Patent Publication Number: US-8984775-B2

Title: Energy return member for footwear

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/404,247, filed Feb. 24, 2012. 
    
    
     FIELD 
     The present disclosure relates generally to articles of footwear, and, more particularly, to resilient members incorporated in the soles of footwear. 
     BACKGROUND 
     Footwear, particularly athletic footwear, is worn in a variety of activities including running, walking, hiking, other team and individual sports, and any activity where the protection and support of human feet is desired. In one configuration, an article of footwear includes a sole and an upper that form a cavity in which a user places his or her foot. The sole of the footwear engages the bottom of the foot and separates the foot from the ground. The sole often consists of one or more layers of materials including leather, rubber, foam, and plastics that provide shock absorption and support to the foot. The upper extends outwardly from an outer peripheral edge of the sole and covers at least a portion of the foot to hold the footwear in place. Uppers in athletic shoes are usually formed from one or more pieces of fabric, leather, and/or plastic that are stitched or otherwise attached together. Various fasteners including shoelaces and hook and loop fasteners are used to secure the foot in place within the footwear. 
     In an article of footwear, the sole provides cushioning and support for the foot and helps to maintain traction between the foot and the ground while running or walking. The sole deforms as the shape of the foot changes during each stride, and then returns to an undeformed configuration as the foot leaves the ground. 
     Proper engagement between the foot and the upper and sole of the shoe can improve the comfort and protection that the shoe provides to a wearer. The human foot has various sections including the forefoot, midfoot, and heel. During walking or running, the human foot transfers energy into the ground through the sole. Some mechanical energy is also stored in the sole as the sole deforms during a stride, and the mechanical energy is released as the foot and the sole leave the ground. Thus, improvements to footwear that enable each section of the foot to engage the footwear comfortably and improvements that reduce the effort needed to walk or run while wearing the footwear would be beneficial. 
     SUMMARY 
     In at least one embodiment, an article of footwear includes a sole defining a lateral side and a medial side, an upper attached to the sole, and a resilient member positioned within the sole. The resilient member includes a plurality of arms including a medial arm extending along the medial side of the sole and a lateral arm extending along the lateral side of the sole, wherein an end of the medial arm is connected to an end of the lateral arm. 
     In at least one other embodiment, an article of footwear includes an upper, a sole attached to the upper, and a spring plate embedded in the sole. The sole includes a forefoot region, a midfoot region, and a heel region. The spring plate includes a first cantilever arm, a second cantilever arm, and a central portion. The first and second cantilever arms extend from the midfoot region into the forefoot region of the sole. 
     In at least one other embodiment, an article of footwear configured for a foot of a human wearer includes a sole, an upper attached to the sole, and a spring plate positioned within the sole. The sole includes a medial side and a lateral side and further includes a forefoot region and a heel region. The upper and sole define a foot cavity configured to receive the foot. The spring plate includes a central member positioned posterior to the forefoot region of the sole, a first medial arm extending from the central member to the forefoot region of the sole on a medial side of the sole, a first lateral arm extending from the central member to the forefoot region of the sole on a lateral side of the sole, and at least one posterior arm extending from the central member to the heel region of the sole. The first medial arm and the first lateral arm are configured to resiliently deform in response to a force on the sole during a stride of the wearer and resiliently recover in response to the force being removed from the sole. 
     The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. While it would be desirable to provide an apparatus that provides one or more of these or other advantageous features as may be apparent to those reviewing this disclosure, the teachings disclosed herein extend to those embodiments which fall within the scope of any appended claims, regardless of whether they include or accomplish one or more of the advantages or features mentioned herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of an athletic shoe. 
         FIG. 2  is a medial-side perspective view of the athletic shoe of  FIG. 1 . 
         FIG. 3  is a lateral-side perspective view of the athletic shoe of  FIG. 1-FIG .  2 . 
         FIG. 4  is a perspective view of the athletic shoe of  FIG. 1-FIG .  3  with a portion of a heel member in an upper of the shoe retracted to depict a forefoot member of the upper and the heel member of the upper in greater detail. 
         FIG. 5  is a top view of the athletic shoe of  FIG. 1-FIG .  4  with an outline view of an energy return plate that is incorporated with a sole of the athletic shoe. 
         FIG. 6  is a bottom view of the athletic shoe of  FIG. 1-FIG .  5  depicted a sole and tread of the athletic shoe with an outline view of the energy return plate incorporated in the sole. 
         FIG. 7  is a block diagram of a process for producing an article of footwear. 
         FIG. 8A  is a view of one embodiment of an energy return plate that is incorporated in an article of footwear. 
         FIG. 8B  is a view of another embodiment of an energy return plate that is incorporated in an article of footwear. 
         FIG. 9  is a cross-sectional view of layers forming the sole and upper of the athletic shoe of  FIG. 1-FIG .  6  taken along line  180  depicted in  FIG. 6 . 
         FIG. 10A  is a side view of the energy return plate of  FIG. 8A  depicting the configuration of the energy return plate when the athletic shoe lies flat on a surface. 
         FIG. 10B  is a side view of the energy return plate of  FIG. 8A  depicting how the energy return plate flexes during a pronated stride. 
         FIG. 10C  is a side view of the energy return plate of  FIG. 8A  depicting how the energy return plate flexes during a supinated stride. 
         FIG. 11  is an exploded view of the athletic shoe depicted in  FIG. 1-FIG .  6 . 
         FIG. 12  is a prior art view of the bones of a human foot and a sole of a shoe. 
     
    
    
     DETAILED DESCRIPTION 
     For a general understanding of the details for the footwear disclosed herein, the drawings are referenced throughout this document. In the drawings, like reference numerals designate like elements. As used herein the term “foot” may refer to a portion of the human foot, a full human foot, and to the ankle. Various portions of the foot include, but are not limited to, the forefoot, midfoot, upper foot, heel, and ankle. As used in this document, the heel is considered to be the posterior end of the foot and the portion of an article of footwear that engages the heel is the posterior end of the article of footwear. The toes of the foot and toe-end of the article of footwear are considered to be the anterior ends of the foot and article of footwear, respectively. The terms “medial” and “medial side” refer to the inner side of a foot extending from the large toe to the heel, and the terms “lateral” and “lateral side” refer to the outer side of the foot extending from the small toe to the heel. Similarly, articles of footwear include medial and lateral sides that conform to the medial and lateral sides, respectively, of the foot. Some footwear embodiments include different contours on each of the medial and lateral sides to improve the fit of the footwear to the foot. The term “user” may refer to a person wearing an article of footwear. 
     The terms “forefoot” “midfoot” and “heel” as used herein with reference to an article of footwear refer to regions of the footwear configured to engage the forefoot, midfoot, and heel, respectively, of a human foot when a human wears the article of footwear. As used herein, the forefoot of a human foot includes the phalange bones that form the toes, the midfoot is the region posterior from the forefoot that includes the metatarsal bones, and the heel includes the posterior end of the foot including the tarsus bones. 
     Various articles of footwear may engage only portions of each section of the foot. For example, a low-top athletic shoe may not engage portions of the heel including the calcaneus and talus bones, or an open-toed shoe may not directly engage each of the phalanges in the toes of the wearer.  FIG. 12  depicts a prior art article of footwear  1200  with a skeletal view of a human foot  1204  positioned in the footwear  1200 . The foot  1204  includes a heel  1212 , midfoot  1216 , and forefoot  1220 . The footwear  1200  includes an upper  1208 , depicted in dashed lines, and a sole  1210 . The upper  1208  and sole  1210  include a heel region  1224 , midfoot region  1228  and forefoot region  1232  that engage the heel  1212 , midfoot  1216 , and forefoot  1220  of the foot  1204 , respectively. As described in more detail below, a single section of the shoe may engage more than one portion of the foot. For example, a sole of the shoe can engage an entire ventral portion of the human foot. A forefoot section of the upper of a shoe can engage some or all of the sides and dorsal (top) surface of the forefoot and midfoot, and a heel section of the upper can engage some or all of the sides of the heel and sides and dorsal surface of the midfoot. 
     General Arrangement of The Article of Footwear 
       FIG. 1-FIG .  6  depict different views of one embodiment of footwear, shown as an athletic shoe  100  that is configured to be worn on a left human foot. The athletic shoe  100  includes a sole  132  and an upper  114  formed from a heel member  104  and forefoot member  120 . In the upper  114 , the heel member  104  covers at least a portion of the heel region and midfoot region of the athletic shoe  100 , and the forefoot member  120  covers at least a portion of the forefoot region and midfoot region of the athletic shoe  100 . The athletic shoe  100  has a length depicted along axis  101  and a width depicted along axis  102 . The sole  132 , heel member  104 , and forefoot member  120  form a foot cavity  140  with an opening formed by the heel member  104  and a tongue  126  that is attached to the forefoot member  120 . A user inserts his or her foot into the foot cavity  140  when putting on the shoe, with the toes and forefoot moving forward in the foot cavity  140  to engage the forefoot member  120 , while the heel and a portion of the midfoot engage the heel member  104 . In the embodiment of the athletic shoe  100 , an insole  144  positioned at the top of the sole  132  engages the bottom of the foot in the foot cavity  140 . The heel member  104 , forefoot member  120  cover at least a portion of the top, sides, and posterior of the foot in the foot cavity  140  to hold the athletic shoe firmly in place on the foot. The sole  132  covers the bottom of the foot in the foot cavity to provide support and cushioning to the foot while the user wears the athletic shoe  100 . The upper  114  and the sole  132  envelop the human foot and provide protection and support for the human foot in the foot cavity  140  during a wide range of activities including athletic activities. As used herein, the term “envelop” refers to a complete or substantially complete enclosure of a human foot, allowing for a possible exception of an insubstantial portion of the foot not being covered, such as a small region below the ankle or other insubstantial uncovered portion. Accordingly, most convention running shoes would envelop the human foot while conventional sandals would not envelop the human foot. 
     Referring  FIG. 1 , the upper  114  is depicted along the length  101  of the athletic shoe  100 . The forefoot member  120  is attached to the sole  132  and extends from the forefoot of the shoe  100  through a portion of the midfoot. The heel member  104  is attached to the sole  132  and extends from the heel of the shoe  100  to the midfoot. In the athletic shoe  100 , a portion of the forefoot member  120  and heel member  104  overlap in the midfoot region. The heel member  104  is positioned on the exterior of the forefoot member  120  in this overlapping region.  FIG. 1  depicts a medial leading edge  108  and lateral leading edge  110  of the heel member  104 . The forefoot member  120  extends past the medial leading edge  108  and lateral leading edge  110  of the heel member  104  toward the heel of the athletic shoe  100 , and the heel member  104  covers the forefoot member  120  in the overlapping region of the upper  114 . 
     The heel upper  114  is typically formed from one or more layers of various materials including fabrics, natural or synthetic leather, natural and synthetic rubber, foams, and plastics. In the athletic shoe  100 , the heel member  104  includes a posterior cushioning member  112  that engages the posterior of the heel and includes a fabric layer covering a foam layer that cushions the foot. Various types of synthetic fabric including nylon, polytetrafluoroethylene (sold commercially as Gore-Tex®), and HeatGear®, sold by Under Armour, Inc. of Baltimore, Md., can be used in forming the upper members  104  and  120 . The heel member  104  and forefoot member  120  can also include rigid or semi-rigid components such as thermoplastic or metal supports that resist bending and provide support to the foot. 
     The forefoot member  120  also includes a stretchable fabric section  122  which stretches to accommodate insertion of a foot into the foot cavity  144  and conforms to the top and sides of the foot in the foot cavity  144 . The stretchable fabric section  122  can be formed from various materials including elastane fabric. In the athletic shoe  100 , the overlap of the heel member  104  over the forefoot member  120  leaves a portion of the stretchable fabric  122  exposed on the lateral side of the athletic shoe  100  as depicted in  FIG. 3 , while the heel member  104  fully covers the stretchable fabric  122  on the medial side of the athletic shoe  100 , as depicted in  FIG. 2 . Other embodiments include larger or smaller sections of stretchable fabric, or can omit the stretchable fabric. 
     The forefoot member includes a tongue  126 . In the embodiment of the athletic shoe  100 , the tongue  126  is attached to the forefoot member  120  around substantially the entire anterior side, lateral side, and medial side of the tongue  126 , which are depicted with broken line  128  in  FIG. 4  and  FIG. 11 . At least a portion of the sides of the tongue  128  are attached to the stretchable fabric  122  in the forefoot member  120 . In the example of the athletic shoe  100 , the tongue  126  is stitched to the forefoot member  120  around the outer perimeter  128 , but in other embodiments the tongue is adhered to the forefoot member or formed from an integral piece of material that forms the forefoot member  120 . The stretchable fabric  122  enables adjustment of the tongue  126  to improve the fit of the athletic shoe  100 , even though the sides of the tongue  126  are attached to the forefoot member  120 . In alternative embodiments, the tongue  126  is attached to the forefoot member  120  along the anterior side of the tongue  126  and is substantially detached from the forefoot member  120  along the medial and lateral sides. 
     Both the heel member  104  and forefoot member  120  include eyelets that accept a single shoe lace  130  that laces the heel member  104  and forefoot member  120  together in the athletic shoe  100 . In the embodiment of  FIG. 1 , the forefoot member includes a plurality of eyelets  124  formed from fabric loops that are positioned on the lateral and medial sides of the tongue  126 . The heel member  104  includes eyelet holes  106  that are formed through the material of the heel upper  104 . As used herein the term “eyelet” refers to any suitable structure for engaging a shoe lace to an article of footwear. Examples of other eyelet embodiments include hooks and tubular engagement members that accept the shoe lace. 
     The sole  132  further includes multiple members that support the bottom of a foot placed in the foot cavity  140 . As depicted in  FIG. 9  and  FIG. 11 , the sole  132  includes a midsole board  148 , resilient layer  154 , energy return plate  160  and treads  152 .  FIG. 9  also depicts a cushioning insole layer  144  that is positioned above the midsole board  148 . In the article of athletic shoe  100 , the midsole board  148  is attached to both the heel member  104  and forefoot member  120  in the upper  114 . Various alternative embodiments of the sole  132  include additional layers or omit some of the layers described herein. 
       FIG. 2  and  FIG. 3  depict the medial and lateral sides, respectively, of the shoe  100 .  FIG. 2  and  FIG. 3  depict the sole  132  including a welt  138 . The welt  138  in the athletic shoe  100  is a black plastic member that is an integral member of the sole  132  that extends upward to provide a surface to attach both the heel member  104  and forefoot member  120  to the sole  132 . The welt  138  extends upward around a perimeter of the sole  132  depicted as dashed line  136 . Alternative footwear embodiments omit the welt and attach the forefoot and heel members to other layers of the sole  132  directly. 
     Separate Heel and Forefoot Members 
     As described above, the heel member  104  and forefoot member  120  are directly attached to one another along a common length  116  of the sole  132 , which common length  116  is directly below the overlapping region of the forefoot member  120  and heel member  104  in the upper  114 , as best depicted in  FIG. 4  and  FIG. 11 . Notwithstanding this overlap, the heel member  104  is separate from the forefoot member  420  above the sole  132  such that the upper  114  does not provide an attachment between the heel member  104  and the forefoot member  120 . In one configuration, the forefoot member  120  is strobled or sewn to the sole  132  first, and the heel member  104  is then strobled or sewn to the sole  132  after the forefoot member, with the overlapping portions of the heel member  104  being strobled to the sole  132  through a portion of the forefoot member  120  along common length  116 . Thus, in the athletic shoe  100 , the heel member  104  and forefoot member  120  are both attached to the midsole board  148  along a common length  116  of the sole  132  on the medial and lateral sides of the sole  132 . However, the heel member  104  and forefoot member  120  are separated from each other above the sole  132 . Nevertheless, some overlap between the heel member  104  and the forefoot member  120  generally occurs above the sole  132 . As depicted in  FIG. 9  and  FIG. 11 , the forefoot member  120  is attached to the midsole board  148  and the heel member  104  overlaps the forefoot member  120 . The strobling process forms stitches through the heel member  104 , forefoot member  120 , and the midsole board  148  to attach the heel member  104  and forefoot member  120  to the sole  132  along the common length  116  of the sole  132 . In other embodiments, the heel member  104  and forefoot member  120  are attached to the sole  132  via adhesives or other fastening means. 
     When worn on a foot, the shoelace  130  laces through eyelets  124  and  106  in both the forefoot member  120  and heel member  104 . The upper  114  does not, however, provide any attachment between the forefoot member  120  and the heel member  104  other than the common length  116  of the sole  132  where the heel member  104  and forefoot member  120  are attached to the sole  132 . More specifically, the heel member  104  is not sewn, adhered, or otherwise affixed to the forefoot member  120  above the sole  132 , thus enabling the heel member  104  to be moved independent of the forefoot member  120  as depicted in  FIG. 4 . The shoelace  130  engages the heel member  104  and the forefoot member  120 . However, because of the separation between the heel member  104  and forefoot member  120 , the heel member  104  and forefoot member  120  can be adjusted independently of one another. 
     The separate configuration of the forefoot member  120  and the heel member  104  in the upper  114  enables each section of the upper to be adjusted to different parts of a foot individually to improve the fit of the athletic shoe  100 . For example, the wearer can pull on the tongue  126  to fit the forefoot member  120  to the forefoot and midfoot while the fit of the heel member  104  remains substantially unchanged. Similarly, adjustments to the heel member  104  do not substantially affect the separate forefoot member  120 . When adjusting the shoelace  130 , the wearer can selectively loosen or tighten the portions of the shoe lace extending through the eyelets  106  to adjust the fit of the heel member  104 , or loosen or tighten portions of the shoe lace  130  extending through the eyelets  124  to adjust the fit of the forefoot member  120 . 
     The athletic shoe  100  shown in  FIGS. 1-4  is one example of an article of footwear with separated heel and forefoot members, but it will be recognized that other embodiments are also envisioned. In one alternative embodiment, the heel member  104  is attached to the sole  132  and a portion of the forefoot member  120  overlaps a portion of the heel member  104  (instead of the heel member  104  overlapping the forefoot member  120  as shown in  FIGS. 1-4 ). In another alternative embodiment, the heel member  104  and forefoot member  120  do not overlap on the upper  114  or the sole  132 , but are instead attached to separate sections of the perimeter  136  around the sole  132 . In still another alternative embodiment, the heel member  104  and forefoot member  120  are attached together above the sole for only a fraction of a height of the two upper members. In one alternative configuration, the heel member  104  is attached to the forefoot member  120  near the medial and lateral leading edges  108  and  110  for a few centimeters or less of a height  103  of the heel member  104  extending upward from the sole  132 . Sufficient portions of the partially attached heel member  104  and forefoot member  120  remain detached and overlap each other to enable individual adjustment of the heel member  104  and forefoot member  120  to fit the foot inserted into the foot cavity  140 . 
     Method of Making the Article of Footwear 
       FIG. 7  depicts a process  700  for producing an article of footwear. The athletic shoe  100  described above is one example of an article of footwear that can be produced using process  700 , and is described with process  700  for illustrative purposes. Process  700  begins by assembling the heel member  104  and forefoot member  120  as two separate pieces (block  704 ). The heel and forefoot members can be assembled concurrently or at different times as needed. In one embodiment of process  700 , the tongue  126  is attached to the forefoot member  120  as part of the assembly of the forefoot member  120 . Various assembly methods known to the art including sewing and adhesion of the various components in each of the heel and forefoot uppers are used to assemble both of the forefoot and upper members. As depicted in  FIG. 11 , the heel member  104  and forefoot member  120  of the upper  114  are assembled as separate pieces. However, during the process  700 , the heel member  104  and forefoot member  120  do not take the shape depicted in the assembled athletic shoe  100  illustrated in  FIG. 1-FIG .  5  until engaged with a last as described below. 
     After assembly, the separate heel and forefoot members lack the shape of an upper in a completed article of footwear. Both the heel member and the forefoot member engage a last that shapes the forefoot and heel members (block  708 ). A last is a form having a size and shape approximating a size and shape of the foot cavity  140  in the athletic shoe  100 . In common manufacturing processes, a last is a shaped plastic or wood form. The heel member  104  and forefoot member  120  are stretched over the last in the shape of the upper in the athletic shoe  100 . Some process embodiments also heat the heel and forefoot members as the members are stretched over the last to form the shape of the upper in the completed athletic shoe. The forefoot member  120  engages a forefoot end of the last and stretches toward the heel. The heel member  104  engages a heel end of the last and stretches toward the forefoot. The heel member  104  and forefoot member  120  engage the last separately and are not attached to each other. In the embodiment of athletic shoe  100 , a portion of the heel member  104  overlaps a portion of the forefoot member  120  in the midfoot region of the last. 
     After forming the heel and forefoot members on the last, the forefoot member is attached to a member of the sole (block  712 ). Some manufacturing processes attach the forefoot member to a midsole board, such as midsole board  148  in the sole  132 , which is typically a cardboard or polymer member that conforms to the shape of the sole. The midsole board is positioned on the bottom of the last and the forefoot member is strobled or otherwise attached to the midsole board. In shoes that employ a welt to attach the forefoot member to the sole, the welt is attached to the midsole board and then the forefoot member is attached to the welt. In some embodiments, the midsole board is integrated with other layers in the sole prior to attaching the forefoot member to the midsole board. In other embodiments, the remaining layers of the sole are attached to the midsole board after both the forefoot and heel members of the upper are attached to the midsole board. Some articles of footwear do include a midsole board. Process  700  attaches the upper forefoot member to another one of the layers of the sole for articles of footwear that omit the midsole board. 
     Process  700  continues by attaching the heel member to a member of the sole (block  716 ). The heel member is attached to the sole member in a similar manner to the forefoot member. In the example of the athletic shoe  100 , one embodiment of process  700  attaches the heel member  104  to the sole member such as the midsole board or another layer of the sole after attaching the forefoot member  120  to the sole member. The heel member  104  is attached after the forefoot member  120  due to the overlap of the heel member  104  outside of a portion of the forefoot member  120 . In alternative embodiments, the forefoot member  120  is attached after the heel member  104 , or the two members are attached simultaneously. In each alternative embodiment, the forefoot member  120  and the heel member  104  are attached to the sole member  132  without attaching the forefoot member  120  and the heel member  104  above the sole member  132 . 
     After both the forefoot and heel members are attached to a member of the sole, the last is removed from the article of footwear (block  720 ). In the athletic shoe  100 , the heel member  104 , forefoot member  120 , and sole  132  form the foot cavity  140  that accommodates a foot having a size and shape similar to the last. 
     Energy Return Plate 
     In at least one embodiment, the athletic shoe  100  includes an energy return plate  160  integrated within the sole  132  in the athletic shoe  100 . With reference to  FIG. 8A , the energy return plate  160  includes a central portion  162 , medial forefoot arm  164 , lateral forefoot arm  166 , medial heel arm  168 , and lateral heel arm  170 . In one alternative embodiment depicted in  FIG. 8B , an energy return plate  190  includes a central portion  192 , medial forefoot arm  194 , lateral forefoot arm  196 , and a heel arm  198 . During a stride of a human wearing the shoe  100 , the energy return plate deforms and absorbs mechanical energy from the stride. As the foot and athletic shoe  100  leave the ground, the energy return plate returns to an un-deformed configuration and returns some of the mechanical energy to the foot. The energy return plate is also referred to as a “spring plate” because the energy return plate includes multiple leaf spring members that store mechanical energy from various regions of the foot during a stride. It will be recognized that although the energy return plate  160  is described herein in association with the athletic shoe  100  having a separate heel member  104  and forefoot member  120  in the upper  114 , in other embodiments the energy return plate  160  could be incorporated into a shoe with a conventional or differently constructed upper  114 . 
     With particular reference to  FIG. 8A , the medial forefoot arm  164  extends from the central portion  162  along the length of the medial side of the foot cavity to an area of the forefoot region proximate to the hallux (big toe). The lateral forefoot arm  166  extends from the central portion  162  along the length of the lateral side of the foot cavity to an area of the forefoot region proximate the fifth toe (little toe). Each of the medial and lateral forefoot arms  164  and  166  can extend under multiple toes and other regions of the forefoot and midfoot in the foot cavity based on the length and width selected for each arm. The medial heel arm  168  extends in the posterior direction from the central portion  162  toward the heel region along the medial side of the foot cavity and the lateral heel arm  170  extends in the posterior direction from the central portion along the lateral side of the foot cavity. The arms  164 ,  166 ,  168 , and  170  have an upward curvature near the distal end of each arm to conform to the sole and the foot. In the embodiment of  FIG. 8A , the energy return plate  160  is formed from a single plate of a carbon fiber reinforced polymer, but other embodiments can be formed from one or more resilient materials, including polymers and metals, and can be formed from multiple pieces. 
     In the energy return plate  160  of  FIG. 8A , the arms  164 ,  166 ,  168 , and  170  form an “H” shaped configuration with the central portion  162  forming the horizontal member of the “H”. Each of the arms  164 ,  166 ,  168 , and  170  has two ends with one end integrally formed with the central portion  162 , and the other end being free to move independently from the other arms in the energy return plate  160 . The configuration of the energy return plate  160  is cantilevered since each of the arms  164 - 170  is connected to the central portion  162  and the other arms at only one end. Each of the arms  164 - 170  is a leaf spring that is configured to deform and store mechanical energy when the athletic shoe  100  contacts the ground during a stride and to return at least some of the mechanical energy to the foot as the athletic shoe  100  leaves the ground. 
       FIG. 6  and  FIG. 9  depict the energy return plate  160  in the sole  132  of the athletic shoe  100 .  FIG. 6  depicts the outline of the energy return plate  160  incorporated into the sole  132 . The sole  132  fully encloses the energy return plate  160 , which extends along the length of the sole  132  in parallel with the length of the foot cavity  140 . In the athletic shoe  100 , the central portion  162  of the energy return plate  160  is positioned posterior to the forefoot region under a portion of the foot cavity where the midfoot meets the heel. In alternative configurations, the central portion  162  can be positioned farther in the anterior direction under the midfoot region or farther in the posterior direction under the heel region. The configuration of the forefoot and heel arms in the energy return plate  160  is asymmetrical along the length  101  of the athletic shoe  100 . For example, the medial forefoot arm  164  extends further toward the forefoot end of the athletic shoe  100  than the lateral forefoot arm  166 . Additionally, the medial forefoot arm  164  includes a bulge  172  that increases the rigidity of the medial forefoot arm  164  near the central portion  162 . In the embodiment of the energy return plate  160  used in the athletic shoe  100 , the lateral heel arm  170  extends in the posterior direction under the heel farther than the medial heel arm  168 . The shapes, curvatures, and sizes of each arm in the energy return plate  160  can be varied to fit various footwear designs. 
       FIG. 9  depicts various layers in the sole  132  in more detail in a cross-sectional view of a selected portion of the athletic shoe  100  taken along line  180 . The sole  132  depicted in  FIG. 9  is exemplary of one configuration that incorporates an energy return plate. The sole  132  includes treads  152 , a resilient layer  154  that is joined with a transparent polymer  156 , the energy return plate  160 , the midsole board  148 , and an insole layer  144 . The resilient layer  154  and treads  152  are referred to as outsole layers that form portions of the exterior of the sole  132 . Different designs of soles can include a larger or lesser number of layers in the outsole and can be formed from various combinations of materials. The treads  152  engage the ground when the athletic shoe  100  is worn and are typically formed from vulcanized rubber. The treads  152  are positioned and shaped to provide a firm grip between the athletic shoe  100  and the ground during a stride. 
     The resilient layer  154  provides structural support for the sole  132  and engages the treads  152  and a bottom side of the energy return plate  160 . The resilient layer  154  can be formed from various materials including vulcanized rubber and polyurethane foam. The design of the athletic shoe  100  optionally includes a transparent polymer layer  156  that is co-planar with portions of the resilient layer  154 . The transparent polymer layer  156  encloses the energy return plate  160  in areas where the resilient layer  154  does not extend across the entire width of the sole  132 . The transparent polymer layer  156  visually exposes portions of the energy return plate  160  for aesthetic purposes, and seals the energy return plate from dirt or other contaminants that contact the sole  132 . Other embodiments of the athletic shoe  100  omit the transparent polymer layer  156  and include a resilient layer  154  that covers the bottom side of the energy return plate  160 . 
     The midsole board  148  engages the resilient layer  154  and a top side of the energy return plate  160 . The midsole board  148  is also attached to the welt  138 , heel member  104  and forefoot member  120  as described above. The insole layer  144  is positioned over the midsole board  148  and forms the bottom of the foot cavity  140  in the athletic shoe  100 . The insole layer  144  provides support, cushioning, and shock absorption for the foot and is typically formed from one or more layers of compression foam, silicone gels, or other cushioning materials. In some embodiments the insole layer  144  can be removed from the athletic shoe  100  and replaced with a different insole. 
       FIG. 8B  depicts an alternative energy return plate  190 . The energy return plate  190  includes a single central portion  192  that extends in the posterior direction to a heel end  198 . A medial forefoot arm  194  and lateral forefoot arm  196  extend from the central portion  192  along the medial and lateral sides of the foot cavity under the midfoot and forefoot regions of the foot. In the energy return plate  190 , both the medial and lateral forefoot arms include a plurality of indentations  200  formed through the top side of the energy return plate  190 . The indentations  200  enable a uniform deformation of both the medial and lateral forefoot arms  194  and  196 , respectively, during a stride. Different embodiments of the energy return plates  190  and  160  optionally include one or more indentations in both the forefoot and heel arms. The indentations  200  are arranged transverse to the length of the foot cavity  101  to accommodate deformation of either or both of the medial and lateral forefoot arms  194  and  196  during a stride. The medial and lateral forefoot arms are asymmetric in the embodiment of the energy return plate  190  with a bulge  202  that increases the rigidity of the medial forefoot arm  194  near the central portion  192 . The energy return plate  190  is incorporated into the sole of an article of footwear in a similar manner to the energy return plate  160  depicted above. 
     The energy return plate  190  is formed in a “Y” shaped configuration, with the forefoot arms  194  and  196  forming the forked members of the “Y” and the central portion  192  and the central portion  192  forming the base of the “Y” shape. The forefoot arms are both connected at only one end to the central portion  192  in a cantilevered configuration. The central portion  192  also serves as a single heel arm extending under the heel region of a foot in the athletic shoe  100 . The arms  194  and  196  and the central portion  192  are each a leaf spring that is configured to deform and store mechanical energy when the athletic shoe  100  contacts the ground during a stride and to return at least some of the mechanical energy to the foot as the athletic shoe  100  leaves the ground. 
       FIG. 10A  depicts the energy return plate  160  in isolation when the athletic shoe  160  lies flat on surface such as the ground. In  FIG. 10A , the forefoot arms  164  and  162  (hidden behind forefoot arm  164  in  FIG. 10A ) and heel arm  168  and  170  are each in an un-deformed position with no biasing force applied to the energy return plate  160 . During a stride, each of the arms  164 - 170  deforms to absorb mechanical energy from the stride, and then return at least a portion of the mechanical energy when the energy return plate returns to the un-deformed configuration. 
       FIG. 10B  depicts the energy return plate  160  in isolation during a pronated stride. A pronated stride occurs when the heel initially contacts the ground on the lateral side of the foot and then rolls inwards toward the medial side of the foot during the stride. During a pronated stride, the foot places an uneven force on the medial and lateral sides of the energy return plate  160 . The medial forefoot arm  164  and medial heel arm  168  of the energy return plate deform at a somewhat greater rate than the lateral forefoot arm  166  and lateral heel arm  170  in the energy return plate  160  in response to the force of the foot. Since the foot angles inward toward the medial side during a pronated stride, the medial forefoot arm  164  and medial heel arm  168  are positioned at a lower level than the lateral forefoot arm  166  and lateral heel arm  170 . 
     The cantilevered configuration of the forefoot arms  164  and  166  enables the medial forefoot arm  164  to deform to a greater degree than the lateral forefoot arm  166  since the forefoot ends of both arms are free ends that are only connected to each other through the central portion  162 . The cantilevered configuration of the heel arms  168  and  170  enables the heel arm  168  to deform to a greater degree than the lateral heel arm  170  as well. Both the medial and lateral sides of the energy return plate  160  experience some deformation as depicted in  FIG. 10B . As the athletic shoe  100  leaves the ground, the energy return plate  160  and sole  132  return to an un-deformed configuration and energy stored in the energy return plate urges the athletic shoe  100  and the foot of the wearer upward as the foot lifts during the stride. 
       FIG. 10C  depicts the energy return plate  160  in isolation during a supinated stride. In a supinated stride, the heel initially contacts the ground on the lateral side and then does not roll inwardly toward the medial side by a significant amount during the stride. During a supinated stride, the foot places an uneven force on the medial and lateral sides of the energy return plate  160  with a different distribution of force than in the pronated stride. The lateral forefoot arm  166  and lateral heel arm  170  deform at a somewhat greater rate than the medial forefoot arm  164  and medial heel arm  168  in the energy return plate  160  in response to the force of the foot. 
     Since the lateral side of the foot experiences a greater force during the supinated stride, the medial forefoot arm  164  and medial heel arm  168  are positioned at a higher level than the lateral forefoot arm  166  and lateral heel arm  170 . Both the medial and lateral sides of the energy return plate  160  experience some deformation as depicted in  FIG. 10C . The cantilevered configuration of the arms  166 - 170  in the energy return plate  160  enables the lateral forefoot arm  166  and lateral heel arm  170  to deform to a greater degree than the corresponding medial forefoot arm  164  and medial heel arm  168 . As the athletic shoe  100  leaves the ground, the energy return plate  160  and sole  132  return to an un-deformed configuration and energy stored in the energy return plate urges the athletic shoe  100  and the foot of the wearer upward as the foot lifts during the stride. 
     While  FIG. 10B  and  FIG. 10C  depict the energy return plate  160  during pronated and supinated strides, respectively, another form of stride has “neutral” pronation in which the force of the stride is distributed approximately evenly between the medial and lateral arms of the energy return plate  160 . The medial and lateral arms in the energy return plate  160  deform by approximately equal amounts during a neutrally pronated stride. 
     The upward force from the energy return plate  160  is also referred to as a “rebound” force, and the rebound force reduces the energy and effort needed to lift the foot during the next stride. The configuration of the energy return plates  160  and  190  enable the athletic shoe  100  to deliver a rebound force evenly across the foot and to accommodate wearers with both pronated and supinated strides. 
     The energy return plate embodiments described above provide several advantages to a person wearing the athletic shoe  100 . First, the energy return plates extend for substantially the entire length of the foot extending from under the heel to under some or all of the toes of the foot in the foot cavity. The length of the energy plate enables the energy plate to store more mechanical energy for release as the athletic shoe leaves the ground during a stride. Second, the energy return plate provides return energy to both the medial and lateral sides of the foot. Third, the asymmetric configuration of the energy return plate accommodates wearers who have both pronated and supinated strides. 
     Although the present invention has been described with respect to certain preferred embodiments, it will be appreciated by those of skill in the art that other implementations and adaptations are possible. Moreover, there are advantages to individual advancements described herein that may be obtained without incorporating other aspects described above. Therefore, the spirit and scope of any appended claims should not be limited to the description of the preferred embodiments contained herein.