shoe sole material such as to allow natural deformation . it is an important feature because , by following the natural deformation of the human foot , the naturally deforming shoe sole can avoid interfering with the natural biomechanics of the foot and ankle . fig1 c also represents with reasonable accuracy a shoe sole design corresponding to fig1 b , a naturally contoured shoe sole with a conventional built - in flattening deformation , except that design would have a slight crimp at 145 . seen in this light , the naturally contoured side design in fig1 b is a more conventional , conservative design that is a special case of the more generally fully contoured design in fig1 a , which is the closest to the natural form of the foot , but the least conventional . in its simplest conceptual form , the applicant &# 39 ; s fig1 invention is the structure of a conventional shoe sole that has been modified by having its sides bent up so that their inner surface conforms to the shape of the outer surface of the foot sole of the wearer ( instead of the shoe sole sides being flat on the ground , as is conventional ); this concept is like that described in fig3 of the applicant &# 39 ; s &# 39 ; 819 patent . for the applicant &# 39 ; s fully contoured design , the entire shoe sole — including both the sides and the portion directly underneath the foot — is bent up to conform to the shape of the unloaded foot sole of the wearer , rather than the partially flattened load - bearing foot sole shown in fig3 of the &# 39 ; 819 patent . this theoretical or conceptual bending up must be accomplished in practical manufacturing without any of the puckering distortion or deformation that would necessarily occur if such a conventional shoe sole were actually bent up simultaneously along all of its the sides ; consequently , manufacturing techniques that do not require any bending up of shoe sole material , such as injection molding manufacturing of the shoe sole , would be required for optimal results and therefore is preferable . it is critical to the novelty of this fundamental concept that all layers of the shoe sole are bent up around the foot sole . a small number of both street and athletic shoe soles that are commercially available are naturally contoured to a limited extent in that only their bottom soles , which are about one quarter to one third of the total thickness of the entire shoe sole , are wrapped up around portions of the wearer &# 39 ; s foot soles ; the remaining sole layers , including the insole , the midsole and the heel lift ( or heel ) of such shoe soles , constituting over half of the thickness of the entire shoe sole , remains flat , conforming to the ground rather than the wearers &# 39 ; feet . consequently , in existing contoured shoe soles , the shoe sole thickness of the contoured side portions is much less than the bore foot , it will deform easily to provide this designed - in custom fit . the greater the flexibility of the shoe sole sides , the greater the range of individual foot size . this approach applies to the fully contoured design described here in fig1 a and in fig1 of the &# 39 ; 819 patent . as discussed earlier by the applicant , the critical functional feature of a shoe sole is that it deforms under a weight - bearing load to conform to the foot sole just as the foot sole deforms to conform to the ground under a weight - bearing load . of course , it is optimal in terms of preserving natural foot biomechanics , which is the primary goal of the applicant , for the shoe sole to conform to the foot sole when on the foot , not just when under a weight - bearing load . and , in any case , all of the essential structural support and propulsion elements must be supported by the foot sole . to the extent the shoe sole sides are easily flexible , as has already been specified as desirable , the position of the shoe sole sides before the wearer puts on the shoe is less important , since the sides will easily conform to the shape of the wearer &# 39 ; s foot when the shoe is put on that foot . in view of that , even shoe sole sides that conform to a shape more than slightly smaller than the shape of the outer surface of the wearer &# 39 ; s foot sole would function in accordance with the applicant &# 39 ; s general invention , since the flexible sides could bend out easily a considerable relative distance and still conform to the wearer &# 39 ; s foot sole when on the wearer &# 39 ; s foot . fig3 shows in a real illustration a foot 27 in position for a new biomechanical test that is the basis for the discovery that ankle sprains are in fact unnatural for the bare foot . the test simulates a lateral ankle sprain , where the foot 27 — on the ground 43 — rolls or tilts to the outside , to the extreme end of its normal range of motion , which is usually about 20 degrees at the heel 29 , as shown in a rear view of a bare ( right ) heel in fig3 . lateral ( inversion ) sprains are the most common ankle sprains , accounting for about three - fourths of all . the especially novel aspect of the testing approach is to perform the ankle spraining simulation while standing stationary . the absence of forward motion is the key to the dramatic success of the test because otherwise it is impossible to recreate for testing purposes the actual food and ankle motion that occurs during a lateral ankle sprain , and simultaneously to do it in a controlled manner , while at normal running speed or even jogging slowly , or walking . without the critical control achieved by slowing forward motion all the way down to zero , any test subject would end up with a sprained ankle . that is because actual running in the real world is dynamic and involves a repetitive force maximum of three times one &# 39 ; s fully body weight for each footstep , with sudden peaks up thoroughly five or six times for quick stops , missteps , and direction changes , as might be experienced when spraining an ankle . in contrast , in the static simulation test , the forces are tightly controlled and moderate , ranging from no force at all up to whatever maximum amount that is comfortable . the stationary sprain simulation test ( ssst ) consists simply of standing stationary with one foot bare and the other shod with any shoe . each foot alternatively is carefully tilted to the outside up to the extreme end of its range of motion , simulating a lateral ankle sprain . the stationary sprain simulation test clearly identifies what can be no less than a fundamental flaw in existing shoe design . it demonstrates conclusively that nature &# 39 ; s biomechanical system , the bare foot , is far superior in stability to man &# 39 ; s artificial shoe design . unfortunately , it also demonstrates that the shoe &# 39 ; s severe instability overpowers the natural stability of the human foot and synthetically creates a combined biomechanical system that is artificially unstable . the shoe is the weak link . the test shows that the bare foot is inherently stable at the approximate 20 degree end of normal joint range because of the wide , steady foundation the bare heel 29 provides the ankle joint , as seen in fig3 . in fact , the area of physical contact of the bare heel 29 with the ground 43 is not much less when titled all the way out to 20 degrees as when upright at 0 degrees . the new stationary sprain simulation test provides natural yardstick , totally missing until now , to determine whether any given show allows the foot within it to function naturally . if a shoe cannot pass this simple litmus test , it is positive proof that a particular shoe is interfering with natural foot and ankle biomechanics . the only question is the exact extent of the interference beyond that demonstrated by the new test . conversely , the applicant &# 39 ; s designs are the only designs with shoe soles thick enough to provide cushioning ( thin - soled and heel - less moccasins do pass the test , but do not provide cushioning and only moderate protection ) that will provide naturally stable performance , like the bare foot , in the stationary sprain simulation test . fig4 shows that , in complete contrast the foot equipped with a conventional running shoe , designated generally by the reference numeral 20 and having an upper 21 , though initially very stable while resting completely flat on the ground , becomes immediately unstable when the shoe sole 22 is tilted to the outside . the tilting motion lifts from contact with the ground all of the shoe sole 22 except the artificially sharp edge of the bottom outside corner . the shoe sole instability increases the farther the foot is rolled laterally . eventually , the instability induced by the shoe itself is so great that the normal load - bearing pressure of full body weight would actively force an ankle sprain if not controlled . the abnormal tilting motion of the shoe does not stop at the barefoot &# 39 ; s natural 20 degree limit , as you can see from the 45 degree tilt of the shoe heel in fig4 . that continued outward rotation of the shoe past 20 degrees causes the foot to slip within the shoe , shifting its position within the shoe to the outside edge , further increasing the shoe &# 39 ; s structural instability . the slipping of the foot within the shoe is caused by the natural tendency of the foot to slide down the typically flat surface of the tilted shoe sole ; the more the tilt , the stronger the tendency . the heel is shown in fig4 because of its primary importance in sprains due to its direct physical connection to the ankle ligaments that are torn in an ankle sprain and also because of the heel &# 39 ; s predominant role within the foot in bearing body weight . it is easy to see in the two figures how totally different the physical shape of the natural bare foot is compared to the shape of the artificial shoe sole . it is strikingly odd that the two objects , which apparently both have the same biomechanical function , have completely different physical shapes . moreover , the shoe sole clearly does not deform the same way the human foot sole does , primarily as a consequence of its dissimilar shape . fig5 a illustrates that the underlying problem with existing shoe designs is fairly easy to understand by looking closely at the principal forces acting on the physical structure of the shoe sole . when the shoe is tilted outwardly , the weight of the body held in the shoe upper 21 shifts automatically to the outside edge of the shoe sole 22 . but , strictly due to its unnatural shape , the tilted shoe sole 22 provides absolutely no supporting physical structure directly underneath the shifted body weight where it is critically needed to support that weight . an essential part of the supporting foundation is missing . the only actual structural support comes from the sharp corner edge 23 of the shoe sole 22 , which unfortunately is not directly under the force of the body weight after the shoe is tilted . instead , the corner edge 23 is offset well to the inside . as a result of that unnatural misalignment , a lever arm 23 a is set up through the shoe sole 22 between two interacting forces ( called a force couple ): the force of gravity on the body ( usually known as body weight 133 ) applied at the point 24 in the upper 21 and the reaction force 134 of the ground , equal to and opposite to body weight when the shoe is upright . the force couple creates a force moment , commonly called torque , that forces the shoe 20 to rotate to the outside around the sharp corner edge 23 of the bottom sole 22 , which serves as a stationary pivoting point 23 or center of rotation . unbalanced by the unnatural geometry of the shoe sole when tilted , the opposing two forces produce torque , causing the shoe 20 to tilt even more . as the shoe 20 tilts further , the torque forcing the rotation becomes even more powerful , so the tilting process becomes a self - reinforcing cycle . the more the shoe tilts , the more destabilizing torque is produced to further increase the tilt . the problem may be easier to understand by looking at the diagram of the force components of body weight shown in fig5 a . when the shoe sole 22 is tilted out 45 degrees , as shown , only half of the downward force of body weight 133 is physically supported by the shoe sole 22 ; the supported force component 135 is 71 % of full body weight 133 . the other half of the body weight at the 45 degree tilt is unsupported physically by any shoe sole structure ; the unsupported component is also 71 % of full body weight 133 . it is therefore produces strong destabilizing outward tilting rotation , which is resisted by nothing structural except the lateral ligaments of the ankle . fig5 b show that the full force of body weight 133 is split at 45 degrees of tilt into two equal components ; supported 135 and unsupported 136 , each equal to 0 . 707 of full body weight 133 . the two vertical components 137 and 138 of body weight 133 are both equal to 0 . 50 of full body weight . the ground reaction force 134 is equal to the vertical component 137 of the supported component 135 . fig6 show a summary of the force components at shoe sole tilts of 0 , 45 and 90 degrees . fig6 which uses the same reference numerals as in fig5 shows that , as the outward rotation continues to 90 degrees , and the foot slips within the shoe while ligaments stretch and / or break , the destabilizing unsupported force component 136 continues to grow . when the shoe sole has tilted all the way out to 90 degrees ( which unfortunately does happen in the real world ), the sole 22 is providing no structural support and there is no supported force component 135 of the full body weight 133 . the ground reaction force at the pivoting point 23 is zero , since it would move to the upper edge 24 of the shoe sole . at that point of 90 degree , tilt , all of the full body weight 133 is directed into the unresisted and unsupported force component 136 , which is destabilizing the shoe sole very powerfully . in other words , the full weight of the body is physically unsupported and therefore powering the outward rotation of the shoe sole that produces an ankle sprain . insidiously , the farther ankle ligaments are stretched , the greater the force on them . in stark contrast , untilted at 0 degrees , when the shoe sole is upright , resting flat on the ground , all of the force of body weight 133 is physically supported directly by the shoe sole and therefore exactly equals the supported force component 135 , as also shown in fig6 . in the untilted position , there is no destabilizing unsupported force component 136 . fig7 illustrates that the extremely rigid heel counter 141 typical of existing athletic shoes , together with the motion control device 142 that are often used to strongly reinforce those heel counters ( and sometimes also the sides of the mid - and forefoot ), are ironically counterproductive . though they are intended to increase stability , in fact they decrease it . fig7 shows that when the shoe 20 is tilted out , the foot is shifted within the upper 21 naturally against the rigid structure of the typical motion control device 142 , instead of only the outside edge of the shoe sole 22 itself . the motion control support 142 increases by almost twice the effective lever arm 132 ( compared to 23 a ) between the force couple of body weight and the ground reaction force at the pivot point 23 . it doubles the destabilizing torque and also increases the effective angle of tilt so that the destabilizing force component 136 becomes greater compared to the supported component 135 , also increasing the destabilizing torque . to the extent the foot shifts further to the outside , the problem becomes worse . only by removing the heel counter 141 and the motion control devices 142 can the extension of the destabilizing lever arm be avoided . such an approach would primarily rely on the applicant &# 39 ; s contoured shoe sole to “ cup ” the foot ( especially the heel ), and to a much lesser extent the non - rigid fabric or other flexible material of the upper 21 , to position the foot , including the heel , on the shoe . essentially , the naturally contoured sides of the applicant &# 39 ; s shoe sole replace the counter - productive existing heel counters and motion control devices , including those which extend around virtually all of the edge of the foot . fig8 shows that the same kind of torsional problem , though to a much more moderate extent , can be produced in the applicant &# 39 ; s naturally contoured design of the applicant &# 39 ; s earlier filed applications . there , the concept of a theoretically - ideal stability plane was developed in terms of a sole 28 having a lower surface 31 and an upper surface 20 which are spaced apart by a predetermined distance which remains constant throughout the sagittal frontal planes . the outer surface 27 of the foot is in contact with the upper surface 30 of the sole 28 . though it might seem desirable to extend the inner surface 30 of the shoe sole 28 up around the sides of the foot 27 to further support it ( especially in creating anthropomorphic designs ), fig8 indicates that only that portion of the inner shoe sole 28 that is directly supported structurally underneath by the rest of the shoe sole is effective in providing natural support and stability . any point on the upper surface 30 of the shoe sole 28 that is not supported directly by the constant shoe sole thickness ( as measured by a perpendicular to a tangent at that point and shown in the shaded area 143 ) will tend to produce a moderate destabilizing torque . to avoid creating a destabilizing lever arm 132 , only the supported contour sides and non - rigid fabric or other material can be used to position the foot on the shoe sole 28 . fig9 illustrates an approach to minimize structurally the destabilizing lever arm 32 and therefore the potential torque problem . after the last point where the constant shoe sole thickness ( s ) is maintained , the finishing edge of the shoe sole 28 should be tapered gradually inward from both the top surface 30 and the bottom surface 31 , in order to provide matching rounded or semi - rounded edges . in that way , the upper surface 30 does not provide an unsupported portion that creates a destabilizing torque and the bottom surface 31 does not provide an unnatural pivoting edge . the gap 144 between shoe sole 28 and foot sole 29 at the edge of the shoe can be “ caulked ” with exceptionally soft sole material as indicated in fig9 that , in the aggregate ( i . e . all the way around the edge of the shoe sole ), will help position the foot in the shoe sole . however , at any point of pressure when the shoe tilts , it will deform easily so as not to form an unnatural level causing a destabilizing torque . fig1 illustrates a fully contoured design , but abbreviated along the sides to only essential structural stability and propulsion shoe sole elements as shown in fig2 of the &# 39 ; 819 patent combined with the freely articulating structural elements underneath the foot as shown in fig2 of the &# 39 ; 819 patent . the unifying concept is that , on both the sides and underneath the main load - bearing portions of the shoe sole , only the important structural ( i . e . bone ) elements of the foot should be supported by the shoe sole , if the natural flexibility of the foot is to be paralleled accurately in shoe sole flexibility , so that the shoe sole does not interfere with the foot &# 39 ; s natural motion . in a sense , the shoe sole should be composed of the same main structural elements as the foot and they should articulate with each other just as do the main joints of the foot . fig1 e shows the horizontal plane bottom view of the right foot corresponding . to the fully contoured design previously described , but abbreviated , that is , having indentations along the sides to only essential structural support and propulsion elements which are all concavely rounded bulges as shown . the concavity of the bulges exists with respect to an intended wearer &# 39 ; s foot location in the shoe . shoe sole material density can be increased in the unabbreviated essential elements to compensate for increased pressure loading there . the essential structural support elements are the base and lateral tuberosity of the calcaneus 95 , the heads of the metatarsals 96 , and the base of the fifth metatarsal 97 ( and the adjoining coboid in some individuals ). they must be supported both underneath and to the outside edge of the foot for stability . the essential propulsion element is the head of the first distal phalange 98 . fig1 shows that the naturally contoured stability sides need not be used except in the identified essential areas . weight savings and flexibility improvements can be made by omitting the non - essential stability sides . the design of the portion of the shoe sole directly underneath the foot shown in fig1 allows for unobstructed natural inversion / eversion motion of the calcaneus by providing maximum shoe sole flexibility particularly at a midtarsal portion of the sole member , between the base of the calcaneus 125 ( heel ) and the metatarsal heads 126 ( forefoot ) along an axis 120 . an unnatural torsion occurs about that axis if flexibility is insufficient so that a conventional shoe sole interferes with the inversion / eversion motion by restraining it . the object of the design is to allow the relatively more mobile ( in inversion and eversion ) calcaneus to articulate freely and independently from the relatively more fixed forefoot instead of the fixed or fused structure or lack of stable structure between the two in conventional designs . in a sense , freely articulating joints are created in the shoe sole that parallel those of the foot . the design is to remove nearly all of the shoe sole material between the heel and the forefoot , except under one of the previously described essential structural support elements , the base of the fifth metatarsal 97 . an optional support for the main longitudinal arch 121 may also be retained for runners with substantial foot pronation , although would not be necessary for many runners . the forefoot can be subdivided ( not shown ) into its component essential structural support and propulsion elements , the individual heads of the metatarsal and the heads of the distal phalanges , so that each major articulating joint set of the foot is paralleled by a freely articulating shoe sole support propulsion element , an anthropomorphic design ; various aggregations of the subdivision are also possible . the design in fig1 features an enlarged structural support at the base of the fifth metatarsal in order to include the cuboid , which can also come into contact with the ground under arch compression in some individuals . in addition , the design can provide general side support in the heed area , as in fig1 e or alternatively can carefully orient the stability sides in the heel area to the exact positions of the lateral calcaneal tuberosity 108 and the main base of the calcaneus 109 , as in fig1 e ( showing heel area only of the right foot ). fig1 a - d show frontal plane cross sections of the left shoe and fig1 e shows a bottom view of the right foot , with flexibility axes 120 , 122 , 111 , 112 and 113 indicated . fig1 f shows a sagittal plane cross section showing the structural elements joined by very thin and relatively soft upper midsole layer 147 . fig1 g and 10h show similar cross sections with slightly different designs featuring durable fabric only ( slip - lasted shoe ), or a structurally sound arch design , respectively . fig1 i shows a side medial view of the shoe sole . fig1 j shows a simple interim or low cost construction for the articulating shoe sole support element 95 for the heel ( showing the heel area only of the right foot ); while it is most critical and effective for the heel support element 95 , it can also be used with the other elements , such as the base of the fifth metatarsal 97 and the long arch 121 . the heel sole element 95 shown can be a single flexible layer or a lamination of layers . when cut from a flat sheet or molded in the general pattern shown , the outer edges can be easily bent to follow the contours of the foot , particularly the sides . the shape shown alloys a flat or slightly contoured heel element 95 to be attached to a highly contoured shoe upper or very thin upper sole layer like that shown in fig1 f . thus , a very simple construction technique can yield a highly sophisticated shoe sole design . the size of the center section 119 can be small to conform to a fully or nearly fully contoured design or larger to conform to a contoured sides design , where there is a large flattened sole area under the heel . the flexibility is provided by the removed diagonal sections , the exact proportion of size and shape can vary . fig1 illustrates an expanded explanation of the correct approach for measuring shoe sole thickness according to the naturally contoured design , as described previously in fig2 and 24 of the &# 39 ; 819 patent . the tangent described in those figures would be parallel to the ground when the shoe sole is tilted out sideways , so that measuring shoe sole thickness along the perpendicular will provide the least distance between the point on the upper shoe sole surface closest to the ground and the closest point to it on the lower surface of the shoe sole ( assuming no load deformation ). fig1 shows a non - optimal but interim or low cost approach to shoe sole construction , whereby the midsole and heel lift 127 are produced conventionally , or nearly so ( at least leaving the midsole bottom surface flat , through the sides can be contoured ), while the bottom or outer sole 128 includes most or all of the special contours of the new design . not only would that completely or mostly limit the special contours to the bottom sole , which would be molded specially , it would also ease assembly , since two flat surfaces of the bottom of the midsole and the top of the bottom sole could be mated together with less difficulty than two contoured surfaces , as would be the case otherwise . the advantage of this approach is seen in the naturally contoured design example illustrated in fig1 a , which shows some contours on the relatively softer midsole sides , which are subject to less wear but benefit from greater traction for stability and ease of deformation , while the relatively harder contoured bottom sole provides good wear for the load - bearing areas . fig1 - 15 show frontal plane cross sectional views of a shoe sole according to the applicant &# 39 ; s prior inventions based on the theoretically ideal stability plane , taken at about the ankle joint to show the heel section of the shoe . the concept of the theoretically ideal stability plane , as developed in the prior applications as noted , defines the plane 51 in terms of a locus of points determined by the thickness ( es ) of the sole . fig1 shows , in a rear cross sectional view , the inner surface of the shoe sole conforming to the natural contour of the foot and the thickness of the shoe sole remaining constant in the frontal plane , so that the outer surface coincides with the theoretically ideal stability plane . fig1 shows a fully contoured shoe sole design that follows the natural contour of all of the foot , the bottom as well as the sides , while retaining a constant shoe sole thickness in the frontal plane . the fully contoured shoe sole assumes that the resulting slightly rounded bottom when unloaded will deform under load and flatten just as the human foot bottom is slightly rounded unloaded but flattens under load ; therefore , shoe sole material must be of such composition as to allow the natural deformation following that of the foot . the design applies particularly to the heel , but to the rest of the shoe sole as well . by providing the closest match to the natural shape of the foot , the fully contoured design allows the foot to function as naturally as possible . under load , fig2 would deform by flattening to look essentially like fig1 . seen in this light , the naturally contoured side design in fig1 is a more conventional , conservation design that is a special case of the more general fully contoured design in fig1 , which is the closest to the natural form of the foot , but the least conventional . the amount of deformation flattening used in the fig1 design , which obviously varies under different loads , is not an essential element of the applicant &# 39 ; s invention . fig1 and 14 both show in frontal plane cross sections the theoretically ideal stability plane , which is also theoretically ideal for efficient natural motion of all kinds , including running , jogging or walking . fig1 shows the most general case , the fully contoured design , which conforms to the natural shape of the unloaded foot . for any given individual , the theoretically ideal stability plane 51 is determined , first , by the desired shoe sole thickness ( es ) in a frontal plane cross section , and , second , by the natural shape of the individual &# 39 ; s foot surface 29 . for the special case shown in fig1 , the theoretically ideal stability plane for any particular individual ( or size average of individuals ) is determined , first , by the given frontal plane cross section shoe sole thickness ( es ); second , by the natural shape of the individual &# 39 ; s foot ; and third , by the frontal plane cross section width of the individual &# 39 ; s load - bearing footprint 30 b , which is defined as the upper surface of the shoe sole that is in physical contact with and supports the human foot sole . the theoretically ideal stability plane for the special case is composed conceptually of two parts . shown in fig1 , the first part is a line segment 31 b of equal length and parallel to line 30 b at a constant distance ( s ) equal to shoe sole thickness . this corresponds to a conventional shoe sole directly underneath the human foot , and also corresponds to the flattened portion of the bottom of the load - bearing foot sole 28 b . the second part is the naturally contoured stability side outer edge 31 a located at each side of the first part , line segment 31 b . each point on the contoured side outer edge 31 a is located at a distance which is exactly shoe sole thickness ( es ) from the closest point on the contoured side inner edge 30 a . in summary , the theoretically ideal stability plane is used to determine a geometrically precise bottom contour of the shoe sole based on a top contour that conforms to the contour of the foot . it can be stated unequivocally that any shoe sole contour , even of similar contour , that exceeds the theoretically ideal stability plane will restrict natural foot motion , while any less than the plane will degrade natural stability , in direct proportion to the amount of the deviation . the theoretical ideal was taken to be that which is closest to natural . fig1 illustrates in frontal plane cross section another variation that uses stabilizing quadrants 26 at the outer edge of a conventional shoe sole 28 b illustrated generally at the reference numeral 28 . the stabilizing quadrants would be abbreviated in actual embodiments .
a shoe sole particularly for athletic footwear for supporting the foot of an intended wearer having multiple rounded bulges existing as viewed in a frontal plane of the sole when the shoe is upright and in an unloaded condition . the bulges include concavely rounded inner and outer portions for approximating the structure of and support provided by the natural foot . the bulges can be located proximate to important structural support areas of an intended wearer &# 39 ; s foot on either or both sides of the shoe sole or the middle portion of the shoe sole , or on various combinations of these locations . the bulges include side and upper midsole portions to improve stability while also improving cushion and comfort . the bulges can be tapered as viewed in a horizontal plane to improve flexibility and reduce unnecessary weight .