Shoe soles

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 shoe soles, and more particularly to an improved structure that enables a more natural forefoot running style when running, without hindering forefoot movement by forcing the heel to rise quickly after landing. [Background technology]

[0002] In recent years, the forefoot running style, in which the foot strikes the ground, has become mainstream for efficient long-distance running. Forefoot running has the advantage of reducing stress on the knees and shortening ground contact time, easing muscle strain. Forefoot running is thought to 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 stretch / contraction). Here, running economy is an indicator of how little energy (oxygen intake) is required to run at a certain speed. The better (i.e., higher) running economy is, the less oxygen intake is required and the more efficient the running.

[0003] However, mastering the forefoot sprinting technique requires a certain level of skill. Specifically, first, ground contact skills are required to enable the forefoot / midfoot to land on the ground just before contact. Second, during contact, leg strength (muscle strength and endurance) is required to prevent heel drop (descent) and withstand the stretching of the muscles and tendons, as well as the need to lock the ankle. For this reason, mastering the forefoot sprinting technique is not easy for beginner runners, and whether they can sustain a forefoot sprinting technique is largely dependent on the runner's ability.

[0004] Incidentally, soles incorporating a high-rigidity plate (e.g., a CFRP plate) are now in practical use to support the heel when the heel drops in. In such soles, when the load shifts to the forefoot, the forefoot portion of the plate is pushed downward, causing a seesaw effect that lifts the heel portion of the plate upward, thereby supporting the heel.

[0005] However, such soles with built-in plates are not designed 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 a forefoot running style, as shown in Japanese Patent Application Laid-Open No. 2020-163084 (see paragraphs

[0020] to

[0024] ,

[0028] to

[0030] , and Figure 9 of the same publication). In this sole, the position of the rearmost 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 with the bottom surface of the heel on the surface on the sole contact side positioned parallel to the horizontal plane, 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 positioned 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 relationship m1≧h holds, and the angle that the line connecting position Sm1 and position Sh makes with the horizontal plane is θ1, the position where a vertical line drawn from position Sm1 intersects with the ground contact surface is Sm1', and the position where a vertical line drawn from position Sh intersects with the ground contact surface is Sh', and the angle that the line connecting position Sm1' and position Sh' makes with the horizontal plane is θ2, then the relationship θ2≧θ1 holds, 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 position Sh, which is 0.16×L from the origin, is smaller than the sole thickness m1 at position Sm1, which is (0.4 to 0.6)×L from the origin. Furthermore, the angle θ2 between the horizontal plane and the line connecting positions Sm1' and Sh' is larger than the angle θ1 between the horizontal plane and the line connecting positions Sm1 and Sh. This prevents the heel from touching the ground when landing, preventing heel strike and promoting contact with the forefoot. Furthermore, the sole thickness m2 at position Sm2 is larger than the sole thickness m1 at position Sm1. This prevents the sole from tilting backward and causing the heel to drop downward when the sole initially touches the ground at position Sm1' on the sole's ground-contact surface, allowing the sole to quickly transition to rolling forward after initial contact. Furthermore, the sole thickness f at position Sf, which is 0.7 x 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 enable forefoot running, the inventors of the present application have found that there is room for further improvement in the soles 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 Japanese Patent Application Laid-Open No. 2023-96397 and Japanese Patent Application Laid-Open No. 2023-95714.

[0010] In the example shown in JP 2023-96397 A, a reference posture is maintained when the sole 1 makes contact with the ground R at point C. In this reference posture, the sole underside 31 in the heel and toe areas is positioned away from the ground R. This prevents unintended contact of the heel with the ground and promotes and makes it possible to maintain a natural forefoot posture. In addition, in the reference posture, when the angle formed by the line connecting the heel center position 20h, located 0.15 × L from the origin O along the sole upper surface 20, and the metatarsophalangeal joint position 20j, located 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 above the forefoot portion (i.e., in a heel-up state), thereby conforming to a forefoot posture (see paragraphs

[0025] to

[0026] ,

[0033] to

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

[0011] Next, in the phase immediately after sole 1 touches the ground, the heel of sole 1 drops or descends a distance d toward ground R, but since sole 1 is placed in a reference posture in which it touches ground R at point C, which is forward of the ankle and 0.45×L from origin O (see FIG. 8(a)), not only can the sole undersurface 31 provide a natural support effect from the time of contact, but the shoe wearer's muscles and tendons can also function as springs, preventing excessive heel depression and reducing 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-mentioned publication). As a result, the distance until the heel is lifted after sole 1 touches the ground can be shortened, allowing for a quick transition to the heel-lift phase shown in FIG. 8(c). In this way, it becomes possible to smoothly transfer from the heel to the forefoot after landing, and a smooth shift of the center of gravity from the heel to the toe can be achieved (see paragraph

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

[0012] Furthermore, Japanese Patent Application Laid-Open No. 2023-96397 discloses that the compressive 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 midsole at the metatarsophalangeal joint deforms more downward than the heel, which prevents excessive descent of the heel after the sole hits the ground and allows for smooth forward load transfer (see paragraphs

[0045] to

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

[0013] On the other hand, in the shoe shown in Patent Publication No. 2023-95714, 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 lower forefoot sole 2B1 undergoes a relatively large compressive deformation, causing the sole 1 to sink downward. This causes the toes to flex significantly and the plantar fascia PF to stretch, resulting in the arch SA rising, promoting the windlass effect and increasing propulsion during running. Also, after the sole touches the ground, when the heel tries to sink downward, the curved plate P can support the heel, thereby reducing the amount of heel drop (descent). Furthermore, when the maximum load acts, the support angle with respect to the sole increases, further enhancing the support and lift effect from the midfoot to the heel, and further increasing the rigidity of the foot, further improving stability. Next, when the toes move into a state of maximum flexion and the sole 1 reaches its maximum flexion, 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 Figure 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 conducted further intensive research into the shoes described in the above publications, and as a result have discovered the following facts: Previous shoes have been designed to achieve a natural forefoot running style by allowing the rear part of the foot (heel) to remain stationary and the front part of the foot to deform relatively more when the sole reaches its maximum sinking amount during running, so that the angle of the foot relative to the ground surface can be maintained.

[0016] However, when runners wearing the shoes were asked to actually run and a sensory evaluation was conducted while running, it was found that with previous shoes, when the sole reached its maximum sinking amount during running, the heel was forced to rise too quickly, which in turn hindered a natural forefoot run. This was thought to be because the angle of the foot relative to the ground contact surface was maintained too long until the latter half of the gait cycle (the running cycle from contact to take-off), which greatly deviated from the natural forefoot run movement.

[0017] The present invention has been made in view of the above-mentioned conventional situation, and the problem that the present invention aims to solve is to provide a shoe sole that allows for a more natural forefoot running without hindering 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 a straight line connecting the position of the rearmost end of the sole upper surface to the position of the tip of the toe is defined as a reference line S, and the position of the rearmost end is defined as an origin O. The distance measured from the origin O along the sole upper surface to the position of the tip of the toe is defined as L, the intersection of a line passing from the origin O along the sole upper surface at a position 0.45×L and perpendicular to the reference line S with the sole lower surface is defined as C, and the intersection of a line passing from the origin O along the sole upper surface at a position 0.60×L and perpendicular to the reference line S with the sole lower surface is defined as D. When the shoe is not being worn by the wearer and no weight is being applied to the sole from the wearer's foot, The sole posture in which the sole touches the ground at points C and D is called the stable posture. death , When the angle formed by the line connecting the heel center position, which is located 0.15 × L from the origin O along the top surface of the sole, and the metatarsophalangeal joint position, which is located 0.68 × L from the origin O, with the ground is θ, in the stable posture, θ is set to be ≥ 5°, points C and D are located at least on the outer edge of the instep on the bottom surface of the sole, and the area on the bottom surface of the sole from points C to D constitutes a flat stable area, and in the stable posture, the stable area is in contact with the ground, and the flat stable area including point C on the bottom surface of the sole, which corresponds to a position 0.45 × L along the top surface of the sole from the origin O, and point D on the bottom surface of the sole, which corresponds to a position 0.68 × L along the top surface of the sole from the origin O, is in contact with the ground. In a stable position, The underside of the sole is At the toe It As you leave the ground, your heel It Off the ground The heel-up start position is provided at a position rearward of the heel-up start position where the foot is lifted up from the ground. The compressive stiffness of the sole in the vertical direction is higher than that at the metatarsophalangeal joint position. In a stable position The heel lift start position is relatively low.

[0019] According to the present invention, when the sole contacts the ground, the sole is in a position of 0.45×L from the origin O. center of heel Point C corresponds to the position, and 0.6 from the origin O 8 ×L metatarsophalangeal joint Since the sole touches the ground at two points, point D, which correspond to the position of the sole, a stable sole posture (stable posture) can be achieved, thereby preventing time loss and power loss.

[0020] Furthermore, according to the present invention, in a stable posture, the underside of the sole at the toe and heel is separated from the ground ( That is, , in the heel area oh If , the rear side from the heel up starting position Heels up (i.e. off the ground) ), unintentional contact of the heel with the ground can be prevented when the foot touches the ground. Furthermore, according to the present invention, in a stable posture, the line connecting the center of the heel and the metatarsophalangeal joint forms an angle of 5 degrees or more with the ground, so that the heel can be maintained in a heel-up position, and the foot can be aligned with the forefoot posture.

[0021] Furthermore, according to the present invention, the compressive stiffness of the sole in the vertical direction is higher than that at the metatarsophalangeal joint position. In a stable positionBecause the heel is relatively low at the start of heel-up, when the sole reaches its maximum sinkage during running, the rear foot (heel) can deform downward to a greater extent than the forefoot. This prevents the angle of the foot relative 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, forefoot movement is not hindered by rushing heel lift after contact, making it possible to achieve 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, The heel-up start position is located rearward of the ankle position, which is located 0.27×L from the origin O along the top surface of the sole.

[0024] In the present invention, In the stable posture, the heel-up starting position is at a position 0.15×L from the origin O along the top surface of the sole, the underside of the sole in the rearward region from the heel-up starting position is off the ground, and the underside of the sole in the forward region from a position 0.68×L from the origin O along the top surface of the sole is off the ground, and the underside of the sole is in contact with the ground in the region forward from a position 0.15×L from the origin O along the top surface of the sole and rearward from a position 0.68×L from the origin O along the top surface of the sole.

[0025] In the present invention, the sole compression stiffness is set so that θ<5° when the wearer is in a static standing position while wearing the shoes in a stable position. In this specification, the term "static standing posture" refers to a posture in which the body stands upright 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 "porosity" refers to the ratio of the volume of open pores to the total volume.

[0029] In the present invention, the heel portion is made of a material with a relatively low hardness, and the forefoot portion is made of a material with a relatively high hardness.

[0030] In the present invention, both the heel and forefoot regions 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 region, while the occupancy rate of the relatively high hardness material region is set relatively high in the forefoot region. 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 flat stable area, and in a 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 when the foot touches the ground, thereby stabilizing the forefoot posture. [Effects 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 hindering forefoot movement by forcing the heel to rise quickly after landing. [Brief explanation 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, viewed obliquely from above. FIG. [Figure 2] FIG. 2 is an overall perspective view of the bottom side of the sole (FIG. 1) as viewed obliquely from below. [Figure 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. [Figure 5] FIG. 2 is a rear view of the sole (FIG. 1) as seen from behind the heel. [Figure 6] 2 is a schematic plan view of the sole (FIG. 1). FIG. [Figure 7] 2 is a schematic bottom view of the sole (FIG. 1). FIG. [Figure 8] 2 is a schematic view of the medial side of the sole (FIG. 1). FIG. [Figure 9] FIG. 2 is a schematic view of the outer instep side of the sole (FIG. 1). [Figure 10] FIG. 8 is a vertical cross-sectional view taken along line XX in FIG. 7. [Figure 11] FIG. 10 is a cross-sectional view taken along the line XI-XI in FIG. [Figure 12] FIG. 8 is a cross-sectional view taken along line XII-XII in FIG. 7. [Figure 13] FIG. 8 is a cross-sectional view taken along line XIII-XIII in FIG. 7. [Figure 14] FIG. 8 is a cross-sectional view taken along line XIV-XIV in FIG. 7. [Figure 15] FIG. 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 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 the 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 acting from the wearer's foot. [Figure 23]19A to 19D are diagrams for explaining the state of the shoe (FIG. 19) when running, showing the movement of the shoe relative to the ground in chronological order from (a) to (d). [Figure 24] 10A to 10D are diagrams for explaining the state of a shoe as a comparative example during running, showing the movement of the shoe relative to the ground in chronological order from (a) to (d). [Figure 25] 8 is a schematic bottom view of a sole according to an embodiment of the present invention, corresponding to FIG. 7. FIG. [Figure 26] FIG. 10 is a schematic bottom view of a sole according to a first modified example of the present invention. [Figure 27] FIG. 10 is a schematic vertical cross-sectional view of a sole according to a second modified example of the present invention. [Figure 28] FIG. 10 is a schematic vertical cross-sectional view of a sole according to a third modified example of the present invention. [Figure 29] FIG. 10 is a schematic vertical cross-sectional view of a sole according to a fourth modified example of the present invention. [Figure 30] FIG. 10 is a schematic vertical cross-sectional view of a sole according to a fifth modified example of the present invention. [Figure 31] FIG. 10 is a schematic vertical cross-sectional view of a sole according to a sixth modified example of the present invention. [Figure 32] FIG. 13 is a schematic vertical cross-sectional view of a sole according to a seventh modified example of the present invention. [Figure 33] FIG. 13 is a schematic vertical cross-sectional view of a sole according to Modification 8 of the present invention. [Figure 34] 1 is a graph showing the negative work of plantar flexion torque at the ankle joint during running in the present invention in comparison with a comparative example and a conventional product. [Figure 35] 10 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%. [Figure 36] 10 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] 10 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]10 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 INVENTION

[0035] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Figures 1 to 25 are diagrams illustrating a sole according to one embodiment of the present invention and a shoe equipped with the sole. In these diagrams, Figures 1 to 5 show the appearance of the sole, Figures 6 to 15 are plan, bottom, side, 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 and bottom views showing the shape of the sole in detail, Figure 23 is a diagram showing the state of the shoe during running in chronological order, and Figure 24 is a diagram showing the state of a comparative shoe during running in chronological order for comparison with Figure 23. Here, sports shoes, particularly running shoes for middle to long distances, are used as an example of shoes.

[0036] In the following explanation (similarly in Modifications 1 to 8 described later), the terms "upper" (upper side / upper) and "lower" (lower side / lower) refer to the vertical positional relationship of the shoe, the terms "front" (front side / front) and "rear" (rear side / rear) refer to the longitudinal positional relationship of the shoe, and the term "width" refers to the left-right direction of the shoe. In other words, in the example of Figure 19, the terms "upper" and "lower" refer to the vertical positional relationship of the shoe in the figure. above How and under The front and rear refer to the directions shown in the figure. right The width direction refers to the direction perpendicular to the paper surface of the drawing.

[0037] As shown in Figures 1 to 5, the sole 1 of this embodiment comprises a midsole 2 extending over the entire length of the sole and an outsole 3 disposed below the midsole 2. The midsole 2 comprises 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 forms the 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 raised portion 20a that rises upward. The outsole 3 is fixed to the lower surface of the lower midsole 2b with an 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. However, the materials constituting the midsole 2 and the outsole 3 are not limited to these, and any other appropriate material may be selected.

[0039] Furthermore, the midsole 2 may be molded not only by the usual injection foam molding method but also by supercritical foaming. Here, "supercritical foaming" refers to a method of injection foam molding in which resin is put 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 and 2b (the details of the plate 4 will be described later).

[0041] A vertical hole (opening) 5 is formed on the underside (bottom surface) of the sole 1. The hole 5 passes through the outsole 3 in the vertical direction, but does not pass through 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-to-back direction from the heel to the longitudinal center of the midfoot. In this example, the opening width of the hole 5 is greatest at the underside (bottom surface) of the sole 1, and is set in a tapered shape that gradually becomes smaller as it moves 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 portion H, a midfoot portion M, and a forefoot portion F, which correspond to the heel region, midfoot region (arch region), and forefoot region of the wearer's foot, respectively, and extends from the heel portion H through the midfoot portion M to the forefoot portion F. The plate 4 extends from the heel portion H of the sole 1 through the midfoot portion M to the front side of the front end (toe portion) of the forefoot portion F. A plurality of ribs 40 that curve and extend in the front-to-rear direction are provided in the front region of the plate 4 (details will be described later). Note that, for convenience of illustration, the ribs 40 of the plate 4 are not shown in FIG. 7. The bottom surfaces 50 of the holes 5 are also visible in FIG. 7.

[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 areas on the side of the sole that have a design (e.g., a textured pattern) and areas that do not have a design (white areas in each figure).

[0044] As shown in FIG. 10 (longitudinal cross-sectional view of the sole), 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 underside of the plate 4. Also, FIG. 10 and FIGS. 13 to 15 (transverse cross-sectional views of the sole) show that the hole 5 is tapered in the front-to-back and left-to-right directions. As shown in FIG. 10, the plate 4 extends in the front-to-back direction while curving, and each rib 40 is provided on its underside. 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 having a thickness of, for example, approximately 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, 2b with an adhesive or the like. A pair of left and right upright wall portions 41 rising upward is formed in the center of the plate 4 in the front-to-rear direction. Each rib 40 is disposed on the underside of the plate 4 and protrudes downward, extending in the front-to-rear direction while protruding downward from the underside 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 can be used. In the example shown in FIGS. 6 and 18 , the ribs 40 are provided symmetrically on both the left and right sides of the center line in the front-to-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 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 plate 4 may also be made of fiber-reinforced plastic (FRP), which uses carbon fiber, aramid fiber, glass fiber, or the like as reinforcing fibers and a thermosetting resin or thermoplastic resin as a matrix resin.

[0047] Next, the sole according to the present invention and the shoe having the same will be described in detail with reference to FIGS. As shown in Figure 19, the shoe SH has a sole 1 have The sole 1 is constructed by fastening an upper (vamp) U to the upper side of the sole 1 by adhesive, sewing, etc. In the drawing, for the sake of simplicity of illustration and explanation, an example is shown in which the sole 1 is constructed from a single-layer midsole 2 and an outsole 3 disposed thereunder.

[0048] As shown in FIG. 19 , a straight line connecting the position So of the rearmost end (rear end of the heel) of the sole upper surface 20 and the position Se of the toe tip 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 shoe SH. Next, the position So of the rearmost end is defined as the origin O, and the distance measured from the origin O to the position Se of the toe tip along the sole upper surface 20 is defined as L. The intersection of a line along the sole upper surface 20 that passes through a position 20m that is 0.45×L from the origin O and intersects perpendicular to the reference line S with the sole lower surface 31 is defined as C. The intersection of a line along the sole upper surface 20 that passes through a position 20n that is 0.60×L from the origin O and intersects perpendicular to the reference line S with the sole lower surface 31 is defined as D. In the same figure, the intersection of the line that passes through position 20m and intersects perpendicular to the reference line S with the reference line S is indicated as Sp, and the intersection of the line that passes through position 20n and intersects perpendicular to the reference line S with the reference line S is indicated as Sq.

[0049] When the sole posture in which the sole 1 contacts the ground R at points C and D is defined as a stable posture, in the stable posture, the sole lower surface 31 is separated (floating) from the ground R at the heel and toe. Therefore, the sole lower surface 31 at the heel is in a heel-up position, and the position at which the sole lower surface 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, which is located below position 20n that 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) formed by a line T connecting a heel center position 20h located at 0.15×L from the origin O along the sole upper surface 20 and a metatarsophalangeal joint position 20j located at 0.68×L from the origin O with the ground R is θ, in a stable posture, θ≧5° is set to.

[0052] Here, 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 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 in the heel portion 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 region rearward from position 20h. Also, as shown in the same figure, the sole lower surface 31 is preferably separated from the ground R in a region forward 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, as shown in FIG. 20 , 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 0.27×L from the origin O along the sole upper surface 20, in the stable posture. In other words, in the stable posture, the sole lower surface 31 comes into contact with the ground R at a position (ankle position) 20k that is 0.27×L from the origin O along the sole upper surface 20. This ankle position 20k corresponds to the approximate boundary between the heel portion H and the midfoot portion M, as will be described later. This allows the contact area of ​​the sole lower surface 31 with the ground R to be expanded in the front-to-rear direction in the stable posture, thereby further stabilizing the forefoot posture. In FIG. 20 , the area surrounded by a dashed line indicates the lateral malleolus LM of the foot. The lateral malleolus LM is located below the fibula FB. Also in the same figure, the symbols TB, TL, and CC indicate the tibia, talus, and calcaneus, respectively.

[0055] The foot skeletal diagram in Figure 20 is included for the sake of convenience in order to explain the shape of the sole 1 in relation to the foot skeleton. On the other hand, Figure 22 shows a state in which a wearer's foot is actually placed on the sole 1 and a load is applied. In this state, the sole compression rigidity is set so that 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 upright with the weight evenly distributed on both feet while not exercising), θ<5°.

[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, that is, θ'<5° In FIG. 22, the straight line T connecting the heel center position 20h (FIG. 20) and the metatarsophalangeal joint position 20j is shown by a two-dot chain line.

[0058] Next, as shown in Figure 21, the heel portion H, midfoot portion M, and forefoot portion F of the sole 1 can be expressed using the distance L measured from the origin O to the tip of the toe Se 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 of the sole 31 are located at positions 0.45 x L and 0.60 x L from the origin O, respectively, on the outer instep edge (including a position closer to the outer instep edge or a position closer to the center in the width direction) and the inner instep edge (including a position closer to the inner instep 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 the sole lower surface 31 extending from the position 0.45 × L to the position 0.60 × L from the origin O is formed flat and forms a stable area. In a stable posture in which the sole 1 contacts the ground R at points C and D, preferably, the entire hatched area (stable area) on the sole lower surface 31 contacts the 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 relative to the ground R in chronological order from (a) to (d), with (a) in the same figure showing the phase at the time of initial contact of the sole 1 with the ground. 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, 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 from (floating above) the ground R at the heel and toe (see Figure 19).

[0063] This prevents the heel from making unintended contact 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 (floats above) the ground R in a region rearward from a position 0.15×L from the origin O and in a region forward 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 initially touches the ground, allowing the runner to maintain a forefoot stance and support a forefoot running style. As a result, the burden on the runner is reduced, improving their sense of security while running.

[0065] Furthermore, in the stable posture, as described above, when the angle θ is the angle formed by the line connecting the heel center position 20h, which is located 0.15×L from the origin O along the sole upper surface 20 in FIG. 20, and the metatarsophalangeal joint position 20j, which is located 0.68×L from the origin O, with the ground, 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 portion of the sole 1 to be positioned above the forefoot portion (i.e., in a heel-up state), thereby achieving a forefoot posture.

[0066] 23(b) shows the phase of the intermediate movement after the initial 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 compressed to the maximum in the vertical direction, but in this case, not only points C and D on the outer side of the sole lower surface 31 but also points C and D on the inner side of the sole lower surface 31 are in contact with the ground R, thereby maintaining a stable posture of the sole 1 and maintaining a forefoot posture.

[0067] Also, as described above, the vertical compressive rigidity 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 (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 initial contact of the sole 1 with the ground, the sole 1 undergoes greater compressive deformation at the heel center position 20h than at the metatarsophalangeal joint position 20j. Therefore, the angle β in Figure 23(b) is smaller than the angle α (Figure 23(a)) at the time of initial contact with the ground (i.e., β<α).

[0068] In this way, when the sole 1 reaches its maximum sinkage amount during load application after initial contact with the ground, the rear foot (heel) side of the sole 1 deforms downward relatively more than the forefoot side. This makes it possible to prevent the angle of the foot relative to the ground contact surface from being maintained too long until the latter half 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 forced to lift quickly after contact with the ground, allowing for a natural heel lift movement to occur, thereby achieving a more natural forefoot running that utilizes the spring-like behavior of the muscles and tendons.

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

[0070] Here, Fig. 24 shows a state of a shoe during running as a comparative example of the present invention. The sole 1' of this shoe SH' has the same shape as the sole 1 of the shoe SH of Fig. 23 (see Fig. 20), but unlike the present invention, the sole 1 ’The compressive stiffness in the vertical direction is higher 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 pressure is lower at the metatarsophalangeal joint position 20j than at the heel lift start position of the heel. ’ At the position of Sole 1 ’ The amount of compressive deformation increases.

[0071] In Fig. 24, similar to Fig. 23, the movement of the shoe SH' relative to the ground surface 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 time of initial ground contact. At this time, the sole 1' is in a stable position, similar to FIG. 23(a), with points C and D (see FIGS. 19 to 22) of the sole lower surface 31' in contact with the ground R. The sole lower surface 31' is positioned away from (floating above) 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] Figure 24(b) shows Sole 1 ’ This shows the intermediate movement phase after the initial contact of the sole. ’ The maximum load acts on the sole 1 ’ At this time, as mentioned above, the sole 1 ’ The vertical compression stiffness of the ’ ) than the metatarsophalangeal joint position 20j ’ Since the sole is relatively low at the ’ When the maximum load is applied to the sole 1 ’ The center of the heel is 20h. ’ Metatarsophalangeal joint position 20J ’Therefore, the angle β' in Figure 24(b) is larger than the angle α' (Figure 24(a)) at the time of initial contact (i.e., β'>α').

[0074] Thus, Sole 1 ’ When the load is applied after the initial contact of the sole ’ When the maximum sinking amount is reached, the forefoot deforms downward relatively more than the rearfoot (heel). As a result, the angle of the foot relative to the ground surface is maintained too long 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 a natural forefoot run.

[0075] In the situation shown in FIG. 24(c), after the heel starts to rise, the sole lower surface 31 ’ The toe of the sole 1 is about to take off from the ground R. ’ completely lifts off the ground R.

[0076] Next, the following performance experiment was carried out to confirm the effect of shoes (products of the present invention) having soles according to the present invention in reducing the burden on the triceps surae of the wearer. The outline of the experiment is as follows. i) Two runners (N=2). The breakdown of the ground contact patterns was one person on the forefoot and one person on the 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) Wearing each shoe, participants ran at a constant speed of 20.0±1.0km / h (race pace). iv) Using a motion capture system (MAC 3D system) manufactured by Motion Analysis and a ground reaction force meter manufactured by Kistler, the body characteristic points and ground reaction forces of each runner were measured during running. 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 the eccentric contraction of the triceps surae, was calculated.

[0077] The calculation results of the ankle 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 angle θ are shown in FIGS. 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 rate = (20 / 50) x 100 = 40% The larger the deformation rate, the smaller the compressive rigidity. The support base refers to the rear foot (heel) area on the underside of the sole that comes into contact with the ground.

[0079] 35 and 36 show examples where the pre-deformation angle θ is 11° (i.e., High), while FIGS. 37 and 38 show examples where the pre-deformation angle θ is 4° (i.e., Low). Also, FIGS. 35 and 37 show the change in angle θ when the deformation rate of the support base is changed from 40% to 55% when the forefoot deformation rate is 40%. Similarly, FIGS. 36 and 38 show the change in angle θ when the deformation rate of the support base is changed from 40% to 55% when the forefoot deformation rate is 45%. The area surrounded by the dotted line in each figure was set based on sensory evaluations obtained from multiple runners who actually ran in a forefoot stance, and indicates the range that divided the evaluations of each runner. In other words, when the angle θ was located below this area, each runner evaluated that a more natural forefoot stance was achieved.

[0080] As shown in Figure 35, when the angle θ before deformation is 11° (High) and the forefoot deformation rate is 40%, the sensory evaluation improves when the deformation rate of the support base exceeds 47% (when the angle θ after deformation is smaller than approximately 5.5°, as shown in the graph). Also, as shown in Figure 36, when the angle θ before deformation is 11° (High) and the forefoot deformation rate is 45%, the sensory evaluation improves when the deformation rate of the support base exceeds 49% (when the angle θ after deformation is smaller than approximately 5.5°, as shown in the graph). In other words, it was found that in both cases, the sensory evaluation improves when the angle θ before deformation (initial angle) is approximately half after deformation.

[0081] On the other hand, as shown in Figure 37, when the angle θ before deformation is 4° (Low) and the forefoot deformation rate is 40%, the sensory evaluation improves when the deformation rate of the support base exceeds 45% (when the angle θ after deformation is smaller than approximately 1.8° from the graph). Also, as shown in Figure 38, when the angle θ before deformation is 4° (Low) and the forefoot deformation rate is 45%, the sensory evaluation improves when the deformation rate of the support base exceeds 49% (when the angle θ after deformation is smaller than approximately 1.8° from the graph). In other words, it was found that in both cases, the sensory evaluation improves when the angle (initial angle) θ before deformation is approximately half after deformation.

[0082] Next, Figure 25 is a schematic bottom view of the sole 1 (corresponding to Figure 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-back direction of the midfoot M, and no holes (openings) are formed in the region from approximately the center in the front-to-back 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 metatarsophalangeal joint position 20j.

[0083] <Variation 1> Figure 26 shows a sole according to Modification 1 of the present invention. In this figure, the same reference numerals as in Figure 25 indicate the same or corresponding parts. As shown in Figure 26, a hole (opening) 50 opening into the sole lower surface 31 is formed in the region of the sole 1 from the heel H to approximately the center of the midfoot M in the front-to-back direction, and a hole (opening) 51 opening into the sole lower surface 31 and communicating with hole (opening) 50 is formed in the region of the sole 1 from approximately the center of the midfoot M in the front-to-back direction to the forefoot F. The opening width W of hole 50 is larger than the opening width w of 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 of the heel (heel center position 20h) than at the metatarsophalangeal joint position 20j.

[0084] <Variation 2> FIG. 27 is a schematic longitudinal cross-sectional view of a sole according to Modification 2 of the present invention. While the above-described embodiment and Modification 1 show examples in which vertical holes are formed in the sole 1, in Modification 2, as shown in FIG. 27, multiple widthwise holes (openings) 52 are formed in the midsole 2 of the sole 1. 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 midfoot M of the sole 1 or in the forefoot F. This results in the vertical compressive rigidity of the sole 1 being relatively lower at the heel-up start position (heel center position 20h) than at the metatarsophalangeal joint position 20j. The holes 52 may also be open on the medial and / or lateral side of the sole 1.

[0085] <Variation 3> FIG. 28 is a schematic longitudinal cross-sectional view of a sole according to Modification 3 of the present invention. In the above-described embodiment, an example was shown in which a single vertical hole was formed in the sole 1. However, in Modification 3, 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 midfoot M of the sole 1 or 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) than at the metatarsophalangeal joint position 20j. Note that each hole 53 may be open on the underside of the sole 1.

[0086] <Variation 4> FIG. 29 is a schematic longitudinal cross-sectional view of a sole according to a fourth modification of the present invention. In the second modification, a plurality of holes 52 are formed in the width direction only in the region of the sole 1 from the heel H to the midfoot M. In this fourth modification, as shown in FIG. 29, a plurality of holes 52 are formed in the region of the sole 1 from the heel H to the midfoot M, and a plurality of holes 52' are formed in the width direction in most of the region of the midfoot M of the sole 1 and in the forefoot 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 metatarsophalangeal joint position 20j. Here, the "hole opening rate" refers to the ratio of the volume of the holes to the total volume (in this example, the ratio of the total volume of each hole 52 (or 52') to the total volume (total hole volume + midsole volume)).

[0087] 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 (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 Figure 26, the hole opening ratio is greater at the heel-up start position of the heel (heel center position 20h) than at the metatarsophalangeal joint position 20j.

[0088] 30 is a schematic vertical cross-sectional view of a sole according to a fifth modified example of the present invention. In the third modified example, a plurality of holes 53 are formed in the vertical direction only in the region from the heel H to the midfoot M of the sole 1. In the fifth modified example, as shown in FIG. 30, a plurality of holes 53 are formed in the vertical direction only in the region from the heel H to the midfoot M of the sole 1. Before A plurality of holes 53' are formed in the vertical direction in the foot F. The diameter of each hole 53 is larger than the diameter of each hole 53'. In this case, as in the fourth modification, the hole opening ratio is larger at the heel lift start position (heel center position 20h) of the heel than at 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 (heel center position 20h) than at the metatarsophalangeal joint position 20j. Note that each of the holes 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, examples have been shown in which holes (openings) are formed in the sole 1 to create differences in compression rigidity of the sole 1, but the application of the present invention is not limited to this.

[0091] 31, the midsole of the sole 1 is composed of a midsole 21 located in a region extending from the heel H to approximately the center of the midfoot M in the front-to-back direction, and a midsole 22 located in a region extending from approximately the center of the midfoot M in the front-to-back direction to the forefoot F, with the midsole 21 being made of a relatively low hardness material and the midsole 22 being made of a relatively high hardness material, 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-to-back 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 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 in this region the proportion of the relatively high hardness midsole 22 (proportion to the entire midsole) is relatively high.

[0094] As a result, the compressive rigidity of the sole 1 in the vertical direction is relatively lower at the heel lift 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 Modification 8, similar to Modification 7, the boundary surface 2d' between the midsoles 21 and 22 extends substantially in the front-to-rear direction, and each of the midsoles 21 and 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 midsole, and the midsole 22 made of a high-hardness material is disposed on the upper midsole.

[0096] Furthermore, 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, as in the above-mentioned variant example 7.

[0097] As a result, the compressive rigidity of the sole 1 in the vertical direction is relatively lower at the heel lift 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, an example has been shown in which 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, but the ribs 40 may be eliminated and a thin plate 4 may be used. Furthermore, the plate 4 may be omitted. Eliminating the plate 4 can promote compressive deformation of the heel portion H of the sole 1 when a load is applied during running. Incidentally, by extending the plate 4 over the entire shoe, support for the foot can be improved and the flexural rigidity of the sole 1 can be improved, so that when pushing off with the toes, the elastic repulsive force of the plate 4 can be used to forcefully strike the ground and generate propulsion.

[0099] <Other variations> The above-described embodiments and modifications are to 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 will be able to devise various modifications and other embodiments that incorporate the principles of the present invention, even if not expressly described herein, without departing from the spirit and essential characteristics of the present invention, when taking into account the teachings set forth above. [Industrial Applicability]

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

[0101] 1: Sole 2, 21, 22: Midsole 20: Top of sole 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: 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] , Figures 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] , Figures 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; 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, the distance measured from the origin O along the sole upper surface to the position of the tip of the toe is defined as L, the intersection of a line from the origin O along the sole upper surface, passing through a position 0.45×L, and perpendicular to the reference line S, with the bottom surface of the sole is defined as C, and the intersection of a line from the origin O along the sole upper surface, passing through a position 0.60×L, and perpendicular to the reference line S, with the bottom surface of the sole is defined as D, and when the shoe is not worn by a wearer and no load from the wearer's foot is acting on the sole, the sole posture in which the sole touches the ground at points C and D is defined as a stable posture. When the angle formed by a line connecting the heel center position, which is located at 0.15×L from the origin O along the upper surface of the sole, and the 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° is set to Point C and point D are located at least on the outer edge of the sole lower surface, and a region from point C to point D on the sole lower surface constitutes a flat stable region, and the stable region is in contact with the ground in the stable posture. In the stable posture in which the flat stable region including point C on the sole underside corresponding to a position of 0.45×L from the origin O along the sole upper surface and point D on the sole underside corresponding to a position of 0.68×L from the origin O along the sole upper surface comes into contact with the ground, the sole underside has a heel-up start position where the toe part leaves the ground and the heel part begins to leave the ground, and is separated from the ground rearward from the heel-up start position, The compressive rigidity of the sole in the vertical direction is relatively lower at the heel-up start position of the heel portion in the stable posture than at the metatarsophalangeal joint position. A shoe sole characterized by:

2. In claim 1, 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 sole upper surface. A shoe sole characterized by:

3. In claim 1, In the stable posture, the heel-up start position is at a position 0.15×L from the origin O along the sole upper surface, the sole lower surface in a rearward region from the heel-up start position is separated from the ground, the sole lower surface in a forward region from a position 0.68×L from the origin O along the sole upper surface is separated from the ground, and the sole lower surface is in contact with the ground in a region forward from the position 0.15×L from the origin O along the sole upper surface and rearward from the position 0.68×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 rigidity is set so that A shoe sole characterized by:

5. In claim 1, the heel portion has an aperture and the forefoot portion does not have an aperture; A shoe sole characterized by:

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

9. In claim 1, the heel portion and the forefoot portion both having a region of relatively low hardness material and a region 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:

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