Patent Publication Number: US-6983553-B2

Title: Shoe with tunable cushioning system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part and claims the benefit of U.S. patent application Ser. No. 10/144,440, filed May 13, 2002 now U.S. Pat. No. 6,807,753, the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The invention generally relates to adjustable cushioning systems for articles of footwear. 
     BACKGROUND INFORMATION 
     Conventional athletic shoes include an upper and a sole. The sole is usually manufactured of a material chosen to optimize a particular function of the shoe, for example, cushioning or stiffness. Typically, the sole includes a midsole and an outsole, either of which can include, for example, a cushioning material to protect a wearer&#39;s foot and leg. One drawback with conventional shoes is that the wearer has to select a specific shoe to get optimum performance for a specific activity. For example, the wearer has to use one type of shoe for running and another type of shoe for basketball, because one shoe has more cushioning while the other is stiffer for greater support during lateral movement. 
     Shoes have been designed that attempt to combine and optimize different functions of sport specific shoes; however, the wearer is still left with a shoe with set functionality that the wearer cannot customize. What may be optimal for one segment of the population is not necessarily optimal for everyone. For example, many shoes are designed with wedges or varying degrees of cushioning across the width of the sole to compensate for pronation or supination. Unfortunately, these shoes are typically limited to compensating for either pronation or supination and the amount of compensation cannot be varied to suit a particular wearer. Furthermore, shoes have been designed that attempt to give a wearer some adjustability with respect to a specific function; however, these shoes may require at least partial disassembly of the shoe and/or the wearer may be limited in the amount of adjustment that can be made. 
     U.S. Pat. No. 5,875,568, the disclosure of which is hereby incorporated herein by reference in its entirety, discloses a cushioning system including a cylindrical shock-absorbing insert located in a heel of a shoe. Similarly, U.S. Pat. Nos. 4,430,810 and 4,573,279, the disclosures of which are hereby incorporated herein by reference in their entireties, also disclose cylindrical inserts located in the heel of the shoe. There are several drawbacks to these cushioning systems. For example, the inserts are isotropic. To adjust the cushioning properties of an isotropic insert, the wearer has to remove the insert and replace the insert with another insert having different cushioning properties. The &#39;568 patent discloses rotating the insert to “renew” the cushioning effect of the insert, but the cushioning effect is the same no matter what orientation is selected. In addition, the inserts can “turn” during use, because there is no mechanism for locking the inserts against rotational movement during use. 
     There is, therefore, a need for a shoe that the wearer can easily, repeatedly, and securely customize. Such a shoe should give the wearer the ability to make numerous adjustments to the functional characteristics of the shoe, for example, increased cushioning, compensation for pronation, compensation for supination, etc. 
     SUMMARY OF THE INVENTION 
     The invention is directed to adjustable cushioning systems for articles of footwear that can be customized by a wearer. The systems include one or more cushioning inserts having an anisotropic property afforded, for example, by a multiple density construction. The systems may also include structural support elements that provide additional stability and support to the foot. The wearer can adjust the degree of cushioning by rotating the insert within the shoe. Alternatively, the insert could be moved, flipped, or otherwise displaced relative to the shoe to adjust the degree of cushioning. The wearer could also remove the insert and replace the insert with a new and/or different insert. In addition, the insert can be locked in a predetermined position to maintain a specific performance characteristic. 
     In one aspect, the invention generally relates to an adjustable cushioning system for an article of footwear. The system includes an insert adapted to be received in an aperture formed in a sole of the article of footwear and a locking mechanism disposed proximate the insert for maintaining the insert in a predetermined position or orientation. The insert has an anisotropic property about a longitudinal axis thereof and can be reoriented rotationally in the article of footwear to modify a performance characteristic thereof. The anisotropic property may be compressibility, resiliency, compliancy, elasticity, damping, energy storage, stiffness, or combinations thereof. In various embodiments, the insert is made of a multiple density foam. In another embodiment, the insert may include a skeletal element. In yet another embodiment, the insert is made of a combination of a skeletal element and a multiple density foam. Alternatively, the insert could be made of a first material having a first hardness, a second material having a second hardness, and a third material having a third hardness, for example. 
     In another aspect, the invention relates to an article of footwear including a sole and an adjustable cushioning system. The system includes an insert adapted to be received in an aperture formed in the sole of the article of footwear and a locking mechanism disposed proximate the insert for maintaining the insert in a predetermined orientation. The insert has an anisotropic property about a longitudinal axis thereof and can be reoriented rotationally in the article of footwear to modify a performance characteristic thereof. The anisotropic property may be compressibility, resiliency, compliancy, elasticity, damping, energy storage, stiffness, or combinations thereof. The system can be located in a heel region and/or a forefoot region of the sole of the article of footwear. In one embodiment, the sole includes an outsole and a midsole, and the insert is disposed at least partially within the midsole of the article of footwear. 
     In one embodiment, the locking mechanism includes a lever coupled to the insert for rotatably positioning the insert and a mating groove for receiving and maintaining the lever and the insert in a predetermined position. The groove may be disposed in a casing disposed about an end of the insert. Alternatively, the groove could be disposed in a portion of the sole or another structural element disposed within the sole. The lever has a locked position and an unlocked position. The locking mechanism may further include a second mating groove for receiving and maintaining the lever in a second predetermined position. The locking mechanism may also include a detent and an engagement mechanism disposed adjacent the detent. The engagement mechanism has a notch that is engageable with the detent to help maintain the orientation of the insert and/or to indicate to a wearer the position of the insert. The locking mechanism may include a visual position indicator, an audible position indicator, or both. The locking mechanism may be at least partially disposed within a retainer ring circumscribing an end of the insert. The locking mechanism may be disposed on a medial side, lateral side, or heel portion of the article of footwear. 
     In additional embodiments, the adjustable cushioning system includes a casing disposed in the sole and defining a recess for receiving the insert. The casing may be a retainer ring that circumscribes an end of the insert. The adjustable cushioning system may include a second casing. The second casing may be a retainer ring that circumscribes an opposite end of the insert. In addition, the casing could be a first plate disposed above the insert and a second plate disposed below the insert and coupled to the first plate at an end thereof. In addition, the adjustable cushioning system may include a second insert adapted to be received in the aperture formed in the sole of the article of footwear and a second locking mechanism disposed proximate the second insert for maintaining the second insert in a predetermined position. The second insert has an anisotropic property about a longitudinal axis thereof and can be reoriented rotationally in the article of footwear to modify a performance characteristic thereof. The second insert may be oriented generally parallel to the first insert. 
     In additional embodiments, the insert may include a shaft generally longitudinally disposed therein. The shaft may be used to facilitate insertion, removal, and reorientation of the insert, for example. The insert may have a generally cylindrical shape and may define one or more generally longitudinally disposed apertures. The insert may further include a cap and/or an orientation indicator disposed on an end thereof. In still other embodiments, the insert includes an internal support and an external cushioning element disposed about at least a portion of the internal support. The external cushioning element may have a lower durometer than the internal support. The insert may include an axle disposed within the internal support. Also, the internal support may include a rib disposed on an external surface thereof. The internal support may have a cross-section, such as polygonal, arcuate, or combinations thereof, and may span an entire width of the insert. 
     In yet another aspect, the invention generally relates to an adjustable cushioning system for an article of footwear. The system includes an insert adapted to be received in an aperture formed in a sole of the article of footwear. The insert has an anisotropic property about a longitudinal axis thereof and can be reoriented rotationally in the article of footwear to modify a performance characteristic thereof. The anisotropic property can be selected from the group consisting of compressibility, resiliency, compliancy, elasticity, damping, energy storage, and stiffness. The insert can include an internal support and an external cushioning element disposed about at least a portion of the internal support. In one embodiment, the external cushioning element has a lower durometer than the internal support. 
     In various embodiments, the adjustable cushioning system includes an axle disposed within the internal support. The insert can have essentially any cross-sectional shape, such as polygonal, arcuate, or combinations of polygonal and arcuate elements. In the present application, the term polygonal is used to denote any shape including at least two line segments, such as rectangles, trapezoids, and triangles. Examples of arcuate shapes include circular and elliptical. In a particular embodiment, the insert has a generally cylindrical shape. The insert can include a handle disposed on an end thereof. Further, the external cushioning element and/or the internal support can include a generally longitudinally disposed aperture. In one embodiment, the aperture can be substantially parallel to the internal support. In another embodiment, the external cushioning element and/or the internal support can include a second generally longitudinally disposed aperture. In additional embodiments, the internal support can include one or more ribs disposed on an external surface thereof. The internal support can have a cross section that is polygonal, arcuate, or combinations thereof. The internal support can span substantially an entire width of the insert. 
     In addition, the adjustable cushioning system can include a structural support casing disposed in a sole of the article of footwear and defining a recess for housing the insert. The structural support casing may have a generally recumbent V or U-shaped cross-sectional profile. Furthermore, the adjustable cushioning system can include a second insert. The second insert can include an internal support and an external cushioning element disposed about at least a portion of the internal support. In an embodiment of the invention that includes a structural support casing, the second insert can be disposed in a second cylindrical recess in the structural support casing. 
     Furthermore, the adjustable cushioning system can be generally longitudinally disposed within the article of footwear and can extend from about the heel region to about an arch region of the article of footwear. Alternatively, the adjustable cushioning system can be generally laterally disposed within the article of footwear and can span substantially an entire width of the article of footwear. In addition, the insert can be diagonally disposed within the article of footwear. The inserts may be removable from the article of footwear so they can be replaced when they wear or when different inserts having different characteristics are desired. 
     In another aspect, the invention generally relates to an adjustable cushioning system for an article of footwear. The system includes an insert adapted to be received in an aperture formed in a sole of the article of footwear, where the insert can be reoriented rotationally in the article of footwear. Also included is a locking mechanism disposed proximate the insert for maintaining the insert in a predetermined angular orientation, where the locking mechanism includes an engagement mechanism for engaging a groove disposed in the insert. 
     In one embodiment, the locking mechanism further includes an actuator for actuating the locking mechanism between a locked position and an unlocked position. The locking mechanism can also be biased into a locked position. In another embodiment, the insert includes a generally cylindrical shape body and the groove circumscribes the insert at one of a proximal end and a distal end of the insert. In a further adaptation, the insert includes a slot disposed adjacent and in communication with the groove for accepting the engagement mechanism, thereby preventing rotation of the insert. In another embodiment, upon actuation of the actuator, the engagement mechanism moves out of the slot and into the groove, thereby allowing the insert to rotate within the sole of the article of footwear. A plurality of slots can also be disposed about the insert adjacent to and in communication with the groove, the slots defining a plurality of locking positions. The slots can also be equally spaced about a circumference of the insert. 
     In another embodiment, the actuator is a spring-loaded button and shaft arrangement. The engagement mechanism, in another embodiment, is disposed at a distal end of the shaft and includes a projection slidably disposed at least partially within the groove. In another adaptation of the invention, the insert includes an anisotropic property about a longitudinal axis, and a performance characteristic of the article of footwear can be modified by reorienting rotationally the insert within the sole. 
     The invention can also include a second insert adapted to be received in an aperture in the sole, the insert including a groove disposed therein for engaging the engagement mechanism of the locking mechanism. In one embodiment, the insert includes a structure for enabling a wearer to rotate the insert. In another embodiment, the structure includes a cap disposed on one end of the insert, the cap defining recesses for receiving the wearer&#39;s fingers. In other embodiments, the groove is disposed on an outer surface of the insert. 
     These and other objects, along with advantages and features of the present invention herein disclosed, will become apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which: 
         FIG. 1  is a schematic view of a medial side of an article of footwear including an adjustable cushioning system in accordance with the invention; 
         FIG. 2A  is a schematic perspective view of an adjustable cushioning system in accordance with the invention and having a single insert; 
         FIG. 2B  is a schematic perspective view of an adjustable cushioning system in accordance with the invention and having two inserts; 
         FIG. 2C  is a schematic end view of the adjustable cushioning system of  FIG. 2B ; 
         FIG. 2D  is a schematic top view of the adjustable cushioning system of  FIG. 2B ; 
         FIG. 2E  is an exploded perspective view of the adjustable cushioning system of  FIG. 2B ; 
         FIG. 2F  is a schematic perspective view of a portion of the adjustable cushioning system of  FIG. 2B  with the inserts removed; 
         FIGS. 3A–3C  are cross-sectional schematic views of various embodiments of one insert of  FIG. 2D  taken at line  3 — 3 ; 
         FIG. 4A  is a schematic end view of the adjustable cushioning system of  FIG. 2B  in a locked configuration; 
         FIG. 4B  is a schematic end view of the adjustable cushioning system of  FIG. 2B  in an unlocked configuration; 
         FIG. 5A  is a schematic perspective view of a positioning mechanism disposed in the adjustable cushioning system of  FIG. 2B , with the inserts removed; 
         FIG. 5B  is another schematic perspective view of the positioning mechanism of  FIG. 5A ; 
         FIG. 5C  is another schematic perspective view of the positioning mechanism of  FIG. 5A ; 
         FIG. 5D  is a partial exploded perspective view of the locking mechanism of  FIG. 4A  and the positioning mechanism of  FIG. 5A ; 
         FIG. 6A  is a partial exploded view of a lateral side of a heel assembly including the adjustable cushioning system of  FIG. 2B ; 
         FIG. 6B  is a partial exploded view of the medial side of the heel assembly of  FIG. 6A ; 
         FIG. 7  is an exploded perspective view of the sole of  FIG. 1  including the adjustable cushioning system of  FIG. 2B ; 
         FIG. 8A  is a schematic perspective view of an alternative embodiment of an insert in accordance with the invention; 
         FIG. 8B  is another schematic perspective view of the insert of  FIG. 8A , without an external cushioning element; 
         FIG. 8C  is a schematic perspective view of an end cap for use with the insert of  FIGS. 8A and 8B ; 
         FIG. 8D  is cross-sectional schematic view of the insert of  FIG. 8A  taken at line  8 D— 8 D; 
         FIG. 8E  is a cross-sectional schematic view of an alternative embodiment of an insert in accordance with the invention; 
         FIG. 8F  is a cross-sectional schematic view of another alternative embodiment of an insert in accordance with the invention; 
         FIG. 9A  is a schematic perspective view of another alternative embodiment of an insert in accordance with the invention; 
         FIG. 9B  is another schematic perspective view of the insert of  FIG. 9A , without an external cushioning element; 
         FIG. 9C  is a schematic perspective view of an end cap and axle for use with the insert of  FIGS. 9A and 9B ; 
         FIG. 9D  is cross-sectional schematic view of the insert of  FIG. 9A  taken at line  9 D— 9 D; 
         FIG. 10A  is a schematic front view of an alternative embodiment of an adjustable cushioning system in accordance with the invention; 
         FIG. 10B  is a schematic left side view of the adjustable cushioning system of  FIG. 10A ; 
         FIG. 10C  is a schematic right side view of the insert of  FIG. 10A ; 
         FIG. 10D  is a cross-sectional schematic view of the insert of  FIG. 10A  taken at line  10 D— 10 D; 
         FIG. 11A  is a schematic view of an article of footwear including an embodiment of an adjustable cushioning system in accordance with the invention disposed within a sole; 
         FIG. 11B  is a partially exploded perspective view of the sole and adjustable cushioning system of  FIG. 11A ; 
         FIG. 12  is a partially exploded perspective view of the sole of  FIG. 11B  including another embodiment of an adjustable cushioning system in accordance with the invention; 
         FIG. 13  is a partially exploded perspective view of the sole of  FIG. 11B  including another embodiment of an adjustable cushioning system in accordance with the invention; 
         FIGS. 14A–14F  are schematic rear views of an article of footwear with an adjustable cushioning system disposed therein in various rotational orientations; 
         FIGS. 15A and 15B  are schematic perspective views of an alternative embodiment of a casing for receiving an adjustable cushioning system in accordance with the invention; 
         FIG. 16  is an exploded perspective view of a casing and a single insert; 
         FIG. 17  is an exploded perspective view of a sole of a shoe including an alternative embodiment of an adjustable cushioning system and a locking mechanism in accordance with the invention; 
         FIG. 18  is a schematic perspective view of a portion of the locking mechanism of  FIG. 17 ; 
         FIG. 19  is an enlarged schematic perspective view of a portion of the locking mechanism of  FIG. 17 , showing the locking mechanism in further detail; and 
         FIG. 20  is an enlarged schematic plan view of a portion of the locking mechanism of  FIG. 17  showing a locking slot and groove. 
     
    
    
     DESCRIPTION 
       FIG. 1  depicts a medial side of an article of footwear  10  including an embodiment of an adjustable cushioning system  12  in accordance with the invention. Generally, the article of footwear  10  includes an upper  14  and a sole  16 . The sole  16  includes a heel region  18 , an arch region  17 , and a forefoot region  19 . The adjustable cushioning system  12  is shown disposed generally in the heel region  18  of the sole  16 ; however, the adjustable cushioning system  12  could be disposed anywhere along the length and width of the article of footwear  10 . Additionally, the adjustable cushioning system  12  shown includes two inserts  20 , as shown in greater detail in  FIG. 2B ; however, the adjustable cushioning system  12  could include a single insert  20  or more than two inserts  20 , as necessary, to suit a particular application. In addition, an upper plate  50  and a lower plate  52  are shown and are described in greater detail hereinbelow. 
       FIGS. 2A–2F  depict various embodiments and views of the adjustable cushioning system  12 .  FIG. 2A  depicts an adjustable cushioning system  12  having a single insert  20 . The insert  20  includes a first end  22  and a second end  24 . A first optional casing  26  is disposed about the first end  22  of the insert  20  and a second optional casing  28  is disposed about the second end  24  of the insert  20 . The optional casings  26 ,  28  act to stiffen and support the insert  20  within the adjustable cushioning system  12 . In one embodiment, the casings  26 ,  28  are flexible and compress with the inserts  20 . The insert  20  can be retained in the casings  26 ,  28  by frictional engagement or other mechanical means. In one embodiment, the casings  26 ,  28  are rigidly mounted within the sole  16  and the insert  20  is rotatably inserted into the casings  26 ,  28 . Located at the first end  22  is an optional locking mechanism  30  for positively maintaining the insert  20  in a predetermined orientation within the adjustable cushioning system  12  and, correspondingly, the article of footwear  10 . In an alternative embodiment, the insert  20  may be retained in place by a frictional fit. Depending on the aggressiveness of use, however, the insert  20  may rotate within the sole to achieve a position of lesser resistance and therefore, use of the locking mechanism may be advantageous. The locking mechanism  30  is described hereinbelow in greater detail with respect to  FIGS. 4A ,  4 B, and  5 A– 5 D. 
       FIG. 2B  depicts the adjustable cushioning system  12  of  FIG. 1 . The adjustable cushioning system  12  includes two inserts  20  disposed generally parallel to one another. In this embodiment, an optional casing  27  is disposed about the first end  22  of each insert  20 . The casing  27  is essentially two retainer rings  31  circumscribing the first ends  22  of the inserts  20 . A second optional casing  29  is shown disposed about the second end of each insert  20 . Each casing  27 ,  29  could be a single integral piece or separate pieces coupled together. The casings  27 ,  29  act to stiffen and support the insert  20  within the adjustable cushioning system  12 . In one embodiment, the casings  27 ,  29  are flexible and compress with the inserts  20 . In an embodiment with two or more inserts  20 , the casings  27 ,  29  also maintain the inserts  20  in their proper positions relative to one another. 
       FIGS. 2C and 2D  are an end view and a top view of the adjustable cushioning system of  FIG. 2B , respectively.  FIG. 2C  depicts the first ends  22  of the inserts  20  and the locking mechanisms  30  disposed thereon. Each locking mechanism  30  includes a lever  32  coupled to a hub  35  and seated within a groove  33 . The locking mechanism  30  is described in greater detail with respect to  FIGS. 4A ,  4 B, and  5 A– 5 D.  FIG. 2D  depicts the adjustable cushioning system  12  having two inserts  20  disposed generally parallel to one another.  FIG. 2D  depicts optional end caps  44 ,  46  disposed on the ends  22 ,  24  of the inserts  20 . Optionally, end caps  44 ,  46  can give the inserts  20  additional support and provide a more finished or ornamental appearance. Additionally, the end caps  44 ,  46  can include indicia relating to the orientation or performance characteristics of the inserts  20 . 
       FIG. 2E  is an exploded perspective view of the adjustable cushioning system  12 . The system  12  includes two inserts  20 , end caps  44 ,  46  disposed on the ends of each insert  20 , and casings  27 ,  29  disposed about the ends of the inserts  20 . The casings  27 ,  29  include retainer rings  31  that circumscribe the ends of the inserts  20 . Also depicted proximate the first end  22  of the adjustable cushioning system  12  are the locking mechanisms  30  that include levers  32 , pins  37 , and shafts  34 . The shafts  34  extend substantially along the entire length of the inserts  20  and include hubs  35  disposed on one end for receiving the pins  37  that pivotably couple the levers  32  to the shafts  34 . In addition, various components of a positioning mechanism  40  are depicted. The positioning mechanism  40  ( FIGS. 5A–5D ) includes a detent assembly  36  and two ratchet wheels  38  disposed at the ends of the inserts  20 . The positioning mechanism  40  may be sized and configured to assist the locking mechanism  30  to maintain the inserts  20  in predetermined orientations and/or provide tactile and audible feedback to a wearer as to the orientation of the inserts  20 .  FIG. 2F  is a partial perspective view of the adjustable cushioning system  12  without the inserts  20  shown.  FIG. 2F  depicts the first end  22  including the casing  27 , the locking mechanisms  30 , and the shafts  34  extending therefrom. 
       FIGS. 3A–3C  are cross-sectional views of various embodiments of the insert  20 .  FIG. 3A  depicts an insert  20  having a generally circular cross-section and an outer wall  58  and a skeletal element  56  defining two apertures  54 . The apertures  54  can extend substantially the entire length of the insert  20 . The apertures  54  shown have generally arcuate, D-shaped cross-sections; however, the apertures  54  could be essentially any polygonal and/or arcuate shape. Additionally, the apertures  54  could be filled with a foam material.  FIG. 3B  depicts an alternative embodiment of an insert  120 . The insert  120  has a generally circular cross-section and an outer wall  158  and two skeletal elements  156  defining three apertures  154 .  FIG. 3C  depicts another alternative embodiment of an insert  220 . The insert  220  has a generally circular cross-sectional shape and is a substantially solid (foamed or non-foamed) piece defining an elongate aperture  254 . The apertures  54 ,  154 ,  254  and skeletal elements  56 ,  156  define, at least in part, the anisotropic properties of the inserts  20 ,  120 ,  220 . The insert  20 ,  120 ,  220  is stiffest, i.e. most difficult to compress, when in a vertical orientation (as shown) and provides the softest cushioning, i.e., easiest to compress, when rotated 90 degrees to a horizontal orientation. Specifically, the insert  20 ,  120 ,  220  has a greater resistance to a force applied as shown by arrows  60 ,  160 ,  260 , and thereby a firmer “ride,” than when exposed to a force applied as shown by arrows  62 ,  162 ,  262 . In other words, the insert  20  is firmest in response to a force applied parallel to the skeletal element  56  (arrows  60 ), as opposed to a force applied perpendicular to the skeletal element  56  (arrows  62 ). 
       FIGS. 4A and 4B  depict enlarged side views of the adjustable cushioning system  12  of  FIG. 1 .  FIG. 4A  depicts the locking mechanism  30  in a locked position and  FIG. 4B  depicts the locking mechanism  30  in an unlocked or open position. In the embodiment shown, the locking mechanism  30  has two locked orientations. The first (and shown) orientation is about −45 degrees relative to a vertical axis  42 . The second orientation is located at about +45 degrees relative to the vertical axis  42 . These two orientations allow for 90 degrees of rotation of the inserts  20  relative to the article of footwear. For example, and with reference to  FIGS. 3A–3C , the insert  20  can be rotated to and locked in the vertical position or the horizontal position. Alternatively, the insert  20  could have essentially any number of orientations in which the insert  20  can be locked, as desired. 
     The locking mechanism  30  depicted is a dual position mechanism configured to provide a toggle function, i.e., the mechanism  30  is stable in either open or closed positions. The lever  32  is coupled to the hub  35  and, correspondingly to the insert  20 , by a pin  37 . The pin  37  is coupled to the lever  32  via holes  64  disposed in the lever  32 . The pin  37  may be held in place by bonding, frictional engagement, or other mechanical means. Other types of actuators and other methods of coupling the lever  32  to the insert  20  are contemplated and within the scope of the invention. The pin  37  may be made of spring steel and may have a slight bend to effect the toggle function of the lever  32 . 
     To unlock and orient the insert  20 , the wearer lifts the lever  32  out of the groove  33  to the unlocked position. In the unlocked position, the lever  32  extends outwardly away from the insert  20 . The wearer can use the lever  32  as a handle to rotate the hub  35  and shaft  34  into the desired orientation. The insert  20  rotates with the hub  35  and shaft  34 . The insert  20  can include an anti-friction coating that can assist the rotation of the insert  20 . In the embodiment shown, the grooves  33  are located in the casing  27  corresponding to various predetermined angular orientations of the inserts  20 . To lock the insert  20  into the desired orientation, the wearer pivots the lever  32  so as to be generally flush with the sole  16  and into the groove  33 . The groove  33  acts as a stop to prevent rotation of the lever  32 , thereby preventing the insert  20  from rotating when in the locked position. 
       FIGS. 5A–5D  are perspective views of the positioning mechanism  40 . In the embodiment shown, the positioning mechanism  40  is at least partially disposed within the casing  27  located at the first end  22 ; however, the positioning mechanism  40  could be disposed on either end of the adjustable cushioning system  12 . The positioning mechanism  40  includes a detent assembly  36  that is disposed within the casing  27  between the two retainer rings  31 . The assembly  36  includes two detents  39 , one disposed adjacent each retainer ring  31 . The positioning mechanism  40  also includes a ratchet wheel  38  for each insert  20  that provides an audible and physical indication of orientation to the wearer. The positioning mechanism  40  depicted includes two ratchet wheels  38  that are generally circular in cross-section and are disposed generally concentrically with the retainer rings  31  of the casing  27 . The ratchet wheel  38  may, in one embodiment, circumscribe an end of the insert  20 . The ratchet wheel  38  includes four notches  41  disposed equidistantly about the ratchet wheel  38 . The notches  41  correspond to various predetermined orientations of the insert  20  and engage the detents  39  to indicate (audibly and/or physically) to the wearer when the insert  20  is in a desired orientation. 
       FIG. 5C  depicts the engagement mechanism assembly  40  with one ratchet wheel  38  removed. It can be seen that the detent  39  extends into the retainer ring  31  of the casing  27 . Also shown are the lever  32  and pin  37  components of the locking mechanism  30 .  FIG. 5D  is an exploded view of the components of the locking mechanism  30  and the positioning mechanism  40 . The lever  32  is configured to fit substantially flush with the end cap  46 . In operation, the ratchet wheel  38  is coupled to the lever  32 , such that rotation of the lever  32  and insert  20  causes the ratchet wheel  38  to rotate. The notches  41  engage the detents  39  as the insert  20  and ratchet wheel  38  rotate. Once the wearer has reached the desired orientation, as indicated by the audible and/or tactile feedback of the positioning mechanism  40 , the wearer can return the lever  32  to the locked position. In an alternative embodiment, the positioning mechanism  40  and the locking mechanism  30  can be located on opposite ends of the adjustable cushioning system  12 . For example, the locking mechanism  30  can be located on the medial side of a shoe and the positioning mechanism  40  can be located on the lateral side of the shoe. 
       FIGS. 6A and 6B  depict partially exploded views of the heel  18  of  FIG. 1 , as seen from the lateral side and the medial side, respectively. In one embodiment, the adjustable cushioning system  12  is disposed between an upper plate  50  and a lower plate  52 . The upper plate  50  and the lower plate  52  may provide structural support and stability for the article of footwear  10  and may house and protect the adjustable cushioning system  12 . The plates  50 ,  52 , in one embodiment, may be coupled forward of the adjustable cushioning system  12  (see  FIG. 1 ). Coupling the plates  50 ,  52  can provide greater structural stability to the article of footwear and can create a tunnel torsion element  66  in the shank area  68  ( FIG. 1 ) of the sole  16 . The plates  50 ,  52  can form a single, recumbent V or U-shaped housing. The upper plate  50  may include a heel counter formed in a top surface thereof and/or projections on a bottom surface thereof that engage at least one of the casings  27 ,  29 . The lower plate  52  can lock the inserts  20  and system  12  in place relative to the sole  16 . Additionally, because the lower plate  52  can provide structural support to the article of footwear, less material may be necessary for the outsole. For example, the lower plate  52  can be insert injection molded with one or more rubber outsole elements. Additionally, the lower plate  52  can be transparent to allow a wearer visual access to the adjustable cushioning system  12 . 
       FIG. 7  depicts the sole  16  of  FIG. 1 . In addition to the adjustable cushioning system  12  and plates  50 ,  52  described hereinabove, the sole  16  can include heel outsole elements  70 , a forefoot outsole  74 , a heel strike cushioning element  72 , and a midsole  76 . 
       FIGS. 8A–8D  depict an alternative embodiment of an adjustable cushioning system  800  in accordance with the invention. The adjustable cushioning system  800  includes one or more inserts  810 .  FIG. 8A  is a perspective schematic view of the insert  810  including an end cap  812 , an internal support  814 , and an external cushioning element  816 . The insert  810  has a dual density construction, where the internal support  814  and external cushioning element  816  are manufactured from materials of differing durometer. The term “dual density” is used herein according to its ordinary meaning, e.g., the insert includes two materials of differing density. The term dual density is, however, also used to cover an insert comprising a single material surrounding a void(s), such that the insert exhibits anisotropic characteristics. 
     The internal support  814  extends axially from the end cap  812  and the external cushioning element  816  is disposed about at least a portion of the internal support  814 . The insert  810  has a generally cylindrical shape in the embodiment shown; however, the shape can be chosen to suit any particular application. 
     The end cap  812  ( FIG. 8C ) is optional and can be disposed at either one and/or both ends of the insert  810 . As shown, the end cap  812  is disposed at the proximal end  817  of the insert  810 . The end cap  812  is substantially cylindrical in shape. The end cap  812  has a lip  813  that defines a recess  815 . The end cap  812  can function as structural support for the insert  810  and/or serve an aesthetic purpose. For example, the end cap  812  can be used as a handle to rotate and/or remove the insert  810  from an article of footwear. In addition, the end cap  812  could include a locking mechanism to hold the insert  810  in place within the article of footwear. The end cap  812  can also include indicia on an outer surface thereof that indicates the orientation of the insert  810  within the article of footwear. 
       FIG. 8B  is a perspective schematic view of the end cap  812  and internal support  814  extending axially therefrom. The internal support  814  is coupled to the end cap  812  by frictional engagement and/or an interference fit. Alternatively, the internal support  814  may be held in place by adhesive bonding, solvent bonding, mechanical retention, or similar techniques. Typically, the internal support  814  fills the recess  815  and may be bonded to the lip  813  and/or the recess  815 . Alternatively, the internal support  814  is not coupled to the end cap  812 . The internal support  814  can have a cross-sectional shape, such as polygonal, arcuate, or combinations thereof. In the embodiment shown in  FIG. 8B , the internal support  814  is substantially rectangular in shape and extends the entire length and width of the insert  810 . Typically, the internal support  814  is made of a high durometer dense foam or a substantially rigid material. Generally, the internal support  814  is made of a harder material than the external cushioning element  816 . 
     The external cushioning element  816  is shown as two separate pieces, one disposed on each side of the internal support  814 ; however, the external cushioning element  816  can be a single piece that completely surrounds the internal support  814 . The external cushioning element  816  is affixed to the internal support  814  by adhesive bonding, solvent bonding, mechanical retention, or similar techniques. The external cushioning element  816  extends from the cap  812  and has a length that is slightly less than the length of the internal support  814 . The external cushioning element  816 , however, can extend the entire length of the internal support  814  or be longer than the internal support  814 . The external cushioning element  816  shown has a chamfer  823  disposed at its distal end  819 . Typically, the external cushioning element  816  is made of a soft foam and has a durometer less than that of the internal support  814 . 
       FIG. 8D  is a cross-sectional schematic view of the insert  810  of  FIG. 8A  taken at line  8 D— 8 D. The insert  810  has a generally circular cross-section while the internal support  814  has a generally rectangular cross-section and spans substantially the entire width of the insert  810 . The external cushioning element  816  is disposed on both sides of the internal support  814 . 
       FIGS. 8E and 8F  depict schematic cross-sectional views of alternative inserts  860 ,  870 . In  FIG. 8E , the internal support  864  has an elliptical cross-sectional shape and the external cushioning element  866  surrounds the internal support  864 . The external cushioning element  866  also includes an aperture  868  located on one side of the internal support  864 . The aperture  868  can extend substantially the entire length of the external cushioning element  866  and can run generally parallel to the internal support  864 . The aperture  868  shown has a generally rectangular cross-sectional shape; however, the aperture  868  could be essentially any polygonal and/or arcuate shape. Alternatively, a second aperture  868  could be located on the other side of the internal support  864 . In  FIG. 8F , the internal support has been removed. The external cushioning element  876  has two apertures  878  generally longitudinally disposed therein. The apertures  878  are “crescent” shaped and run generally parallel to the external cushioning element  876 . Alternatively, the apertures  878  could be “kidney” shaped. In this embodiment, the insert  870  is stiffest, i.e. most difficult to compress, when in the vertical orientation shown in  FIG. 8F . The insert  870  provides the softest cushioning, i.e., easiest to compress, when rotated 90 degrees so that the apertures  878  are oriented one above the other. 
       FIGS. 9A–9C  are perspective schematic views of an alternative insert design. The size, shape, and material choices for the insert  910  and its various components are essentially the same as those discussed above with respect to  FIGS. 8A–8D . The insert  910  includes an end cap  912 , an internal support  914 , an external cushioning element  916 , and an axle  918 . The axle  918  is bonded to the end cap  912  and extends axially therefrom. Alternatively, the axle  918  could be integrally formed with the end cap  912 . The axle  918  is a generally thin, elongate element that adds stiffness to the internal support  914 . The axle  918  can include one or more apertures  925  disposed along its length to reduce weight. The size, shape, and number of apertures can be varied to suit a particular application. The internal support  914  is disposed about the axle  918 . In the embodiment shown, the internal support  914  is supported by the axle  918  and does not contact the end cap  912 . The internal support  914  has a series of three ribs  920  disposed on each side thereof. 
       FIG. 9D  is a cross-sectional schematic view of the insert  910  of  FIG. 9A  taken at line  9 D— 9 D. The insert  910  has a generally circular cross-section while the internal support  914  has a generally rectangular cross-section and spans substantially the entire width of the insert  910 . The internal support  914  surrounds the axle  918  and includes three ribs  920  disposed equidistantly on each side of the internal support  914 . The ribs  920  are generally arcuate in shape. The number, shape, size, and placement of the ribs  920  can be varied to suit a particular application. The external cushioning element  916  includes two pieces, with one piece disposed on each side of the internal support  914 . As discussed above with respect to  FIGS. 8E and 8F , the external cushioning element  916  can include one or more apertures disposed therein. 
     The various components of the adjustable cushioning systems described herein can be manufactured by, for example, injection molding or extrusion and optionally a combination of subsequent machining operations. Extrusion processes may be used to provide a uniform shape, such as a single monolithic frame. Insert molding can then be used to provide the desired geometry of the open spaces, or the open spaces could be created in the desired locations by a subsequent machining operation. Other manufacturing techniques include melting or bonding additional portions. For example, the internal walls or skeletal elements  56 ,  156  may be adhered to the insert  20 ,  120  with a liquid epoxy or a hot melt adhesive, such as ethylene vinyl acetate (EVA). In addition to adhesive bonding, components can be solvent bonded, which entails using a solvent to facilitate fusing of various components. In another example, the end cap  912  could be fused to the internal support  914  during a foaming process, or could be integrally formed with the axle  918 . 
     The various components can be manufactured from any suitable polymeric material or combination of polymeric materials, either with or without reinforcement. Suitable materials include: polyurethanes, such as a thermoplastic polyurethane (TPU); EVA; thermoplastic polyether block amides, such as the Pebax® brand sold by Elf Atochem; thermoplastic polyester elastomers, such as the Hytrel® brand sold by DuPont; thermoplastic elastomers, such as the Santoprene® brand sold by Advanced Elastomer Systems, L.P.; thermoplastic olefin; nylons, such as nylon 12, which may include 10 to 30 percent or more glass fiber reinforcement; silicones; polyethylenes; acetal; and equivalent materials. Reinforcement, if used, may be by inclusion of glass or carbon graphite fibers or para-aramid fibers, such as the Kevlar® brand sold by DuPont, or other similar method. Also, the polymeric materials may be used in combination with other materials, for example rubber. Other suitable materials will be apparent to those skilled in the art. 
     The insert  20  can be made of one or more various density foams, non-foamed polymer materials, and/or skeletal elements. In an optional embodiment, an external surface  21  of the insert  20  may be coated with an anti-friction coating, such as a paint including Teflon® material sold by DuPont or a similar substance. The insert  20  can be color coded to indicate to a wearer the specific performance characteristics of the insert  20 . The size and shape of the insert  20  and the casings  26 ,  28  can vary to suit a particular application. The inserts can be about 10 mm to about 40 mm in diameter, preferably about 20 mm to about 30 mm, and more preferably about 25 mm. The length of the insert  20  can be about 50 mm to about 100 mm, preferably about 75 mm to about 90 mm, and more preferably 85 mm. The casings  26 ,  27 ,  28 ,  29  can be about 5 mm to about 20 mm deep, preferably about 8 mm to about 12 mm, and more preferably about 10 mm. The inside diameter of the retainer rings  31  is about 10 mm to about 40 mm, preferably about 20 mm to about 30 mm, and more preferably about 25 mm. 
     In addition, the insert  810  can be integrally formed by a process called reverse injection, in which the external cushioning element  816  itself forms the mold for the internal support  814 . Such a process can be more economical than conventional manufacturing methods, because a separate internal support  814  mold is not required. The insert  810  can also be formed in a single step called dual injection, where two or more materials of differing densities are injected simultaneously to create integrally the external cushioning element  816  and the internal support  814 . The materials chosen for the various insert components should be “compatible,” such that the various components are able to chemically bond to each other at discrete mating locations. In various embodiments, the insert  20  could be a dual density polyurethane foam (40 and 75 asker Shore C hardnesses) or an extruded thermoplastic olefin, for example. The casings  26 ,  27 ,  28 ,  29  could be made of Pebax and the plates  50 ,  52  could be injection molded TPU. 
       FIGS. 10A–10D  depict another alternative embodiment of an insert  1010  in accordance with the invention. The insert  1010  includes two optional end caps  1012  and an internal support  1014  surrounded by an external cushioning element  1016 . The end cap  1012  located at the distal end  1019  of the insert  1010  includes an orientation indicator  1028  disposed thereon. The indicator  1028  ( FIG. 10B ) can be formed in the end cap  1012  or can be indicia printed on the end cap  1012  that indicates to the wearer the orientation of the insert  1010  within the article of footwear. In an alternative embodiment, the end cap  1012  could include a locking mechanism to hold the insert  1010  in place within the article of footwear. A semi-circular handle  1024  ( FIG. 10C ) is located on the proximal end  1017  of the insert  1010 . The handle  1024  can be formed as part of the end cap  1012  or can be mechanically coupled to the end cap  1012 . Alternatively, the handle  1024  can be integrally formed or coupled to the internal support  1014  and/or external cushioning element  1016  and can pass through an opening in the end cap  1012 . In a particular embodiment, the handle  1024  is an extension of the internal support  1014  and there is no end cap  1012  disposed on the proximal end  1017  of the insert  1010 . The handle  1024  can be used by the wearer to rotationally orient the insert  1010  within the article of footwear and/or remove the insert  1010  from the article of footwear. In alternative embodiments, the handle  1024  and orientation indicator  1028  can be located on the same end of the insert  1010 . In one embodiment, the handle  1024  can form at least a portion of the orientation indicator  1028 . In addition, the insert  1010  and/or end caps  1012  can be visible to an observer and can indicate to the observer what type of insert  1010  is installed in the footwear. Also, the insert  1010  and/or end caps  1012  can have decorative features. As shown in  FIG. 10D , the insert  1010  has a generally circular cross-section and the internal support  1014  has a cross-section including polygonal and arcuate elements. The external cushioning element  1016  surrounds the internal support  1014 . 
       FIGS. 11A and 11B  depict an article of footwear  1160  including an upper  1162 , a sole  1164 , and an adjustable cushioning system  1112  in accordance with the invention. FIG.  11 A is a schematic side view of the article of footwear  1160 . The adjustable cushioning system  1112  includes two inserts  1120  generally laterally disposed in a heel region  1168  of the sole  1164 . The inserts  1120  can span substantially the entire width of the article of footwear  1160 . In one embodiment, the sole  1164  can include an outsole  1170  and a midsole  1166 , and the system  1112  can be disposed at least partially within the midsole  1166 . Typically, the inserts  1120  are laterally disposed within the article of footwear  1160  for running and to adjust the roll of the footwear  1160 . 
       FIG. 11B  is a perspective schematic view of the sole  1164  of the article of footwear  1160  of  FIG. 11A  with the inserts  1120  removed. The inserts  1120  could be any of the types described hereinabove. The inserts  1120  are shown in different orientations. As will be discussed later with respect to  FIGS. 14A–14F , the orientation of the insert  1120  affects the performance characteristics of the article of footwear  1160 . The insert  1120  is coupled to the article of footwear  1160  by frictional engagement and/or interference fit. Other ways of coupling the insert  1120  to the article of footwear  1160  are possible, as long as the insert  1120  maintains a secure, but rotatable fit within the article of footwear  1160 . 
       FIG. 12  depicts an alternative embodiment of an adjustable cushioning system  1212  disposed in the sole  1164  of  FIG. 11B . The adjustable cushioning system  1212  is shown removed and includes two inserts  1220  generally longitudinally disposed in a heel region  1168  of the sole  1164 . Typically, the inserts  1220  are longitudinally disposed within the sole  1164  to control pronation and/or supination. The inserts  1220  can be inserted through the back of the heel region  1168  and extend to about the arch region  1172  of the sole  1164 . The length of the insert  1220  and its position within the sole  1164  can vary to suit a particular application and/or a particular type of article of footwear. For example, the insert  1220  may not extend beyond the heel region  1168 . In one embodiment, the sole  1164  can include an outsole  1170  and a midsole  1166 , and the system  1212  can be disposed at least partially within the midsole  1166 . Alternatively, the adjustable cushioning system  1212  can include only a single insert  1220  disposed either on-center or offset from the midline of the sole  1164 . 
       FIG. 13  depicts the sole  1164  of  FIG. 11B  and another alternative embodiment of an adjustable cushioning system  1312 . The adjustable cushioning system  1312  is shown removed from the sole  1164 . The adjustable cushioning system  1312  includes a single insert  1320  generally diagonally disposed in the heel region  1168  of the sole  1164 . The insert  1320  shown includes a casing  1326 ,  1328  located on each end. The insert  1320  can span substantially the entire width of the sole  1164 . In one embodiment, the adjustable cushioning system  1312  can be disposed at least partially within a midsole. In another embodiment, the insert  1320  can be positioned diagonally across the heel strike zone of the sole  1164 . 
       FIGS. 14A–14F  are rear views of a right footed article of footwear  1460  in accordance with the invention. The article of footwear  1460  includes an upper  1462 , a sole  1464 , and an adjustable cushioning system  1412  with two inserts  1420  generally longitudinally disposed within a heel region  1468  of the sole  1464 . In various embodiments, the system  1412  could include only one insert  1420  or more than two inserts  1420 , and the inserts  1420  could be generally laterally or diagonally disposed in the sole  1464 . Each view represents a possible combination of insert orientations. The examples shown are not meant to be exhaustive and other combinations are possible. The wearer can customize the level of cushioning in the footwear  1460  by rotating the insert  1420  relative to the article of footwear  1460 . Additionally, inserts  1420  having different properties can be substituted for further customization of the article of footwear  1460 . 
     In  FIG. 14A , the inserts  1420 , as represented by orientation indicators  1428 , are both in a “vertical” position, i.e. perpendicular to the ground, which results in the firmest possible cushioning. The internal structure, for example the skeletal element(s)  56 , act as joists to increase support and stiffen the ride of the article of footwear  1460 .  FIG. 14B  depicts both inserts  1420  in a “horizontal” position, i.e., parallel with the ground, which results in the softest cushioning. In the horizontal position, the insert  1420  allows the article of footwear  1460  more flex. The wearer can further customize the performance characteristics of the article of footwear  1460  by positioning each insert  1420  between the horizontal position and the vertical position. 
       FIGS. 14C and 14D  depict two other possible combinations where the inserts  1420  are oriented symmetrically. In both views, the inserts  1420  are positioned at about 45 degrees to normal, resulting in a moderate amount of cushioning. 
     Alternatively, the inserts  1420  can be oriented in non-symmetrical positions, as shown in  FIGS. 14E and 14F . In  FIG. 14E , the insert  1420  located on the medial side  1474  is oriented to maximize the stiffness of the medial side  1474  of the sole  1464  relative to the lateral side  1476  of the sole  1464 , where the insert  1420  is oriented to maximize cushioning. In such an arrangement, the increased stiffness on the medial side  1474  helps to prevent pronation. The wearer can vary the position of the insert  1420  to vary the amount of compensation for pronation. 
     In  FIG. 14F , the insert  1420  located on the lateral side  1476  is oriented to maximize the stiffness of the lateral side  1476  of the sole  1464  relative to the medial side  1474  of the sole  1464 , where the insert  1420  is oriented to maximize cushioning. In such an arrangement, the increased stiffness on the lateral side  1476  helps to prevent supination. The wearer can vary the position of the insert  1420  to vary the amount of compensation for supination. 
       FIGS. 15A and 15B  are top and bottom perspective schematic views, respectively, of an alternative casing  1540  for use with an adjustable cushioning system  1512  ( FIG. 16 ) in accordance with the invention. The casing  1540  is typically disposed in a heel region of the article of footwear and may provide stability and support to the wearer&#39;s foot, while the inserts  1520  provide the adjustable cushioning. The casing  1540  is a substantially recumbent U-shape with a top platform  1542 , a bottom platform  1544 , and two recesses  1546  generally laterally disposed within the casing  1540  for receiving the two inserts  1520 . Alternatively, the casing  1540  can have one recess  1546  or more than two recesses  1546 , depending on the number of inserts  1520  that make up a particular embodiment of the adjustable cushioning system  1512 . Also, the casing size and shape can vary to suit a particular application and/or a particular type of article of footwear. The casing  1540  has an optional aperture  1548  generally centrally disposed in the top platform  1542  and an optional slot  1552  that runs generally longitudinally along the bottom platform  1544 . In the embodiment shown, the slot  1552  runs along the bottom platform  1544  and up to the top platform  1542 . The casing  1540  can include stiffening ribs  1550  that hold the inserts  1510  in place, while adding stiffness to the overall casing  1540 . The casing  1540  can also be manufactured of any of the materials and any of the processes discussed hereinabove. 
       FIG. 16  is an exploded perspective view of an adjustable cushioning system  1512  in accordance with the invention. The system  1512  includes an insert  1520  and a casing  1540 . The casing  1540  is a single molded piece with a single, laterally disposed recess  1546  for receiving the insert  1520 . Alternatively, the recess  1546  and insert  1520  could be longitudinally or angularly disposed within the casing  1540 . 
       FIG. 17  is an exploded perspective view of a sole of a shoe including an alternative embodiment of an adjustable cushioning system  1612  and a locking mechanism  1630  in accordance with one embodiment of the invention. The cushioning system  1612  is similar to the cushioning systems described hereinabove. For example, the cushioning system  1612  is disposed below the midsole  1676  in the heel region  1618  of the sole  1616  between an upper plate  1650  and a lower plate  1652 . The locking mechanism  1630  can be used on any type of removable or rotatable insert, for instance a generally cylindrically shaped isotropic type insert that is made of a single type of foam material having a constant durometer throughout. The locking mechanism  1630  includes an actuator  1680 , a spring loaded shaft  1682  coupled to the actuator  1680 , and an engagement mechanism, such as a pair of forks  1684  coupled to the spring loaded shaft  1682 . Also included as part of the locking mechanism  1630  is a groove  1686  ( FIG. 20 ) that is disposed circumferentially about a distal end  1621  of the insert  1620 . Adjacent to the groove  1686  are a plurality of locking slots  1688 . When the locking mechanism  1630  is in the unlocked position, the forks  1684  are received in the groove  1686 . In the locked position, the forks  1684  are received in the locking slots  1688 , which prevent rotation of the inserts  1620  within the cushioning system  1612 . Also included as part of the locking mechanism  1630  are a pair of rings  1609  disposed on the upper plate  1650  that accept the spring loaded shaft  1682  to secure the spring loaded shaft  1682  in the shoe. 
     With reference to  FIGS. 18–20 , to unlock the locking mechanism  1630  and rotate the inserts  1620  to a new position within the retainer rings  1631  of the casing  1627 , a wearer of the shoe activates the actuator  1680 , for example a button. In the illustrated embodiment, the actuator  1680  is located on the lateral side of the shoe. Pressing and holding the button  1680  causes the spring loaded shaft  1682  along with the forks  1684 , which are coupled to the shaft  1682 , to advance (arrow  1683 ) towards the medial side of the shoe. As the shaft  1682  and the forks  1684  advance, the forks  1684  disengage the locking slots  1688  and engage the groove  1686  circumscribing the insert  1620 . When the forks  1684  engage the groove  1686 , the wearer can rotate the inserts  1620  to a desired position by using any of the positioning mechanisms  1640  previously described. In the embodiment shown, a positioning mechanism, such as a cap  1640  disposed on one end of the insert  1620  (proximal end  1622 ), is adapted to accommodate a wearer&#39;s fingers for turning the insert  1620 . For example, the cap  1640  may include recesses  1641  for accepting the wearer&#39;s fingers. In an alternative embodiment, the position of the locking mechanism  1630  can be reversed, such that the actuator  1680  is located on the medial side of the shoe and the forks  1684  move towards the lateral side of the shoe when actuated. In this reversed arrangement, the groove  1686  circumscribes the proximal end  1622  of the insert  1620 . 
     Once the user has rotated the inserts  1620  to a desired position, the wearer releases the button  1680 , causing the spring loaded shaft  1682  to move back towards the lateral side of the shoe, as a result of the force applied by the spring  1685 . If either insert  1620  is not aligned in a predefined position, such that the corresponding fork  1684  aligns with the locking slot  1688 , the wearer rotates the insert  1620  until the corresponding fork  1684  springs back into the locking slot  1688 . When the forks  1684  are aligned with the locking slots  1688 , releasing the button  1680  causes the inserts  1620  to be locked in that position. In one embodiment, there are four locking positions equally spaced about each insert  1620 . Each 90 degree turn of the insert  1620  enables the wearer to utilize a different locking position, with each locking position corresponding to the points at which the locking slots  1688  and forks  1684  engage. In other embodiments, fewer or more than four locking positions can be provided, depending on the number of adjustment positions available to the wearer. In one embodiment, the insert  1620  is rotatable 360 degrees and the groove  1686  circumscribes the entire insert  1620 . In another embodiment, the groove  1686  circumscribes only a portion of the insert  1620 , which correspondingly limits the amount of adjustability of the adjustable cushioning system  1612 . 
     The locking mechanism  1630  of the current embodiment simplifies and reduces the time required to manufacture the shoe of the present invention. For instance, a shaft is no longer required to run through the center of the inserts  1620 , since the recesses located near the end portions of the inserts  1620  enable the inserts  1620  to be locked in place. Another advantage is that the wearer is less likely to damage the locking mechanism by forcing the inserts  1620  to turn through an angle greater than 90 degrees. 
     Having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. For example, the inserts and the mating apertures in the casings can be splines or have non-circular cross-sections, so that the inserts must be removed to be reoriented and then reinstalled. In this manner, the need for separate locking mechanisms can be obviated. Accordingly, the described embodiments are to be considered in all respects as only illustrative and not restrictive.