Abstract:
A stair stepping apparatus comprising: a plurality of stairs forming a treadmill or endless belt on which a user steps, wherein each stair comprises: a first link comprised of a major step portion joined to a minor riser portion by a rigid elbow, and a second link comprised of major riser portion joined to a minor step portion by a rigid elbow.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims the benefit of priority to U.S. application Ser. No. 15/000380 filed Jan. 19, 2016 the disclosure of which is incorporated in its entirety by reference as if fully set forth herein. 
         [0002]    This application incorporates by reference the disclosures of all of the following in their entirety as if fully set forth herein: U.S. Pat. No. 783,769, U.S. Pat. No. 3,497,215, U.S. Pat. No. 3,592,466, U.S. Pat. No. 4,687,195, U.S. Pat. No. 4,927,136, U.S. Pat. No. 5,769,759, U.S. Patent Publication No. 20120238409, U.S. Pat. No. US 7,717,831, U.S. Pat. No. 4,725,054, U.S. Pat. No. 7,666,123, U.S. Pat. No. 8,070,658, U.S. Pat. No. 7,278,955, U.S. Pat. No. 8,025,609, U.S. Pat. No. 7,727,128, U.S. Pat. No. D486,535, U.S. Pat. No. D490,127, U.S. Patent Publication No. 2003/0092541, U.S. Patent Publication No. 2007/0173384, U.S. Patent Publication No. 2006/0270531, U.S. Patent Publication No. 2008/0167169, U.S. Patent Publication No. 2010/0204021. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates to machines that provide a stair climbing exercise for a user and more particularly to an escalator or treadmill that mounts a series of interconnected steps that move along a track as the user steps on successive steps. 
       BACKGROUND OF THE INVENTION 
       [0004]    Exercise machines for providing stair-climbing exercises such as U.S. Pat. No. 783,769, U.S. Pat.No. 3,497,215, U.S. Pat. No. 3,592,466, U.S. Pat. No. 4,687,195, U.S. Pat. No. 4,927,136, U.S. Pat. No. 5,769,759, U.S. Patent Publication No. 20120238409 are known. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with the invention there is provided a stair stepping apparatus comprising: 
         [0006]    a plurality of stairs mounted on a frame and pivotably interconnected to each other in succession to form a treadmill or endless belt on which a user steps, the treadmill or endless belt being rotatably mounted on the frame for rotation around a path of travel having a longitudinal axis, 
         [0007]    wherein each stair comprises: 
         [0008]    a first link comprised of a major step portion joined to a minor riser portion by a rigid elbow, and 
         [0009]    a second link comprised of major riser portion joined to a minor step portion by a rigid elbow, 
         [0010]    the major step portion of each first link having a rearwardmost edge pivotably interconnected to a forwardmost edge of the minor step portion of the second link of a successively interconnected stair, 
         [0011]    the major riser portion of each second link having a rearwardmost edge pivotably interconnected to a forwardmost edge of the minor riser portion of the first link of a successively interconnected stair. 
         [0012]    The major step portion of the first link preferably has a generally planar upper surface for receiving a sole of the user&#39;s foot, the forwardmost edge of the minor riser portion extending above the generally planar surface of the major step portion, 
         [0013]    the minor step portion of the second link preferably having a generally planar upper surface for receiving the sole of the user&#39;s foot, the rearwardmost edge of the major riser portion extending below the generally planar surface of the major step portion. 
         [0014]    The forwardmost edge of the minor riser portion typically extends a selected first normal distance away from a plane coincident with the generally planar surface of the major step portion, 
         [0015]    the rearwardmost edge of the major riser portion extends a selected second normal distance away from a plane coincident with the generally planar surface of the minor step portion. 
         [0016]    The pivotable interconnections of the apparatus described above preferably comprise a male hinge disposed on one of the rearwardmost and forwardmost edges and a female hinge disposed on the other of the rearwardmost and forwardmost edges, the male hinge comprising a curved finger rotatably received within a complementary receiving aperture of the female hinge, the curved finger being adapted to rotate within and completely enclose the receiving aperture to form a continuous exterior surface between the female hinge and the male hinge at all angles of rotation of the male hinge within the receiving aperture. 
         [0017]    The selected first normal distance is preferably between about 1 and about 5 inches. 
         [0018]    The minor step portion preferably has a minor effective front to back length of between about 1 and about 5 inches. 
         [0019]    The selected first normal distance is preferably between about  1  and about  5  inches and the minor step portion has a minor effective front to back length of between about 1 and about 5 inches. 
         [0020]    The major step portion preferably has a major effective front to back length, the sum of the major and minor effective front to back lengths being between about 9 and about 15 inches. 
         [0021]    The sum of the first normal distance and the second normal distance is preferably between about 5 and 10 inches. 
         [0022]    The treadmill or endless belt is typically mounted on the frame for rotation along a path of travel such that the generally planar surfaces of the major and minor step portions of successively interconnected stairs are disposed in a generally co-planar orientation along at least a portion of the path of travel of the treadmill or endless belt. 
         [0023]    The treadmill or endless belt is preferably mounted for rotation such that the stairs travel in a backwardly downwardly directed path of travel on rotation of the treadmill, the major and minor portions of successively interconnected stairs providing a step surface on which a user can step with a user&#39;s foot during at least some portion of the backwardly downwardly directed path of travel of the stairs. 
         [0024]    The treadmill is typically interconnected to a resistance device that exerts a selected degree of resistance to rotation of the treadmill, the treadmill being rotatably driven against the resistance by force of the user&#39;s weight WT or by the user&#39;s exertion of downwardly directed force on a step surface of one or more of the stairs. 
         [0025]    The longitudinal axis of the path of travel is typically disposed at an angle of between about 30 and about 36 degrees relative to horizontal. 
         [0026]    In another aspect of the invention there is provided a method of performing an exercise by a user using the apparatus of claim  1 , the method comprising the user&#39;s stepping on a stair of the apparatus of claim  1  while the treadmill of the apparatus rotates in a backward and downward direction. 
         [0027]    In another aspect of the invention there is provided a stair stepping apparatus comprising: 
         [0028]    a plurality of stairs mounted on a frame and pivotably interconnected to each other in succession to form a treadmill or endless belt, the treadmill or endless belt being rotatably mounted on the frame for rotation around a path of travel, 
         [0029]    wherein each stair comprises: 
         [0030]    a first link comprised of a major step portion joined to a minor riser portion by a rigid elbow, and 
         [0031]    a second link comprised of major riser portion joined to a minor step portion by a rigid elbow, 
         [0032]    the major step portion of each first link having a rearwardmost edge pivotably interconnected to a forwardmost edge of the minor step portion of the second link of a successively interconnected stair, 
         [0033]    the major riser portion of each second link having a rearwardmost edge pivotably interconnected to a forwardmost edge of the minor riser portion of the first link of a successively interconnected stair, 
         [0034]    the major step portion of the first link having a generally planar upper surface for receiving a sole of the user&#39;s foot, the forwardmost edge of the minor riser portion extending normally away from the generally planar surface of the major step portion, 
         [0035]    the minor step portion of the second link having a generally planar upper surface for receiving the sole of the user&#39;s foot, the rearwardmost edge of the major riser portion extending normally away from the generally planar surface of the major step portion. 
         [0036]    The forwardmost edge of the minor riser portion typically extends a selected first normal distance away from a plane coincident with the generally planar surface of the major step portion, 
         [0037]    the rearwardmost edge of the major riser portion typically extends a selected second normal distance away from a plane coincident with the generally planar surface of the minor step portion. 
         [0038]    The selected first normal distance is preferably between about 1 and about 5 inches. 
         [0039]    The treadmill or endless belt is typically mounted on the frame for rotation along a path of travel such that the generally planar surfaces of the major and minor step portions of successively interconnected stairs are disposed in a generally co-planar orientation along at least a portion of the path of travel of the treadmill or endless belt. 
         [0040]    The treadmill or endless belt is preferably mounted for rotation such that the stairs travel in a backwardly downwardly directed path of travel on rotation of the treadmill, the major and minor portions of successively interconnected stairs providing a step surface on which a user can step with a user&#39;s foot during at least some portion of the backwardly downwardly directed path of travel of the stairs. 
         [0041]    The treadmill is typically interconnected to a resistance device that exerts a selected degree of resistance to rotation of the treadmill, the treadmill being rotatably driven against the resistance by force of the user&#39;s weight WT or by the user&#39;s exertion of downwardly directed force on a step surface of one or more of the stairs. 
         [0042]    The path of travel has longitudinal axis preferably disposed at an angle of between about 30 and about 36 degrees relative to horizontal. 
         [0043]    In another aspect of the invention there is provided a method of performing an exercise by a user using the apparatus of claim  14 , the method comprising the user&#39;s stepping on a stair of the apparatus of claim  14  while the treadmill of the apparatus rotates in a backward and downward direction. 
         [0044]    In another aspect of the invention there is provided a stair stepping apparatus comprising: 
         [0045]    a plurality of stairs mounted on a frame and hingedly interconnected to each other in succession to form a treadmill or endless belt, the treadmill or endless belt being rotatably mounted on the frame for rotation around a path of travel, 
         [0046]    wherein each stair comprises: 
         [0047]    a step having a generally planar upper step surface having a front to rear length extending from a front edge to a rear edge, the step being comprised of a front foot support and a rear foot support hingedly joined to each other between the front and rear edges of the upper step surface. 
         [0048]    Each stair can further comprise a riser having a top to bottom vertical length extending from the rear edge of the upper step surface to a bottom edge of the riser, 
         [0049]    the riser comprising an upper riser and a lower riser hingedly joined to each other between the rear edge of the step surface and bottom edge of the riser. 
         [0050]    The upper riser is preferably rigidly interconnected to the rear foot support at the rear edge of the upper step surface by an elbow that disposes the upper rise normally below the upper step surface, the lower riser being rigidly interconnected by an elbow to a front foot support of a successive step at the front edge of the upper step surface. 
         [0051]    Each the front foot support typically has a front upper generally planar surface and the rear foot support has a rear upper generally planar surface, the treadmill or endless belt being mounted on the frame for rotation along a path of travel such that the front and rear foot supports pivot into a position where the front and rear upper generally planar surfaces are disposed in a generally co-planar orientation along at least a portion of the path of travel of the treadmill or endless belt. 
         [0052]    The treadmill or endless belt is preferably mounted for rotation such that the stairs travel in a backwardly downwardly directed path of travel on rotation of the treadmill, the front and rear foot supports of successively interconnected stairs providing a step surface on which a user can step with a user&#39;s foot during at least some portion of the backwardly downwardly directed path of travel of the stairs. 
         [0053]    The treadmill is preferably interconnected to a resistance device that exerts a selected degree of resistance to rotation of the treadmill, the treadmill being rotatably driven against the resistance by force of the user&#39;s weight or by the user&#39;s exertion of downwardly directed force on a step surface of one or more of the stairs. 
         [0054]    The path of travel of the treadmill typically has a longitudinal axis disposed at an angle of between about 30 and about 36 degrees relative to horizontal. 
         [0055]    In another aspect of the invention there is provided a method of performing an exercise by a user using the apparatus described immediately above, the method comprising the user&#39;s stepping on a stair of the apparatus while the treadmill of the apparatus rotates in a backward and downward direction. 
         [0056]    The front foot support and the rear foot support of the apparatus described immediately above are typically hingedly joined by a male hinge disposed on one of the front and rear foot supports and a female hinge disposed on the other of the front and rear foot supports, the male hinge comprising a curved finger rotatably received within a complementary receiving aperture of the female hinge, the curved finger being adapted to rotate within and completely enclose the receiving aperture to form a continuous exterior surface between the female hinge and the male hinge at all angles of rotation of the male hinge within the receiving aperture. 
         [0057]    In another aspect of the invention there is provided a stair stepping apparatus  5  comprising: 
         [0058]    a plurality of stairs  70  mounted on a frame  10  and hingedly interconnected  72 ,  82  to each other in succession to form a treadmill or endless belt  20 , the treadmill or endless belt being rotatably mounted on the frame for rotation BR around a path of travel, 
         [0059]    wherein each stair  70  comprises: 
         [0060]    a step  50  having a generally planar upper step surface SS extending from a front edge  74   f  to a rear edge  50   e  and a riser  60  having an outside surface OS having a front edge  60   e  pivotably joined to the step  50  by a hinge  72  formed between the front edge  60   e  of the riser and the rear edge  50   e  of the step, 
         [0061]    the hinge  72  comprising at least one male hinge member  300  disposed on one of the rear edge  50   e  of the step and the front edge  60   e  of the riser and at least a pair of male hinge members  302  disposed on the other of the rear edge  50   e  of the step and the front edge  60   e  of the riser, the pair of male hinge members  302  being spaced apart to form an aperture or recess  7   rr  that is complementary to and receives the at least one male hinge member  300 , 
         [0062]    each of the male hinge members  300 ,  302  comprising a center arcuate member  300   c ,  302   c  having an outside wall  300   w ,  302   w  that extends continuously from the upper step surface SS of the step and the outside surface OS of the riser at least about  180  degrees around the rear  50   e  and front  60   e  edges of the step  50  and the riser  60  respectively, 
         [0063]    each of the male hinge members  300 ,  302  further comprising a pair of lateral arcuate fingers  300   f ,  302   f  disposed on opposing lateral sides of the center arcuate member  300   c ,  302   c , the lateral arcuate fingers  300   f ,  302   f  having an outside surface  300   fw ,  302   fw  that extends continuously from the upper step surface SS of the step  50  and from the outside surface OS of the riser about 90 degrees around the rear  50   e  and front edges  60   e  of the step and the riser, 
         [0064]    the male hinge members  300 ,  302  each having a longitudinal aperture  300   ap ,  302   ap  with a common axis APX for receiving a pin or rod  72   p  that extends through the longitudinal aperture  300   ap ,  302   ap  along the axis APX and pivotably interconnects the step  50  to the riser  60  forming the hinge  72 , 
         [0065]    the longitudinal apertures  300   ap ,  302   ap , the center arcuate members  300   c ,  302   c  and the lateral fingers  300   f ,  302   f  being adapted to arrange the outside wall  300   w ,  302   w  of the center arcuate member  300   c ,  302   c  and the outside surfaces  300   fw ,  302   fw  of the lateral arcuate fingers  300   f ,  302   f  such that a continuous surface is formed around the hinge when the step  50  and the riser  60  are pivoted relative to each other around at least 90 degrees. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0066]    The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: 
           [0067]      FIG. 1  is a side schematic view of a generic exercise stair stepper or climbing apparatus according to the invention showing the arrangement of a treadmill or belt of sequentially pivotably interconnected stairs and showing the generally upright disposition of a human being user climbing the stairs while the stairs rotate backwardly and downwardly in response to the user&#39;s exertion of force on the stairs. 
           [0068]      FIG. 2  is a top side perspective view of a series of pivotably interconnected stairs of the  FIG. 1  apparatus. 
           [0069]      FIG. 2A  is a top side perspective view of a prior art stair climber stair. 
           [0070]      FIG. 3  is a top side perspective exploded view of the major stair and major riser components of a stair that makes up the treadmill of stairs of the  FIGS. 1-2  apparatuses. 
           [0071]      FIG. 4  is a top rear perspective exploded view of the components of  FIG. 3  showing the details of a hinge mechanism that pivotably connect the front and rear step components of a stair. 
           [0072]      FIG. 5  is a side view of the  FIG. 4  components when the components are disengaged from each other showing the details of the hinge. 
           [0073]      FIG. 6  is a side view of the  FIG. 4  components when the components are connected by their hinge showing the components in an angular position where the upper step surfaces are angled at about 90 degrees relative to each other. 
           [0074]      FIG. 7  is a side view of the  FIG. 4  components when the components are connected by their hinge showing the components in an angular position where the upper step surfaces are angled at about 45 degrees relative to each other. 
           [0075]      FIG. 8  is a view similar to  FIGS. 6 and 7  showing the two step components in an angular position where the upper step surfaces are coplanar. 
           [0076]      FIG. 9  is a side schematic view of a stair with a hinge disposed on the rear edge and a stair with a hinge disposed a selected distance along the step surface. 
           [0077]      FIG. 10  is a side schematic view similar to  FIG. 9  showing a second position of the two stairs with different hinge locations. 
           [0078]      FIG. 11  is a side schematic view of a single stair of the apparatus of  FIGS. 1-10 , the stair shown mounted on a chain that is driven by the pulley,  FIG. 11  showing the path of travel EPN of the outermost edge  74   r  of a stair according the  FIGS. 1-10  embodiment of the invention and the path of travel EPC of the outermost edge  700   e  of a conventional treadmill stair  500 ,  600 . 
           [0079]      FIG. 12A  is an enlarged bottom perspective exploded view of the rear and front edges of the forward and rear links of a stair according to the  FIGS. 1-10  embodiment showing the details of a preferred hinge structure. 
           [0080]      FIG. 12B  is an enlarged top perspective exploded view of the rear and front edges of the forward and rear links of a stair according to the  FIGS. 1-10  embodiment showing the details of a preferred hinge structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0081]      FIG. 1  shows a stair climbing apparatus  5  comprised of a frame  10  on which is mounted a treadmill or endless belt  20  that has a rotation axis AX. The treadmill or belt  20  is mounted for rotation in a backwardly downwardly direction BD on pulleys  30  that drive the rotation of the treadmill  20  via gear teeth  32  adapted to mesh with complementary apertures in the links of chains, belts or the like  40  that support the individual forward link  50  and rearward link  60  of each stair via a rod  45  that extends between the drive chains  40 , belts or the like that are meshed or driven by front and rear pulleys  30   f ,  3   r.    
         [0082]    The angle of incline A of the axis AX is selectively adjustable by the user  7  to any desired angle A relative to horizontal by conventional devices such as by way of a controller  14  having a manually operable user interface  14   i , the controller  14  being interconnected to and containing instructions that controllably drive a motor or other drive device  12  that is mechanically interconnected to the treadmill assembly in a manner that controllably moves the front axle  38   f  or pulley  30   f  in a generally up and down UD direction relative to the rear axle  38   r  and rear pulley  30   r.    
         [0083]    Most preferably the instructions contained within the controller  14  enable the user  7  to adjust the angle A of the longitudinal axis AX to an angle that enable the user to perform a stepping exercise or motion or action as shown in  FIG. 1  such that the longitudinal axis LA of the user&#39;s upper torso  9  is disposed in a generally vertical V orientation when the user&#39;s upper torso or spine is disposed in a generally straight orientation as shown in  FIG. 1 . Preferably the instructions contained within the controller  14  enable the longitudinal axis AX to be adjusted to an angle A of between about 30 and about 36 degrees, most preferably between about 32 and about 34 degrees. 
         [0084]    Beginning from a start exercise motionless position of the treadmill or belt  20  at which point in time the treadmill is motionless, the treadmill  20  is held in a motionless position by an on-off brake  102  that prevents rotational movement of the pulleys  38   r ,  38   f  and the treadmill  20  until the on-off brake  102  is released by the user  7 . Upon release of the on-off brake  102 , movement of the treadmill or belt  20  is preferably resisted during a run-up from  0  rotational speed to X in rotational speed, X being a preselected rotational speed greater than zero, solely by drag, friction and weight of the moving mechanical components of the apparatus such as the treadmill  20 , pulleys  30   f ,  30   r , chains or belts  40  and associated components such as bearings and the like. Starting from the motionless position, the treadmill  20  can be rotatably driven upwards in rotational velocity BR in a backwardly downwardly BD direction by the user&#39;s stepping on a stair surface SS or by exerting the force of the user&#39;s weight WT or a downwardly user exerted force DF,  FIG. 1  by the user&#39;s muscles. The apparatus  5  is adapted so that the treadmill  20  can be driven from 0 rotational speed upwardly to a preselected rotational speed BR at which preselected rotational speed a resistance device  100  begins to exert a resistance to rotation BR. The treadmill  20  is preferably interconnected to a resistance device  100 , such as an eddy current brake device that exerts a resistance to rotation BR that increases exponentially or non-linearly with an increase of the rotational speed BR of the treadmill or belt  20 . 
         [0085]    As shown in  FIGS. 1-4 , the treadmill  20  is comprised of a plurality of serially or successively pivotably interconnected stairs  70 , each stair comprising a forward link  50  and rear link  60  that are pivotably or hingedly interconnected along a line  72  that extends across the width W of the step surface SS. The hinge along line  72  is formed by a series of complementary forward fingers  72   ff  (each comprised of lateral fingers  300   f ,  FIGS. 12A, 12B ) and forward recesses  72   fr  formed on rear edge of the forward link  50  that mate with a complementary series of rearward recesses  72   rr  and rearward fingers  72   rf  (each comprised of lateral fingers  302   f ) formed on a forward edge of the rear link  60 . A connecting pin  72   p  is insertable through a complementary aperture PA provided in fingers  72   ff  and  72   rf  so as to pivotably connect the forward link  50  to the rear link  60  along the hinge line  72 . 
         [0086]    The step hinge line  72  is disposed some selected distance along the overall step length SL that extends between the forward edge  74   f  and the rear edge  74   r  of each step surface SS of each stair  70 . The step surface SS is comprised of a forward step surface SSF formed on the upper surface of the forward link  50  and a rearward step surface SSR formed on the upper surface of the rear link  60 . The forward SSF and rear SSR step surfaces are generally planar such that the two surfaces SSF and SSR form an overall step surface SS that is generally continuous and planar when the forward  50  and rear  60  links pivot into angular alignment with each other along a portion POT of the overall path of rotational travel of the treadmill  20 . 
         [0087]    Preferably, the hinge line  72  is spaced a distance RSL of between about 1 and about 5 inches from the rear edge  72  of a step surface SS. Typically, the overall length SL of a step surface is between about 10 and about 15 inches. 
         [0088]    Each stair  70  is also comprised of an upper riser UR and a lower riser LR. The upper riser UR of each stair  70  extends downwardly from the rear edge  74   r  of the stair surface SS and terminates at a lower edge in a second hinge line  82  where the UR riser portion of the stair  70  pivotably interconnects to an upper edge of the lower riser LR portion of stair  70 . The lower riser portion LR of stair  70  comprises an upward extension of the first link  50   s  of an immediately successive stair  70   s  to the immediately preceding stair  70  as shown in  FIG. 2 . 
         [0089]    The lower riser LR extends upwardly from the forward step surface SSF such that the riser hinge line  82  of the lower riser is disposed a normal height or distance of between about 1 and about 5 inches above or away from the forward step surface SSF. 
         [0090]    Similar to hinge line  72 , the hinge is formed along riser hinge line  82  by the mating of complementary upper recesses  82   uf  formed on the lower edge of link  60  with lower riser fingers  82   lf  formed on the upper edge of the lower riser LR. A connecting pin  82   p  is insertable through a complementary aperture PA provided in fingers  82   uf  and  82   lf  so as to pivotably connect the forward link  50 s to the rear link  60  along the hinge line  82 . 
         [0091]      FIG. 5  is a side view of the  FIG. 4  components showing the forward and rear links disengaged from each other and showing details of the hinge components. The forward link  50  includes a series of forward fingers  72   ff  each having a curved connection portion  90   f  (shown in dashed lines). Forward link  50  also includes a series of forward recesses  72   fr  each having at least one curved guide unit  94   f  and a concave surface  96   f  (both shown in dashed lines). Similarly, the rear link  60  includes a series of rearward fingers  72   rf  each having a curved connection portion  90   r . Furthermore, rear link  60  includes a series of rearward recesses  72   rr  each having at least one curved guide unit  94   r  and a concave surface  96   r . The curved connection portions  90   f  and  90   r  angularly extend from the generally planar step surface toward the lower surface of the step. In some embodiments, the curved connection portions  90   f  and  90   r  can extend from the generally planar step surface along an arc between about 45 degrees and about 135 degrees. 
         [0092]    As shown in  FIGS. 6-8 , each of the curved connection portions is rotatably received between the complementary curved guide unit(s) and concave surface to pivotably interconnect the forward link  50  to the rear link  60  via forward and rearward fingers  72   ff  and  72   rf . A connecting pin  72   p  is insertable through a complementary aperture PA provided in fingers  72   ff  and  72   rf  to secure the connection between the forward link  50  and the rear link  60  along the hinge line  72 . Once connected, the forward and rearward fingers  72   ff  and  72   rf  completely enclose their complementary forward and rearward recesses to form a continuous exterior surface throughout all angles of rotation of the pivotable interconnection. 
         [0093]    When the forward and rearward step surfaces are substantially perpendicular to one another, they can be connected by their hinge as shown in  FIG. 6 . Each curved connection portion  90   f  included in the forward fingers  72   ff  of the forward link  50  is rotatably received between the complementary curved guide unit(s)  94   r  and concave surface  96   r  included in the complementary rearward recess  72   rr  of the rear link  60 . Similarly, each curved connection portion  90   r  in the rearward fingers  72   rf  disposed on the rear link  60  is rotatably received between the complementary curved guide unit(s)  94   f  and concave surface  96   f  in the complementary forward recess  72   fr  disposed on the forward link  50 . Furthermore,  FIG. 6  shows that each of the forward and rearward fingers  72   ff  and  72   rf  completely encloses their complementary forward and rearward recesses  72   fr  and  72   rr  to form a continuous exterior surface  104 . 
         [0094]      FIG. 7  is a side view showing the front and rear links in an angular position where the step surfaces are angled at about 45 degrees relative to each other. In comparison with  FIG. 6 , it can be seen that each of the curved connection portions  90   f  and  90   r  is further rotatably engaged between the complementary curved guide unit(s) and concave surface. Moreover, the forward and rearward recesses  72   fr  and  72   rr  remain completely enclosed by each of the forward and rearward fingers  72   ff  and  72   rf  thereby maintaining the continuous exterior surface  104 . 
         [0095]      FIG. 8  is a side view similar to  FIGS. 6 and 7  showing the front and rear links in an angular position where the step surfaces are coplanar. In this configuration, each of the curved connection portions  90   f  and  90   r  is fully rotatably engaged between the complementary curved guide unit and concave surface. When the front and rear step components are coplanar, a radially inward protrusion in each of the curved connection portions  90   f  and  90   r  contacts a front face of the complementary curved guide unit to form an abutment  108 . Furthermore,  FIG. 8  shows that each of the forward and rearward fingers  72   ff  and  72   rf  still completely encloses their complementary forward and rearward recesses  72   fr  and  72   rr  and the continuous exterior surface  104  remains. 
         [0096]      FIGS. 9, 10 and 11  show a comparison between stair  70  having a hinge disposed along hinge line  72  and a stair  120  (shown in dashed lines) having a hinge disposed along hinge line  112 . Hinge line  72  is disposed some selected distance along the overall step length that extends between the forward edge  74   f  and the rear edge  74   r  of the step surface of stair  70 . On the other hand, hinge line  112  is disposed on the rear edge  74   r  of the step surface. Each of stairs  70  and  120  are pivotably connected to a belt or chain  40  at points  122  and  124  and are configured to move along a path outlined by belt or chain  40  in a backward and downward direction BD. 
         [0097]      FIG. 9  illustrates a first stair position in which both stair  70  and stair  120  form a generally continuous and planar step surface. As a user steps on the step surface of stairs  70  and  120 , the user&#39;s weight or a downwardly user exerted force causes each of stairs  70  and  120  to move in a backward and downward direction BD into a second stair position illustrated in  FIG. 10 . In the second stair position, stairs  70  and  120  have pivoted about their respective hinge lines  72  and  112  to accommodate the path outlined by the chain or belt  40 . Due to the difference in the position of hinge lines  72  and  112 , stair  120  extends a distance H below stair  70 . 
         [0098]      FIG. 11  shows in schematic a single stair  70  of the apparatus of  FIGS. 1-10  mounted on a chain  40  that is driven by the pulley  30   r  and in particular the path of travel EPN of the outermost edge  74   r  of a stair  70  according the  FIGS. 1-10  apparatus relative to the path of travel EPC of the outermost edge  700   e  of a conventional treadmill stair  500 ,  600 . As shown, the radial distance RDN to which the outermost edge  74   r  of a stair  70  according to the invention extends from the center of the pulley  38   r  is significantly reduced or less relative to the radial distance RDC to which the outermost edge of a conventional stair  500 ,  600  extends where the conventional stair  500 ,  600  has about the same step length CSL and riser length CRL as the step length (FSL plus RSL) and riser length (URL plus LRL) of a stair  70  according to the invention. Such a reduction in distance of extension RDN relative to conventional stair distance of extension RDC. Such reduction in extension RDN in particular reduces the vertical height H of the outermost edge  74 R of the stair  70  off of the ground G when a stair  70  is in its closest to ground G position at the most vertical V disposition over the course of rotation of the treadmill  20  around its angled path of travel. Such reduction and thus reduces the minimum height off of the ground by which the stair surface SS can be mounted which in turn reduces the overall height of the apparatus relative to ground G and the height off the ground that a user must step up in order to step on the lowest stair on the treadmill  20  when the apparatus  5  is mounted on the frame  10 . 
         [0099]      FIGS. 12A, 12B  show the details of a preferred hinge  72  structure of an apparatus  5  according to the invention. As shown the hinge  72  comprises at least one male hinge member  300  disposed on one of the rear edge  50   e  of the step and the front edge  60   e  of the riser and at least a pair of male hinge members  302  disposed on the other of the rear edge  50   e  of the step and the front edge  60   e  of the riser, the pair of male hinge members  302  being spaced apart to form an aperture or recess  7   rr  that is complementary to and receives the at least one male hinge member  300 . 
         [0100]    Each of the male hinge members  300 ,  302  comprises a center arcuate member  300   c ,  302   c  having an outside wall  300   w ,  302   w  that extends continuously from the upper step surface SS of the step and the outside surface OS of the riser at least about  180  degrees (angle B) around the rear  50   e  and front  60   e  edges of the step  50  and the riser  60  respectively. 
         [0101]    Each of the male hinge members  300 ,  302  further comprises a pair of lateral arcuate fingers  300   f ,  302   f  disposed on opposing lateral sides of the center arcuate member  300   c ,  302   c , the lateral arcuate fingers  300   f ,  302   f  having an outside surface  300   fw ,  302   fw  that extends continuously from the upper step surface SS of the step  50  and from the outside surface OS of the riser about 90 degrees (angle C) around the rear  50   e  and front edges  60   e  of the step and the riser. The male hinge members  300 ,  302  each have a longitudinal aperture  300   ap ,  302   ap  with a common axis APX for receiving a pin or rod  72   p  that extends through the longitudinal aperture  300   ap ,  302   ap  along the axis APX and pivotably interconnects the step  50  to the riser  60  forming the hinge  72 . The longitudinal apertures  300   ap ,  302   ap , the center arcuate members  300   c ,  302   c  and the lateral fingers  300   f ,  302   f  are adapted to arrange the outside wall  300   w ,  302   w  of the center arcuate member  300   c ,  302   c  and the outside surfaces  300   fw ,  302   fw  of the lateral arcuate fingers  300   f ,  302   f  such that a continuous surface is formed around the hinge when the step  50  and the riser  60  are pivoted relative to each other around at least 90degrees.