Sole for shoe

Abstract

To achieve a forefoot running in a more natural manner during running without encumbering a forefoot movement.SOLUTION: In a stable posture, in which a path length measured along a sole upper surface 20 from an origin O to a toe distal end Se is L, an intersection between a sole bottom surface 31 and a line perpendicular to the reference line S through a position of 0.45×L from the origin O along the sole upper surface 20 is C, an intersection between the sole bottom surface 31 and line perpendicular to the reference line S through a position of 0.60×L from the origin O is D, and a sole 1 is in contact with the ground R at the points C and D, the sole bottom surface 31 at the toe portion is separated from the ground R, the sole bottom surface 31 at the heel portion is separated from the ground R to be in a heel-up state, and an inequality, θ≥5° is satisfied where θ is an angle formed by the ground R and a line T that connects the heel central position 20h of 0.15×L from the origin O with the metatarsophalangeal joints position 20j of 0.68×L. The sole compressive rigidity in a vertical direction is relatively lower at the heel-up starting position of the heel portion than at the metatarsophalangeal joints position.SELECTED DRAWING: Figure 20

Description

[Technical field]

[0001] The present invention relates to a shoe sole, and more particularly to an improved structure that enables a more natural forefoot running style to be achieved when running, without impeding forefoot movement by hastily raising the heel after landing. [Background technology]

[0002] In recent years, forefoot running, in which the foot lands on the forefoot, has become mainstream for efficient long-distance running. Forefoot running has the advantage of reducing the burden on the knees and shortening the time the foot is on the ground, easing the burden on the muscles. It is believed that forefoot running can achieve efficient movement and excellent running economy by making good use of the spring-like behavior of the Achilles tendon and calf muscles (i.e., muscle contraction / relaxation and Achilles tendon stretching and contraction). Here, running economy is an index of how little energy (oxygen intake) is required to run at a certain speed, and the better (i.e., higher) the running economy, the less oxygen is consumed and the more efficient the running is.

[0003] However, a certain level of skill is required to master the forefoot running technique. Specifically, first, ground contact skills are required to be able to land on the forefoot / midfoot just before the foot strikes the ground, and secondly, leg strength (muscle strength and endurance) is required to prevent the heel from dropping (descent) and withstand the stretching of the muscles and tendons during the ground contact phase, as well as the need to lock the ankle. Therefore, it is not easy for beginner runners to master the forefoot running technique, and whether they can continue to use the forefoot running technique is mainly dependent on the runner's ability.

[0004] Incidentally, soles incorporating a high-rigidity plate (e.g., a CFRP plate) are in practical use to support the heel when the heel drops in. In such soles, when the load is transferred to the forefoot, the forefoot part of the plate is pushed downward, and the heel part of the plate is lifted upward by a seesaw effect, thereby supporting the heel.

[0005] However, such soles with built-in plates are not configured to naturally encourage a forefoot running style as a sole alone, and are insufficient to make a forefoot running style sustainable.

[0006] Therefore, the applicant of the present application has proposed a shoe sole for realizing the forefoot running style as shown in JP 2020-163084 A (see paragraphs

[0020] to

[0024] ,

[0028] to

[0030] , and FIG. 9 in the same publication). In this sole, the position of the rear end of the surface on the sole contact side is set as the origin, the distance to the position of the tip of the toes measured along the surface on the sole contact side is set as L, and the bottom surface of the heel on the surface on the sole contact side is arranged parallel to the horizontal plane. In this state, the sole thickness at a position Sh that is 0.16×L from the origin is set as h, the sole thickness at a position Sm2 that is (0.3 to 0.5)×L is set as m2, the sole thickness at a position Sm1 that is (0.4 to 0.6)×L (however, m1 is arranged forward of Sm2) is set as m1, and the sole thickness at a position Sf that is 0.7×L is set as f. Then, m2≧m1 and m1≧f and When the relational equation m1≧h is satisfied, and θ1 is the angle that the line connecting position Sm1 and position Sh makes with the horizontal plane, Sm1' is the position where a vertical line drawn from position Sm1 intersects with the ground contact surface, and Sh' is the position where a vertical line drawn from position Sh intersects with the ground contact surface, and θ2 is the angle that the line connecting position Sm1' and position Sh' makes with the horizontal plane, the relational equation θ2≧θ1 is satisfied, and the ground contact surface has a downwardly convex curved shape at the forefoot.

[0007] According to the sole described in the above publication, the sole thickness h at the position Sh, which is 0.16×L from the origin, is smaller than the sole thickness m1 at the position Sm1, which is (0.4-0.6)×L from the origin, and the angle θ2 between the line connecting the position Sm1' and the position Sh' and the horizontal plane is larger than the angle θ1 between the line connecting the position Sm1 and the position Sh and the horizontal plane, so that the heel does not touch the ground when landing, preventing heel strike and promoting ground contact at the forefoot when landing. Also, the sole thickness m2 at the position Sm2 is larger than the sole thickness m1 at the position Sm1, so that when the sole initially touches the ground at the position Sm1' on the sole ground contact surface, the sole is prevented from tilting backward and the heel from dropping downward, and the sole can quickly transition to rolling forward after the initial contact. Furthermore, the sole thickness f at position Sf, which is 0.7×L from the origin, is smaller than the sole thickness m1 at position Sm1, and the sole contact surface has a downwardly convex curved shape at the forefoot, which allows the sole to roll forward smoothly.

[0008] As a result of further intensive research into soles that would enable forefoot running, the inventors of the present application have discovered that there is room for further improvement in the sole described in the above publication in order to naturally encourage and sustain a forefoot running style while running, as well as to increase running efficiency when running on the forefoot.

[0009] Therefore, the applicant of the present application has proposed the methods shown in JP-A-2023-96397 and JP-A-2023-95714.

[0010] In the example shown in JP 2023-96397 A, the reference posture is maintained at the time of contact when the sole 1 touches the ground R at point C, and in the reference posture, the sole underside 31 of the heel and toe is disposed away from the ground R. This prevents unintended contact of the heel with the ground, and promotes a natural forefoot posture that can be sustained. In addition, in the reference posture, when the angle formed by the straight line connecting the heel center position 20h located at 0.15×L from the origin O along the sole upper surface 20 and the metatarsophalangeal joint position 20j located at 0.68×L from the origin O with the ground is θ, the inequality θ≧5° is satisfied. This allows the heel portion of the sole 1 to be positioned upward relative to the forefoot portion (i.e., in a heel-up state), thereby conforming to a forefoot posture (see paragraphs

[0025] -

[0026] ,

[0033] -

[0034] , Figures 4, 5, and 8(a) of the above publication).

[0011] Next, in the phase immediately after the sole 1 touches the ground, the heel of the sole 1 drops or descends by a distance d toward the ground R, but since the sole 1 is in a reference posture in which it touches the ground R at point C, which is 0.45×L from the origin O and is forward of the ankle joint when the sole 1 touches the ground (see FIG. 8(a)), not only can the sole underside 31 provide a natural support effect from the time of touching the ground, but the shoe wearer can also use the muscles and tendons of the foot as springs, which prevents the heel from dropping excessively and reduces the amount of descent, reducing the load on the shoe wearer and improving running efficiency (see paragraph

[0035] and FIG. 8(b) of the above publication). As a result, the distance until the heel is lifted after the sole 1 touches the ground can be shortened, and the heel can be quickly moved to the phase of lifting the heel as shown in FIG. 8(c). In this way, it becomes possible to smoothly transfer from the heel to the forefoot after landing, and it is possible to achieve a smooth shift of the center of gravity from the heel to the toes (see paragraph

[0036] and Figure 8(c) of the above publication).

[0012] In addition, JP 2023-96397 A discloses that the compression stiffness of the midsole is set low at the metatarsophalangeal joint and high at the heel. In this case, when a load is applied during running, the metatarsophalangeal joint of the midsole is deformed more downward than the heel, which prevents the heel from dropping too far after the sole hits the ground and allows the load to be transferred smoothly forward (see paragraphs

[0045] to

[0047] , Figures 10 to 11, etc.).

[0013] On the other hand, in the shoe shown in JP 2023-95714 A, a curved plate P is arranged inside the sole 1 (see paragraph

[0023] and Figure 1 of the same publication), and the compression rigidity of the sole body 1A is made relatively low at the metatarsophalangeal joint (MP joint) position 20j (see paragraph

[0033] and Figures 3 and 3A of the same publication).

[0014] In this case, when the maximum load acts on the sole 1 after the sole touches the ground, the sole forefoot lower part 2B1 undergoes a relatively large compression deformation, causing the sole 1 to sink downward. Then, the toes bend significantly and the plantar fascia PF is stretched, resulting in the arch SA rising, promoting the windlass effect and increasing the propulsive force during running. In addition, when the heel tries to sink downward after the sole touches the ground, the curved plate P can support the heel, thereby reducing the amount of drop (descent) of the heel. Furthermore, when the maximum load acts, the support angle with respect to the sole increases, so that the support and lifting effect from the midfoot to the heel can be further increased, and the rigidity of the foot can be further increased, further improving stability. Next, when the toes move into a maximum flexed state and the sole 1 reaches its maximum flexion state, the plantar fascia PF is further stretched, causing the arch SA to rise further and further promoting the windlass effect (see paragraphs

[0039] to

[0046] and FIG. 3 of the above-mentioned publication). Summary of the Invention [Problem to be solved by the invention]

[0015] The inventors of the present application have further studied the shoes described in the above-mentioned publications and have found the following facts. Previous shoes have been designed to achieve a natural forefoot running style by being designed so that when the sole reaches its maximum sinking amount while running, the rear part of the foot (heel) does not deform and the forefoot part deforms relatively more so that the angle of the foot relative to the ground surface can be maintained.

[0016] However, when a runner was asked to actually run wearing the shoes and a sensory evaluation was conducted while running, it was found that in previous shoes, when the sole reached its maximum sinking amount while running, the heel was forced to rise quickly, which resulted in the natural forefoot running being hindered. This was thought to be caused by the angle of the foot relative to the ground contact surface being maintained too long into the latter movement stage of the gait cycle (the running cycle from contact to take-off), which resulted in a large deviation from the natural forefoot running movement.

[0017] The present invention has been made in consideration of the above-mentioned conventional situation, and the problem which the present invention aims to solve is to provide a shoe sole which allows for a more natural forefoot running without impeding forefoot movement by forcing the heel to rise quickly after landing. [Means for solving the problem]

[0018] The sole of the shoe according to the present invention extends from the heel portion through the midfoot portion to the forefoot portion, has a sole upper surface and a sole lower surface, and has a reference line S as a straight line connecting the rearmost end position of the sole upper surface and the position of the tip of the toe, the position of the rearmost end being the origin O, the distance from the origin O to the position of the tip of the toe measured along the sole upper surface being the reference line S, the intersection point C between the line passing from the origin O along the sole upper surface at a position of 0.45×L and perpendicular to the reference line S and the sole lower surface, and the intersection point D between the line passing from the origin O along the sole upper surface at a position of 0.60×L and perpendicular to the reference line S and the sole lower surface, and the sole is at points C and When the sole posture in which it touches the ground at point A and point B is defined as a stable posture, in the stable posture, the underside of the sole at the toe part is away from the ground and the underside of the sole at the heel part is away from the ground with the heel up, and when the angle that a straight line connecting the center of the heel, which is located 0.15×L from the origin O, along the upper surface of the sole, to the metatarsophalangeal joint position, which is located 0.68×L from the origin O, makes with the ground is θ, in the stable posture, θ is set to ≧5° and the compressive rigidity of the sole in the vertical direction is relatively lower at the heel part's heel up start position than at the metatarsophalangeal joint position.

[0019] According to the present invention, when the sole touches the ground, the sole touches the ground at two points, namely, point C, which corresponds to a position 0.45×L from the origin O, and point D, which corresponds to a position 0.60×L from the origin O, so that a stable sole posture can be taken, thereby preventing time loss and power loss.

[0020] According to the present invention, the bottom surface of the sole of the toe and heel is away from the ground in the stable posture (i.e., the heel is heeled up), so that unintended contact of the heel with the ground can be prevented when the foot touches the ground. Furthermore, according to the present invention, the straight line connecting the center of the heel and the metatarsophalangeal joint in the stable posture forms an angle of 5 degrees or more with the ground, so that the heel can be kept heeled up and can be aligned with the forefoot posture.

[0021] Moreover, according to the present invention, the vertical sole compression stiffness is relatively lower at the heel-up start position than at the metatarsophalangeal joint position, so that when the sole reaches its maximum sinking amount during running, the rear foot (heel) side can deform downward relatively more than the forefoot side. This makes it possible to prevent the angle of the foot with respect to the ground contact surface from being maintained too long until the latter half of the gait cycle (the running cycle from contact to take-off), and as a result, it is possible to prevent the heel from being hastily raised after contact and hinder the forefoot movement, and to realize a more natural forefoot running that utilizes the spring-like behavior of the muscles and tendons.

[0022] Here, in this specification, "sole compression rigidity" is a concept that represents the resistance of a sole to deformation under a compressive load, and when the same compressive load is applied, a sole with high compressive rigidity will have a small amount of deformation, while a sole with low compressive rigidity will have a large amount of deformation.

[0023] In the present invention, in the stable posture, the underside of the sole in a rearward region along the sole top surface is away from the ground from a position 0.15×L from the origin O, and the underside of the sole in a forward region along the sole top surface is away from the ground from a position 0.68×L from the origin O, and the underside of the sole is in contact with the ground in a region along the sole top surface forward from a position 0.15×L from the origin O and rearward from a position 0.68×L from the origin O.

[0024] In the present invention, the heel-up start position is located rearward of the ankle position, which is located at a distance of 0.27×L from the origin O along the upper surface of the sole.

[0025] In the present invention, the sole compression stiffness is set so that in a stable posture, when the wearer is in a static standing posture while wearing the shoes, θ<5°. In this specification, the term "static standing posture" refers to a posture in which the body stands straight with the weight evenly distributed on both feet when not exercising.

[0026] In the present invention, the heel portion has apertures and the forefoot portion does not have apertures.

[0027] In the present invention, the heel and forefoot portions have openings, and the opening width of the opening in the heel portion is set larger than the opening width of the opening in the forefoot portion.

[0028] In the present invention, the heel portion and the forefoot portion have apertures, and the aperture ratio of the heel portion is set to be greater than the aperture ratio of the forefoot portion. In this specification, the term "opening ratio" refers to the ratio of the volume of open pores to the total volume.

[0029] In the present invention, the heel portion is constructed from a material having a relatively low hardness, and the forefoot portion is constructed from a material having a relatively high hardness.

[0030] In the present invention, both the heel and forefoot have a relatively low hardness material region and a relatively high hardness material region, and the occupancy rate of the relatively low hardness material region is set relatively high in the heel, while the occupancy rate of the relatively high hardness material region is set relatively high in the forefoot. Here, in this specification, "occupancy rate" refers to the proportion of each material region to the entire area.

[0031] In the present invention, points C and D are located at least on the outer edge of the sole lower surface.

[0032] In the present invention, the area from point C to point D on the underside of the sole constitutes a stable area formed flat, and in the stable posture, the stable area comes into contact with the ground. In this case, the flat region (stable region) extending from point C to point D can stabilize the sole posture at the time of contact with the ground, and can stabilize the forefoot posture. Effect of the Invention

[0033] As described above, according to the present invention, it is possible to realize a shoe sole that allows for a more natural forefoot running motion without impeding the forefoot movement by forcing the heel to rise quickly after landing. [Brief description of the drawings]

[0034] [Figure 1] 1 is an overall perspective view of a sole (for a left foot) according to an embodiment of the present invention, as viewed obliquely from above. FIG. [Diagram 2] FIG. 2 is an overall perspective view of the bottom side of the sole (FIG. 1) as viewed obliquely from below. [Diagram 3] FIG. 2 is an overall perspective view of the bottom side of the sole (FIG. 1) as viewed obliquely from below. [Figure 4] FIG. 2 is an overall perspective view of the bottom side of the sole (FIG. 1) as viewed obliquely from below. [Diagram 5] FIG. 2 is a rear view of the sole (FIG. 1) seen from behind the heel. [Figure 6] FIG. 2 is a schematic plan view of the sole (FIG. 1). [Figure 7] FIG. 2 is a schematic bottom view of the sole (FIG. 1). [Figure 8] FIG. 2 is a schematic view of the medial side of the sole (FIG. 1). [Figure 9] FIG. 2 is a schematic view of the outer instep side of the sole (FIG. 1). [Figure 10] 8 is a vertical cross-sectional view taken along line XX in FIG. 7. [Figure 11] 10 is a cross-sectional view taken along the line XI-XI in FIG. [Figure 12] 8 is a cross-sectional view taken along line XII-XII in FIG. 7. [Figure 13] 8 is a cross-sectional view taken along line XIII-XIII in FIG. 7. [Figure 14] 8 is a cross-sectional view taken along line XIV-XIV in FIG. 7. [Figure 15] 8 is a cross-sectional view taken along line XV-XV in FIG. 7. [Figure 16] FIG. 2 is an overall perspective view of a plate provided on the sole (FIG. 1), as viewed obliquely from above. [Figure 17]FIG. 17 is a schematic side view of the plate (FIG. 16). [Figure 18] FIG. 17 is a partial perspective view of the bottom surface side of the plate (FIG. 16) as viewed obliquely from below. [Figure 19] 1 is a schematic side view of a shoe incorporating a sole according to the present invention. [Figure 20] FIG. 19 is a schematic side view of the sole (FIG. 19) together with a skeletal diagram of a wearer's foot. [Figure 21] FIG. 20 is a schematic bottom view of the sole (FIG. 19). [Figure 22] FIG. 21 is a diagram showing the sole (FIG. 20) in a static standing position with a load applied from the wearer's foot. [Diagram 23] 19 is a diagram for explaining the state of the shoe (FIG. 19) during running, and shows the movement of the shoe relative to the ground in chronological order from (a) to (d). [Figure 24] FIG. 13 is a diagram for explaining the state of a shoe as a comparative example during running, and shows the movement of the shoe relative to the ground in chronological order from (a) to (d). [Diagram 25] FIG. 8 is a schematic bottom view of a sole according to an embodiment of the present invention, corresponding to FIG. 7. [Figure 26] FIG. 2 is a schematic bottom view of a sole according to a first modified example of the present invention. [Figure 27] FIG. 11 is a schematic vertical cross-sectional view of a sole according to a second modified example of the present invention. [Figure 28] FIG. 11 is a schematic vertical cross-sectional view of a sole according to a third modified example of the present invention. [Figure 29] FIG. 11 is a schematic vertical cross-sectional view of a sole according to a fourth modified example of the present invention. [Diagram 30] FIG. 11 is a schematic vertical cross-sectional view of a sole according to a fifth modified example of the present invention. [Diagram 31] FIG. 13 is a schematic vertical cross-sectional view of a sole according to a sixth modified example of the present invention. [Diagram 32] FIG. 13 is a schematic vertical cross-sectional view of a sole according to a seventh modified example of the present invention. [Diagram 33] FIG. 13 is a schematic vertical cross-sectional view of a sole according to an eighth modified example of the present invention. [Diagram 34] 1 is a graph showing the negative work of ankle plantar flexion torque during running by the product of the present invention in comparison with the comparative example and a conventional product. [Diagram 35] 13 is a graph showing the correlation between the deformation rate of the support base and the angle θ after deformation (11° before deformation) when the deformation rate of the forefoot is 40%. [Diagram 36] 13 is a graph showing the correlation between the deformation rate of the support base and the angle θ after deformation (11° before deformation) when the deformation rate of the forefoot is 45%. [Figure 37] 13 is a graph showing the correlation between the deformation rate of the support base and the angle θ after deformation (4° before deformation) when the deformation rate of the forefoot is 40%. [Figure 38] 13 is a graph showing the correlation between the deformation rate of the support base and the angle θ after deformation (4° before deformation) when the deformation rate of the forefoot is 45%. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Figures 1 to 25 are diagrams for explaining a sole according to an embodiment of the present invention and a shoe equipped with the sole. In these diagrams, Figures 1 to 5 are diagrams showing the appearance of the sole, Figures 6 to 15 are plan views, bottom views, side views and cross-sectional views of the sole, Figures 16 to 18 are diagrams showing the appearance of the plate, Figures 19 to 22 are schematic side views and bottom views showing the shape of the sole in detail, Figure 23 is a diagram showing the state of the shoe when running in time series, and Figure 24 is a diagram showing the state of a shoe as a comparative example when running in time series for comparison with Figure 23. Here, sports shoes, particularly running shoes for middle and long distances, are taken as an example of shoes.

[0036] In the following explanation (as well as in Modifications 1 to 8 described later), the terms "upper" (top) and "lower" (bottom) refer to the vertical positional relationship of the shoe, the terms "front" (front side) and "rear" (rear side) refer to the front-to-rear positional relationship of the shoe, and the "width" refers to the left-to-right direction of the shoe. In other words, in the case of Fig. 19 as an example, the terms "upper" and "lower" refer to the left and right of the figure, respectively, the terms "front" and "rear" refer to the top and bottom of the figure, respectively, and the "width" refers to the direction perpendicular to the plane of the figure.

[0037] As shown in Figs. 1 to 5, the sole 1 of this embodiment includes a midsole 2 extending over the entire length of the sole and an outsole 3 disposed below the midsole 2. The midsole 2 includes an upper midsole 2a disposed on the upper side and a lower midsole 2b disposed below the upper midsole 2a. The upper surface (sole upper surface) 20 of the upper midsole 2a constitutes a sole contact surface against which the sole of the wearer's foot comes into contact directly or indirectly via an insole or the like. The outer peripheral edge of the upper surface 20 is provided with a rising portion 20a that rises upward. The outsole 3 is fixed to the lower surface of the lower midsole 2b by adhesive or the like.

[0038] The midsole 2 (i.e., the upper and lower midsoles 2a, 2b) is preferably made of a soft elastic material, specifically, a thermoplastic synthetic resin such as ethylene-vinyl acetate copolymer (EVA) or a foam thereof, a thermosetting resin such as polyurethane (PU) or a foam thereof, or a rubber material such as butadiene rubber or chloroprene rubber or a foam thereof. The outsole 3 is preferably made of a hard elastic material, specifically, a thermoplastic resin such as thermoplastic polyurethane (TPU) or polyamide elastomer (PAE), a thermosetting resin such as epoxy resin, or rubber. Note that the materials of the midsole 2 and the outsole 3 are not limited to these, and any other appropriate materials may be selected.

[0039] The midsole 2 may be molded by supercritical foaming, not limited to the usual injection foaming method. Here, "supercritical foaming" refers to a method of performing injection foaming by making the resin into a supercritical fluid state under high temperature and pressure. Supercritical foaming makes it possible to further reduce the weight of the midsole 2.

[0040] A plate 4 is inserted between the upper midsole 2a and the lower midsole 2b, and the plate 4 is sandwiched between the upper and lower midsoles 2a, 2b (the details of the plate 4 will be described later).

[0041] A vertical hole (opening) 5 is formed on the lower surface (bottom surface) of the sole 1. The hole 5 penetrates the outsole 3 in the vertical direction, but does not penetrate the midsole 2. In this example, the hole 5 has a spindle shape (i.e., a biconvex lens shape) when viewed from the bottom, and extends in the front-rear direction from the heel to the longitudinal center of the midfoot. In this example, the opening width of the hole 5 is maximum at the lower surface (bottom surface) of the sole 1, and is set to a tapered shape that gradually becomes smaller toward the inside of the sole 1.

[0042] As shown in FIG. 6 (sole plan view) and FIG. 7 (sole bottom view), the sole 1 has a heel part H, a midfoot part M, and a forefoot part F, which respectively correspond to the heel region, midfoot region (arch region), and forefoot region of the wearer's foot, and extends from the heel part H through the midfoot part M to the forefoot part F. The plate 4 extends from the heel part H of the sole 1 through the midfoot part M to the front side of the front end part (toe part) of the forefoot part F. The front region of the plate 4 is provided with a plurality of ribs 40 that are curved and extend in the front-rear direction (details will be described later). Note that in FIG. 7, the ribs 40 of the plate 4 are omitted for convenience of illustration. Also, in FIG. 7, the bottom surface 50 of the hole 5 is visible.

[0043] Figure 8 (side view of the inner upper side of the sole) and Figure 9 (side view of the outer upper side of the sole) show both parts of the sole side that have a design (e.g., a embossed pattern) and parts that do not have a design (white areas in each figure).

[0044] As shown in FIG. 10 (sole longitudinal cross-sectional view), the hole 5 penetrates the lower midsole 2b of the midsole 2 in the up-down direction (left-right direction in the same figure), and its bottom surface 50 is formed by the lower surface of the plate 4. Also, FIG. 10 and FIGS. 13 to 15 (sole transverse cross-sectional views) show that the hole 5 is tapered in the front-rear and left-right directions. As shown in FIG. 10, the plate 4 extends in the front-rear direction while curving, and each rib 40 is provided on its lower surface. The upper midsole 2a is in contact with the upper surface of the plate 4 (see FIGS. 10, 12 to 15), and the lower midsole 2b is in contact with each rib 40 of the plate 4 (see FIGS. 10 and 12).

[0045] As shown in Figs. 16 to 18, the plate 4 is a thin sheet-like member, and its thickness is, for example, about 1 to 2 mm. The plate 4 is disposed inside the midsole 2 by insert molding, or is bonded to the interface between the upper and lower midsoles 2a and 2b by adhesive or the like. A pair of left and right standing wall portions 41 rising upward are formed in the center of the plate 4 in the front-rear direction. Each rib 40 disposed on the lower surface of the plate 4 and protruding downward extends in the front-rear direction while protruding downward from the lower surface of the plate 4. The cross-sectional shape of each rib 40 is not limited to a rectangular shape as in this example, and any appropriate shape may be adopted. In the example shown in Figs. 6 and 18, each rib 40 is provided symmetrically on both the left and right sides of the center line in the front-rear direction, and these left and right ribs 40 form a spindle shape or a biconvex shape when viewed from the bottom. As shown in Figs. 17 and 10, the plate 4 is curved slightly convex downward on the forefoot side and heel side, and is curved slightly convex upward on the midfoot side.

[0046] The plate 4 is made of, for example, a thermoplastic resin such as thermoplastic polyurethane (TPU), polyamide elastomer (PAE), or ABS resin, which are relatively elastic materials, or a thermosetting resin such as epoxy resin or unsaturated polyester resin. The material of the plate 4 may be fiber reinforced plastic (FRP), which uses, for example, carbon fiber, aramid fiber, or glass fiber as reinforcing fibers and a thermosetting resin or thermoplastic resin as a matrix resin.

[0047] Next, the sole and the shoe having the sole according to the present invention will be described in detail with reference to Figs. As shown in Fig. 19, a shoe SH is composed of a sole 1 and an upper (vamp) U fixed to the upper side of the sole 1 by adhesion, sewing, etc. For the sake of simplicity of illustration and explanation, the figure shows an example in which the sole 1 is composed of a single-layer midsole 2 and an outsole 3 arranged thereunder.

[0048] As shown in FIG. 19, a straight line connecting the position So of the rear end (rear end of the heel) of the sole upper surface 20 and the position Se of the tip of the toe is defined as a reference line S. Here, the sole upper surface 20 matches the shape of the bottom surface of the last (shoe mold) used when assembling the shoes SH. Next, the position So of the rear end is defined as the origin O, and the distance from the origin O to the position Se of the tip of the toe measured along the sole upper surface 20 is defined as L. The intersection point between the line passing through the position 20m of 0.45×L from the origin O along the sole upper surface 20 and perpendicular to the reference line S and the sole lower surface 31 is defined as C, and the intersection point between the line passing through the position 20n of 0.60×L from the origin O along the sole upper surface 20 and perpendicular to the reference line S and the sole lower surface 31 is defined as D. In the figure, the intersection point between the line passing through the position 20m and perpendicular to the reference line S and the reference line S is indicated as Sp, and the intersection point between the line passing through the position 20n and perpendicular to the reference line S and the reference line S is indicated as Sq.

[0049] When the sole posture in which the sole 1 touches the ground R at points C and D is defined as a stable posture, in the stable posture, the heel and toe of the sole underside 31 are separated (floating) from the ground R. Therefore, the sole underside 31 at the heel is in a heel-up state, and the position where the sole underside 31 starts to heel-up at the heel (i.e. starts to separate from the ground R) is defined as the heel-up start position.

[0050] Figure 20 is a diagram in which a skeletal diagram of a wearer's foot is added to Figure 19. As shown in the figure, point D on the sole lower surface 31 located below position 20n, which is 0.60×L from origin O along the sole upper surface 20, corresponds to the position of the ball of the little toe of the shoe wearer's foot (i.e., near the base of the fifth toe (little toe)).

[0051] As shown in FIG. 20, when the angle (acute angle) that a straight line T that connects a heel center position 20h, which is located at 0.15×L from the origin O along the sole upper surface 20, and a metatarsophalangeal joint position 20j, which is located at 0.68×L from the origin O, makes with the ground R is θ, in the stable posture, θ≧5° is set to.

[0052] Here, the compressive rigidity in the vertical direction of the sole 1 (sole compressive rigidity: the resistance of the sole to deformation under compressive load) is relatively lower at the heel-up start position of the heel than at the metatarsophalangeal joint position 20j. Therefore, when the same compressive load is applied, the amount of compressive deformation of the sole 1 is greater at the heel-up start position of the heel than at the metatarsophalangeal joint position 20j.

[0053] The heel-up start position of the sole lower surface 31 at the heel part is preferably a position 20h that is 0.15×L from the origin O along the sole upper surface 20 in a stable posture, as shown in FIG. 20. In this case, the sole lower surface 31 is separated from the ground R in a rearward region from the position 20h. Also, preferably, as shown in the same figure, the sole lower surface 31 is separated from the ground R in a forward region from a position 0.68×L from the origin O along the sole upper surface 20. Furthermore, preferably, the sole lower surface 31 is in contact with the ground R in a region forward from a position 0.15×L from the origin O along the sole upper surface 20 and rearward from a position 0.68×L from the origin O along the sole upper surface 20 (see FIG. 20).

[0054] More preferably, the heel-up start position of the sole lower surface 31 in the heel portion is located rearward of the ankle position, which is located at a position 20k 0.27×L from the origin O along the sole upper surface 20 in the stable posture, as shown in FIG. 20. In other words, in the stable posture, the sole lower surface 31 is in contact with the ground R at a position (ankle position) 20k 0.27×L from the origin O along the sole upper surface 20. This ankle position 20k corresponds to the approximate boundary position between the heel portion H and the midfoot portion M, as described later. As a result, in the stable posture, the ground contact area of ​​the sole lower surface 31 with respect to the ground R can be expanded in the front-rear direction, and the forefoot posture can be further stabilized. In FIG. 20, the area surrounded by the dashed line indicates the lateral ankle LM of the foot. The lateral ankle LM is located below the fibula FB. In addition, in the same figure, the symbols TB, TL, and CC indicate the tibia, talus, and calcaneus, respectively.

[0055] The foot skeletal diagram in Fig. 20 is drawn for the sake of convenience in order to explain the shape of the sole 1 in relation to the foot skeleton. Meanwhile, Fig. 22 shows a state in which the wearer's foot is actually placed on the sole 1 and a load is applied. In this state, the sole compression stiffness is set so that θ<5° in a stable posture when the wearer is in a static standing posture while wearing the shoes (i.e., a posture in which the wearer stands straight with the weight evenly distributed on both feet while not exercising).

[0056] 22, in a loaded state where a load from the foot acts on sole upper surface 20, the sole compressive rigidity is smaller on the heel side than on the forefoot side, so the amount of compressive deformation on the forefoot side is relatively small and the amount of compressive deformation on the heel side is relatively large. Therefore, sole upper surface 20 hardly sinks at metatarsophalangeal joint position 20j, but sinks significantly at heel center position 20h, and as a result, the heel center position after load application drops from 20h to 20h' below.

[0057] Here, when the angle (acute angle) that the straight line (dotted line) T' that connects the heel center position 20h' and the metatarsophalangeal joint position 20j makes with the ground R is θ', in the stable posture, θ'<θ, i.e. θ'<5° In addition, in FIG. 22, a straight line T connecting the heel center position 20h (FIG. 20) and the metatarsophalangeal joint position 20j is indicated by a two-dot chain line.

[0058] Next, as shown in FIG. 21, the heel portion H, midfoot portion M, and forefoot portion F of the sole 1 can be expressed using the distance L from the origin O to the tip of the toes Se measured along the sole top surface 20 as follows: i) Heel: 0~0.25×L and rear edge of heel ii) Midfoot: 0.25×L~0.60×L iii) Forefoot: 0.60×L~1.00×L

[0059] In the example shown in Figure 21, points C and D on the underside 31 of the sole are located at positions 0.45 x L and 0.60 x L from the origin O, respectively, on the lateral edge (including a position closer to the lateral edge or a position closer to the center in the width direction) and on the medial edge (including a position closer to the medial edge or a position closer to the center in the width direction) of the outsole 31.

[0060] Preferably, as shown in the hatched area in Fig. 21 and Figs. 19 and 20, the area on sole underside 31 extending from a position of 0.45 x L to a position of 0.60 x L from origin O is formed flat and forms a stable area. In a stable posture in which sole 1 touches ground R at points C and D, preferably, the entire hatched area (stable area) on sole underside 31 touches ground R.

[0061] Next, the effects of this embodiment will be described with reference to FIG. Figure 23 shows the movement of the shoe SH against the ground R in chronological order from (a) to (d), with (a) showing the initial contact state of the sole 1. At this time, the sole 1 is in a sole posture in which it is in contact with the ground R at points C and D (Figures 19 to 22) on the sole underside 31, for example at two points C and D (Figure 21) on the outer instep side of the sole underside 31, and maintains a stable posture.

[0062] As described above, in a stable posture in which the sole 1 is in contact with the ground R at two points C and D, the sole underside 31 is positioned away (floating) from the ground R at the heel and toe (see Figure 19).

[0063] This prevents unintended contact of the heel with the ground at the time of initial contact with the ground, naturally encouraging a forefoot running style and stabilizing the forefoot posture, while also allowing for smooth rolling onto the toes, naturally encouraging a forefoot running style.

[0064] Preferably, the sole lower surface 31 is positioned away from (floating) the ground R in the rear region from a position 0.15×L from the origin O and in the front region from a position 0.68×L from the origin O, and more preferably, the sole lower surface 31 is in contact with the ground R at a position 0.27×L from the origin O (see FIG. 20). This prevents the sole 1 from collapsing toward the heel even when the front end of the heel touches the ground at the initial contact, making it possible to maintain a forefoot posture and support a forefoot running style. As a result, the burden on the runner is reduced and the sense of security during running is increased.

[0065] In addition, in the stable posture, as described above, when the angle between the line connecting the heel center position 20h located at 0.15×L from the origin O along the sole upper surface 20 in FIG. 20 and the metatarsophalangeal joint position 20j located at 0.68×L from the origin O and the ground is θ, the inequality θ≧5° is satisfied. The angle α in FIG. 23(a) corresponds to the angle θ (in this example, the angle α is set to be larger than the angle θ). This allows the heel of the sole 1 to be positioned above the forefoot (i.e., in a heel-up state) to match the forefoot posture.

[0066] Fig. 23(b) shows the phase of the intermediate movement after the initial ground contact of the sole 1. At this time, as shown in the figure, the maximum load acts on the sole 1, and the sole 1 is maximally compressed in the vertical direction, but in this case, not only points C and D on the outer instep side of the sole lower surface 31 but also points C and D on the inner instep side of the sole lower surface 31 are in contact with the ground R, so that the stable posture of the sole 1 is maintained and the forefoot posture is maintained.

[0067] Also, at this time, as described above, the compressive rigidity of the sole 1 in the vertical direction (sole compressive rigidity: the resistance of the sole to deformation under compressive load) is relatively lower at the heel-up start position (heel center position 20h) of the heel than at the metatarsophalangeal joint position 20j. Therefore, when a load acts on the sole 1 after the sole 1 initially touches the ground, the sole 1 is compressed and deformed to a greater extent at the heel center position 20h than at the metatarsophalangeal joint position 20j. Therefore, the angle β in FIG. 23(b) is smaller than the angle α (FIG. 23(a)) at the time of initial contact (i.e. β<α).

[0068] In this way, when the load is applied to the sole 1 after the initial contact with the ground, the rear foot (heel) side of the sole 1 deforms downward relatively more than the forefoot side when the sole 1 reaches the maximum sinking amount. This makes it possible to prevent the angle of the foot with respect to the ground contact surface from being maintained too long until the latter movement stage of the gait cycle (the running cycle from contact with the ground to take-off), and as a result, the forefoot movement is no longer hindered by the heel being hurriedly raised after contact with the ground, and the heel can be naturally raised, making it possible to realize a more natural forefoot running that utilizes the spring-like behavior of the muscles and tendons.

[0069] Next, Fig. 23(c) shows the state after the heel starts to lift. At this time, as shown in the figure, the toe of the sole underside 31 is about to leave the ground R. In the state shown in Fig. 23(b) just before the transition to the state shown in the figure, a stable forefoot posture is maintained by the ground contact at points C and D, so the transition from this state to Fig. 23(c) can be made smoothly. This allows the runner to be guided to a natural lifting motion without waste or strain while running. Next, in Fig. 23(d), the sole 1 completely leaves the ground R.

[0070] Fig. 24 shows the state of a shoe during running as a comparative example of the present invention. The sole 1' of this shoe SH' has a similar shape to the sole 1 of the shoe SH in Fig. 23 (see Fig. 20), but unlike the present invention, the compressive rigidity in the vertical direction of the sole 1 is relatively lower at the metatarsophalangeal joint position 20j than at the heel-up start position of the heel. In this case, when the same compressive load is applied, the amount of compressive deformation of the sole 1 is greater at the metatarsophalangeal joint position 20j than at the heel-up start position of the heel.

[0071] In Fig. 24, similarly to Fig. 23, the movement of the shoe SH' relative to the ground R is shown in chronological order in the order of (a) to (d). Each phase (a) to (d) in Fig. 24 corresponds to each phase (a) to (d) in Fig. 23. In Fig. 24, the same reference numerals as in Fig. 23 indicate the same or corresponding parts.

[0072] Fig. 24(a) shows the state of the sole 1' at the initial contact with the ground. At this time, the sole 1' is in a stable position with points C and D (see Figs. 19 to 22) of the sole lower surface 31' in contact with the ground R, as in Fig. 23(a). The sole lower surface 31' is positioned away (floating) from the ground R at the heel and toe. The angle α' in Fig. 24(a) corresponds to the angle θ (≧5°) in Fig. 20. In this case, the angle α' is equal to the angle α.

[0073] Fig. 24(b) shows a phase of an intermediate movement after the sole 1 initially touches the ground, during which the maximum load acts on the sole 1 and the sole 1 is maximally compressed in the vertical direction. As described above, the vertical compression stiffness of the sole 1 is relatively lower at the metatarsophalangeal joint position 20j than at the heel-up start position (heel center position 20h) of the heel part, so when the maximum load acts on the sole 1, the sole 1 is compressed and deformed more at the metatarsophalangeal joint position 20j than at the heel center position 20h. Therefore, the angle β' in Fig. 24(b) is larger than the angle α' (Fig. 24(a)) at the time of initial contact (i.e., β'>α').

[0074] In this way, when the load is applied to the sole 1 after the initial contact with the ground, the forefoot side is deformed downward relatively more than the rearfoot (heel) side when the sole 1 reaches the maximum sinking amount. As a result, the angle of the foot with respect to the ground contact surface is maintained too much until the latter half of the gait cycle (the running cycle from contact to take-off), which causes the heel to rise too quickly and inhibits natural forefoot running.

[0075] In the state shown in Figure 24(c), after the heel starts to rise, the toe portion of the sole lower surface 31 is about to leave the ground R. Then, in Figure 24(d), the sole 1 has completely left the ground R.

[0076] Next, in order to confirm the effect of reducing the burden on the triceps surae of a wearer with shoes having a sole according to the present invention (product of the present invention), the following performance experiment was carried out. The outline of the experiment is as follows. i) Two runners (N=2). The breakdown of ground contact patterns is one forefoot and one midfoot. ii) The following three types of shoes were prepared: The product of the present invention, the comparative example (see paragraph

[0070] ), and the conventional product (which does not have a heel-up sole shape like the product of the present invention and the comparative example, and has a flat shape on the underside of the sole from the heel to the forefoot). iii) While wearing each shoe, the participants ran at a constant speed of 20.0 ± 1.0 km / h (race pace). iv) Using a motion capture system (MAC 3D system) manufactured by Motion Analysis and a ground reaction force gauge manufactured by Kistler, the body characteristic points and ground reaction forces of each runner were measured during the running motion. v) Using information on the body's characteristic points and ground reaction force, the ankle plantar flexion torque was calculated using inverse dynamics calculations, and then the negative work of the ankle plantar flexion torque, which is a general indicator of eccentric contraction of the triceps surae, was calculated.

[0077] The calculation results of the ankle joint plantar flexion torque for each shoe are shown in Figure 34. As is clear from the figure, the comparative example has a greater effect of reducing the burden on the triceps surae than the conventional product, and the product of the present invention has an even greater effect of reducing the burden on the triceps surae than the comparative example.

[0078] Next, graphs showing the correlation between the deformation rate of the forefoot and rearfoot (heel) and the above-mentioned angle θ are shown in Figs. 35 to 38. Here, the "deformation rate" is Deformation rate = [(deformation amount) / (sole thickness before deformation)] x 100(%) For example, if the sole thickness before deformation is 50 mm and the sole thickness after deformation is 30 mm, the deformation amount is 20 mm, so Deformation ratio = (20 / 50) x 100 = 40% The larger the deformation rate, the smaller the compression stiffness. The support base refers to the rear foot (heel) area of ​​the underside of the sole that comes into contact with the ground.

[0079] 35 and 36 show an example in which the angle θ before deformation is 11° (i.e., High), and FIG. 37 and 38 show an example in which the angle θ before deformation is 4° (i.e., Low). In addition, FIG. 35 and FIG. 37 show the change in the angle θ when the deformation rate of the support base is changed from 40 to 55% when the deformation rate of the forefoot is 40%. Similarly, FIG. 36 and FIG. 38 show the change in the angle θ when the deformation rate of the support base is changed from 40 to 55% when the deformation rate of the forefoot is 45%. In each figure, the area surrounded by the dotted line is an area set based on the sensory evaluation obtained from each runner after actually having multiple runners run on their forefoot, and shows the range that is the dividing line of the evaluation of each runner. In other words, when the angle θ is located below the corresponding area, each runner evaluated that a more natural forefoot running was achieved.

[0080] As shown in Fig. 35, when the angle θ before deformation is 11° (High) and the deformation rate of the forefoot is 40%, if the deformation rate of the support exceeds 47% (the graph shows that the angle θ after deformation is smaller than about 5.5°), the sensory evaluation improves. Also, as shown in Fig. 36, when the angle θ before deformation is 11° (High) and the deformation rate of the forefoot is 45%, if the deformation rate of the support exceeds 49% (the graph shows that the angle θ after deformation is smaller than about 5.5°), the sensory evaluation improves. That is, it was found that in either case, the sensory evaluation improves when the angle (initial angle) θ before deformation is approximately half after deformation.

[0081] On the other hand, as shown in Fig. 37, when the angle θ before deformation is 4° (Low) and the deformation rate of the forefoot is 40%, if the deformation rate of the support exceeds 45% (when the angle θ after deformation is smaller than about 1.8° according to the graph), the sensory evaluation improves. Also, as shown in Fig. 38, when the angle θ before deformation is 4° (Low) and the deformation rate of the forefoot is 45%, if the deformation rate of the support exceeds 49% (when the angle θ after deformation is smaller than about 1.8° according to the graph), the sensory evaluation improves. That is, it was found that in either case, the sensory evaluation improves when the angle (initial angle) θ before deformation is approximately half after deformation.

[0082] 25 is a schematic bottom view of the sole 1 (corresponding to FIG. 7), and as shown in the figure, holes (openings) 5 opening into the sole underside 31 are formed in the region from the heel H of the sole 1 to approximately the center in the front-to-rear direction of the midfoot M, and no holes (openings) are formed in the region from approximately the center in the front-to-rear direction of the midfoot M of the sole 1 to the forefoot F. As a result, the compressive rigidity in the up-down direction of the sole 1 is relatively lower at the heel-up start position of the heel (heel center position 20h) than at the position of the metatarsophalangeal joint position 20j.

[0083] <Variation 1> FIG. 26 shows a sole according to the first modified example of the present invention. In the figure, the same reference numerals as those in FIG. 25 indicate the same or corresponding parts. As shown in FIG. 26, a hole (aperture) 50 opening on the sole underside 31 is formed in the region from the heel H of the sole 1 to the approximate center in the front-rear direction of the midfoot M, and a hole (aperture) 51 opening on the sole underside 31 and communicating with the hole (aperture) 50 is formed in the region from the approximate center in the front-rear direction of the midfoot M of the sole 1 to the forefoot F. The opening width W of the hole 50 is larger than the opening width w of the hole 51 (i.e., W>w). As a result, the compressive rigidity in the vertical direction of the sole 1 is relatively lower at the heel-up start position (heel center position 20h) of the heel than at the position of the metatarsophalangeal joint position 20j.

[0084] <Variation 2> FIG. 27 is a schematic vertical cross-sectional view of a sole according to a second modified example of the present invention. In the above embodiment and the first modified example, an example was shown in which a hole was formed in the sole 1 in the vertical direction. In the second modified example, as shown in FIG. 27, a plurality of holes (openings) 52 are formed in the midsole 2 of the sole 1 in the width direction. Each hole 52 is formed in the region from the heel H to the midfoot M of the sole 1, but no holes (openings) are formed in most of the region of the midfoot M of the sole 1 and in the forefoot F. As a result, the compression stiffness in the vertical direction of the sole 1 is relatively lower at the heel-up start position (heel center position 20h) of the heel than at the position of the metatarsophalangeal joint position 20j. Each hole 52 may be open on the medial side surface and / or the lateral side surface of the sole 1.

[0085] <Modification 3> FIG. 28 is a schematic vertical cross-sectional view of a sole according to a third modified example of the present invention. In the above embodiment, an example in which one vertical hole is formed in the sole 1 has been shown, but in this third modified example, as shown in FIG. 28, a plurality of vertical holes (openings) 53 are formed in the midsole 2 of the sole 1 (the number of holes 53 is not limited to this). Each hole 53 is formed in the region from the heel H to the midfoot M of the sole 1, but no holes (openings) are formed in most of the region of the midfoot M of the sole 1 and in the forefoot F. As a result, the vertical compression stiffness of the sole 1 is relatively lower at the heel-up start position (heel center position 20h) of the heel than at the position of the metatarsophalangeal joint position 20j. Each hole 53 may be open on the underside of the sole 1.

[0086] <Variation 4> FIG. 29 is a schematic vertical cross-sectional view of a sole according to a fourth modified example of the present invention. In the second modified example, a plurality of holes 52 are formed in the width direction only in the region from the heel part H to the midfoot part M of the sole 1. In the fourth modified example, as shown in FIG. 29, a plurality of holes 52 are formed in the region from the heel part H to the midfoot part M of the sole 1, and a plurality of holes 52' are formed in the width direction in most of the region of the midfoot part M of the sole 1 and in the forefoot part F (the number of holes 52, 52' is not limited to this). The diameter of each hole 52 is larger than the diameter of each hole 52'. In this case, the hole opening rate is larger at the heel-up start position (heel center position 20h) of the heel than at the position of the metatarsophalangeal joint position 20j. Here, the "hole opening rate" refers to the ratio of the volume of the openings to the total volume (in this example, the ratio of the total volume of each hole 52 (or 52') to the total volume (total volume of holes + midsole volume)).

[0087] As a result, the compressive stiffness in the vertical direction of the sole 1 is relatively lower at the heel-up start position of the heel (heel center position 20h) than at the metatarsophalangeal joint position 20j. Note that each hole 52, 52' may open on the medial side and / or lateral side of the sole 1. Similarly, in the example shown in Fig. 26, the hole opening rate is higher at the heel-up start position of the heel (heel center position 20h) than at the metatarsophalangeal joint position 20j.

[0088] <Variation 5> Fig. 30 is a schematic vertical cross-sectional view of a sole according to the fifth modified example of the present invention. In the third modified example, a plurality of vertical holes 53 are formed only in the region of the sole 1 from the heel H to the midfoot M. In the fifth modified example, as shown in Fig. 30, a plurality of vertical holes 53 are formed in the region of the sole 1 from the heel H to the midfoot M, and a plurality of vertical holes 53' are formed in most of the region of the midfoot M of the sole 1 and in the forefoot F. The diameter of each hole 53 is larger than the diameter of each hole 53'. In this case, as in the fourth modified example, the hole opening rate is larger at the heel-up start position (heel center position 20h) of the heel than at the position of the metatarsophalangeal joint position 20j.

[0089] As a result, the compressive rigidity in the vertical direction of the sole 1 is relatively lower at the heel-up start position of the heel part (heel center position 20h) than at the position of the metatarsophalangeal joint position 20j. Note that each hole 53, 53' may open on the underside of the sole 1.

[0090] <Variation 6> 31 is a schematic vertical cross-sectional view of a sole according to Modification 6 of the present invention. In the above-described embodiment and Modifications 1 to 5, an example was shown in which holes (openings) were formed in the sole 1 to create a difference in compression rigidity of the sole 1, but application of the present invention is not limited to this.

[0091] 31, the midsole of the sole 1 is composed of a midsole 21 arranged in a region extending from the heel H to approximately the center of the midfoot M in the front-to-rear direction, and a midsole 22 arranged in a region extending from approximately the center of the midfoot M in the front-to-rear direction to the forefoot F, with the midsole 21 being made of a material with a relatively low hardness and the midsole 22 being made of a material with a relatively high hardness, and the boundary surface 2d between the midsoles 21 and 22 extending substantially in the vertical direction. As a result, the vertical compression stiffness of the sole 1 is relatively lower at the heel-up start position of the heel (heel center position 20h) than at the metatarsophalangeal joint position 20j.

[0092] <Variation 7> Fig. 32 is a schematic vertical cross-sectional view of a sole according to Modification 7 of the present invention. In Modification 6, an example was shown in which the boundary surface 2d between the midsoles 21 and 22 extends substantially in the up-down direction, but in Modification 7, as shown in Fig. 32, the boundary surface 2d' between the midsoles 21 and 22 extends substantially in the front-rear direction. That is, each of the midsoles 21 and 22 extends from the heel H of the sole 1 through the midfoot M to the forefoot F. The midsole 21 made of a low hardness material is disposed on the upper side of the midsole, and the midsole 22 made of a high hardness material is disposed on the lower side of the midsole.

[0093] Furthermore, in this case, in the region from the heel H to the midfoot M, the thickness of the midsole 21 is thicker than the thickness of the midsole 22, so that in this region, the occupancy rate (percentage of the total midsole) of the relatively low hardness midsole 21 is relatively high, and in the forefoot F, the thickness of the midsole 22 is thicker than the thickness of the midsole 21, so that in this region, the occupancy rate (percentage of the total midsole) of the relatively high hardness midsole 22 is relatively high.

[0094] As a result, the compressive rigidity in the vertical direction of the sole 1 is relatively lower at the heel-up start position of the heel portion (heel center position 20h) than at the position of the metatarsophalangeal joint position 20j.

[0095] <Variation 8> 33 is a schematic vertical cross-sectional view of a sole according to Modification 8 of the present invention. In this Modification 8, similarly to Modification 7, the boundary surface 2d' between the midsoles 21, 22 extends substantially in the front-rear direction, and each of the midsoles 21, 22 extends from the heel H through the midfoot M to the forefoot F, but the midsole 21 made of a low hardness material is disposed on the lower side of the midsole, and the midsole 22 made of a high hardness material is disposed on the upper side of the midsole.

[0096] Also, in the region from the heel H to the midfoot M, the thickness of the midsole 21 is thicker than the thickness of the midsole 22, so that the proportion of the relatively low hardness midsole 21 (proportion to the entire midsole) is relatively high, and in the forefoot F, the thickness of the midsole 22 is thicker than the thickness of the midsole 21, so that the proportion of the relatively high hardness midsole 22 (proportion to the entire midsole) is relatively high, which is the same as in the seventh variant.

[0097] As a result, the compressive rigidity in the vertical direction of the sole 1 is relatively lower at the heel-up start position of the heel portion (heel center position 20h) than at the position of the metatarsophalangeal joint position 20j.

[0098] <Variation 9> In the above embodiment, the plate 4 is provided inside the midsole 2 of the sole 1, and a plurality of ribs 40 are provided on the plate 4. However, the ribs 40 may be eliminated to use a thin plate 4. Furthermore, the plate 4 may be omitted. Eliminating the plate 4 can promote compressive deformation of the heel part H of the sole 1 when a load is applied during running. By extending the plate 4 over the entire shoe, the support for the foot can be improved, and the flexural rigidity of the sole 1 can be improved. When pushing off with the toes, the elastic repulsive force of the plate 4 allows the foot to be kicked powerfully off the ground to obtain propulsion.

[0099] <Other Modifications> The above-described embodiment and each modification should be considered in all respects as merely illustrative of the present invention, and not restrictive. Those skilled in the art to which the present invention pertains may, when considering the teachings above, construct various modifications and other embodiments that incorporate the principles of the present invention without departing from the spirit and essential characteristics of the present invention, even if not expressly described herein. [Industrial Applicability]

[0100] As described above, the present invention is useful for shoe soles that enable a more natural forefoot running style to be achieved when running using the forefoot running technique, without the forefoot movement being hindered by having to quickly raise the heel after landing. [Explanation of symbols]

[0101] 1: Sole 2, 21, 22: Midsole 20: Sole top 20h: Heel center position 20j: Metatarsophalangeal joint position 20K: Heel position 5, 50~53': Hole (open hole) 3: Outsole 31: Underside of sole S: Reference line So: The rearmost position Se: Toe tip position O: Origin L: Journey C, D: Intersection SH: Sports shoes (shoes) R: Ground H: Heel M: Midfoot F: Forefoot [Prior art documents] [Patent documents]

[0102] [Patent Document 1] JP 2020-163084 A (see paragraphs

[0020] to

[0024] ,

[0028] to

[0030] , and FIG. 9) [Patent Document 2] JP 2023-96397 A (see paragraphs

[0025] to

[0026] ,

[0033] to

[0036] ,

[0045] to

[0047] , Figs. 4, 5, 8(a) to 8(c), 10 to 11, etc.) [Patent Document 3] JP 2023-95714 A (see paragraphs

[0023] ,

[0033] ,

[0039] to

[0046] , Figs. 1, 3, and 3A)

Claims

1. A sole of a shoe, The shoe extends from the heel portion through the midfoot portion to the forefoot portion, and has a sole upper surface and a sole lower surface; When a straight line connecting the rearmost end position of the sole upper surface and the position of the tip of the toe is defined as a reference line S, the position of the rearmost end is defined as an origin O, a distance measured from the origin O to the position of the tip of the toe along the sole upper surface is defined as L, a point of intersection between a line passing from the origin O along the sole upper surface to a position of 0.45×L and perpendicular to the reference line S and the sole lower surface is defined as C, and a point of intersection between a line passing from the origin O along the sole upper surface to a position of 0.60×L and perpendicular to the reference line S and the sole lower surface is defined as D, and a sole posture in which the sole touches the ground at points C and D is defined as a stable posture, In the stable posture, the sole lower surface at the toe portion is separated from the ground and the sole lower surface at the heel portion is separated from the ground to be in a heel-up position; When an angle formed by a straight line connecting a heel center position, which is located at 0.15×L from the origin O along the upper surface of the sole, and a metatarsophalangeal joint position, which is located at 0.68×L from the origin O, and the ground is θ, in the stable posture, θ≧5° It is set to The vertical compression stiffness of the sole is relatively lower at the heel-up start position of the heel portion than at the metatarsophalangeal joint position. A shoe sole characterized by:

2. In claim 1, In the stable posture, the sole underside in a rear region from a position of 0.15×L from the origin O along the sole upper surface is separated from the ground, and the sole underside in a front region from a position of 0.68×L from the origin O along the sole upper surface is separated from the ground, and the sole underside is in contact with the ground in a region forward from the position of 0.15×L from the origin O along the sole upper surface and rearward from the position of 0.68×L from the origin O along the sole upper surface. A shoe sole characterized by:

3. In claim 1, The heel-up start position is located rearward of the ankle position, which is located at a position 0.27×L from the origin O along the sole upper surface. A shoe sole characterized by:

4. In claim 1, In the stable posture, when the wearer is in a static standing posture while wearing shoes, θ<5° The sole compression stiffness is set so that A shoe sole characterized by:

5. In claim 1, the heel portion having an aperture and the forefoot portion having no aperture; A shoe sole characterized by:

6. In claim 1, The heel portion and the forefoot portion have an opening, and the opening width of the opening in the heel portion is set larger than the opening width of the opening in the forefoot portion. A shoe sole characterized by:

7. In claim 1, The heel portion and the forefoot portion have openings, and the opening rate of the heel portion is set to be larger than the opening rate of the forefoot portion. A shoe sole characterized by:

8. In claim 1, The heel portion is made of a material having a relatively low hardness, and the forefoot portion is made of a material having a relatively high hardness. A shoe sole characterized by:

9. In claim 1, the heel portion and the forefoot portion both having regions of relatively low hardness material and regions of relatively high hardness material; The occupancy rate of the relatively low hardness material region is set relatively high in the heel portion, and the occupancy rate of the relatively high hardness material region is set relatively high in the forefoot portion. A shoe sole characterized by:

10. In claim 1, Point C and point D are disposed at least on the outer edge of the sole lower surface. A shoe sole characterized by:

11. In claim 1, The area from point C to point D on the bottom surface of the sole constitutes a flat stable area, and the stable area is in contact with the ground in the stable posture. A shoe sole characterized by:

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