Abstract:
Each year in North America there are approximately 175,000 non-contact ACL injuries. One of the main causes of these injuries is the rotational and translational forces created when a player makes a sudden change in direction or stops. Every athlete subjects their lower extremities to various forces that are unique to his or her mass, speed, and strength. These forces are affected by composition of the playing field surface, shoe sole design and construction, and other factors. Using these and other factors, the level of force at which injury is inevitable (pre-injury force) is determined and an athletic shoe is created which will provide a mitigating deformation induced by a particular athlete&#39;s pre-determined, pre-injury force threshold. A mitigating deformation of as little as 2 degrees can significantly reduce injurious forces. After the athlete has progressed through that particular force-generating movement, the shoe&#39;s sole instantly returns to its original shape.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and incorporates by reference U.S. patent application 62/156,276 filed on 3 May 2015. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       SEQUENCE LISTING 
       [0003]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    Each year in North America there are approximately 250,000 ACL injuries—about 70% of which are non-contact incidents. [Griffin LY. Noncontact Anterior Cruciate Ligament Injuries: Risk Factors and Prevention Strategies. [Journal of the American Academy of Orthopaedic Surgeons: 2000; 8:141-150] A near universally accepted and scientifically supported explanation for this non-contact statistic is the rotational and translational forces created when a player makes a sudden change in direction or stops. Exacerbating this natural force generation is athletic-shoe/playing-surface interfacetraction. Decades of private and academic studies prove a causal relationship between the increased desire for traction at the athletic-shoe/playing-surface interface and injurious forces that traction puts on the ACL. At some point, the human body is naturally unable to compensate for this force. Boden, Griffin and Garrett posit in their 2000 paper titled “Etiology and Prevention of Noncontact ACL Injury” the hormonal, anatomic and neuromuscular factors that may predispose athletes to ACL injuries. Regardless, athletic shoe manufacturers continue to produce shoes with ever more traction. Today, those shoes are being used on artificial turf, which is also designed to provide maximum traction. 
         [0005]    Clearly, the conditions exist for even higher incidences of non-contact ACL injuries that sideline athletes of every age, gender and skill level. Yet few attempts at preventing non-contact ACL injuries have involved a viable athletic-shoe solution. Results have yielded shoe designs with unstable vertical profiles that compromise athletic performance and increase injury risk. U.S. Pat. No. 3,668,792 A (York) Jan. 8, 1971, entitled Breakaway Athletic Safety Shoe describes a breakaway system that, under duress, separates a spring-biased lower sole of the shoe from the upper section of the sole. U.S. Pat. No. 7,254,905-B2 (Dennison) Aug. 14, 2007, entitled Releasable Athletic Shoe Sole details a fully detachable lower sole with a mechanism designed to release when a pre-determined and specifically longitudinally directed force is applied. Published US Application 2013/0318832 A1 (Brown, et al) Dec. 5, 2013, entitled Self-Recovering Impact Absorbing Footwear, proposes an athletic shoe design which will allow the wearer of the shoe uninterrupted usage while dampening forces that surpass an injury threshold using a system of internal beams of various heights coupled with an internal air valve system. In spite of these, the incidence of non-contact ACL injuries continues to rise—painful proof that a practical solution has yet to be realized. 
       SUMMARY OF THE INVENTION 
       [0006]    As they progress through an athletic event, every athlete generates and subjects their lower extremities to various forces that are unique to his or her mass, speed, and strength. This force is also affected by the composition of the playing field surface, by shoe sole design and construction, as well as by other factors. By determining, according to these and other factors, the level of force at which injury is inevitable (pre-injury force), an athletic shoe sole can be created to provide a mitigating deformation induced by a particular athlete&#39;s pre-determined, pre-injury force threshold. A mitigating deformation of as little as 2 degrees can reduce by threefold injurious forces such as torque (Groeger, Lena, “Injury Risks for the Female Athlete—Part 1”). After the athlete has progressed through that particular force-generating movement, the shoe&#39;s sole instantly returns to its original shape. 
         [0007]    The present invention involves three embodiments of an athletic shoe designed to provide a mitigating deformation induced by a particular athlete&#39;s pre-determined, target, pre-injury force threshold and a method of preventing injury to an athlete&#39;s lower extremity joints. As different athletes, according to mass, speed, strength, playing surface conditions, etc. generate a wide range of forces, a wide range of force thresholds must be contemplated. Each embodiment of the invention permits an athletic shoe sole to be designed and constructed to permit a mitigating deformation induced by a particular athlete&#39;s pre-determined, target, pre-injury force threshold. This construction method allows a fine-tuning of the force threshold, allowing an individual athlete to have a shoe built to protect him or her from injurious forces. 
         [0008]    The first embodiment is a shoe whose sole comprises multiple thin layers of specifically engineered composite materials. Each of the sole&#39;s layers comprises a filler material with embedded fibers in various anisotropic orientations. The assembled layers provide both translational (heel to toe) as well as lateral (side to side) and rotational (twisting) rigidity and strength, similar in performance to a traditional athletic shoe&#39;s thermoplastic elastomer or carbon fiber sole. Because an anisotropic composition provides strength and rigidity against forces perpendicular to the fibers, the inventive sole can be constructed to provide rigidity and strength only up to a pre-determined, target, pre-injury force threshold. When an athlete&#39;s pre-determined, target pre-injury force threshold is reached, the sole deforms, mitigating the stress. After the athlete has progressed through that particular force-generating movement, the shoe&#39;s sole instantly returns to its original shape. 
         [0009]    The second embodiment is a shoe whose sole has a series of cut-outs comprising channels [or voids] cut into the sole material. The sole is designed to provide both translational (heel to toe) as well as lateral (side to side) and rotational (twisting) rigidity and strength, similar in performance to a traditional athletic shoe&#39;s thermoplastic elastomer or carbon fiber sole. However, because of the width, depth, area, location and orientation of the channels, the sole can be constructed to provide rigidity and strength only up to a pre-determined, target pre-injury force threshold. When an athlete&#39;s pre-determined, target pre-injury force threshold is reached, the sole deforms, mitigating the stress. As with the first embodiment, after the athlete has progressed through the particular force-generating movement, the shoe&#39;s sole instantly returns to its original shape. 
         [0010]    The third embodiment is a shoe whose sole has a series of cut-outs comprising geometric shapes which are then filled with an elastomeric material similar to the material of the remainder of the sole, but with differing force-resisting properties than the rest of the sole. The sole of the third embodiment also provides both translational (heel to toe) as well as lateral (side to side) and rotational (twisting) rigidity and strength, similar in performance to a traditional athletic shoe&#39;s thermoplastic elastomer or carbon fiber sole. Because of the geometry, size, location and orientation of the filled in cut-outs in the sole, and because of the force-resisting properties of the filler material, the sole is constructed to provide rigidity and strength only up to a pre-determined, target pre-injury force threshold. When an athlete&#39;s pre-determined, pre-injury force threshold is reached, the sole deforms, mitigating the stress. As with the first and second embodiments, after the athlete has progressed through the particular force-generating movement, the shoe&#39;s sole instantly returns to its original shape. 
         [0011]    The invention also involves a method of preventing injury to an athlete&#39;s lower extremity joints comprising the step of determining for a specific athlete in a specific playing field situation a series of target, pre-injury force thresholds. With these force thresholds determined, an athletic shoe is constructed with a sole which is designed to temporarily deform when the shoe sole is subjected to the pre-determined target pre-injury force threshold and to then return to its original form when the force applied to the shoe sole falls below the pre-determined target pre-injury force threshold. 
         [0012]    As different athletes, according to mass, speed, strength, playing surface conditions, etc. generate a wide range of force, a wide range of force thresholds must be contemplated. By constructing the sole of the shoe of the first embodiment with multiple thin layers, each with a unique and specific anisotropic fiber orientation, those layers can be combined into hundreds of different combinations. This construction method allows a fine-tuning of the force threshold, allowing an individual athlete to have a shoe built to protect him or her from injurious forces. 
         [0013]    In the shoe of the first embodiment, the rigidity and strength of a particular layer will depend on the number, orientation, composition and individual strength of the fibers embedded within that layer. Several layers will have fiber orientation specifically related to providing rigidity and strength, as well as force-mitigating deformation against translational force (forward, heel to toe). Other of the layers, while adding to overall forward-force characteristics, will be oriented to provide rigidity and strength, as well as force-mitigating deformation against rotational force (torque). Still other of the layers, while adding to overall forward-force and torque characteristics, will be oriented to provide rigidity and strength, as well as force-mitigating deformation against lateral (side to side) force. Each layer will be evaluated in the context of it being combined with other layers to create the desired athlete-specific force-mitigating deformation. 
         [0014]    In the shoe of the second embodiment, the rigidity and strength of the shoe sole will depend on the width, depth, area, location and orientation of the channels, the sole can thus be constructed to provide rigidity and strength only up to the pre-determined, target pre-injury force threshold. 
         [0015]    In the shoe of the third embodiment, the rigidity and strength of the shoe sole will depend on the geometry, size, location and orientation of the filled in cut-outs in the sole, and the force-resisting properties of the filler material. The sole can thus be constructed to provide rigidity and strength only up to the pre-determined, target pre-injury force threshold. It is noted that this filler material may be a material similar to the fibrous material used to construct the sole of the first embodiment shoe. 
         [0016]    The fibers bound into the sole materials may include, but are not limited to, carbon, silicon carbide, graphene, glass, nylon, metallic, aramid fibers, and various other natural and/or synthetic materials. The matrix binding and protecting the fibers may include, but will not be limited to, various polymers, natural and/or synthetic rubbers, thermoplastics, polyvinyl chloride, polyethylene, polypropylene, styrene butadiene, isobutylene, isoprene butadiene, and the like. The materials comprising the filler material of the third embodiment sole may be the same materials described above in regard to the matrix binding and protecting the fibers. The filler material may or may not include the bound fibers described above. 
         [0017]    For all embodiments of the invention, construction of the shoe sole is contemplated as a 3-D printed process, with printed layers forming a collective printed sole originating with different materials, chemistries, optional reinforcing and arrayed fibers, etc. to allow for full, athlete-specific customization of the properties of the structure of the sole. For the all embodiments sole materials will comprise various layers with specific elasticity, flexural and tensile strength characteristics spanning a wide overall range of said characteristics. For the third embodiment, sole materials will be similar to those of the first two embodiments and the filler material, as noted above, will be similar to the sole materials but may or may not include bound fibers. 
         [0018]    The invention involves three embodiments of an athletic shoe whose composition and construction will provide rigid lateral stability and strength during normal athletic movement. However, at a pre-determined, athlete-specific, target pre-injury force threshold the sole temporarily deforms to prevent injury to the athlete&#39;s lower extremity joints. The invention is intended to encompass cleated and/or nubbed field shoes as well as tennis, handball, volleyball, basketball and other athletic footwear. The primary joint of concern is the knee&#39;s ACL. 
         [0019]    The invention also comprises a method of preventing injury to an athlete&#39;s lower extremity joints. The method comprises determining for a specific athlete in a specific playing environment a unique target pre-injury force threshold. Given this target pre-injury force threshold, a customized athletic shoe having a composite sole comprising multiple thin layers of specifically engineered composite materials is built for a specific athlete in a specific playing environment. Shorten, et al surmised that the ‘ . . . interaction (between shoe and playing surface) suggests that appropriate shoe selection for a given surface is an important element in risk reduction.’ (Shorten, Hudson, and Himmelsbach, “Shoe-Surface Traction of Conventional and In-Filled Synthetic Turf Football Surfaces”). The composite sole of the shoe will provide the athlete sufficient traction and stability in the specific playing environment but will temporarily deform when the shoe is subjected to the target pre-injury force threshold, thus preventing injurious force from being applied to the athlete&#39;s lower extremity joints. 
         [0020]    Given the current state of the art in shoe construction, it is possible to calculate the target force threshold and construct a unique and athlete-specific athletic shoe for a given playing environment and other factors using modern 3D printing technology. It is possible, for example, to provide a customized athletic shoe for a particular athlete in a specific playing environment (natural grass vs. synthetic turf, wet vs. dry, etc., etc.), or even for the first part of an athletic event and then to provide another customized athletic shoe for the athlete to wear during another portion of the same athletic event. As an example, a customized athletic shoe could be built for an athlete for a football or soccer game on a particular day with a specific playing environment as described supra. If the specific playing environment changes during the athletic event, for example, due to rain or snow or playing field deterioration which could affect the target force threshold, another shoe could available or could be built in time for the athlete to wear the new shoe in the second half [or later portions] of the game. 
         [0021]    This method will also accommodate changes in the athlete&#39;s physical situation, which often occur during an athletic event. For example, an injury to the athlete&#39;s leg or foot may mandate a different target force threshold; in that instance, a new shoe can be constructed to immediately accommodate this changed physical situation. Muscle fatigue, for example, could warrant constructing another shoe for the second half of the athletic event. Orchard and Powell concluded by analyzing 5,910 NFL games that not only field composition affected injury rates, but also cold weather vs. hot weather, wet vs. dry conditions, and even early season vs. later season condition of athletes as well as playing surfaces. The factors that lowered shoe/playing surface traction (and resulting force) also reduced injury risk (Orchard, J. W., Powell, J. W., “Risk of Knee and Ankle Sprains Under Various Weather Conditions in the National Football League,” 1993, July). By using pre-constructed portions of the athletic shoe specific to a given athlete and/or venue, it may even be possible to make new shoes, as necessary, for each quarter of a football game. 
         [0022]    Use of 3-D printing construction method allows fine-tuning of the composite sole to construct a sole that can prevent the generation of injurious force to an athlete&#39;s lower extremities. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a perspective view of the composite athletic shoe according to a first embodiment of the invention. 
           [0024]      FIG. 2  is a view of the sole of the athletic shoe of  FIG. 1 . 
           [0025]      FIG. 3  is a blown-up view of a portion of the shoe sole of  FIG. 2 . 
           [0026]      FIG. 4  is another view of the sole of  FIG. 2  showing the cutting plane A-A that determines the perspective of  FIG. 5 . 
           [0027]      FIG. 5  shows a section of the sole of  FIG. 2  now under a rotational stress and taken along the plane A-A as shown in  FIG. 4 . 
           [0028]      FIG. 6  is an enlarged view of the section of  FIG. 5  inside the circle B. 
           [0029]      FIG. 7  shows a section of the sole of  FIG. 2  also taken along the plane A-A as shown in  FIG. 4 . The sole is now being subjected to longitudinal stress. 
           [0030]      FIG. 8  is an enlarged view of the section of  FIG. 7  inside the circle C. 
           [0031]      FIG. 9  is a cross-section of an athletic shoe according to the first embodiment of this invention but with more individual layers in the sole. 
           [0032]      FIG. 10  is an exploded view of the shoe shown in  FIG. 9 . 
           [0033]      FIG. 11  is a flow chart illustrating a method of the invention. 
           [0034]      FIG. 12  is a plan view of the sole of a second embodiment of the invention. 
           [0035]      FIG. 13  is a view taken along the plane D-D of the sole shown in  FIG. 12 . 
           [0036]      FIG. 14  is a plan view of the sole shown in  FIG. 12  deforming under the effects of an external torsion [torque] force. 
           [0037]      FIG. 15  is a plan view of another version a sole constructed according to the second embodiment of the invention. 
           [0038]      FIG. 16  is a plan view of a first variation of a sole constructed according to the third embodiment of the invention. 
           [0039]      FIG. 17  is a view taken along the plane E-E of the sole shown in  FIG. 16 . 
           [0040]      FIG. 18  is a plan view of a second variation of a sole constructed according to the third embodiment of the invention. 
           [0041]      FIG. 19  is a plan view of third variation of a sole constructed according to the third embodiment of the invention. 
           [0042]      FIG. 20  is a plan view of a fourth variation of a sole constructed according to the third embodiment of the invention. 
           [0043]      FIG. 21  is a plan view of the sole shown in  FIG. 20  deforming under the effects of an external torsion [torque] force. 
           [0044]      FIG. 22  is a plan view of a fifth variation of a sole constructed according to the third embodiment of the invention. 
           [0045]      FIG. 23  is a plan view of the sole shown in  FIG. 22  deforming under the effects of an external longitudinal force. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]    The athletic shoe  10  according to a first embodiment of the invention is shown in  FIGS. 1-8 . The athletic shoe soles shown in  FIGS. 1-8  are designed to protect an athlete&#39;s lower extremities against both injurious torsional [torque] forces and injurious longitudinal forces. 
         [0047]    The shoe sole shown in  FIGS. 1-8  comprises an upper body  12  and a multi-layer composite sole  14 . Multi-layer composite sole  14  is shown in  FIGS. 2-8  as comprising 5 thin layers of materials, although the exact number of layers could be more or less than 5 depending upon the specific situation the shoe is designed for. As shown in  FIG. 3 , sole  14  comprises layers  20 ,  21 ,  22 ,  23  and  24 . Layers  20 , and  24  are designed to provide rigid translational (straight ahead) stability during competition, like a traditional athletic shoe, only up to a pre-determined, athlete-specific, pre-injury target force threshold. These layers will also contribute limited rigidity during lateral as well as rotational (twisting) force generation. Layers  21  and  23  also will contribute to overall translational rigidity, as well as rotational stability only up to a pre-determined, athlete-specific, pre-injury force threshold (the target, pre-injury force threshold). The athlete-specific/target-force-specific anisotropic fiber orientation in the sole&#39;s layers will allow the sole to temporarily deform in response to, and to dissipate, the specific target force that would otherwise cause injurious stress to that particular athlete&#39;s lower extremities. 
         [0048]    Sole  14  is shown in  FIG. 4  in its unstressed condition. As shown in  FIGS. 5 and 6 , sole  14  has been subjected to a rotational force equivalent to the pre-determined, target, pre-injury force threshold at which point layers  21  and  23  have temporarily deformed about the shoe&#39;s rotational axis to alleviate and prevent the application of injurious force to the athlete&#39;s lower extremities. 
         [0049]    As shown in  FIG. 6 , the anisotropic fibers in layers  21  and  23  have caused the layers to temporarily deform under the application of the pre-determined target pre-injury force threshold. When the event that generated the target force threshold has passed, the layers immediately return to their unstressed condition. 
         [0050]    Sole  14  is also shown in  FIGS. 7 and 8 . Sole  14  is shown as having 5 layers of material, although—as noted above—the exact number of layers could be more or less than 5 depending upon the specific situation the shoe is designed for. As shown in  FIGS. 7 and 8 , sole  14  comprises layers  20 ,  21 ,  22 ,  23 , and  24  as in  FIGS. 5 and 6 . Layers  20 ,  22  and  24  are designed to provide rigid translational (straight ahead) stability during competition, like a traditional athletic shoe, only up to a pre-determined, athlete-specific, pre-injury target force threshold (the target, pre-injury force threshold). These layers will also contribute limited rigidity during lateral and rotational (twisting) force generation. Layers  21  and  23  also will contribute to overall translational rigidity, as well as lateral and rotational strength and stability only up to a pre-determined, athlete-specific, pre-injury force threshold (the target, pre-injury, force threshold). The athlete-specific/target-force-specific anisotropic fiber orientation in the sole&#39;s layers will allow the sole to temporarily deform in response to, and to dissipate, the specific target force that might otherwise cause injurious force to that particular athlete&#39;s lower extremities. 
         [0051]      FIGS. 7 and 8  illustrate the sole being subjected to a longitudinal (heel to toe) force equivalent to the pre-determined target, pre-injury force threshold. The layers  20 ,  22  and  24  have temporarily deformed in the longitudinal direction to alleviate and prevent the application of injurious longitudinal force to the athlete&#39;s lower extremities. As shown in  FIG. 8 , the anisotropic fibers in layers  20 ,  22  and  24  have caused the layers to temporarily deform in the longitudinal direction under the application of the target, pre-injury force threshold. When the event that generated the target, pre-injury force threshold has passed, the layers immediately return to their unstressed condition. 
         [0052]      FIG. 9  illustrates a variation of the first embodiment of the athletic shoe with a seven-layer sole. Shoe  30  comprises upper  31  and multi-layered sole  32 . Shoe  30  also has a sock liner  33 . Sole  32  comprises layers  34 ,  35 ,  36 ,  37 ,  38 ,  39 , and  40 . Certain of these layers can be designed to deform upon application of a longitudinal target, pre-injury force threshold. Certain of the other layers can be designed to deform upon application of a lateral target, pre-injury force threshold and of a rotational target, pre-injury force threshold. 
         [0053]    Shoe  30  is shown in an exploded view in  FIG. 10 . In this embodiment layers  35 -and  37  are the layers that temporarily deform upon application of the longitudinal target, pre-injury force threshold. Layers  36  and  38  will temporarily deform upon application of the rotational target, pre-injury force threshold and layers  34  and  39  will temporarily deform upon application of the lateral (side-to-side) target, pre-injury force threshold. 
         [0054]    It is noted that in the above example in  FIG. 10  there is no particular significance as to which layers temporarily deform to mitigate which type of target, pre-injury force threshold. Obviously, any of the layers could be selected to mitigate any particular type of target, pre-injury force threshold. Nor is there any particular significance in this example as to how many individual layers will temporarily deform to mitigate a particular target, pre-injury force threshold. In this example, two layers were used to mitigate each of the three types of target-pre-injury force thresholds, but more layers or fewer could also have been used, depending upon the exact circumstances of the particular athlete-specific factors and the particular environmental factors. With this embodiment, the athlete&#39;s lower extremities can be protected against injurious longitudinal, rotational and lateral (side-to-side) forces. 
         [0055]    The method  50  of the invention is illustrated in  FIG. 11 . The method comprises determining for a particular athlete, in a specific playing environment, the athlete-specific factors contributing to the longitudinal, rotational and lateral (side-to-side) target, pre-injury force thresholds. These factors are then inputted at  51 . Next, the environment-specific factors contributing to the longitudinal, rotational and lateral (side-to-side) target, pre-injury force thresholds are determined. These factors are inputted at  52  and the longitudinal, rotational and lateral (side-to-side) target, pre-injury force thresholds are determined at  53 . This information is then used to build an athletic shoe sole customized for the particular athlete in the specific playing environment at  54 . A customized athletic shoe is then built at  55  using the customized sole built at  54 . The athlete then uses the customized shoe in a playing event. At certain, pre-determined times during the playing event, the athlete-specific factors are re-evaluated at  56 . Also at these pre-determined times, the environmental-specific factors are re-evaluated at  57 . The changes to these factors are evaluated at  57  and if they have been significantly changed, new longitudinal, rotational and lateral (side-to-side) target, pre-injury force thresholds are determined and a new customized sole and shoe are built for use by the athlete for the remainder of the event. Using modern 3-D printing technology, it is possible to build several customized shoes for the athlete during the course of an event. 
         [0056]      FIGS. 12-14  show an athletic shoe sole constructed according to the second embodiment of the invention. The three figures will be described together with it being understood that elements shown in one figure may or may not be shown in the other figures. 
         [0057]    Sole  70  is a multi-layer composite sole similar in construction to the first embodiment soles shown and described above. Multi-layer composite sole  70  is shown as comprising composite layers  73 ,  74 , and  75 , although the exact number of layers could be more or less, as desired. Sole  70  comprises materials similar to those of the first embodiment. Multi-layer sole  70  has a cut-out or channel  72  incised into the outer surface of layer  73 . Channel  72  is shown in the figures as being incised into the forward portion of sole  70 . It should be understood that the exact placement of channel  72  can and will vary depending upon the desired force-resisting characteristics of sole  70  just as the width, depth and exact pathway of channel  72  can and will be varied depending upon the desired force-resisting characteristics of sole  70 . It is noted that even though channel  72  is only shown in the figures as being incised into an outer layer of the sole, it could also be incised into an internal layer, if desired. 
         [0058]    Channel  72  follows a somewhat serpentine pathway and is designed to strategically weaken sole  70  such that sole  70  will temporarily deform in response to, and to dissipate, the specific target force that might otherwise cause injurious force to that particular athlete&#39;s lower extremities. Layers  73 ,  74 , and  75  will also provide limited rigidity during lateral and rotational (twisting) force generation. Layers  73 ,  74 , and  75  also will contribute to overall translational rigidity, as well as lateral and rotational strength and stability. The width, depth and exact pathway of channel  72  can be varied to provide the exact response desired to provide a mitigating deformation induced by a particular athlete&#39;s pre-determined, pre-injury force threshold. 
         [0059]      FIG. 14  shows Sole  70  deforming under stress from an externally applied torque. The rear end of sole  70  has twisted upwardly in response to the stress and the portion of sole  70  containing channel  72  has distorted in response to the stress. The twisted portion of sole  70  is shown at  70 ′ and the untwisted portion is shown [by a dashed line] at  70 . The undistorted channel  72  is shown as a dotted line while the distorted channel is shown as a solid line at  72 ′. 
         [0060]      FIG. 15  shows a variation of the second embodiment of the invention with a channel  104  incised into the outer surface of sole  100 . Channel  104  is somewhat shallower than channel  72  shown in  FIGS. 12-14  and extends for a much greater length with more undulations than channel  72 . As in the soles show above, the exact width, depth and pathway of channel  104  can be varied to provide the exact response desired to provide a mitigating deformation induced by a particular athlete&#39;s pre-determined, pre-injury force threshold. 
         [0061]      FIGS. 16-23  show a third embodiment of the invention. In this embodiment the sole is strategically weakened to provide the desired temporary deformation via inserts in the sole rather than by incising a channel in the sole.  FIGS. 16 and 17  will be described together with it being understood that elements shown in one figure may or may not be shown in the other figure. It is noted that the inserts are all shown in the forward [toe] portion of the sole. Obviously, one or more inserts could be positioned in the mid portion of the sole, or even in the heel portion of the sole, if desired. 
         [0062]    Sole  110  is a multi-layer composite sole similar in construction to the first and second embodiment soles shown and described above. The forward portion of sole  110  contains 4 inserts,  112 ,  112 ′,  114  and  114 ′. These inserts are made of a composite filler material similar to the sole materials described above; however, the filler material may or may not include bound fibers. The filler material of the inserts will have force-resisting characteristics that are different [and perhaps substantially so] than the materials comprising remaining portions of sole  110 . These differences in material properties assist in providing the desired weakening in sole  110  to permit it to provide a mitigating deformation induced by a particular athlete&#39;s pre-determined, pre-injury force threshold. In addition, the exact location of the inserts within the sole, the number of inserts, their geometric shape, and their depth are all characteristics which can be varied in order to provide the exact response desired to provide a mitigating deformation of sole  110  induced by a particular athlete&#39;s pre-determined, pre-injury force threshold. 
         [0063]    Sole  110  is a multi-layer composite sole comprising layers  111 ,  111 ′ and  111 ″. As with the other embodiments of the invention, the number and composition of layers in sole  110  can and will vary depending upon the exact force-resisting response desired. In  FIG. 17 , insert  114 ′ is shown as being the same thickness as layer  111 . Obviously, the thickness of the inserts can also be varied as desired. Inserts  112 ,  112 ′,  114  and  114 ′ are shown as being contained within the outer layer of sole  110 ; however, they could be placed in other layers of sole  110 , if desired. 
         [0064]      FIG. 18  shows a variation of the third embodiment of the invention. Multi-layer composite sole  115  is shown with four inserts  116 ,  116 ′,  117  and  117 ′. These inserts comprise a material with significantly different force-resisting characteristics than the material comprising inserts  112 ,  112 ′,  114  and  114 ′. As an example, a shoe with the inventive sole may be designed for a specific athlete for a specific event. During the event, which could be a football game, a soccer game or perhaps a rugby match, the weather changes substantially and the playing field becomes much slicker due to heavy rain. Following the method shown and described above, a new shoe using sole  115  could be constructed for the specific athlete [for instance, during the halftime break]. Since conditions are much slicker on the playing field, a shoe with sole  110  having inserts  112 ,  112 ′,  114  and  114 ′ might be too stiff for the changed playing conditions and a new shoe would be constructed with sole  115  having inserts  116 ,  116 ′,  117  and  117 ′ made of a material significantly less stiff than the material comprising inserts  112 ,  112 ′,  114  and  114 ′. 
         [0065]      FIG. 19  shows another variation of the third embodiment of the invention. Multi-layer composite sole  120  is shown with four inserts  121 ,  121 ′,  122  and  122 ′. The previous examples of the third embodiment have had inserts all made from the same filler material. It is possible to provide in one sole inserts made from different filler materials. This is illustrated in  FIG. 19 . Inserts  121  and  121 ′ are made from a material similar to that used for inserts  116 ,  116 ′,  117  and  117 ′ of sole  115  shown in  FIG. 18 . Inserts  122  and  122 ′ are made from a material that has different force-resisting characteristics than the material used for the inserts for sole  115 . This variation permits fine-tuning of the force-resisting characteristics of sole  115 . 
         [0066]      FIGS. 20-23  show yet another variation of the third embodiment of the invention. In previous variants of the third embodiment, the inserts have been oriented in a generally longitudinal [heel to toe] direction within the sole. In this embodiment, inserts  135  are oriented generally transverse to the sole  130 . This is illustrated in  FIG. 20  by lines  138 . In  FIG. 21  sole  130  is shown being stressed and deformed by a torsional force [torque]. The original position of the rear portion of sole  130 ′ is shown by a dashed line. The deformed position is shown at  130  by a solid line. Inserts  135  have changed shape in response to the torsional force as shown in  FIG. 21  and have also assumed a different orientation as shown by lines  138 ′. As in previous versions of this embodiment, the size, orientation, geometric shape, placement within the sole outline, and composition of the insert filler material are all factors that will assist in determining the force-mitigating properties of the particular sole. Also as indicated above, it is possible to have some or all of the inserts  135  be in a layer within the shoe sole and not on an outer layer. 
         [0067]      FIGS. 22 and 23  show a shoe sole similar to that shown in  FIGS. 20 and 21 ; however, this sole is being stressed by a longitudinal [heel to toe] force. Sole  140  has multiple inserts  145  shown on the outer layer of the sole. As shown in  FIG. 23 , when sole  140  is subjected to a longitudinal force, inserts  145  temporarily deform to essentially “shorten” the shoe and in doing so provide a force-mitigating deformation of the particular shoe to prevent injury to the athlete&#39;s lower extremities and joints. The Dennison reference cited above in §[0005] is concerned with providing protection from just such an injurious longitudinal force. 
         [0068]    Each embodiment of the invention provides protection from injurious force to an athlete&#39;s lower extremity joints by providing a temporary force-mitigating deformation in the athlete&#39;s specifically configured shoe. Unlike other attempts to correct this problem, applicants have provided a shoe with a sole that is designed to temporarily deform when the sole is subjected to the pre-determined target pre-injury force threshold and to then return to its original form when the force applied to the shoe sole falls below the pre-determined target pre-injury force threshold.