The present invention relates to a midsole, according to Claim 1, for a sports shoe, and a sports shoe comprising such a midsole. The midsole comprises a flexible body element, which extends essentially over the entire length of the sole of the foot, a flexible heel element located under the body element, which extends from under the heel bone (calcaneus) at least partly into the area of the cuboid bone (os cuboideum), and a plate-like stiffener element located at least partly between the body element and the heel element.

Prior art

It is natural for human beings to move on bare feet. However, in sport, the mechanical strain acting on the feet makes it practically essential to use sports shoes. Shoes, however, always change the operation, i.e. the bio-mechanics, of the foot and the leg, in turn affecting the efficiency, i.e. the so- called 'economy', of running, and, when running a great deal, also the paths of movement and physical condition of the sportsperson's feet in the long term.

The product development of running shoes, which started in the 1970s, has largely concentrated on creating various types of attenuation and support systems. Development has been particularly directed at attenuation systems for softening impacts in the area of the heel, i.e. so-called heel- attenuation. At least part of the reason for this has been the increase in stress injuries in the area of the foot and the entire kinetic chain. In development, the basic assumption has been that increased running requires a shoe that will protect the heel area in the heel-impact stage. In the case of support systems, the main object of development has been to prevent over-pronation of the foot structures, i.e. excessive inwards torsion of the foot, during the support stage, or, on the other hand, to prevent over-supination, excessive outwards torsion. A drawback with such solutions is that they do not use effectively the natural attenuation system of the foot and substantially alter the path of movement of the foot during a stride. In the worst case, the choice of shoe forces the runner into completely the wrong kind of stride, which can result in long-term detriments and even increased stress injuries.

One known solution comprising over-pronation or over-supination support and heel attenuation is disclosed in US patent application publication 2004/0154188. The solution is based on a stiffener element, which prevents pronation and supination and is shaped, together with the other parts of the sole, in such a way that a heel-attenuation 'pillar' remains in the area of the heel. US patent 6502330 discloses another, slightly different, stiffener element improving lateral stability.

Another solution, which is in many ways similar, is known from US patent 4757620. It discloses a sole construction for a sports shoe, which comprises a suspension and support structure located between the outer sole and the midsole. This suspension and support structure comprises a flexible toe part extending from the toe to essentially the area of the ball of the foot and a flexible body piece arranged above the heel part, thinning like a wedge from the rear edge of the shoe towards the toe of the shoe and extending at least over the area of the heel, which body piece is substantially stiffer and harder than the said heel part and toe part. Such a sole construction effectively receives the impact acting on the runner's heel, in the stage when the foot makes contact with the ground. In the foot's rolling stage, the sole construction supports the plantar arch, thus reducing the strains acting on the foot. In the propulsion stage, unnecessary slipping of the shoe is avoided.

In recent years, footwear solutions have also been presented, which seek to guide the stride in a more natural direction. Such a solution is disclosed in, for example, FI patent 117541, which represents the prior art closest to the present invention. In the sole construction presented in it, there is a midsole, in which there is a flexible body element, which extends over the entire length of the shoe, a flexible heel-attenuation element, which extends to the area of the heel, and a heel element fitted between them, which extends from the area of the heel to the area of the ball of the foot. The heel element is of a less flexible material than the body and heel-attenuation elements that delimit it above and below.

It is possible to say roughly that, when running barefoot, the loading on the sole of the foot is distributed evenly between the heel and the area of the ball of the foot. However, it has been observed that the heightened heel part typically contained in a heel-attenuated shoe, i.e. its heel, alters the loading of the sole of the foot in such a way that the heel has about 40 percent and the ball of the foot area 60 percent of the loading. This unequal loading emphasizes the importance of the correct action of the sole of the foot and especially of the ball-of-the-foot area. In known sole solutions for shoes, however, practically no attention has been paid to this, perhaps still generally unrecognized, factor.

In addition, a drawback of several known sole solutions is that the sense of the attitude of the foot is weak. As a result, the muscle functioning of the foot too cannot be optimal. In an optimal situation, the muscles of the foot act like an elastic spring and support operation of the natural arch structures of the sole of the foot. This can be achieved, however, only if a good tactile sense of the running surface, and in turn of the attitude of the foot, is retained. In several studies, the development of a sense of attitude, i.e. co-ordination, has been observed to reduce the number of injuries to the sole of the foot and the legs.

In terms of the action of the sole of the foot and the leg, shoes that are excessively attenuated and supported thus cause several important problems, for instance a weakened sense of attitude, a passivation of the small muscles of the foot, and a shortening of the aponeurosis plantaris. The latter can in turn lead to unequal loading of the foot, resulting in a shortening of the Achilles tendon. Over a long period of time, such a change can even become permanent. This is because the latest studies have shown that the frequent use of shoes that are too supportive may passivize the important support structures of the foot. Therefore, there exists a need for new types of model of sports shoes.

Summary of the invention

The intention is particularly to create a new type of sole construction, which will eliminate at least some of the aforementioned and drawbacks and which will thus have a significant effect on stride. The invention is particularly intended to create a sole construction, with the aid of which the stride can be made more economic and natural. Further, the invention's purpose is to prevent stress injuries from arising.

The basic idea of the present invention is, instead of designing powerful heel attenuation and support systems, to design the sole of the shoe in such a way that the stride is guided from the heel- impact stage through the middle-support stage of the stride to the ball-of-the-foot propulsion stage according to the natural path of movement of the foot, equalizing the strain on the foot.

This is achieved by means of a sole-construction solution, which generally comprises a flexible body element, which extends essentially over the entire length of the sole of the foot, a flexible heel element located under the body element, which extends from under the heel bone at least partly into the area of the cuboid bone, as well as a plate-like stiffener element located at least partly between the body element and the heel element.

According to the first aspect of the invention, the stiffener element extends from the area of the heel forwards farther on the lateral side of the sole of the foot than on the medial side of the sole of the foot. This feature has been observed to have a significant effect guiding the movement towards the natural pressure centre-line of the foot, especially in the middle stage of the stride. According to a preferred embodiment, the stiffener element extends on the lateral side at least over the level of the mid-tarsal joint, and on the medial side to at most the level of the mid-tarsal joint. This ensures a sufficient asymmetry and thus a guiding effect.

According to one embodiment, the front part of the stiffener element comprises one, and preferably two forwards-facing protrusions/prongs, of which the lateral-side protrusion/prong extends into the area of the first phalange of the small toe (metatarsal V). Such a protrusion/prong arranged on the side further ensures the desired effect.

According to one embodiment, the stiffener element consists of a material, the bending stiffness of which in the lateral direction is greater than in the longitudinal direction. The stiffener element preferably comprises carbon-fibre, or consists entirely of carbon-fibre, in which there are oriented fibres.

According to one embodiment, the rear part of the stiffener element comprises an opening following die shape of the calcaneus, which permits the activation of the calcaneus in the correct manner in the initial stage of the stride. According to the second aspect of the invention, the heel element comprises a longitudinal groove delimiting its lateral parts and rear part, which is directed forwards from the area of the calcaneus essentially to the lateral side of the sole of the foot from the centre-line of the sole of the foot. By means of this feature, the movement is guided more laterally compared to the path determined by a traditional running shoe, and thus towards the natural pressure centre-line of the foot, at each moment in time.

According to one embodiment, the groove is further delimited by the upper part of the heel element, i.e. in other words it is a downwards-opening recess in the heel element. This permits the heel element to be connected to the constructions above it better and more tightly. According to one embodiment, the groove is open in the direction under the shoe, at least as far as the outer sole. According to one embodiment, the heel element is formed from at least two parts, which are attached, or can be attached on top of each other, and longitudinally in the longitudinal direction of the sole of the foot, and which together form the said groove. The parts can be manufactured from materials with different flexibilities. The rearmost of the said two parts is preferably of a more flexible material than the foremost. According to one embodiment, the rear part of the heel element comprises part of a groove penetrating it in the thickness direction and the front part comprises part of a groove in its under- surface, in which case when joined the said groove forms a foremost part on top of and in front of the rearmost part. By means of this solution, it is possible to improve the foot's sense of attitude together with its natural movement.

According to one embodiment, the body element comprises in its under-surface and/or the heel element in its upper surface a recess, the shape of which corresponds precisely to the shape of the stiffener element and the heel element is arranged to fit precisely into the said recess. In this way, a tight sole-totality is created.

According to a third aspect of the invention, the sole comprises a flexible element, which is of a more flexible material than the body element, essentially delimited to the area of the distal ends of the big toe and indirectly also of its adjacent toe (metatarsals I and II). This ensures in the final stage of the stride a more even propulsion take-off from the entire area of the ball of the foot and gives good support to the primary propulsion point.

According to one embodiment, a recess for the said flexible element is arranged in the body element, essentially at the location of the metatarsophalangeal joint of the big toe. The aspects described above and depicted later in greater detail each separately have a positive effect on achieving the desired economical and natural running stride and each aspect by itself can act as a basis for a new patent application and a distributed patent application. Further, a better effect can be obtained with the aid of a sole that comprises two or all of the aspects described above. The solution that is the subject of the present application is defined more precisely in the independent Claims.

The invention also relates to a sports shoe, which comprises an inner sole coming into contact with the foot or sock, an outer sole coming into contact with the running surface, and a midsole according to one or several of the aspects or embodiments described above and fitted between the inner sole and the outer sole. Considerable advantages are achieved with the aid of the aspects of the invention. In particular, the sole construction disclosed makes greater allowance than known running-shoe solutions for the natural manner in which human beings run and exploits the foot's own built-in attenuation system. In particular, the running shoe according to the invention and described in greater detail below conforms as precisely as possible to the natural operating model of the foot and leg, retains the foot's attitude sense, and activates the small muscles of the foot to act like a spring, i.e. to store and release the kinetic energy arising in active muscle work. The most important task of a running shoe is to permit each runner's own individual movement model during running loading, so that the power output through the support surface formed by the shoe is transmitted to the running surface in the most natural manner possible. The totality formed by a running shoe should support and conform to the runner's own natural biomechanics in the various stages of the running stride. These objectives are achieved by means of the present solution.

The influences on the invention are, among others, the following observations:

- The toes have an important balancing function in shoe solutions. Also when a person moves barefoot, in the so-called central-support stage of walking and running (the weight of the body is supported on one foot/leg) the toes grip the base lightly. The toes stabilize particularly the action of the foot, but at die same time also of the whole leg. As a result of this, toes that act effectively guide the propulsion to be directed forwards, thus improving the power output of the propulsion.

- Human beings have a shock-absorbing mechanism as 'standard equipment'. When walking in shoes, the heel generally impacts the surface first, after which the entire foot follows by rolling. There is thus a powerful impact on the calcaneus. When moving barefoot, the foot descends on the surface in a nearly horizontal position. As a result, the impact strain acting on the calcaneus is reduced, because the harder impact is received by the front-middle part of the foot which has a larger surface area and more flexible construction, instead of the passive calcaneus, which has a smaller surface area. When the front-middle part of the foot strikes the surface first, the muscles affecting the operation of the foot are already activated, i.e. it is justified to say that the impact is received by the body's automatically operating active shock-absorbing mechanism. Further, after the contact of the front-middle part, the heel descends lightly towards the surface, when both the stretching reflex of the Achilles tendon and the operation of the calf muscles are optimized, and as a result of this operation, powerful forward-moving propulsion arises.

In the following, embodiments of the invention are examined in greater detail with reference to the accompanying drawings.

Brief description of the drawings

Figure 1 shows an exploded view of the midsole construction according to one embodiment, as well as the outer sole and arch support attached to it. Figures 2a - 2b show the rearmost part of the heel element , seen from above (a) and as a perspective view (b).

Figures 3a and 3b show the front part of the heel element, seen from below (a) and as a perspective view (b), as well as a side cross-section (c). Figures 4a and 4b show the stiffener element by itself and combined with the body element.

Figures 5a - 5c show the sole construction assembled, seen from three different angles.

Figures 6a and 6b show the body element with the flexible-element recess in the second toe (a), as well as a suitable flexible element for this (b).

Figure 7 shows two views from different angles of the second element of the arch-support system, which conforms to the natural arch of the foot.

Detailed description of embodiments

With reference to Figure 1, the midsole construction 10 described here in detail comprises six pieces 12 - 15, 20, 21 of different shapes, each of which has its own unique task. The components are the body element 12, the stiffener element 15, the front part 14 of the heel element, the rear part 13 of the heel element, and the arch support 21. The parts of the outer sole are marked with the reference number 11 in Figure 1. In the following, the construction and operation of the components is examined in greater detail.

The body element 12 of the sole is designed to be essentially the same length as the entire foot, so that, when standing, the foot rests in a natural position over its entire length. The conditions for a natural model of movement are then preserved. The body element 12 typically comprises a shallow recess, into which the foot fits. In other words, on the upper surface of the body element there are edges on the sides and rear, which rise upwards.

The body element 12 can be made from a flexible polymer material. The material can be, for example, EVA (ethylene-vinyl acetate). Such a material provides the action of the foot with the conditions that support and conform to natural movement.

A heel element, consisting of two parts 13, 14, is fitted under the body element, in the area of the heel and the arch of the foot. The parts form a totality, the shapes of which conform to the natural anatomy of the rear part of the foot. The rear part 13 of the heel element acts as an equalizer and stabilizer of movement and the asymmetrical construction of its under part reinforces the operation of the other parts of the shoe. The front part 14 of the heel element fits together with the rear part 13 and indeed their operation takes place as a totality. The essential feature of the totality is the outwards-facing groove that they form. The shape of such a groove is also different from that in known solutions and ensures the desired combined operation of the elements.

Figures 2a and 2b show the rear part 13 of the heel element in greater detail. The part has preferably an asymmetrical U shape, when viewed from above. It comprises two side prongs 31 and 32, as well as a rear curve 33 joining the prongs. The prongs 21, 32 and the curve 33 define the groove 34. The groove 34 preferably begins to curve outwards from the curve 33, when seen from in front. The curve 33 is preferably designed to be thicker than the prongs 31, 32. As can be seen from the figures, the prongs 31, 32 preferably thin towards the front of the sole, i.e. they are wedge shaped.

The front part 14 of the heel element fits into the rear part 13 of the heel element, particularly into its prongs 31, 32 and the inner surface of the curve 33, which is illustrated more clearly in Figures 3a - 3c. It comprises a rear part 43, which fits together with the inner surface of the curve 33. The side constructions 41 and 42 of the part 14 in turn define the groove 44, which clearly curves outwards from the rear part 43, when viewed looking forward. The groove 44 fits together with the rearmost part 34. The groove that is created as a result is thicker in the rear part of the shoe than farther forward. The shape of the groove in the finished sole construction can be seen best in Figure 5b, in which it is marked with the reference number 78.

As stated, the groove 78 curves outwards, i.e. in the direction of the fifth metatarsal, when viewed looking forward. At the rear, the groove is preferably on the centre-line of the heel element and thus also of the shoe. The groove curves preferably at least 20°, typically 25 - 45°, i.e. the groove's longitudinal direction deviates by this amount in front from its direction in the rear. Further, the groove can curve essentially evenly, i.e. approximately along the curvature of a circle.

The width of the groove 78 can average, for example, 1 - 2.5 cm. According to one embodiment, the groove has a shape with an essentially even width.

As can be seen from the figures, the front and rear parts 13 and 14 of the heel element are bevelled in such a way that they are placed both one after the other in the front-rear direction and partly on top of each other. By means of this solution, their joint operation and the correct directing of the forces during both the heel impact and the middle stage of the stride are ensured, i.e. the forces are distributed better to the front part of the heel part, instead of only to the calcaneus. The front part 14 is preferably of a greater hardness than the rear part 13 and the body element 12, which equalizes naturally the distribution of the strain in the initial stage of the stride.

In its entirety, the heel element 13, 14 extends essentially behind the calcaneus right to the area of the cuboid bone and can also continue over this. With reference to Figures 4a and 4b in addition to Figure 1, the stiffener element comprises a preferably oval hole that follows the shapes of the calcaneus. Such a shape permits the normal operation of the calcaneus and distributed the heel-impact pressure. Thanks to the hole, the stiffener element does not, however, act strongly as part of the heel attenuation, but promotes the active operation of the foot, by conforming to the calcaneus and at the same time stabilizing the operation of the rear part of the foot by permitting a natural movement model and free operation.

A particular feature of the stiffener element is that its forwards facing prongs 53 and 54 of the ball- of-the-foot plate are of different dimensions. Further, the outer-edge prong 54 is longer that the inner-edge prong 53. In the solution, the longer outer-edge prong 54 supports the operation of the foot's fifth toe, in which case the pressure is naturally moved forward and permits an effective forwards-directed propulsion.

The thickness of the stiffener element can be, for example, 0.5 mm - 3 mm, preferably 0.5 mm - 1.5 mm, even more preferably about 1 mm. The stiffener element is typically not completely flat, but is gently shaped to fit between the body element and the heel element and in turn the shapes of the foot. With reference to Figures 6a and 6b in addition to Figure 1, there is a recess 19 in the upper surface of the body element 12 at the metatarsophalangeal joint of the big toe, into which is fitted a propulsion base 20 making the pushing of the ball of the foot more effective. The propulsion base 20 is made from an elastic special material, which returns to its original shape immediately after the termination of loading. The hardness of the propulsion-base material is less than that of the body element.

As can be seen from the figure, the propulsion base 20 is preferably fitted only in the ball-of-the- foot area of the first toe, or at most of the first and second toe. Its shape conforms to the anatomical shape of the metatarsophalangeal joint of the big toe. It is preferably approximately D shaped. This ensures that the strain at the end of the propulsion stage is distributed better under the

metatarsophalangeal joint of the big toe, so that the propulsion is directed horizontally and as effectively as possible. At the start of the propulsion stage, the other toes too participate in balancing by gripping the base lightly, so that they increase the power output and equalize the operation of the entire foot. Combined with the shapes of the heel element and/or the stiffener element depicted here, the movement is balanced from the beginning to the end of the stride. It can even be said that the operation of the propulsion base 20 is based to some extent on the active support of propulsion, and not on the passive attenuation of impact as in the known solutions. The orientation of the flexing grooves in the bottom of the outer-sole elements 11 supports the operation of the other elements and permits the use of new types of solution in the shoe. In order to transfer the loading forward more naturally to the ball of the foot, the outer edge of the outer sole of the shoe is made flexible mainly with the aid of transverse flexing grooves, which extend towards the longitudinal centre line of the shoe. There are preferably three flexing grooves. On the inner edge of the outer sole of the shoe, two flexing grooves oriented towards the propulsion base are correspondingly formed in the area of the ball of the foot. These aforementioned flexing grooves permits two very important operations in the ball-of-the-foot area of the sole construction, i.e. the toes are able to grip the inner sole of the shoe, as happens when moving barefoot, and at the end of the ball-of-the-foot propulsion the pressure in under the metatarsophalangeal joint of the big toe, to that the movement model remains natural throughout the entire ball-of-the-foot propulsion stage.

A foot arch support construction, the arch support 21, is preferably fitted under the front part 14 of the heel element of the sole construction. The task of the arch support 21 is to support and to conform to the arch constructions of the middle part of the foot, during the middle-support stage of the operation of the arch constructions. In addition, a plate-like piece conforming to and supporting the natural arch of the foot can be fitted above the outer sole under the support construction of the foot arch, and is illustrated in greater detail in Figure 7. The arch-support system can thus exceptionally consist of two separate parts, in place of the traditional single part.

The arch support 21 can be manufactured from, for example, PVC plastic.

In the following, the parts of the sole construction are further described in greater detail, with emphasis on their operation guiding and equalizing movement:

The recess 19 in the body element 12, and the propulsion base 20 fitted into it, are formed under the metatarsophalangeal joint of the big toe (metatarsal I), preferably to conform to the construction of its bones, as well as the anatomical construction of the adjacent toe (metatarsal II), which act mutually in synergy at the end of the ball-of-the-foot propulsion stage. These two toes (first radius and second radius) play a decisive role in directing the power output forwards in the ball-of-the- foot propulsion. It can be further seen from Figures 1 and 6a that the propulsion base 20 is formed to extend from close to the inner side of the sole towards the longitudinal centre line, so that the big toe and the toe next to it can act in the most natural manner possible. The rear part 13 of the heel element is a plate-like piece, the edge of which on the foot arch side is shaped to fit the special shape of the front part 14 of the heel element. In the middle of the under- surface of the rear part 13 of the heel element is a recess, the purpose of which is for its part to facilitate the horizontal directing of the reaction forces arising in the heel impact. At the start of the contact stage of the running stride a clear impact peak appears, as a result of which a large momentary loading acts on the body, which is linked to the arising of stress injuries, if the power output is not kept directed forwards.

With the aid of the described construction of the rear part of the heel element, the pressure arising in the heel impact is distributed to the front-middle part of the foot, which is structurally the strongest and most active part of the foot. The part 13 can be made from the same or a similar material as the body element 12, for example, from ethylene-vinyl acetate.

The front part 14 of the heel element, which is made from a denser material than the more flexible body element 12 and the front part 13 of the heel element, is at least partly between the rear part 13 of the heel element and the body element 12. A suitable material for the front part is, for example, EVA (ethylene-vinyl acetate), the density of which is, however, greater than that of the body element 12 and the rear part 13 of the heel element 13. The front part 14 of the heel element extends from the area of the heel to the side of the ball-of-the-foot area, preferably to the level of the so-called lower ankle joint (mid-tarsal joint), or immediately behind this. Tlianks to its shape, it significantly accelerates the rolling of the running stride, and conforms to and supports the action of the foot's longitudinal constructions in the running loading. The front part 14 of the heel element comprises a specially shaped rear part 43 and in turn a specially shaped front part 41, between which remains a curved groove 44 that is important in terms of guiding movement.

Figure 3c shows a shallow recess 45 formed in the upper surface of the front part 14 of the heel element 45. It is intended to receive stiffener element 15 made preferably from carbon fibre, the task of which is, together with the front part 14 of the heel element, to stabilize the natural action of the foot in the middle support stage of the stride and at the start of the ball-of-the-foot propulsion. The shape of the stiffener element 15 is preferably designed in such a way that in the ball-of-the- foot area is extends behind the lower ankle joint (mid-tarsal joint) on the inner edge (prong 53) and over the outer edge of the same joint (prong 54), so that is supports the action of the little toe (metatarsal V) in the ball-of-the-foot propulsion state. The loading pressure is then distributed in the front part of the foot to the load-bearing constructions (metatarsals I and V). The fibres of the stiffener element 15 are preferably oriented to that the transvers stiffness is greater than the longitudinal stiffness, so that it retains its flexibility in the longitudinally acting pressure variation, so that the centre of gravity of the stride follows a natural path. The stiffener element 15 is equipped with an opening 52 coming under the calcaneus. A loop 51 runs around the opening 52. The opening 52 permits the activation of the calcaneus in pronation that takes place automatically (the natural shock-absorbing mechanism of the foot), as well as permitting the distribution of the loading pressure arising in the heel impact to the front-middle parts of the foot, which is structurally the most durable and active area of the foot. Thus, the stiffener element 15 conforms precisely to the outer edges of the calcaneus, so that the vector forces acting laterally are distributed naturally, in order words the stride progresses along the pressure centre line at each moment in time. The stiffener element is preferably shaped in a curve, so that when viewed from the side it forms a very gentle letter S. This shape corresponds essentially to the upper surface of the front part 14 of the heel element and typically also to the shape of the under-surface of the body element 12, so that the parts act together in synergy and form a totally, by means of which the shortest possible contact with the base is created.

The arch support 21 is shaped in such a way that it guides the movement to the pressure centre line, on the natural path of movement of the foot. The action differs from the generally used solutions in that it particularly directs the stride in a natural direction and does not restrict pronation or supination, as do the generally used solutions. The shapes of the arch support are directed to the lateral side, contrary to the generally used manner, as a result of which the guiding of the direction of movement to the pressure centre line is reinforced, along with the other features of the invention.

In the heel part of the outer sole 11 a rubber material is preferably used, which will resist wear extremely well and thus prolong the service life of the shoe. The rubber material of the heel part is preferably grooved in such a way that the support surface in contact with the running surface is made as small as possible, the advantage of which is a clearly smaller friction surface, which for its part increases the natural sense of the running surface. The rubber material of the ball-of-the-foot area is elastic, so that it permits the natural action of the small muscles of the foot in the ball-of-the- foot propulsion stage. The small muscles of the foot act like a spring, storing and releasing the kinetic energy arising in the various stages of the stride. As can be seen particularly in Figure 5b, in order to transfer the loading better to the ball of the foot, the outer edge of the outer sole 11 of the shoe is formed to be flexible mainly with the aid of transverse flexing grooves 23, which extend towards the longitudinal centre line of the shoe, preferably without, however, crossing it. There are typically from two to five, preferably three, of these flexing grooves 23 in the outer edge of the outer sole, the intention of which is to support and conform to the natural action of the ball-of-the- foot area, so that the muscle activeness will be on the best possible level. There are typically from one to four, preferably two, essentially transverse flexing grooves 24 directed towards the ball of the foot's propulsion base 20, formed in the ball-of-the-foot area on the inner edge of the outer sole 11 of the shoe, the task of which is to permit the natural action of the metatarsophalangeal joint of the big toe in the final stage of the ball-of-the-foot propulsion. The dimensions of the flexing grooves 23, 24 are larger than those of the fine constructions of the sole construction, their width being typically at least 2 mm. In summary, it can be stated that the running shoe sole construction presented above, which comprises an outer sole 11 supporting natural movement and a midsole 10 conforming to and supporting the natural shapes of the foot, which midsole 10 comprises a body element 12 extending over the entire length of the shoe, a multi-part totality extending to the area of the heel, in which there is a rear part 13 of the heel element, which distributes the heel-impact pressure to the foot's active front-middle part, as well as a front part 14 of the heel element, with a lesser flexibility and fitted between the rear part 13 of the heel element and the body element 12, the intention of which is to support and conform to the action of the longitudinal arch of the foot under running loading. In addition, the construction comprises a shaped stiffener element 15 fitted into a recess 45 formed in the upper surface of the front part 14 of the heel element, which extends farther into the ball-of- the-foot area on the wide of the outer side of the shoe than on the side of the inner side of the shoe. An opening 51 following the shapes of the calcaneus is formed at the location of the calcaneus in the rear part of the stiffener 15, in such a way that under the heel the stiffener element 15 follows the shapes of the outer edge of the calcaneus, the intention of which is to support the action of the rear part of the foot (calcaneus and talus), in such a way mat the calcaneus can activate the inwards rotation (pronation) taking place from the lower ankle joint. In addition to this, the shapes of the stiffener element 15 distribute the heel-impact pressure to the front-middle part of the foot, when the activeness of the foot's small muscles will be at the best possible level and they can act like a spring, storing and releasing kinetic energy, when the power output will remain horizontal and the loading pressure in the ball-of-the-foot area is distributed to its load-bearing constructions.