JPH0431682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to athletic shoes, and more particularly to athletic shoes for running and other sports of the type having a closed cell polymeric foam midsole.

Currently, Slitsplast and Boardlast running (or jogging) shoes, as well as other types of athletic shoes, typically rest on a flexible outsole and are bonded to a single-celled polymeric foam intermediate layer. Laminated sole structures with soles have been manufactured. Slitsplast running shoes differ from boardlast running shoes primarily in that they do not have an insole, but instead have a closed textile sole that wraps completely around the foot like a slipper. In boardlast running shoes, the upper has an open sole that is closed by a midsole board that rests on the midsole. Foam midsoles are lightweight and have shock absorbing properties that cushion the wearer's feet from impact while running.
It is used for both types.

Slitplast-type athletic shoes are generally preferred over boardlast-type athletic shoes because they are typically more comfortable to wear. However, due to the lack of a midsole board, slitplast athletic shoes are typically less stable than boardlast athletic shoes. This is because concentrated stress occurs in the foam midsole during running, leading to uneven deterioration of the foam midsole to an undesirable extent. Foamed intermediate soles therefore significantly lose their effectiveness as shock absorbers due to uneven deterioration.

Deterioration of the foamed midsole occurs due to continuous stress caused by the periodically repeated deformation and restoring of the midsole during running. This deterioration may manifest itself in the form of permanent compressive deformation of the midsole, ie, compressive sag. Further, where the closed cells within the foamed midsole are destroyed, the foam may deteriorate without compression set.

Midplant deterioration is often localized due to concentration patterns that result from a runner's unique running style. For example, at the back of the heel,
Localized deterioration may occur at the posterior outer edge of the shoe. Midsole degradation also occurs throughout the shock absorbing portion of the midsole as a result of compressive forces that cause the midsole to expand outwardly of the shoe.

Localized midsole deterioration on the medial center of the shoe and localized midsole deterioration on the lateral side of the shoe are both particularly troublesome because they tend to cause the shoe to tilt and lose its stability when the runner's foot strikes the ground. Runners may adjust their running style to compensate for this instability, which can in turn injure their feet and ankles. Moreover, since deterioration of the intermediate sole often occurs before the life of the outsole is over, the problem of intermediate sole deterioration is magnified.

The foam midsoles of Boardlast running shoes also deteriorate with use, but this cooling is not as uneven as the midsoles of Slitsplast athletic shoes. This is because the midsole of a boardlast type athletic shoe disperses the force acting on the midsole to some extent unless the midsole board itself deteriorates.

Midsole boards also disperse forces acting on the foam midsole to some extent, but if the midsole board were made stiff enough to distribute the forces across the foam midsole, the athletic shoe would become too stiff and the wearer's It makes it very uncomfortable to wear. On the other hand, a low-strength midsole board that satisfies the wearer's wearing comfort is susceptible to deterioration, and even in boardlast type athletic shoes, the midsole deteriorates extremely unevenly.

The general object of the invention is to improve the stability of an athletic shoe without making the shoe uncomfortably stiff and without using components that reduce the foot storage volume of the upper. and reduce deterioration of the intermediate sole,
and to provide a novel structure that increases the anatomical support of the wearer's foot. A further unique object of the invention is to sufficiently prevent uneven deterioration of the midsole of Slitsplast type athletic shoes without relying on the midsole board and without impairing the comfort of the Slitsplast type athletic shoe. The objective is to provide a novel structure that reduces the This is usually accomplished by bonding the foam midsole with a special layer in the portions underlying the upper surface of the midsole in order to stiffen the surfaces of preselected portions of the midsole. In the embodiment shown, this special layer is in the form of a thin, stiff, almost inextensible layer, a so-called stiffening board, which has two intermediate layers between the upper and lower surfaces of the intermediate sole. Located between and bonded to the bottom layer. The stiffening board is sufficiently stiff to effectively distribute the forces acting on the shoe over the area covered by the board to more evenly distribute the forces acting on the shoe. There is a need.

Its geometry is particularly important since the stiffening board of the invention effectively stiffens the foam midsole support under the foot. In the illustrated embodiment, the stiffening board is located entirely under the wearer's rear foot or heel, and anteriorly, also under the medial arch of the foot, approximately the first, second, and third metatarsal heads. It is shaped so that it extends up to the center of the wearer's foot, but does not extend to the outside of the middle arch of the wearer's foot.

Since only selected areas are covered with the stiffening board, this stiffening board does not interfere with the flexibility required by the shoe. Therefore, the stiffening board may be made as stiff as possible without becoming too stiff and brittle.

By distributing the forces acting on the midsole, the stiffening board of the invention clearly reduces harmful and uneven midsole deterioration and greatly extends the service life of the shoe. The fact that the stiffening board is bonded to the opposing midsole layer has the effect of itself restraining the outward expansion of the midsole due to compressive forces, thereby preventing the midsole from expanding outwardly due to this outward expansion. Reduce deterioration. This deterioration due to the outward expansion of the intermediate sole is manifested in the destruction of the cell due to shear forces acting on the intermediate sole.

By providing the stiffening board of the present invention at a position midway between the upper and lower surfaces of the midsole and using a boardless midsole (i.e., a slitplast structure without a midsole board), the foot support portion can be lowered. arise.
The foam intermediate sole layer below the stiffening board serves only to absorb the force due to the impact of the foot on the ground.
The midsole layer above the stiffening board also acts as a shock absorber and also cushions the wearer's foot, so the shoe does not feel stiff due to the stiffening board. Furthermore, the foam midsole layer on top of the stiffening board in the rear foot area of the wearer is thick enough to match the shape and construction of the wearer's heel, so that the shoe's Increases comfort.

By stiffening the foam midsole as described above, the extent to which a runner's foot sinks into the midsole is advantageously reduced as the stiffness of the midsole material is selectively increased. By extending the stiffening board to a portion of the midsole below the medial arch or mid-arch supporting portion, the stiffening board and foam midsole also work well as a comfortable dynamic arch support. This feature of the invention eliminates the need for conventional arch support inserts, such as treadlocks, which disadvantageously reduce the foot storage volume of the shoe upper.

The midsole stiffening layer of this invention conveniently allows podiatrists and orthopedic surgeons to modify existing running shoes to compensate for leg and foot asymmetries or solve other problems. It can be manufactured separately from the shoes as a custom item so that it can be used as a shoe. Various shoe inserts have traditionally been used for this purpose, such as heel cushions, arch supports, and other so-called muscle and joint reinforcement restoration devices. All of them have the common disadvantage of creating some degree of discomfort by encroaching on the foot storage space within the shoe leather.

In contrast to these conventional shoe inserts, the stiffening layer of the present invention is within the midsole and not within the upper, leaving the volume within the upper completely intact to provide comfort to the wearer's foot. Can be covered.

With the foregoing in mind, it is a further object of the present invention to stiffen the foam midsole by adding a stiffening layer between the top and bottom surfaces of the foam midsole along a preselected surface of the area under the foot. An object of the present invention is to provide athletic shoes having a novel intermediate sole structure.

Yet another object of the present invention is to provide an athletic shoe with a novel midsole structure in which a special layer is bonded to the foam midsole body to reduce or slow down the harmful uneven deterioration of the foam midsole. The goal is to provide the following.

Yet another object of this invention is to provide a novel midsole construction athletic shoe with dynamic arch support.

Another object of the invention is to provide an athletic shoe with a new and economical midsole structure that is easy to manufacture and achieves the above objectives.

Another object of this invention is to provide a new, custom-made layer for modifying existing athletic shoes to accommodate the wearer's unique anatomy and asymmetries.

Another object of this invention is a novel method of utilizing the above-described custom shoe modification layer to compensate for weight differences and leg length differences.

In this specification, "hindfoot" refers to the part of the heel of the foot that includes the calcaneus, and "midfoot" refers to the part adjacent to the hindfoot that together forms the beginning of the arch of the foot. It refers to the middle part of the foot that includes five bones, and the "forefoot" refers to the part of the foot that is adjacent to the midfoot and includes the metatarsal bones.

Although the midsole stiffening layer of the present invention is incorporated into a slitplast-type athletic shoe in the illustrated embodiment, the principle of the invention is that the midsole board functions as the special stiffening layer of the present invention. It will be appreciated that this also applies to competition running shoes having an insole board made sufficiently flexible so as not to damage the performance.

The present invention has an upper and a sole, the upper overlying and attached to a portion of the sole, and the sole overlying and attached to a flexible outsole. an athletic shoe for running or other sports having a fixed flexible shock-absorbing midsole, the midsole being formed from a foamed polymeric material; In order to stiffen the midsole and support the central arch part, a separate part from the midsole is installed between the upper and lower surfaces of the midsole in a region below the heel and the central arch part of the midsole. It is characterized in that a formed stiffening layer is inserted.

In the athletic shoe of the present invention, the stiffening layer evenly distributes the load in that region to the midsole, thereby preventing local deterioration of the midsole.

The present invention also provides a step of cutting the intermediate sole in order to provide a space between the upper and lower layers of the intermediate sole for providing a stiffening layer, and a step of cutting the intermediate sole along a preselected plane to stiffen the intermediate sole. , a method of modifying an existing running or other sports athletic shoe having a polymeric foam midsole, comprising the steps of inserting the stiffening layer and adhering the stiffening layer to the midsole. It is something.

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIGS. 1 and 2, competitive running shoes incorporating the principles of the present invention include a flexible slitplast-type upper 10 and a sole 12 beneath the upper 10. and a flexible and bendable slitplast type insole 13 (second
(see figure). The upper 10 has a closed fabric sole 15 that extends completely around the foot in the usual manner.
The inner sole 13 fits into the upper skin 10, and the cloth sole 15
overlap on top of.

The carapace 10 may be of any suitable structure as long as it has a normal structure.
4, a mud catcher 16, a heel part 18, a moon shape 20 that wraps around the back of the heel, and a throat 2 for tightening with a string 24 that opens along the mud catcher 16.
2 and a padded tongue 26 along the throat 22
and a padded rim 28 around the foot opening.

The sole 12 has a flexible outsole 32 that contacts the ground.
and a shock-absorbing midsole 33 overlying and bonded to the skin 32.
Outsole 32 may be of any suitable construction and may be made of synthetic or natural rubber. The contact surface of the outsole 32 preferably has a suitable road surface pattern 36. The intermediate sole 33 has approximately the same shape as the outer sole 32. The upper 10 is secured along the fabric sole 15 to the midsole 33 by adhesive or other suitable method.

The midsole 33 is formed from a suitable closed cell polymeric foam shock absorbing material. For example, midsole 33 is made from a mixture of ethylene vinyl acetate and polyethylene, cross-linked with peroxide during molding.
This foam material is approximately 0.2 per cubic centimeter.
It is preferable to use a material having a density of 1 gram or a light material with a slightly lower density.

The midsole 33 is thickest at the rearfoot or heel portion 39 of the shoe, which is under the heel or rearfoot of the shoe wearer. In the illustrated embodiment, the heel portion 39 of the midsole is of generally uniform thickness. As shown in FIGS. 1 and 2, the shoe is tapered toward the middle portion before the heel portion 39, forming a wedge shape. This wedge portion may be made separately from the intermediate sole 33, in which case it may be superimposed on or below the intermediate sole.

In the illustrated embodiment, the midsole stiffening layer of the present invention is a thin, stiff, flat, flat-sided layer 37.
It is called a stiffening board. This stiffening board 37 is formed separately from the foam midsole 33 and is incorporated into the midsole in a manner described in detail below.

In the illustrated embodiment, the midsole 13 is made of a soft, flexible, flat cushioning liner 38 for the wearer's sock. A liner 38 overlies the fabric sole 15 of the upper 10 and may be made of any suitable flexible material, such as foam or terry. A feature of the midsole 13 is that it does not have a midsole board.

As shown in FIGS. 1-5, the stiffening board 37 is located within the midsole 33 within a gap 42 between the upper and lower surfaces of the midsole that partially divides the midsole 33 into an upper layer 44 and a lower layer 46. inserted. Stiffening board 37
are the lower surface of the upper layer 44 of the intermediate sole and the lower layer 4 of the intermediate sole.
6 by adhesive or other suitable method. Any suitable adhesive may be used to adhere the stiffening board 37 to the upper and lower layers 44 and 46 of the midsole. The adhesive is applied to the stiffening board 37 and the intermediate sole upper layer 4.
It is desirable to coat the entire contact surface between the stiffening board 37 and the intermediate sole lower layer 46.

The split 42 is parallel, or at least generally parallel, to the outsole 32 when the sole is uncurved and straight.

The rearmost end of the heel of the intermediate sole may be tapered as shown in FIG. 2, but other than this, the intermediate sole lower layer 46 has a generally uniform thickness over the entire length and width of the split 42. . Upper layer 4 of the midsole under the wearer's rear foot or heel
The hind leg of the 4 also has a generally uniform thickness.

The crack 42 is formed in the intermediate sole 33 at the center or slightly below the upper and lower ends of the rear foot portion of the intermediate sole. In any case, the location of the cracks 42 is such that there is sufficient thickness in the upper layer of the midsole to prevent the wearer's foot from being pushed up by the stiffening board during the maximum anticipated impact on the midsole. must be low. The thickness and other dimensions of the midsole 33 may be any conventional and suitable values currently used in the shoe industry for the manufacture of running shoes.

At the wearer's rear foot, or below the center of the heel, the total thickness of the midsole 33 is, for example, about 3/4 inch (19 mm), and the height of the split 42 is about 5/4 inch above the lower surface of the midsole. It is 16 inches (8 mm).

As shown in FIGS. 1 to 3, the crack 42
The shape and contour of the stiffening board 37 match the shape and contour of the stiffening board so that the stiffening board 37 can fit completely into the structure. The split 42 is formed in the midsole 3 so that it opens completely to the rear and both sides at the rear foot of the midsole.
It has spread to the entire hindfoot or heel of 3.
From the rearfoot portion of the midsole 33, the cleft 42 extends forward and opens at the medial or mid-edge of the shoe, below the medial arch of the wearer and approximately at the head of the first metatarsal bone.

The stiffening board 37 may be assembled to the intermediate sole by any suitable method. For example, after creating a crack 42 in the midsole and applying adhesive to both sides of the stiffening board 37, the stiffening board is fully inserted into the crack 42. Next, the upper and lower layers 44 and 46 of the intermediate layer are pressed against the stiffening board 37, and the stiffening boards are firmly bonded to the upper and lower layers of the intermediate sole.

Stiffening board 37 is formed from a suitable, durable, substantially non-extensible material. For example, a rigid composite sheet consisting of a polyester resin and woven or shredded glass fibers in which the amount of glass fibers is about 25% of the sheet by volume.

The minimum bending modulus of the stiffening board required to sufficiently distribute the forces acting on the midsole 33 depends on the thickness of the stiffening board. The thickness of the stiffening board 37 typically needs to be at least about 0.05 inch (1.3 mm);
Preferably about 0.06 inch (1.5 mm) (about 1/16 inch)
is desirable. A 0.06 inch (1.5 mm) thick stiffening board requires a bending modulus of at least 1000000 psi
(70000Kg/cm ² ), preferably about 2000000psi (140000psi
Kg/cm ² ) is more desirable.

As shown in FIG. 3, the stiffening board 37 extends from the entire rearfoot portion of the sole to the outer edge of the heel and from one side of the midsole to the other. From the rear of the midsole 33, the stiffening board 37 extends forward along the medial or medial edge of the shoe to a location 50 proximal to the head of the wearer's first metatarsal. From here, the edge or perimeter of the stiffening board 37 arcs posterolaterally along a line 51 proximal to the heads of the wearer's second and third metatarsals. The edge of the stiffening board further curves back along a longitudinal line 52 towards the base of the wearer's cuboid bone and reversely arcs at 53 to form the midsole rearfoot or heel region. 3
9 to the lateral edge of the sole along a line 54 that is generally perpendicular to the longitudinal axis of the shoe.

With the construction described above, the stiffening board 37 extends forward over the entire rear foot of the wearer along the central edge until it is below the medial side of the wearer's foot, but on the outside of the wearer's arch, i.e. It is clear that the forefoot extends anteriorly to the first, second, and third metatarsal heads. Since the stiffening board 37 only covers a specific area, it does not interfere with the flexibility required for running shoes. Therefore, it can be made as stiff as desired as long as it does not become brittle.

When the wearer steps on the sole of the shoe, the stiffening board 37, as shown at 56 in FIG. It is desirable to taper the thickness along the leading edge (see lines 51-54) to draw its curve. In addition, the rear lateral or outer corners 58 (see FIG. 3) are also designed to avoid stress concentrations in that area, where the heel most commonly strikes the ground, and to provide stiffening boards 37. It is also recommended to run diagonally to eliminate or significantly reduce the harmful and accelerated wear of the soles.

The midsole underlayer 46 only functions as a shock absorber to absorb the forces resulting from the impact of the runner's foot as it strikes the ground. The midsole upper layer 44 also acts as a shock absorber to absorb this force, but in addition there is a stiffening board 37 that provides cushioning for the wearer's feet so that the shoe does not feel stiff. Additionally, the wearer's rear foot or heel portion of the midsole upper layer 44 closely conforms to, or is shaped like, the shape of the wearer's heel to further enhance wearing comfort. It has enough thickness.

By stiffening the midsole 33 as described above, the extent to which the runner's foot sinks into the midsole upper layer overlying the stiffening board 37 is reduced compared to a conventional shoe without a stiffening layer of the present invention. conveniently greatly reduced. The stiffening effect during initial deformation and when the wearer's foot sinks into the midsole upper layer 44 is multiplied by the presence of the stiffening board 37, so that energy is absorbed at about twice the rate of a normal shoe. . The maximum force will be greater than a new normal shoe, but still within acceptable limits. In addition, regular shoes wear out due to continuous use, such as when running a marathon distance.
It is known that about half of its energy absorption properties are often lost.

Reducing the degree to which the hindfoot subsides within the midsole 33 has the advantageous effect of allowing the runner greater control over the movement of the hindfoot, thereby increasing the shock absorbing properties of the midsole 33. Increases hindfoot stability without significantly compromising.

By extending the stiffening board 37 to a place below the inside or middle of the runner's arch, the combined effect of the middle sole 33 and the stiffening board 37 below the inside of the arch of the foot allows the wearer to Provides comfortable arch support. This arch support is dynamic in the sense that it is only felt when significant force is applied. For this reason, so-called arcuate keys and conventional anti-step support inserts are not required. These have the disadvantage of being placed within the upper of the shoe and reducing the volume that the foot enters within the upper of the shoe.

The stiffening board 37 serves to reduce interlayer degradation in two ways. First, it is sufficiently stiff to effectively distribute the forces acting on the midsole 33 throughout the stiffening board, thereby distributing the forces acting on the midsole 33 uniformly over the stiffening board portions. have. The stiffening board 37 thus eliminates or significantly reduces patterns of high concentration caused by the runner's unique running style, thereby reducing uneven deterioration of the midsole 33.

Second, the stiffening board 37 has the upper and lower intermediate bottom layers 44
and 46, and due to its essentially inextensible nature, has the effect of restraining the midsole 33 from expanding outwardly under the influence of compressive forces.
The tensile properties of the cell walls of the midsole in contact with the adhesive surface therefore also serve to restrain outward expansion under the influence of compressive forces. Although this compressive force causes some midsole expansion, the outward expansion within each midsole layer 44 and 46 is still much less than that which would occur without the stiffening layer of the present invention. Therefore, the deterioration of the midsole due to this outward expansion is correspondingly reduced by the present invention.

From the above structure, the important thing is the stiffening board 37
It should be recognized that this has the effect of greatly improving the stability of new running shoes that do not suffer from midsole deterioration. In this regard, the stiffening board 37 has the effect of distributing eccentric or unbalanced forces caused by unique running styles. This kind of dispersion power is
This creates a repositioning force that counteracts an imbalance or eccentricity of landing, such as when a runner lands on the outside edge instead of landing flat. In addition, the stiffening board 37 uses the midsole upper layer 44 as a cushion that comfortably conforms to the shape of the wearer's heel while running, and also provides dynamic arch support for the medial or central portion of the runner's arch. This results in improved foot support while running. In addition to the above, the stiffening board 37 greatly reduces uneven deterioration of the midsole, greatly improving the stability of the running shoe over time and greatly extending the trouble-free life of the shoe.

The outward expansion of the intermediate sole is exactly the stiffening board 37
This outward expansion of the midsole is constrained by the inextensibility or tensile properties of the stiffening board and by its adhesion to the midsole upper and lower layers 44 and 46.
This may be alleviated by using a flexible, nearly non-stretchable layer in place of the stiffening board 37 and by gluing this non-stretchable flexible layer to the midsoles 44 and 46.

Instead of being formed in one piece and later being split to fit the stiffening board 37, the midsole 33 may be manufactured as two separate foam layers from the beginning;
The two layers may have different densities.
The stiffening layer of the present invention allows for the use of different foams in the manufacture of running shoes, which were not previously considered suitable for midsoles.

The stiffening board 37 need not be provided horizontally as shown in FIGS. 1-5. Rather than being horizontal, it is tilted in either direction about its longitudinal axis, as shown in FIGS. 6 and 7. In other words, it may rotate.

In FIG. 6, the stiffening board 37 is designed so that at the lateral edge of the sole, the lateral edge of the stiffening board is in the center of the sole, in order to compensate for the forces that occur when the runner's foot is significantly pronated. Or it is tilted in a direction that is lower than the side edge at the inner end. In FIG. 7, the stiffening board 37 is designed so that the side edges of the stiffening board are on the outside of the sole at the center or medial edge of the sole to compensate for the forces that occur when the runner's foot is significantly supinated. The stiffening board is tilted in the opposite direction so that it is lower than the opposite edge of the stiffening board at one end.

The midsole stiffening layer in this invention need not be planar or flat as in the case of stiffening board 37. The stiffening board 37 may therefore be replaced by a stiffening layer of a different shape. For example, the stiffening layer may have a curved shape or may be molded. Furthermore, various elements related to the present invention may be modified as appropriate depending on the circumstances. For example, the thickness of the stiffening layer, the stiffness of the layer, the geometric range and area covered by the stiffening layer, and the height at which the stiffening layer is provided, etc., all depend on the running style, asymmetry of the legs and feet, etc. May be modified to suit your weight.

It is also appreciated that the stiffening layer of the present invention avoids the difficult and costly attempt to modify the running shoe support geometry by using different elastic materials for the midsole foam. It will be.

Additionally, the stiffening layer of the midsole of the present invention advantageously helps to compensate for asymmetries and other problems in the legs and feet, thereby making the shoe custom-tailored to the individual. It can be manufactured separately from running shoes as a custom product for use by a physician or orthopedic surgeon after modification of a ready-made, ie, fully constructed, shoe. For example, the midsole stiffening layer of the present invention can be used to compensate for differences in leg length, but has the advantage that nothing needs to be inserted into the shoe upper itself. The main steps in this method of using a stiffening layer are: first, creating a crack in the foam midsole of the ready-made shoe to accommodate the stiffening layer, or creating a void in the midsole; Alternatively, a specially prepared stiffening layer can be inserted into the gap and the stiffening layer can be glued to the midsole.

The parts of competition running shoes for the right foot are as follows:
It goes without saying that these parts are completely symmetrical to the parts of the running shoes for the left foot that have been described so far.

[Brief explanation of drawings]

FIG. 1 is a perspective view of competition running shoes for the left foot according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view of the competition running shoes shown in FIG. 1. FIG. 3 is a horizontal cross-sectional view taken generally along line 3--3 of FIG. 2, illustrating the shape of a stiffening layer according to one embodiment of the invention. Fourth
The illustration is a longitudinal section taken approximately along line 4--4 of FIG. FIG. 5 is also a longitudinal section taken along line 5--5 of FIG. FIG. 6 is a longitudinal section similar to FIG. 4, but shows one variation that can be applied to runners whose feet are significantly pronated. 7th
The figure is a longitudinal section similar to FIG. 4, but shows one of the other variations that can be applied to runners whose feet are highly supinated. 10... Upper skin, 12... Bottom, 13... Insole,
15...Fabric bottom, 32...Outside sole, 33...Intermediate sole, 37...Stiffening board.

Claims (1)

[Scope of Claims] 1. An upper having an upper and a sole, the upper overlying and attached to a portion of the sole, the lower having a flexible outsole and a flexible outsole above the outsole. an athletic shoe for running or other sports, the midsole being formed from a foamed polymeric material and having a flexible shock-absorbing midsole fixed thereto; In order to stiffen the region located on the intermediate sole and support the central arch portion, a region located below the heel and central arch portion of the intermediate sole is provided between the upper and lower surfaces of the intermediate sole. An athletic shoe characterized by having a separately formed stiffening layer inserted therein. 2. In the athletic shoe according to claim 1, the stiffening layer extends from the edge of the intermediate portion of the sole along a curve near the wearer's first, second, and third metatarsal heads. in the region of the midsole behind a border extending inwardly and then further curved backwards to under the wearer's cuboid bone and further laterally to the lateral edges of the sole; The intermediate sole is stiffened by the stiffening layer over the entire portion rearward of the boundary line. 3. In the athletic shoe according to claim 1, the stiffening layer extends forward from the entire region of the intermediate sole below the wearer's heel and extends below the wearer's central arch. , an athletic shoe that does not extend to the wearer's lateral arches, that is, the portions in front of the wearer's first, second, and third metatarsal heads. 4. In the athletic shoe according to claim 1, the upper is a slitplast type having a cloth sole bonded to the intermediate sole, and the intermediate sole is located above the cloth sole within the upper. An athletic shoe made of soft, flexible material. 5 Any one of claims 1 to 4
The above-mentioned stiffening layer is located between the upper and lower layers of the intermediate sole and is bonded thereto. 6 Any one of claims 1 to 4
The athletic shoe of item 1 has an insole, at least a portion of the insole is divided into an upper layer and a lower layer, and the stiffening layer is located between and adhered to the upper and lower layers,
The upper layer is at least under the wearer's heel to provide a heel cushion, and the insole is at least below the wearer's heel to conform to the shape of the wearer's heel when the wearer's foot makes contact with the ground during running. Athletic shoes that are sufficiently flexible so that the upper layer can be compressed under load. 7 Any one of claims 1 to 4
In the athletic shoes mentioned above, the stiffening layer is a single plate material with almost no extensibility that is located between the upper and lower layers of the intermediate sole and is bonded thereto, and the stiffening layer is a single plate material with almost no extensibility, and the stiffening layer is a plate material with almost no extensibility. an athletic shoe having sufficient rigidity to disperse the force generated by the impact when the foot of the foot contacts the ground and acting on the midsole in the area of the plate material, thereby uniformly distributing the force acting on the area; . 8 Any one of claims 1 to 4
In the athletic shoes mentioned above, at least a portion of the intermediate sole is divided into an upper layer and a lower layer, and the stiffening layer is composed of a plate inserted between the upper and lower layers, and the plate has an outer sole that is straight. When it is not bent, it is approximately parallel to the outsole, and the force generated by the impact when the wearer's foot hits the ground during running acts on the area of the plate, and the plate spreads the force across the entire area. The plate material has little extensibility and is bonded to the upper and lower layers to resist movement of the midsole from expanding laterally under the force. shoes. 9 cutting the intermediate sole in order to provide a space between the upper and lower layers of the intermediate sole for providing a stiffening layer;
A method of modifying an existing running or other sports shoe having a polymeric foam midsole comprising the steps of inserting the stiffening layer and adhering the stiffening layer to the midsole.