The present invention relates to the field of footwear, and in particular to the field of footwear having a sole designed to provide guidance and/or support to the wearer's foot so as to improve the gait of the wearer.

Typically, such a sole comprises in heel-to-toe sequence along the sole: a heel portion, a midfoot portion, a ball portion and a forefoot portion, with the heel, midfoot and ball portions running along the lateral side of an arch region located below the arch of the wearer's foot.

Soles of this type increase user comfort by providing cushioning elements for the foot in some or all of the heel, midfoot, ball and forefoot portions of the sole, primarily for dampening ground impact during running or walking, and/or by providing support elements spread throughout the bottom surface of the sole primarily for stabilizing the foot and preventing or at least minimizing any tilt of the foot in a direction transverse to the running or walking direction (longitudinal direction).

Wearing shoes equipped with soles of this type over extended periods of time contributes to an attitude of indifference and passiveness in persons using these shoes. In the long run, many of these persons will forget how to walk naturally or "correctly". It has been shown that prolonged unnatural or "incorrect" walking may have deleterious effects on the entire body, such as knee, hip and back problems. On the other hand, there are indications that "rediscovering" how to walk naturally can alleviate or even eliminate many problems in a person's body.

The following sequence has been found for practically all humans to be a natural or "correct" gait (except for sprinting):

- the first foot initially contacts the ground with its heel, or with its heel and midfoot simultaneously; - the first foot then begins to roll on the ground with slight foot deformation (and ideally without slipping), the sole of the first foot contacting the ground in sequence by its heel or midfoot, its ball and forefoot portions;

- towards the end of this first foot rolling action, the second foot contacts the ground with its heel, or with its heel and midfoot simultaneously. The first foot is then lifted off the ground;

- the second foot then begins to roll on the ground with slight foot deformation (and ideally without slipping), the sole of the second foot contacting the ground in sequence by its heel or midfoot, its ball and forefoot portions;

- at the end of this second foot rolling action, the second foot is lifted off the ground, and at the same time, the first foot again initially contacts the ground with its heel or with its heel and midfoot simultaneously and the sequence continues.

In the above sequence of alternate foot contact with the ground, a more or less broadened/blurred ground contact line is defined on the sole of each foot. In a person having healthy bones, tendons, muscles and nerves and exhibiting natural gait behavior, this optimal ground contact line typically is a substantially/approximately S-shaped line on the sole of each foot starting at the heel portion, passing along the midfoot and ball portions and ending at the forefoot portion, typically on the medial side of the forefoot portion in the region of the first and second metatarsals and the first and second toes.

The term "pronation" is used to describe the lateral inwards rotation of the foot which normally occurs during its contact with the ground. A certain amount of pronation is considered natural and desirable for a healthy gait. If the foot does not rotate inwards enough, the wearer is said to suffer from supination. If the foot rotates too much, on the other hand, overpronation is said to have occurred. Reference is made in the following description to the "medial" and "lateral" sides of the foot. The term "medial" is intended to refer to the inner side of the foot (the side of the foot facing the other foot), while the term

"lateral" is intended to refer to the outer side of the foot (the side of the foot facing away from the other foot).

It is known from US patent US4759136 to correct overpronation and underpronation/supination by means of peripheral sole regions having a higher durometer value (hardness) than the central sole region. This combination obliges the foot to remain between pronation/supination limits during walking or running. The wearer is thereby obliged to follow a particular pronation pattern which is predetermined primarily by the shoe geometry.

It is also known from US patent US5282326 to correct for overpronation and underpronation/supination by means of appropriately placed footwear inserts. These have the advantage of increasing wearer comfort, by compensating for over- and underpronation, but they are ineffective at encouraging the wearer to develop a healthier gait.

It is therefore an object of the present invention to overcome the above and other disadvantages in footwear soles known in the prior art. In particular, it is an objective of the prior art to provide a footwear sole which provides sufficient sensory information to the wearer's foot to encourage the foot to auto-correct overpronation or supination.

To this end, the invention aims to provide a sole for an article of footwear, the sole comprising: a midsole body element for providing resilient support for the wearer's foot, the midsole body element comprising at least an elastically compressible first material having a first durometer and extending over a majority of the area of the sole, a longitudinal pronation guiding element, comprising a second material having a second durometer, greater than the first durometer, for providing the wearer's foot with a longitudinal pronation guide during walking or running, the longitudinal pronation guiding element being substantially narrower than the width of the sole and extending along a predetermined, substantially S-shaped longitudinal line of optimum gait pressure from a heel region of the longitudinal pronation guiding element to a toe region of the longitudinal pronation guiding element, wherein the longitudinal pronation guiding element is located in a foot-facing surface region of the midsole body element.

According to a variant of the invention, the sole may comprise a medial pronation control element for resisting overpronation of the wearer's foot during an initial contact phase of the foot with the ground when walking or running, wherein the medial pronation control element is located on the medial side of the midsole body element and substantially in the rear half of the midsole body element, and wherein the medial pronation control element comprises a resilient third material having a third durometer, greater than the first durometer.

According to a further variant of the invention, the sole may comprise a lateral pronation control element for resisting supination of the wearer's foot during a mid-gait contact phase of the foot with the ground when walking or running, wherein the lateral pronation control element is located in a region of the lateral side of the midsole body element and at least in a portion of the said lateral side which is at a mid-point along the length of the sole, and wherein the lateral pronation control element comprises a resilient fourth material having a fourth durometer, greater than the first durometer.

According to another variant of the invention, the second durometer may be at least 10 Shore greater than the first durometer.

According to another variant of the invention, the second durometer may be at least 20 Shore greater than the first durometer. According to another variant of the invention, the first durometer may be in the range 30 to 50 Shore.

According to another variant of the invention, the longitudinal pronation guiding element comprises, along its length in heel-to-toe order, a heel region, a mid-foot region, a ball region and a toe region, and wherein the sole comprises a gait enhancement element for providing a greater total durometer of the sole at the mid-foot region of the longitudinal pronation guiding element than at the heel or toe regions.

According to another variant of the invention, the gait enhancement element comprises a thickening of the longitudinal pronation guiding element in the mid-foot region.

According to another variant of the invention, the thickness of the longitudinal pronation guiding element is greater, and the thickness of the midsole body element smaller, in the mid-foot region than in the adjacent heel and ball regions, such that the combined durometer of the longitudinal pronation guiding element and the midsole body element in the mid-foot region is substantially greater than the combined durometer of the longitudinal pronation guiding element and the midsole body element in the adjacent heel and ball regions.

According to another variant of the invention, the thickness of the mid-foot region of the longitudinal pronation guiding element is substantially equal to the thickness of the midsole body element in the mid-foot region.

According to another variant of the invention, the sole comprises an outsole for providing a ground-contacting outer surface for the sole, the outsole comprising at least one fifth material having a fifth durometer greater than the first durometer, and extending over a majority of the area of the sole, and the thickness of the mid-foot region of the longitudinal pronation guiding element is substantially equal to the combined thickness of the midsole body element and the outsole in the mid-foot region, and wherein the outsole comprises an opening such that the secondmaterial of the the mid-foot region of the longitudinal pronation guiding element extends into the opening in the outsole.

According to another variant of the invention, at least one of the medial pronation control element, the lateral pronation control element, the longitudinal pronation guiding element and the gait enhancement element is formed as a contiguous region of the midsole body element.

According to another variant of the invention, the longitudinal pronation guiding element has substantially parallel top and bottom surfaces in one or more of the heel, the mid-foot, the ball and the toe regions.

According to another variant of the invention, the top and bottom surfaces of the longitudinal pronation guiding element are angled relative to each other across the longitudinal pronation guiding element such that the longitudinal pronation guiding element has a substantially wedge-shaped transverse cross-section.

According to another variant of the invention, one or both of the top and bottom surfaces of the longitudinal pronation guiding element has a curved shape in transverse cross-section.

Due to the insole at or close to the foot-contact surface of the sole, a walker or runner wearing a shoe provided with the sole according to the invention experiences increased or concentrated pressure between the insole and the bottom surface of his foot. As a result, the walker or runner feels the substantially S-shaped line as a pressure line at the bottom surface of his foot.

Due to extra hardness of the sole in a cross-sectional direction transverse to the locally longitudinal direction or tangential direction along the substantially S-shaped line of optimal ground contact, a wearer will feel more pressure or support from points located on that line than from points located outside that line, ie off that line and thus will experience "instant feedback" and "feel" during walking or running whenever he or she deviates from the line of optimal ground contact. The expressions "pressure" or "support" or "pressure force" or "support force" are used as synonyms in the present text and are all defined as average measured force per unit area where the force is measured using a vertically sensitive force meter having a horizontally planar force receiving surface having a defined area. The "pressure" or "support" or "pressure force" or "support force" value is calculated as "the measured vertical force acting on the force receiving surface divided by the area of the force receiving surface". Typical support force values may relate to the static support forces measured during standing or the instantaneous dynamic support forces measured during walking, more specifically the locally acting reaction forces (ground forces) in the ground-contacting regions of the sole during the rolling action of a foot on the ground.

As long as the direction of the dynamic force vector resulting from the static weight and the dynamic force during the rolling action of each foot passes through the line of optimal ground contact, there is no or at least hardly any tilting action on the foot which would cause the foot to pronate (tilt medially towards the inside) or supinate (tilt laterally towards the outside), ie in a direction transverse to the walking or running direction, with respect to the shinbone.

The person wearing a sole according to the invention is encouraged by the proprioception sensation from the longitudinal pronation guiding element 2 to reposition his or her weight and foot orientation whenever he or she deviates from the line of optimal ground contact, resulting in the desired correction of posture and gait . Thus the wearer perform a subconscious auto- correction of the pronation/supination of the foot, corresponding to the line of optimal ground contact defined by the relatively hard longitudinal pronation guiding element. The foot's heel-to-toe contact line with the ground tends to follow the path of greatest pressure, and the wearer's gait is therefore corrected by providing a path of harder material, having the shape of the desired contact line.

The subconscious auto-correction involves many parts of the body, including ankle joints, knee joints, hip joints, vertebral column and associated tendons, muscles and nerves, and has a beneficial influence on the entire body.

The longitudinal pronation guiding element extending along the substantially S-shaped line and contacting the foot contributes to the feedback to the walker or runner as described above. Thus, the walker's or runner's senses detect any deviation of his foot from its ideal orientation during walking or running. This feedback sensing process is referred to as proprioception.

The invention will now be described with reference to the accompanying drawings, in which:

Figure 1 shows in schematic plan view an example of a sole according to the first, second and third embodiments of the present invention.

Figure 2 shows in schematic perspective view the sole of figure 1 .

Figure 3a shows a schematic side view of the sole of figure 1 according to an example of the first embodiment of the invention.

Figure 3b shows a schematic perspective view of a longitudinal pronation guiding element as included in the sole of figure 3a.

Figure 4a shows a schematic side view of the sole of figure 1 according to an example of a second embodiment of the invention.

Figure 4b shows a schematic side view of the sole of figure 1 according to an example of a third embodiment of the invention. $

Figure 4c shows a schematic perspective view of a longitudinal pronation guiding element as included in the sole of figure 4a or 4b.

Figures 5a to 5i show in schematic cross section some example profiles for the longitudinal pronation guiding element. It should be noted that the drawings are provided in order to aid an understanding of the invention. They should not be taken to imply any limitation on the scope of protection sought, which is set out in the accompanying claims. Where the same reference numbers have been used in different figures, these are intended to refer to the same or corresponding features. However, the use of different reference numbers is not necessarily intended to indicate a difference between the features to which they refer.

The general principles of the invention will now be described with reference to figures 1 and 2, which show in highly schematic form a sole, 1 , for a right foot. The sole is shown with a midsole body element, 3, which may be an essentially planar piece of relatively soft elastomeric sheet, for example having a durometer of between 30 and 50 Shore. Such a midsole body element, 3, may have a thickness of between 5mm and 30mm, for example. In the upper surface of the midsole body element, 3, is shown an example of a longitudinal pronation guiding element, 2. The longitudinal pronation guiding element, 2, may have a constant thickness, as will be described later, or it may be of different thickness in different regions. The longitudinal pronation guiding element, 2, may be formed as a separate piece of elastomeric material, for example, and inserted into a correspondingly shaped recess in the upper surface of the midsole body element, 3, or it may be formed in the same process, such as injection moulding, as the surrounding material of the midsole body element, 3, but with a higher durometer. The durometer of the longitudinal pronation guiding element, 2, may for example be between 55 and 80.

Various different regions of the longitudinal pronation guiding element, 2, and, by extension, of the sole, are indicated in figures 1 and 2 by way of example: the heel region 6, the mid-foot region 7, the ball region 8 and the toe region 9. In addition, a dotted line, 10, indicates an ideal longitudinal proprioception axis. In the heel and mid-foot regions 6 and 7, the

proprioception axis is well to the lateral side of the sole, and the "correct" amount of pronation is low across these regions. In the ball and toe regions, by contrast, the proprioception axis moves across to the medial side of the sole, and the "correct" amount of pronation is higher in these regions. Due to its extra hardness, compared to the hardness of the surrounding midsole body element, 3, the longitudinal pronation guiding element, 2, is easily sensed by the sole of the wearer's foot, and the information about the transverse position of each portion of the longitudinal pronation guiding element, 2, can be used by the wearer's gross motor locomotion system to adjust the pronation of the foot in response, thereby achieving the desired proprioception described above.

Figure 1 also shows a transverse axis M-L running from the M

(medial) side to the L (lateral) side of the sole. This axis will be referred to below when describing various examples of possible cross-sections of the longitudinal pronation guiding element 2.

In preferred embodiments of the invention, the longitudinal pronation guiding element 2 can have a thickness and/or hardness which varies along the transverse direction (parallel to the M-L axis), at least in the heel and/or ball regions, in order to give increased pronation control. Thus, in the heel region 6, the longitudinal pronation guiding element 2 is made thicker on the medial side than on the lateral side. In this way, the transverse profile of the heel region 6 of the longitudinal pronation guiding element, 2, contributes to the desired pronation-resisting (or supination-promoting) effect which is desired in the heel region of the sole. In the ball region, by contrast, the opposite effect is desired.

Medial and lateral pronation control elements (4 and 5) are also shown in figures 1 and 2. These may be used in addition to the longitudinal pronation guiding element, 2, to provide additional correction of pronation and supination as required at different points along the length of the sole. In the example shown, the medial pronation control element 4 may essentially be a region of increased hardness which offers an increased pressure force to resist the pronation of the wearer's foot at the beginning of the contact phase with the ground (ie while much of the wearer's weight is on the heel and being

transferred to the mid-sole portion 7). The lateral pronation control element 5 is designed to have the opposite effect (ie to increase pronation) at a point further forward along the sole. The lateral pronation control element 5 can also be formed as a region of increased hardness in the material of the midsole body element 3. Its function is to assist the foot in pronating at the point in the step cycle when the wearer's weight is being transferred to the ball of the foot. At this point the line of optimal pronation, 10, crosses over from the lateral side to the medial side of the sole, in the ball region indicated as 8 in figure 1 .

Note that the medial and lateral pronation control elements 4 and 5 may alternatively be formed as separate elements and then bonded or otherwise attached to the side of the midsole body element 3. In order to give the required pronation control effect, they should be of a harder material than the midsole body element 3.

By way of example, the relative hardnesses of the various sole components may be configured as follows:

The midsole body element, 3, may have a hardness in the range 30-

50 Shore.

The medial pronation control element 4 may have a hardness in the range 45 to 65 Shore. Its hardness is in any case greater than that of the midsole body element 3, and preferably greater or equal to the hardness of the lateral pronation control element, 5.

The lateral pronation control element 5 may have a hardness in the range 40-60 Shore, but in any case greater than that of the midsole body element, 3.

The longitudinal pronation guiding element 2 may have a hardness in the range 55 to 80 Shore, but in any case greater than that of the lateral and medial pronation control elements 4, 5.

Figure 3a shows an example of a longitudinal cross section taken along the longitudinal pronation axis 10 of figures 1 and 2. In this first example embodiment, the longitudinal pronation guiding element 2 has a substantially rectangular transverse cross-section, corresponding to the shape shown in figure 5b. The sole 1 is shown with an outsole 1 1 on the ground-facing side of the midsole body element 3. Figure 3b shows such a longitudinal pronation guiding element 2 in perspective view. Figures 4a to 4c show examples of alternative embodiments in which the longitudinal pronation guiding element, 2, is thicker in the mid-foot region 7, to form a region 7' of harder material than the surrounding midsole body element 3. This region 7' is also referred to as a gait enhancement element, and its purpose is to enhance the transfer of the wearer's weight from the relatively softer heel region 6 of the sole 1 , in the initial contact phase of the foot with the ground, over the harder mid-foot region 7' to the softer ball region 8 of the sole 1 .

The harder thickened portion 7' may extend down to make contact the outsole 1 1 , as shown in figure 4a, or it may merely be a thickening of the longitudinal pronation guiding element, 2, which only extends part way into the midsole body element 3 (not shown in the figures).

The gait enhancement element 7' is shown in figures 4a and 4b as being contiguous with the longitudinal pronation guiding element, 2. However, the gait enhancement element 7' may alternatively be formed as a separate element formed or inserted below the longitudinal pronation guiding element, 2. It may also have a different durometer from both the longitudinal pronation guiding element, 2, and the midsole body element 3.

In the example third embodiment shown in figure 4b, the gait enhancement element 7' extends all the way through the midsole body element 3 and through an opening in the outsole element 1 1 .

As a result of the increased hardness of the longitudinal pronation control element 2, relative to the softer material of the surrounding midsole, 3, the wearer will feel more pressure and support from points located on this proprioception line than from points located off the proprioception line.

Whenever the person shifts his/her dynamic force vector resulting from the static weight and the dynamic force during the rolling action of each foot such that this dynamic vector no longer passes through this protruding line, the wearer will experience the desired feedback during standing, walking or running whenever the foot senses a deviation from the proprioception line of optimal ground contact. As illustrated in figure 5a, the longitudinal pronation control element 2 may have a trapezoidal cross-section, for example. Other potential cross- section profiles are shown in figures 5b to 5i.

Figures 5d and 5e show variants in which the lower surface of the longitudinal pronation control element, 2, is concave, thereby amplifying the proprioception effect of deviating from the main proprioception line of optimal ground contact.

Figures 5f to 5i show variants in which the cross-section of the longitudinal pronation control element, 2, is wedge-shaped or tapering. The thickness of the longitudinal pronation control element, 2, may thus decrease from the lateral side toward the medial side or vice-versa. As a result, when wearing such a sole during walking or running, the foot's line of maximum contact pressure with the ground will be shifted transversely (from medial to lateral or vice versa). The longitudinal pronation control element, 2, may be made thicker on the lateral side than on the medial side, for example, which can correct the gait of a bow-legged person. Or the longitudinal pronation control element, 2, may be made thicker toward the medial side, in which case it may be used for correcting the gait of a knock-kneed person.

Note that the figures show the longitudinal pronation control element, 2, as being flush with the upper surface of the midsole body element, 3. However, the longitudinal pronation control element, 2, may also be arranged such that its is proud of the surface of the surrounding midsole body element, 3 (by a height of 0.5 to 3mm, for example). By arranging the harder longitudinal pronation control element, 2, to protrude from the softer midsole element, 3, in this way, the proprioception effect can be greatly enhanced.

Alternatively, the longitudinal pronation control element, 2, may be recessed or submerged into the surrounding material of the midsole body element. In this case, the proprioception can be softened somewhat.

Note that the harder longitudinal pronation control element, 2, must not necessarily be less flexible than the surrounding midsole element. It is advantageous to make the longitudinal pronation control element, 2, harder, but more flexible, than the midsole element, so that the foot's contact path (pronation path) can be guided by predetermining the line of increased pressure (optimal contact line), but without reducing the longitudinal flexibility of the sole.

In one preferred embodiment, the heel region 6 of the longitudinal pronation control element may be made thicker on the medial side than on the lateral side, so as to resist overpronation in the initial ground-contact phase of the gait, when the wearer's weight is principally on the heel.

In another preferred embodiment, the ball portion 8 of the longitudinal pronation control element, 2, has first, second, third, fourth and fifth metatarsal regions counting from the medial side M to the lateral side L of the sole, and the thickness and/or hardness of the longitudinal pronation control element, 2, may be configured to increase from the first to fifth metatarsal regions.

As a result, when a foot rolls on the ground with the sole of the foot contacting the ground in sequence by its heel, midfoot, ball and forefoot portions, the above thickness and/or hardness gradient in the ball portion causes the foot to pronate, ie the weight acting on the foot is shifted from its initial position in the midfoot portion at the lateral side L of the sole to the subsequent position in the ball portion at the medial side M. In other words, the foot is encouraged into pronation while the ball portion of the foot and the sole are rolling on the ground. Thus, during a first phase of the foot's rolling on the ground, the weight acting on the lateral side of the midfoot portion and then on the lateral side of the ball portion is shifted from the lateral side of the ball portion toward the medial side of the ball portion, and during a second phase of the foot's rolling on the ground, the weight then acts on the medial side of the ball portion and then on the medial side of the forefoot portion, ie the big toe.

These conditions of the first, second, third, fourth and fifth metatarsal parts in the ball portion of the sole cause the weight during the rolling action of the foot to be shifted form the lateral side L towards the medial side M. More precisely, after the midfoot portion has rolled on ground with the weight located on the lateral side L, the ball portion then rolls on the ground with the weight being shifted from the lateral side L of the ball portion toward the medial side M of the ball portion, and finally the forefoot portion rolls on the ground with the weight located on the medial side M. At the beginning of this shifting action within the ball portion, the fifth metatarsal part of the ball portion provides more support than the neighboring fourth and third metatarsal parts of the ball portion. At the end of this shifting action within the ball portion, the first metatarsal part of the ball portion provides more support than the second metatarsal part of the ball portion. In other words, the fifth metatarsal part on the lateral side L causes the foot to pronate and the first metatarsal part on the medial side M prevents excessive pronation of the foot.

Thus, these conditions of the first, second, third, fourth and fifth metatarsal parts in the ball portion of the sole have an effect similar to two consecutive banked curves placed along the substantially S-shaped line. Using these terms, during the right foot's rolling action along the substantially S- shaped line, the right foot first passes through a banked curve with a left turn at the lateral side L and then through a banked curve with a right turn at the medial side M. Similarly, during the left foot's rolling action along the

substantially S-shaped line, the left foot first passes through a banked curve with a right turn at the lateral side L and then through a banked curve with a left turn at the medial side M.

A similar thickness and/or hardness gradient may be created in the forefoot portion or toe portion of the sole. In this way, the region of the sole associated with or underneath the second toe (T2) may be configured with a lesser thickness and/or hardness than the region of the sole associated with or underneath any of the first, third, fourth and fifth toes. Preferably, this applies to the part of the forefoot or toe portion adjacent to the ball portion. This concave ("cantilever") and/or soft region in the M2 part of the ball portion and optionally in the T2 part of the adjoining forefoot portion provides some pressure relief for the second metatarsal bone. In summary, it should be noted that the amount of local support, ie the local support forces acting from below on the sole of a foot wearing the sole according to the invention, is determined by the overall thickness and/or hardness profile of the sole. At least the midsole body element and the ground- contacting portions (outsole) contribute with their local hardnesses and local geometries, for instance local thickness distribution and distribution of possible slits, to the resulting amount of local support. In addition, the lower and/or upper insole portions may be provided with their additional contribution to the resulting amount of local support. The ground-contacting portions (heel, midfoot, ball and forefoot portions) and the optional insole portions (lower and/or upper insole portion) of the sole all contribute additionally to the support profile defined by the longitudinal pronation control element, 2, extending along the substantially S-shaped line.

A cantilever profile, such as the one shown in Fig. 5d or in Fig. 5e, may be provided in the the ball portion 8 and the forefoot portion 9 of the sole 1 . The region of the sole 1 associated with the second metatarsal bone (M2) has a lesser thickness and/or lesser hardness than the region of the sole associated with the other metatarsal bones. In addition, at least the part of the forefoot portion 9 or toe portion of the sole adjacent to the ball portion 8, ie the region of the sole 1 associated with the second toe (T2) has a lesser thickness and/or lesser hardness than the region of the sole associated with the other toes. Preferably, this applies to the toe portion of the forefoot portion 9. This design reduces pressure to the second metatarsal (M2) and provides some relief for the joint between the second metatarsal (M2) and the second toe (T2) during walking.

In addition, the following conditions may apply to the transverse thickness and/or hardness profile of the ball portion 8 having a first metatarsal part M1 , a second metatarsal part M2, a third metatarsal part M3, a fourth metatarsal part M4 and a fifth metatarsal part M5 between the medial side M and lateral side L of the sole 1 :

a) The thickness and/or hardness of M2 is less than the thickness and/or hardness of any of M1 , M2, M3 and M4, preferably with M1 , M3, M4 and M5 all having the same thickness and/or hardness. ("M2 < M1 , M3, M4, M5 and preferably M1 = M3 = M4 = M5") b) The thickness and/or hardness of M1 is greater than the thickness and/or hardness of M2, with M3, M4 and M5 all having a thickness and/or hardness in between the thickness and/or hardness of M1 and M2.

("M2 < M3, M4, M5 < M1 ")

c) The thickness and/or hardness of M1 is greater than the thickness and/or hardness of M2, with M3, M4 and M5 all having a thickness and/or hardness greater than the thickness and/or hardness of M1 .

("M2 < M1 < M3, M4, M5")

d) The thickness and/or hardness of M1 is greater than the thickness and/or hardness of M2, with M3 having a thickness and/or hardness greater than the thickness and/or hardness of M4 and M4 having a thickness and/or hardness greater than the thickness and/or hardness of M5.

("M2 < M1 and M3 > M4 > M5")

e) The thickness and/or hardness of M1 is greater than the thickness and/or hardness of M2, with M3 having a thickness and/or hardness less than the thickness and/or hardness of M4 and M4 having a thickness and/or hardness less than the thickness and/or hardness of M5, preferably with M2 having a thickness and/or hardness less than the thickness and/or hardness of any of M3, M4 and M5. Condition e) is the most preferred condition.

("M2 < M1 and M3 < M4 and M4 < M5" and preferably M2 < M3, M4, M5")

These conditions of the first, second, third, fourth and fifth metatarsal parts M1 , M2, M3, M4 and M5 in the ball portion 5 of the sole 1 cause the weight during the rolling action of the foot to be shifted form the lateral side L towards the medial side M.

More precisely, after touching ground with the heel portion 3 and the subsequent rolling action of the midfoot portion 7 on ground with the weight located on the lateral side L, the ball portion 8 then rolls on the ground with the weight being shifted from the lateral side L of the ball portion 8 toward the medial side M of the ball portion 8, and finally the forefoot portion 9 rolls on the ground with the weight located on the medial side M. At the beginning of this shifting action within the ball portion 8, the fifth metatarsal part M5 of the ball portion 8 provides more support than the neighboring fourth and third metatarsal parts M4 and M3 of the ball portion 8. At the end of this shifting action within the ball portion 8, the first metatarsal part M1 of the ball portion 8 provides more support than the second metatarsal part M2 of the ball portion 8. Thus, the fifth metatarsal part M5 on the lateral side L causes the foot to pronate and the first metatarsal part M1 on the medial side M prevents excessive pronation of the foot.

In addition, similar conditions may apply to the transverse thickness and/or hardness profile of the forefoot portion 6 having a first toe part T1 , a second toe part T2, a third toe part T3, a fourth toe part T4 and a fifth toe part T5 between the medial side M and lateral side L of the sole 1 :

a) The thickness and/or hardness of T1 is greater than the thickness and/or hardness of any of T2, T3, T4 and T5, preferably with T2, T3, T4 and T5 all having the same thickness and/or hardness.

("T1 > T2, T3, T4, T5 and preferably T2 = T3 = T4 = T5")

b) The thickness and/or hardness of T1 is greater than the thickness and/or hardness of T2 and the thickness and/or hardness of T2 is greater than the thickness and/or hardness of T3, and the thickness and/or hardness of T3 is greater than the thickness and/or hardness of T4, and the thickness and/or hardness of T4 is greater than the thickness and/or hardness of T5.

("T1 > T2 > T3 > T4 > T5")

c) The thickness and/or hardness of T1 is less than the thickness and/or hardness of any of T2, T3, T4 and T5, preferably with T2, T3, T4 and T5 all having the same thickness and/or hardness.

("T1 < T2, T3, T4, T5 and preferably T2 = T3 = T4 = T5")

d) The thickness and/or hardness of T1 is less than the thickness and/or hardness of T2, and the thickness and/or hardness of T2 is less than the thickness and/or hardness of T3, and the thickness and/or hardness of T3 is less than the thickness and/or hardness of T4, and the thickness and/or hardness of T4 is less than the thickness and/or hardness of T5.

("T1 < T2 < T3 < T4 < T5")

e) The thickness and/or hardness of T1 is greater than the thickness and/or hardness of T2, with T2 having the same thickness and/or hardness as T3, and the thickness and/or hardness of T3 is less than the thickness and/or hardness of T4, with the thickness and/or hardness of T4 being equal or less than the thickness and/or hardness of T5.

("T1 > T2 and T2 = T3 and T3 < T4 and T4 < T5")

In the above transverse profiles, the transition between the thickness and/or hardness sections M1 , M2, M3, M4, M5 and T1 , 12, T3, T4, T5, respectively, may be a stepwise or a smooth transition.

The longitudinal pronation guiding element, 2, can be solid elastomeric material, or it can be a moulded or hollow shape filled with loose material such as a granulate or powder material.