Abstract:
Attachable and detachable footwear components are disclosed which contribute to the development of certain muscles and tendons in the lower body, including the gluteus maximus, gluteus medius, sartorius, plantaris, and the like. The disclosed footwear components are inflatable in some embodiments and made in the preferred embodiment of flexible elastomeric polymers. The disclosed components detach to and from the soles of common footwear commonly available in the market, and comprise a distal ball, a proximal ball, and some embodiments, one or more mid-balls. When affixed to standard footwear, the disclosed components destabilize the foot longitudinally and laterally, and plyometrically stress tendons and muscles in the legs of a wearer, toning and strengthening the wearer&#39;s legs with time.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to footwear, and more particularly relates to attachable and detachable athletic footwear components which intensify plyometric athletic benefit experienced by wearers. 
         [0003]    2. Description of the Related Art 
         [0004]    The present invention is an athletic improvement to standard footwear well-known and commonly available in the art. The soles of most commonly available athletic and casual footwear are largely planar in shape, and usually designed to rest flat on the ground or a walking surface during use. 
         [0005]    Recent advances in the art include shoes comprising a frontal platform conjoined to and beneath the distal end of the foot for athletic training while walking Cox (U.S. Pat. No. 3,739,500) discloses a full-shoe version of the frontal platform. These platforms elevate the whole of a wearer&#39;s foot above the ground, but provide support only to the distal end of the foot (underlying the ball of the foot and toes). Unlike conventional footwear, frontal platforms destabilize the tendons and muscles in the legs, and in so doing gradually activate and strengthen dormant tendons and muscles to provide foot support including the gluteus maximus, gluteus medius, gastrocnemius, soleus, and fibularis longus. 
         [0006]    However, even the frontal platforms are planar in shape across the lateral axis and longitudinal axis. Footwear configured with these frontal platforms benefit the wearer only as far as the front platforms do not extend or provide support to the proximal ends of the feet. For this reason, frontal platforms do not destabilize muscles or tendons used to provide lateral stabilization of the feet of a wearer, or muscles or tendons which may provide longitudinal stabilization across the distal end of the foot. 
         [0007]    Further advances in the art include footwear with non-planar soles that are curved, or convex, through the longitudinal plane, including shoes such as Reebok EasyTone®, Sketcher Shape-Up, and Masai Barefoot Technology®. This footwear (commonly called “toning shoes”) by design, reduces balance to the wearer and purportedly activate muscles and tendons largely dormant in other footwear by forcing wearers to lift the heel of their feet higher when making forward steps. 
         [0008]    Recent studies, such as that conducted by the American Council on Exercise (ACE) in mid-2010, suggest that toning shoes provide less practical athletic or plyometric benefit to wearers than previously believed in the industry, meaning new advances are needed. 
         [0009]    Additionally, frontal platforms, like the soles of toning shoes, are not detachable from the shoe, and therefore reduce the shoes incorporating those advances in the art to serving only the purpose of plyometric athletic training, rather than for casual or formal use for which footwear is usually used. 
       SUMMARY OF THE INVENTION 
       [0010]    From the foregoing discussion, it should be apparent that a need exists for plyometric footwear that better activates muscles and tendons across the distal and proximal ends of the feet, which footwear does not reduce the practical utility of the footwear for conventional purposes. Beneficially, such footwear would overcome many of the difficulties with prior art by providing a means for wearers to detach the athletic soles from the footwear and which would destabilize the foot laterally. 
         [0011]    The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available footwear. Accordingly, the present invention has been developed to provide a plyometric athletic trainer comprising an elastomeric hemisphere comprising a convex lower surface and a planar top surface, wherein the lower surface comprises a flexible elastomeric material such that the hemisphere undergoes deformation due to an impact load of a loaded shoe, wherein the hemisphere is detachable and attachable to a sole of a shoe. 
         [0012]    The plyometric athletic trainer further comprises, in some embodiments, one of an elastomeric material, lead, a metal, and wood. 
         [0013]    In some embodiments, the top surface is non-planar such that the top surface contours the lower surface of a shoe sole. In other embodiments, the lower surface of the hemisphere comprises one or more ground-engaging component(s), or tread(s). 
         [0014]    The lower surface, in some embodiments, and the top surface define a hollow interior recess isolated atmospherically from ambient air. In other embodiments, the hollow interior recess of the hemisphere is inflated with one or more gases to attenuate shock imposed upon a shoe by the impact of the ground when the hemisphere is used in stepping. 
         [0015]    In still further embodiments, the hollow interior recess of the hemisphere is filled with one of viscoelastic polyurethane foam and gel. In still further embodiments, the plyometric athletic trainer is attachable and detachable to soles of one or more shoes. 
         [0016]    The plyometric athletic trainer may be attachable and detachable using one of Velcro, adhesives, screws, clamps, straps, ties, hooks, bands, and snaps. The plyometric athletic trainer may also be shaped as one of polyhedral, toroidal polyhedral, spherical cap, and egg. 
         [0017]    The plyometric athletic trainer may also comprise a door on the lower surface providing access to hollow interior recess. The hollow interior recess may also serve as a receptacle, the receptacle accessible through the door, the receptacle for receiving one or more of a weight, a shock absorber, and one or more electrical devices from the group consisting of a GPS tracker, an odometer, and a step counter. 
         [0018]    In still further embodiments, the hollow interior recess provides user storage. In still further embodiments, the lower surface and the planar top surface define a plurality of hollow interior recess(es) isolated atmospherically from ambient air, the hollow interior recesses separated by one or more interior walls affixed to both the top surface and the lower surface. 
         [0019]    The plyometric athletic trainer may further comprise a solid core encased by the lower surface and the top surface, the solid core comprising one or more of an elastomeric material, lead, a shock absorber, a metal, and wood. 
         [0020]    The present invention also provides a plyometric athletic trainer comprising a plurality of elastomeric hemispheres, the hemispheres each comprising a convex lower surface and a planar top surface, wherein both the lower surface and the planar top surface comprise an elastomeric material, wherein the hemisphere is detachable and attachable to a sole of a shoe; and wherein the lower surface and the top surface of each hemisphere define a hollow interior recess isolated atmospherically from ambient air; and wherein each hemisphere is interconnected to one or more of the other hemispheres such that each hemisphere is oriented in substantially the same direction and such that the top surface of each hemisphere rest in substantially the same plane. 
         [0021]    The present invention further provides a detachable convex plyometric athletic trainer to be worn by a wearer for athletic training, the detachable convex plyometric athletic trainer. The detachable convex plyometric athletic trainer comprises a shoe comprising: a sole having a top side, an underside, oppositely disposed lateral edges including an inside lateral edge and an outside lateral edge, and two or more ground-engaging components on the underside, the ground-engaging components being approximately disposed in a common plane, with a longitudinal axis extending from the proximal end of the shoe to the distal end of the shoe, and with a lateral axis extending from the inside lateral edge to the outside lateral edge. 
         [0022]    The detachable convex plyometric athletic trainer further comprises a distal ball affixed to the underside of the sole, the distal ball convex in shape and comprising an outer surface made of a pliable durable non-porous polymer material, wherein the diameter of the distal ball at its largest magnitude is more than half the distance between the inside lateral edge and the outside lateral edge, wherein the outer surface defines a recess within the distal ball. 
         [0023]    The detachable convex plyometric athletic trainer further comprises a proximal ball affixed to the underside of the sole, the proximal ball convex in shape and comprising an outer surface of a pliable durable non-porous polymer material, wherein the diameter of the proximal ball at its largest magnitude is more than half the distance between the inside lateral edge and the outside lateral edge, wherein the outer surface defines a recess within the proximal ball. 
         [0024]    In some embodiments, the distal ball is affixed to the sole using a removable distal screw, and the proximal ball is affixed to the sole using a removable proximal screw. 
         [0025]    In other embodiments, the distal ball and proximal ball are inflated with air. 
         [0026]    In still further embodiments, one or more of the outer surface of the distal ball and the outer surface of the proximal are lined with tread. 
         [0027]    In still further embodiments, one or more of the distal ball and the proximal ball may be filled with one of viscoelastic polyurethane foam and silicone gel. 
         [0028]    The outer surface of the distal ball may comprise an impermeable and flexible exterior surface with a hollow cores interiorly isolated atmospherically from ambient air and filled with one of air, water, noble gases, viscoelastic polyurethane foam, and permeable, silicone gel. 
         [0029]    The detachable convex plyometric athletic trainer may further comprise a plurality of mid-balls disposed between the proximal ball and the distal ball, the mid-balls identical in shape as the proximal ball. 
         [0030]    These features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which: 
           [0032]      FIG. 1A  is a top elevational perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0033]      FIG. 1B  is a top elevational perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0034]      FIG. 1C  is a lower elevational perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0035]      FIG. 1D  is a lower elevational perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0036]      FIG. 2  is a lower elevational perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0037]      FIG. 3A  is a side perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0038]      FIG. 3B  is a side perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0039]      FIG. 4A  is a bottom perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; 
           [0040]      FIG. 4B  is a bottom perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention; and 
           [0041]      FIG. 4C  is a bottom perspective view of a detachable convex plyometric athletic trainer in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]    Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
         [0043]    Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
         [0044]      FIG. 1A  is a top elevational perspective view of a detachable convex plyometric athletic trainer  100  in accordance with the present invention. The detachable convex plyometric athletic trainer  100  comprises a shoe  102 , a shoe sole  104 , a distal ball  106 , a proximal ball  108 , a top surface  110   a , a top surface  110   b , an outer surface  112   a , and an outer surface  112   b.    
         [0045]    The shoe  102  is well-known to those of skill in the art. The shoe  102  may comprise any kind of shoes well-known to those of skill in the art, including running, track, hiking, climbing, bowling, casual, flip-flops, dress and the like. The shoe  102  comprises a distal end and a proximal end. The distal end of the shoe  102  comprises the forward half of the shoe  102  furthest away longitudinally from the heel of the foot of the wearer and under the ball of the foot of the wearer. The proximal end of the shoe  102  comprises the rearward half of the shoe  102  situated under the heel of the foot of the wearer and further away longitudinally from the ball of the foot of the wearer. 
         [0046]    The longitudinal axis of the shoe  102  runs from the proximal end of the shoe to the distal end, while the lateral axis of the shoe  102  runs from the inside edge of the shoe  102  to the outside edge. The inside edge of the shoe  102  is the lateral edge of the shoe  102  in closest proximity to a sister shoe being worn by the wearer on the opposite foot. 
         [0047]    The shoe sole is well-known to those of skill in the art. The shoe sole  104  comprises a top side, an underside, oppositely disposed lateral edges including an inside lateral edge and an outside lateral edge, and two or more ground-engaging components on the underside, the ground-engaging components being approximately disposed in a common plane, with a longitudinal axis extending from the proximal end of the shoe to the distal end of the shoe, and with a lateral axis extending from the inside lateral edge to the outside lateral edge. 
         [0048]    In some embodiments of the present invention, the shoe sole  104  is made of polymers or various species of rubber, in other embodiments the shoe sole  104  is made of leather or other pliable and durable materials. 
         [0049]    The distal ball  106 , in the shown embodiment, comprises a roughly half-spherical (or hemispherical), pod-like, dome-like, convex component. The distal ball  106  attaches and detaches below the distal end of the shoe sole  104 . 
         [0050]    The distal ball  106 , or hemisphere  106 , is attached to the sole of a piece of footwear, and comprises a lower surface (i.e. an outer surface  112   b ) and a top surface  110   a ; the distal ball  106  comprising at least one convexly rounded projection on the lower surface (which is some cases spans the lower surface  112   b ) as viewed in a frontal plane cross-section when the distal ball  106  is attached to the shoe in an upright position, said convexity being determined relative to the shoe sole. In alternative embodiments, the distal ball  106  and/or the proximal ball  108  may be concave. 
         [0051]    The distal ball  106  is affixed to the underside of the shoe sole  106 . In some embodiments, the distal ball  106  is detachable using screws, rails, clamps or rubbers cement. The distal ball  106  is convex in shape and comprises an outer surface  112   b  of a pliable durable non-porous polymer material, wherein the width of the proximal ball is more than half the distance between the inside lateral edge and the outside lateral edge. 
         [0052]    The distal ball  106  comprises an outer surface  112   b , or shell, made of rubber, leather and/or another pliable and durable material which completely encompasses the distal ball  106 . The lower surface  112   b  of the distal ball  106 , and the top surface  110   b  of the distal ball  106 , together define a recess within the distal ball  106 . In some embodiments of the present invention, this recess is filled with compressed air. In some embodiments of the present invention, the distal ball  106  is inflatable by the wearer using means known to those of skill in the art. In other embodiments of the present invention, the distal ball  106  is filled with one of viscoelastic polyurethane foam and silicone gel. 
         [0053]    The compressed air may comprise ambient air, or any combination of one or more elements in a gaseous state. In still further embodiments, the compressed air may comprise, or be substituted for, elements, or a mixture of elements, in semi-solid, solid, or liquid state, in a liquid state of any measurably viscosity. 
         [0054]    The outer surface of the distal ball  106 , in some embodiments, comprises an impermeable and flexible exterior surface with a hollow core interiorly isolated atmospherically from ambient air and filled with one of air, water, noble gases, viscoelastic polyurethane foam, and permeable, silicone gel. 
         [0055]    The proximal ball  108 , in the shown embodiment, comprises a roughly half-spherical, dome-like or hemispherical, convex component. The proximal ball  108  attaches and detaches below the proximal end of the shoe sole  104 . 
         [0056]    The proximal ball  108  is affixed to the underside of the shoe sole  106 . In some embodiments, the proximal ball  108  is detachable using screws, rails, clamps or rubbers cement. In other embodiments, the proximal ball  108 , like the distal ball  106 , is attachable and detachable using Velcro, adhesives, straps, ties, hooks, bands, and snaps (snaps being metal buttons, one which “snaps” into the other). 
         [0057]    In one embodiment of the present invention, between one and ten straps lined on one side with Velcro® are each affixed to either the lower surfaces  112   a - b  or the top surfaces  110   a - b  of the distal ball  106  and the proximal ball  108 . The Velcro lining may be Velcro hook lining, or Velcro hoop lining. In either case, the shoe  102  is lined with opposing hook or hoop Velcro lining for detachably receiving the straps and thus detachably and attachably receiving the balls  106 ,  108  to which the strap are coupled. 
         [0058]    In various embodiments of the present invention, one or more plastic or metal rings are affixed to either side of the outer surfaces  112   a - b  using means well-known to those of skill in the art. In some embodiments, Velcro straps are removably inserted through these rings and strapped over the shoe  102  to secure the balls  106 ,  108  to the shoe  102  before a user commences physical training activities. 
         [0059]    In various embodiments of the present invention, the rings are attachable and detachable. The rings may be fashioned in any color, and may be designed to look fashionable, or to complement colors and/or shapes featured on the balls  106 ,  108  and/or the shoe  102 . 
         [0060]    In other embodiments of the present invention, the rings are substituted for fasteners, such as cam fasteners comprising a cam lever for gripping knurled tie-downs, or over-center fasteners, or ratchet fasteners. In those embodiments comprising fasteners, tie-downs strapped over the top of the shoe  102  are fastened through the fasteners and used to secure the balls  106 ,  108  to the shoe in much the same fashion that tie-downs and their accompanying hardware are used to secure cargo and freight to truck beds. 
         [0061]    The proximal ball  108  is convex in shape and comprises an outer surface of a pliable durable non-porous polymer material, wherein the width of the proximal ball is more than half the distance between the inside lateral edge and the outside lateral edge. 
         [0062]    The proximal ball  108  comprises an outer surface, or shell, made of rubber, leather and/or another pliable and durable material which completely encompasses the proximal ball  108 . The proximal ball  108  defines a recess within the distal ball  106 . In some embodiments of the present invention, this recess is filled with compressed air. In some embodiments of the present invention, the proximal ball  108  is inflatable by the wearer using means known to those of skill in the art. In other embodiments of the present invention, the proximal ball  108  is filled with one of viscoelastic polyurethane foam and silicone gel. 
         [0063]    The outer surface of the proximal ball  108 , in some embodiments, comprises an impermeable and flexible exterior surface with a hollow core interiorly isolated atmospherically from ambient air and filled with one of air, water, noble gases, viscoelastic polyurethane foam, and permeable, silicone gel. 
         [0064]    In some embodiments of the present invention, the diameter of the proximal ball  108  is ten to forty percent less than the diameter of the distal ball  106 . In other embodiments, the diameter of the distal ball  106  is ten to forty percent less than the diameter of the proximal ball  108 . In other embodiments, the diameter of the proximal ball  108  is less than the diameter of the distal ball  106 , or vice-versa. 
         [0065]    The distal ball  106  and proximal ball  108 , when attached to the shoe sole  104  and used by a wearer, destabilize muscles and tendons in the lower extremities, and strengthen those muscles and tendons, including the gluteus maximus, gluteus medius, gastrocnemius, soleus, fibularis longus, fibularis brevis, plantaris, flexor hallucis longus, medial malleolus, adductor magnus, semitendinosus, sartorius, plantaris, and the like. 
         [0066]    Because the proximal ball  108  and the distal ball  106  have convex outer surfaces, they do not provide lateral stability to wearer of the present invention. The present invention, thus, forces the user to engage in increased plyometric exercise and causes increased strain and strengthening of muscles and tendons in the lower extremities. 
         [0067]    In various embodiments of the present invention, the balls  106 ,  108  may not be hemispherical, but may be shaped in the form of any other geometric shape incorporating one or more non-planar facets, including polyhedral, toroidal polyhedral, spherical cap, and even egg-shaped. In various embodiments of the present invention, the balls  106 ,  108  may be shaped in the form of any one half of the these geometric shapes. 
         [0068]      FIG. 1B  is a top elevational perspective view of a detachable convex plyometric athletic trainer  120  in accordance with the present invention. The detachable convex plyometric athletic trainer  120  comprises a shoe  102 , a shoe sole  104 , a distal ball  106 , and a proximal ball  108 . 
         [0069]    The shoe  102 , shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIG. 1A . 
         [0070]      FIG. 1B  shows a plyometric athletic trainer  120  in its attached configuration, wherein the distal ball  106  and the proximal ball  108  are not detached from the shoe  102  and shoe sole  104 . The distal ball  106  and the proximal ball  108  are attached, in the shown embodiment, using rubber cement well-known to those of skill in the art to the shoe sole  104 , and are roughly centered laterally. 
         [0071]      FIG. 1C  is a lower elevational perspective view of a detachable convex plyometric athletic trainer  140  in accordance with the present invention. The detachable convex plyometric athletic trainer  140  comprises a shoe  102 , a shoe sole  104 , a distal ball  106 , a proximal ball  108 , a distal screw  142 , a proximal screw  144 , a distal screw receiver  144 , and proximal screw receiver  146 . 
         [0072]    The shoe  102 , shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIGS. 1A-1B . 
         [0073]      FIG. 1C  shows a plyometric athletic trainer  140  in its detached configuration, wherein the distal ball  106  and the proximal ball  108  are detached from the shoe  102  and shoe sole  104 . The distal ball  106  and the proximal ball  108  (together the “balls  106 ,  108 ”) are attachable, in the shown embodiment, using two screws  142 ,  144  which traverse the balls  106 ,  108  vertically and secure inside the shoe sole  104 . 
         [0074]    The distal screw  142  and the proximal screw  144  comprise screws well known to those of the skill in the art. In the shown embodiment, the screws  142 ,  144  exceed the height of the balls  106 ,  108 . 
         [0075]    The distal screw receiver  146  and the proximal screw receiver  148  comprise holes within the shoe sole  104  meant to receive and secure the screws  142 ,  144 . In some embodiments, the receivers  146 ,  148  comprise studs. Screw receivers are well-known to those of skill in the art. 
         [0076]    In various embodiments of the present invention, the interior, or core of the balls  106 ,  108  is solid and comprised of the same material as the outer surface  112 . In various other embodiments, the core is an extension of the outer surface  112  or top surface  110 . 
         [0077]    In  FIG. 1C , the balls  106 ,  108  are attached using the screws  142 ,  144  to the shoe sole  104 . In other embodiments, the screws  142 ,  144  attach the balls  106 ,  108  to the shoe sole  104  at, or closer to, the perimeter of the balls  106 ,  108 . Any number of screws  106 ,  108  may be used to secure the distal ball  106  and the proximal ball  108 . 
         [0078]    In various embodiments of the present invention, the top surface  110  of the balls  106 ,  108  may not be planar or substantially planar, but may instead be curved, convex, concave, or otherwise non-planar such that the top surface  110  contours the lower surface of the sole  104  of the shoe  102 . 
         [0079]      FIG. 1D  is a lower elevational perspective view of a detachable convex plyometric athletic trainer  160  in accordance with the present invention. The detachable convex plyometric athletic trainer  160  comprises a shoe  102 , a shoe sole  104 , a distal ball  106 , a proximal ball  108 , a distal screw  142 , and a proximal screw  144 . 
         [0080]    The shoe  102 , shoe sole  104 , distal ball  106 , proximal ball  108 , distal screw  142 , and proximal screw  144  are substantially described above in relation to  FIGS. 1A-1C . 
         [0081]    The balls  106 ,  108  may comprise a shock absorber mounted within one or more of the balls  106 ,  108  to absorb shock, or impact to the balls  106 ,  108 , exerted along the longitudinal axis. 
         [0082]      FIG. 1D  shows the present invention  160  in its assembled configuration. 
         [0083]      FIG. 2  is a lower elevational perspective view of a detachable convex plyometric athletic trainer  200  in accordance with the present invention. The detachable convex plyometric athletic trainer  160  comprises a shoe  102 , a shoe sole  104 , a distal ball  106 , a proximal ball  108 , a distal rail  202   a , distal rail  202   b , a proximal rail  204   a , a proximal rail  204   b , a distal receiving rail  206   a , a distal receiving rail  206   b , a proximal receiving rail  208   a , and proximal receiving rail  208   b.    
         [0084]    The shoe  102 , shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIGS. 1A-1D . 
         [0085]    The distal ball  106  and the proximal ball  108 , in the shown embodiment, comprise rails  202   a - b ,  204   a - b  disposed above the balls  106 ,  108 . 
         [0086]    The distal rails  202   a - b  and proximal rails  204   a - b  (the “rails  202   a - b ,  204   a - b ”), in the shown embodiment, run parallel with the longitudinal axis of the present invention. In other embodiments, the rails  202   a - b ,  204   a - b  run approximately perpendicular to the longitudinal axis. 
         [0087]    The distal rails  202   a - b  slide across and into and lock within the distal receiving rails  206   a - b . The proximal rails  204   a - b  slide into and lock within the proximal receiving rails  208   a - b  using means well-known to those of skill in the art. 
         [0088]    In some embodiments of the present invention, the distal ball  106  optionally connects to the proximal receiving rails  208   a - b  and is interchangeable with the proximal ball  108 . The diameter of the proximal ball  108  may differ from the diameter of the distal ball  106 . Thus, the present invention teaches multiple configurations of the present invention. 
         [0089]    In various embodiments of the present invention, either the distal ball  106  or the proximal ball  108  may be attached detachably below the shoe  102  without the other ball. 
         [0090]    The balls  106 ,  108  may be detachably attached to the shoe  102  using Velcro, adhesives, screws, clamps, straps, ties, hooks, bands, or snaps. When attached with Velcro, the planar top surface of the ball  106 ,  108  comprises a layer of Velcro hooks or loops, made of nylon or polyester, which connect with an alternate layer of hooks or loops affixed to the sole of the shoe  102 . 
         [0091]    Adhesives are well-known to those of skill in the art. In various embodiments of the present invention, the balls  106 ,  108  are glued to the shoe  102 . In some of these embodiments, the balls  106 ,  108  can be removed by dissolving the adhesives. 
         [0092]    The balls  106 ,  108  may be clamped to the sole of the shoe  102  using clamps, clips, clasps, buckles, tie-down straps (including loop straps and two-piece straps), webbing, or other fastening devices affixed to the outer surface of the balls,  106 ,  108  using means well-known to those of skill in the art, including marman clamps, hose clamps, set screws, turn buckles, and the like. 
         [0093]    Straps, ties, and bands may be affixed to the balls  106 ,  108  and/or the shoe  102  for detachably attaching the balls  106 ,  108  to the shoe  102 . 
         [0094]    Snaps are well-known to those of skill in the art, and described above. 
         [0095]    The balls  106 ,  108  may comprise a hollow interior, which may be accessible through a door hingedly connected to the outer surface  112   a - b  of the balls  106 ,  108 , or hingedly connected to the top surface  110   a - b.    
         [0096]    The hollow interior may be used to house one or more electrical devices from the group consisting of a GPS tracker, an odometer, light emitting diodes (LEDs), lights (color coded, in some embodiments, to match the shoe  102  and/or the balls  106 ,  108 ), batteries, and a step counter. The hollow interior may also be used by a wearer to provide user storage, or may be filled with one or more of viscoelastic polyurethane foam and silicone gel, or a non-silicone gel. 
         [0097]      FIG. 3A  is a side perspective view of a detachable convex plyometric athletic trainer  320  in accordance with the present invention. The detachable convex plyometric athletic trainer  300  comprises a shoe  102 , a shoe sole  104 , a distal ball  106 , a proximal ball  108 , a distal screw  142 , and a proximal screw  144 . 
         [0098]    The shoe  102 , shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIGS. 1A-3A . 
         [0099]    The shown embodiment illustrates that, in some embodiments of the present invention, the distal ball  106  and the proximal ball  108  may attach to a shoe sole  104  with a non-planar underside, such as a toning shoe. In the shown embodiment, the shoe sole  104  comprises a convex underside, and the distal ball  106  and the proximal ball  108  comprise concave upsides meant to conform to the shoe sole  104 . 
         [0100]      FIG. 3B  is a side perspective view of a detachable convex plyometric athletic trainer  340  in accordance with the present invention. The detachable convex plyometric athletic trainer  320  comprises a shoe  102 , a shoe sole  104 , a distal ball  106 , a proximal ball  108 , a distal screw  142 , and a proximal screw  144 . 
         [0101]    The shoe  102 , shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIGS. 1A-3A . 
         [0102]    The shown embodiment shows balls  106 ,  108  conjoined to the shoe sole  104 . 
         [0103]      FIG. 4A  is a bottom perspective view of a detachable convex plyometric athletic trainer  400  in accordance with the present invention. The detachable convex plyometric athletic trainer  400  comprises a shoe sole  104 , a distal ball  106 , and a proximal ball  108 . 
         [0104]    The shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIGS. 1A-3B . The balls  106 ,  108  may be multicolored. The colors of the balls  106 ,  108  may be indicative of the height, and consequent degree of destabilization, of the balls  106 ,  108 . The colors of the balls  106 ,  108  may alternatively be indicative of the pressure of the inflated air within the balls  106 ,  108 , and consequent degree of destabilization imparted to a wearer by the balls  106 ,  108 . 
         [0105]    In the shown embodiment, the distal ball  106  is ovoid in shape from the bottom perspective. In alternative embodiments of the present invention, either or both the distal ball  106  and the proximal ball  108  may be ovoid in shape from this perspective view. 
         [0106]      FIG. 4B  is a bottom perspective view of a detachable convex plyometric athletic trainer  420  in accordance with the present invention. The detachable convex plyometric athletic trainer  400  comprises a shoe sole  104 , a distal ball  106 , a proximal ball  108 , concentric tread  422 , and broken tread  424 . 
         [0107]    The shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIGS. 1A-4A . 
         [0108]    The proximal ball  108  and/or the distal ball  106  may comprise broken tread and/or concentric tread disposed on the convex outer surface of the balls  106 ,  108 . 
         [0109]      FIG. 4C  is a bottom perspective view of a detachable convex plyometric athletic trainer  440  in accordance with the present invention. The detachable convex plyometric athletic trainer  400  comprises a shoe sole  104 , a distal ball  106 , a proximal ball  108 , broken rotating tread  442 , and half-circular tread  444 . 
         [0110]    The shoe sole  104 , distal ball  106 , and proximal ball  108  are substantially described above in relation to  FIGS. 1A-4B . 
         [0111]    The proximal ball  108  and/or the distal ball  106  may comprise half-circular tread and/or broken rotating tread disposed on the convex outer surface of the balls  106 ,  108 . 
         [0112]    In some embodiments of the present invention, the balls  106 ,  108  comprise a GPS locator, powered by energy generated from turbine activated by the compression of the one or more of the distal ball  106  and the proximal ball  108 . This feature allows parents, children, spouses, and others to track the location of wearers of the present invention as they run through forested or secluded areas perceived to be higher in danger. 
         [0113]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.