Abstract:
An exercise apparatus comprises: a frame; a crank system comprising first and second crank coupling locations, the crank system being supported by the frame; a right foot support member comprising a first right guide element; a left foot support member comprising a first left guide element; a right movable member comprising a second right guide element; a left movable member comprising a second left guide element; a first flexible support system comprising a first flexible element, the first flexible element coupled to the frame and the first and second right guide elements and operative to move the first crank coupling location when the right foot support member moves; and a second flexible support system comprising a second flexible element, the second flexible element coupled to the frame and the first and second left guide elements and operative to move the second crank coupling location when the left foot support member moves.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 60/780,599 filed on Mar. 9, 2006 entitled “BELT AND CRANK EXERCISE DEVICE” and Ser. No. 60/881,205 filed on Jan. 19, 2007, entitled “LINKAGE AND BRAKE SYSTEMS”, the disclosures of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present description relates generally to an exercise device and, more particularly, it relates to an exercise device with a translating support assembly. 
     BACKGROUND OF THE INVENTION 
     It can be appreciated that exercise devices have been in use for years and include devices that simulate walking or jogging such as cross country ski machines, elliptic motion machines, and pendulum motion machines. Also included are exercise devices that simulate climbing such as reciprocal stair climbers. 
     Elliptic motion exercise machines provide inertia that assists in direction change of the pedals, which makes the exercise smooth and comfortable. However, rigid coupling to a crank typically constrains the elliptic path to a fixed length. Therefore, the elliptic path may be too long for shorter users, or too short for tall users. Further, a running stride is typically longer than a walking stride, so a fixed stride length does not ideally simulate all weight bearing exercise activities. Therefore, typical elliptic machines cannot optimally accommodate all users. Some pendulum motion machines may allow variable stride length, but the user&#39;s feet typically follow the same arcuate path in both forward and rearward motion. Such a motion does not accurately simulate walking, striding, or jogging, where the user&#39;s feet typically lift and lower. Reciprocal stair climbers typically allow the user to simulate a stepping motion, but that motion is generally constrained to a vertically oriented arcuate path defined by a linkage mechanism. Such a motion does not accurately simulate a wide range of real world climbing activities such climbing stairs or climbing sloped terrain. 
     More recently, variable stride exercise devices utilizing crank systems have been developed. These devices, however, may be complex and have high manufacturing costs. 
     BRIEF SUMMARY OF THE INVENTION 
     Various embodiments of the invention relate to exercise devices and methods for use thereof that employ a translating support assembly. In one example, an exercise device includes a frame with a base portion that is supported by the floor. A crank system is coupled to and supported by the frame. Right and left translating support assemblies each have a movable member, a foot support member, and guide elements. Flexible elements couple the crank system to the translating support assembly. Vertical movement of the right and left foot support members applies force to the crank system via the flexible support elements. 
     An example method for operating an exercise machine according to embodiments includes applying alternating forces to the right and left foot support members, rotating the crank shaft and tracing substantially closed paths with the foot support members. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
         FIG. 1  depicts a side view of an example embodiment of an exercise device adapted according to an embodiment of the invention; 
         FIG. 2  depicts a top view of an example embodiment of an exercise device adapted according to an embodiment of the invention; 
         FIG. 3A  depicts an example embodiment of an arcuate motion member path; 
         FIG. 3B  depicts an example embodiment of a foot support member path; 
         FIG. 4  depicts a side view of an example embodiment of an exercise device adapted according to an embodiment of the invention; 
         FIG. 5  depicts a side view of an example embodiment of an exercise device adapted according to an embodiment of the invention; and 
         FIG. 6  depicts an example method for using a machine adapted according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a side view of an embodiment of an exercise device with a translating support assembly.  FIG. 2  shows a top view of the embodiment of  FIG. 1 . Frame  101  includes a basic supporting framework including base  102 , upper stalk  103 , and track section  104 , which is curved in this embodiment. The lower portion of base  102  engages and is supported by the floor. The crank system includes crank arms  112  attached to crank shaft  114 . Although only one crank arm is shown, it is understood that there is an opposing crank arm in this example. Each crank arm  112  is coupled to its respective flexible element  150  at a crank coupling location  117 . Crank shaft  114  is supported by frame  101  so that crank shaft  114  rotates about its longitudinal axis. One or both of crank arms  112  may include a counterweight, such as weight  113 . 
     Although the embodiment shown in  FIG. 1  utilizes a crank shaft with crank arms, other crank system configurations can be utilized. For example, some crank systems may have more than two crank arms. Still other crank systems may forego crank arms and utilize a ring supported and positioned by rollers with crank coupling locations at or near the periphery of the ring. In fact, any kind of crank system now known or later developed may be used in various embodiments 
     In this example, the crank system also includes brake/inertia device  119  coupled to crank shaft  114  through belt  115  and pulley  118 . In other embodiments a brake inertia device may be coupled directly to crank shaft  114 . Rotation of crank arms  112  about the axis of crank shaft  114  causes rotation of brake/inertia device  119 . Brake/inertia device  119  may provide a braking force that provides resistance to the user during exercise, and/or it may provide inertia that smoothes the exercise by receiving, storing, and delivering energy during rotation. Although the embodiment shown in  FIG. 1  uses a single brake/inertia device, it is possible to utilize multiple brake/inertia devices or to separate the braking and inertia functions between two or more devices. Further, although the embodiment of  FIG. 1  shows the crank system and brake system located at the front of frame  101 , it is possible to place the crank system at other locations such as at the rear of frame  101 . 
     The translating support assembly of  FIG. 1  includes foot support member  134 , movable member  137 , arcuate motion member  130 , and guide elements  148  and  149 . Although only the elements of the right side translating support assembly are numbered, it is understood that there is a left side translating support assembly with comparable elements. 
     In the context of this specification, the term “member” includes a structure or link of various sizes, shapes, and forms. For example, a member may be straight, curved, or a combination of both. A member may be a single component or a combination of components coupled to one another. Arcuate motion member  130  has an upper portion  132 . Upper portion  132  can be used as a handle by the user. Arcuate motion member  130  may be straight, curved, or bent. Foot support member  134  has foot plate  136  on which the user stands. Foot support member  134  may be straight, curved, or bent. Foot support member  134  is coupled to movable member  137  at coupling location  138 . Coupling may be accomplished with a pivotal pin connection as shown in  FIG. 1 , but coupling may also be accomplished with any device that allows relative rotation between the arcuate motion member  130  and foot support member  134 . 
     As used herein, the term “coupling” or “coupled” includes a direct coupling or an indirect coupling. Movable member  137  is coupled to arcuate motion member  130  at location  139  and thereby also couples foot support member  134  to arcuate motion member  130 . Coupling of movable member  137  to arcuate motion member  130  may be accomplished with shaft and bushing as shown in  FIG. 1 , but coupling may also be accomplished with any device that allows rotation of movable member  137  relative to arcuate motion member  130 . Moveable member  137  is at least partially supported by roller  121  that engages track  104 . Movable member  137  may be straight, curved, or bent. Arcuate motion member  130  is coupled to frame  101  at coupling location  140 . Coupling may be accomplished with shaft and bushing as shown in  FIG. 1 , but coupling may also be accomplished with any device that allows rotation of arcuate motion member  130  relative to frame  101 . Guide element  148  is coupled to foot support member  134  and guide element  149  is coupled to movable member  137 . 
     As shown in  FIG. 1 , the portion of arcuate motion member  130  coupled to frame  101  is above the portion of arcuate motion member  130  coupled to foot support member  134 . In the context of this specification, one element is “above” another element if it is higher than the other element. The term “above” does not require that an element or part of an element be directly over another element. Conversely, in the context of this specification, one element is “below” another element if it is lower than the other element. The term “below” does not require that an element or part of an element be directly under another element. 
     Flexible element  150  is coupled at one end to crank arm  112  at crank coupling location  117  and at its other end to frame  101  at location  143 . Between its ends, flexible element  150  engages guide element  149  located on movable member  137  and guide element  148  located on foot support member  134 . Guide elements  148  and  149  as shown in  FIG. 1  are pulleys, but they may be any other component that can guide or support a flexible element such as a cog belt pulley, a sprocket, a roller, or a slide block. Flexible element  150  may be a belt, a cog belt, a chain, a cable, or any flexible component able to carry tension. Flexible element  150  may have some compliance in tension, such as a rubber belt, or it may have little compliance in tension, such as a chain. 
     Although the embodiment of  FIG. 1  and the other figures in this specification show only one guide element on movable member  137  and one guide element on foot support member  134 , it is possible to use multiple guide elements on a foot member and/or a movable member. As an example, movable member  137  may be configured with two guide elements so that the first guide element would be located ahead and the second guide element would be located behind foot member guide element  148 . As an alternate example, foot support member  134  could be configured with two guide elements so that the first guide element would be located ahead and the second guide element would be located behind movable member guide element  149 . Further, guide elements could be placed on frame  101  to route flexible element  150  in ways other than that shown in  FIG. 1   
     Arcuate motion member  130  may be oriented in a generally vertical position. In the context of this specification, an element is oriented in a “generally vertical” position if the element, as measured with respect to its connection points to other elements of the system considered within the range of motion for the element, tends to be closer to vertical than horizontal.  FIG. 3A  shows an example of an arcuate motion member that is oriented in a generally vertical position. The frame of reference is fixed relative to coupling location  140 . As arcuate motion member  130  moves through its range of motion about coupling location  140 , coupling location  138  describes an arcuate path  160 . If the width W of arcuate path  160  is greater than its height H, the arcuate motion member  130  is considered to be in a generally vertical position. It is not necessary that arcuate motion member  130  be straight, nor is it necessary that any portion be exactly vertical. Further, it is not necessary that the member be closer to vertical than horizontal at every moment during its use. 
     Foot support member  134  may be oriented in a generally horizontal position. In the context of this specification, an element is oriented in a “generally horizontal” position if the element, as measured with respect to its connection points to other elements of the system considered within the range of motion for the element, tends to be closer to horizontal than vertical.  FIG. 3B  shows an example of a foot support member that is oriented in a generally horizontal position. The frame of reference is fixed relative to coupling location  138 . As foot support member  134  moves through its range of motion about coupling location  138 , it describes an arcuate path  162 . If the height H of arcuate path  162  is greater than its width W, the foot support member is in a generally vertical position. It is not necessary that foot support member  134  be straight, nor is it necessary that any portion be exactly horizontal. Further, it is not necessary that the member be closer to horizontal than vertical at every moment during its use. 
     During operation, the user ascends the exercise device, stands on foot plates  136 , and initiates an exercising motion by placing his/her weight on one or more of foot plates  136 . As the user steps downward, force is transmitted to flexible support element  150  by guide element  148 . In turn, flexible element  150  causes rotation of crank shaft  114  and brake/inertia device  119 . As crank shaft  114  continues to rotate, the distance between crank coupling location  117  on crank  112  and the coupling point  143  on frame  101  continuously changes. This continuous change in the distance described above results in a continuous alternating lifting and lowering motion of foot plate  136 . This lifting and lowering motion simulates the lifting and lowering motion that a user&#39;s foot may undertake during walking, striding, jogging, and climbing. As each foot plate  136  continuously lifts and lowers, the user may simultaneously undertake a striding motion by applying a forward or rearward force to foot plates  136 . This striding motion results in displacement of foot plates  136 , foot members  134 , movable members  137 , and guide elements  148  and  149 . The combination of displacement of the foot plates  136  by the user and the continuous lifting and lowering motion of foot plates  136  results in a substantially closed path that is traced by each foot support member  134 . 
     During use of the machine, the path traced can be referred to as a “substantially closed path.” In other words, while it is generally rare for a user&#39;s exercise path to meet up at its exact beginning (thereby tracing a truly closed path), a user&#39;s path over time can be expected to trace a set of approximately repeated curves, resulting in a recognizable, curved path. Some paths may be egg-shaped, somewhat elliptical, saddle shaped (lower in the middle than at the ends of the horizontal extent), or the like. 
     The length of the path is instantaneously controlled by the user according to the amount of forward or rearward force applied to foot plates  136 . If the user applies little rearward or forward force, the exercise path may be nearly vertical in orientation with little or no horizontal amplitude. Alternately, if the user applies significant rearward or forward force, the exercise path may have significant horizontal amplitude. Alternating weight transfer during exercise from one foot plate to the opposing foot plate transmits force to the crank  112  which sustains rotation of crank  112 , crank shaft  114 , and brake/inertia device  119 . 
     Track section  104  may be curved as shown in  FIG. 1 . In some embodiments, section  104  is a separate curved section coupled to frame  101 , though a curved section integral to the frame may provide the same function. Such curvature provides a restoring force that tends to restore the translating support assembly to a neutral position when the user applies weight to foot plate  136 . Handles  132  may move in an arcuate pattern and may be grasped by the user. If the user were to stand stationary on foot plates  136  for an extended period of time, a simple unweighted crank system might settle into a locked “top dead center” position. However, the inclusion of counterweight  113  in the crank system applies a downward force to offset the crank system from the “top dead center” position. 
     Some embodiments include cross-coupling. For instance, in this example, the right and left side translating support assemblies are cross coupled through the left and right arcuate motion members so that the right and left foot plates  136  move in opposition. Elements  180  are coupled to arcuate motion members  130 . Thus, each of right and left elements  180  moves in unison with each right and left arcuate motion member  130 , respectively. Connectors  182  couple right and left elements  180  to the right and left sides of rocker arm  184 . Rocker arm  184  is pivotally coupled at its mid portion to frame  101  at location  186 . As arcuate motion members  130  move, connectors  182  cause a rocking motion of rocker arm  184 . This rocking motion causes right and left arcuate motion members  130  to move in opposition thus cross coupling the right and left pivotal linkage assemblies. 
     Additional braking systems may be included in the exercise device to resist horizontal movement of the foot plates. The embodiment of  FIG. 1  has two such braking systems. Brake  191  is coupled to the frame  101  and the rocker arm  184 . The brake resists motion of rocker arm  184  which in turn resists motion of arcuate member  130 , foot member  134 , and foot plate  136 . Brake  191  (and/or device  119 ) may be of several types such as frictional, electromagnetic, or fluidic. Rather than direct coupling of brake  191  to rocker arm  184 , brake  191  can be indirectly coupled to rocker arm  184  through a belt and pulley system. Brake  193  is coupled to the movable member  134  and pulley guide element  149 . The brake resists rotary motion of pulley guide element  149  which provides resistance to motion of the movable member  137 , foot member  134 , and foot plate  136 . 
       FIG. 4  shows a side view of another embodiment. This embodiment has many elements that correspond to elements of the embodiments in  FIGS. 1 and 2  (though they may have somewhat different shapes and/or dimensions), and those elements are numbered in the same manner. This embodiment demonstrates, for example, that a foot support member may be coupled to an arcuate motion member, that translating support assemblies may be cross coupled with a continuous belt loop, that a movable member may be support by a link, that the crank system may be located at the rear of the machine, and that the flexible element may not be attached directly to the crank.  FIG. 4  omits most of the left side elements of the embodiment for visual clarity, but it is understood that there are left side elements comparable to the right side elements. 
     Frame  101  includes a basic supporting framework including base  102 , upper stalk  103 , and vertical support  105 . The crank system includes crank arms  112  attached to crank shaft  114 . Crank shaft  114  is supported by frame  101  so that crank shaft  114  rotates about its longitudinal axis. One or both of crank arms  112  may include a counterweight, such as weight  113 . 
     The crank system may also include brake/inertia device, such as device  119 , coupled to crank shaft  114  through belt  115  and pulley  118 . Alternately, a brake inertia device may be coupled directly to crank shaft  114 . Rotation of crank arms  112  about the axis of crank shaft  114  causes rotation of brake/inertia device  119 . Brake/inertia device  119  may provide a braking force that provides resistance to the user during exercise, and/or it may provide inertia that smoothes the exercise by receiving, storing, and delivering energy during rotation. The crank system of the embodiment of  FIG. 4  is located at the rear of the machine, and this location can be used for the crank systems in other embodiments of this specification. 
     The translating support assembly of this embodiment includes foot support member  134 , movable member  137 , arcuate motion member  130 , support link  131 , and guide elements  148  and  149 . Arcuate motion member  130  has an upper portion  132 . Upper portion  132  can be used as a handle by the user. Arcuate motion member  130  may be straight, curved, or bent. Foot support member  134  has foot plate  136  on which the user stands. Foot support member  134  may be straight, curved, or bent. Foot support member  134  is coupled to arcuate motion member  130  at coupling location  138 . Movable member  137  is coupled to arcuate motion member  130  at location  139 . Moveable member  137  is coupled to support link  131  at location  135 . Support link  131  is coupled to vertical support  105  at location  145 . Movable member  137  may be straight, curved, or bent. Arcuate motion member  130  is coupled to frame  101  at coupling location  140 . Guide element  148  is coupled to foot support member  134  and guide element  149  is coupled to movable member  137 . 
     Flexible element  150  is coupled at one end to upper stalk  103  at location  143  and at its other end to vertical support  105  at location  116 . Between its ends, flexible element  150  engages guide element  149  located on movable member  137 , guide element  148  located on foot member  134 , and guide element  111  located on crank  112 . Note that the use of guide element  111  results in coupling of the flexible element to crank  112  and that this coupling method can be used in other embodiments of the invention. 
     During operation, the user ascends the exercise device, stands on foot plates  136 , and initiates an exercising motion by placing his/her weight on one or more of foot plates  136 . As the user steps downward, force is transmitted to flexible support element  150  by guide element  148 . In turn, flexible element  150  causes rotation of crank shaft  114  and brake/inertia device  119 . As crank shaft  114  continues to rotate, the distance between the crank system coupling location (i.e., the portion of guide element  111  that engages flexible element  150 ) and frame coupling point  143  continuously changes. This continuous change in the distance described above results in a continuous alternating lifting and lowering motion of foot plate  136 . This lifting and lowering motion simulates the lifting and lowering motion that a user&#39;s foot may undertake during walking, striding, jogging, and climbing. As each foot plate  136  continuously lifts and lowers, the user may simultaneously undertake a striding motion by applying a forward or rearward force to foot plates  136 . This striding motion results in displacement of foot plates  136 , foot members  134 , movable members  137 , and guide elements  148  and  149 . The combination of displacement of the foot plates  136  by the user and the continuously lifting and lowering motion of foot plates  136  results in a substantially closed path. Supporting link  131  may be oriented in a generally vertical position. Such an orientation provides a restoring force that tends to restore the translating support assembly to a neutral position when the user applies weight to foot plate  136 . 
     As in the embodiment of  FIG. 1  and  FIG. 2 , the right and left side translating support assemblies are cross coupled. The embodiment of  FIG. 4  demonstrates that a cross coupling system may use a continuous belt loop. The cross coupling system includes continuous belt  164 . Continuous belt  164  engages pulleys  166  and  168 . Continuous belt  164  is coupled to movable members  137  at coupling locations  133 . Although only the right side movable member is shown, it is understood that there is a comparable left side movable member and that the continuous belt  164  is coupled to the left side movable member. As one movable member moves forward, the opposing movable member moves rearward. Continuous belt  164  may have a slight amount of compliance that allows it to accommodate the varying geometry of the system as movable members  137  move forward and rearward. This continuous belt loop cross coupling system may be used in other embodiments of the invention. Similarly, the rocker arm cross coupling system of the embodiment of  FIG. 1  and  FIG. 2  may be substituted in the embodiment of  FIG. 4 . In fact, any cross coupling system now known or later developed may be used in various embodiments. 
     As in the  FIG. 1  and  FIG. 2  embodiments, additional braking systems may be included to resist horizontal movement of foot plates  136 . Brake  191  is coupled to pulley  168  and frame  101 , and brake  191  creates resistance to rotary motion of pulley  168 . 
       FIG. 5  shows a side view of another embodiment. This embodiment has many elements that correspond to elements of the embodiments in FIG.  1 , 2  and  4  (though they may have somewhat different shapes and/or dimensions), and those elements are numbered in the same manner. This embodiment demonstrates, for example, that an intermediate linkage assembly may be used to couple the crank system to the flexible element.  FIG. 5  omits most of the left side elements of the embodiment for visual clarity, but it is understood that there are left side elements comparable to the right side elements. 
     Frame  101  includes a basic supporting framework including base  102 , upper stalk  103 , and vertical support  105 . The lower portion of base  102  engages and is supported by the floor. The crank system includes crank arms  112  attached to crank shaft  114 . Crank shaft  114  is supported by frame  101  so that crank shaft  114  rotates about its longitudinal axis. Though not shown in this embodiment, one or both of crank arms  112  may include a counterweight, such as weight  113 . 
     The crank system may also include a brake/inertia device, such as device  119 , coupled to the crank shaft through belt  115  and pulley  118 . Alternately, a brake inertia device may be coupled directly to the crank shaft. Rotation of crank arms  112  about the axis of crank shaft  114  causes rotation of brake/inertia device  119 . Brake/inertia device  119  may provide a braking force that provides resistance to the user during exercise, and/or it may provide inertia that smoothes the exercise by receiving, storing, and delivering energy during rotation. 
     An intermediate linkage assembly is coupled to the crank system. In this example it includes actuating link  173  and engagement roller  172 . Actuating link  173  is coupled to frame  101  at location  175  and is coupled to crank  112  through engagement roller  172 . 
     A translating support assembly may include foot support member  134 , movable member  137 , arcuate motion member  130 , support link  131 , and guide elements  148  and  149 . Arcuate motion member  130  has an upper portion  132 . Upper portion  132  can be used as a handle by the user. Arcuate motion member  130  may be straight, curved, or bent. Foot support member  134  has foot plate  136  on which the user stands. Foot support member  134  may be straight, curved, or bent. Foot support member  134  is coupled to arcuate motion member  130  at coupling location  138 . Movable member  137  is coupled to arcuate motion member  130  at location  139 . Moveable member  137  is coupled to support link  131  at location  135 . Support link  131  is coupled to vertical support  105  at location  145 . Movable member  137  may be straight, curved, or bent. Arcuate motion member  130  is coupled to frame  101  at coupling location  140 . Guide element  148  is coupled to foot support member  134  and guide element  149  is coupled to movable member  137 . 
     Flexible element  150  is coupled at one end to vertical support  105  at location  143  and at its other end to actuating link  173  at location  177 . Between its ends, flexible element  150  engages guide element  149  located on movable member  137  and guide element  148  located on foot member  134 . 
     During operation, the user ascends the exercise device, stands on foot plates  136 , and initiates an exercising motion by placing his/her weight on one or more of foot plates  136 . As the user steps downward, force is transmitted to flexible support element  150  by guide element  148 . In turn, flexible element  150  causes movement of actuating link  173 . Movement of actuating link  173  causes rotation of crank  112 , crank shaft  114 , and brake/inertia device  119 . As crank shaft  114  continues to rotate, the distance between coupling point  177  on actuating member  173  and coupling point  143  on vertical support  105  continuously changes. This continuous change in the distance described above results in a continuous alternating lifting and lowering motion of foot plate  136 . This lifting and lowering motion simulates the lifting and lowering motion that a user&#39;s foot may undertake during walking, striding, jogging, and climbing. As each foot plate  136  continuously lifts and lowers, the user may simultaneously undertake a striding motion by applying a forward or rearward force to foot plates  136 . This striding motion results in displacement of foot plates  136 , foot members  134 , movable members  137 , and guide elements  148  and  149 . The combination of displacement of the foot plates  136  by the user and the continuously lifting and lowering motion of foot plates  136  results in a substantially closed path. Supporting link  131  may be oriented in a generally vertical position. Such an orientation provides a restoring force that tends to restore the translating support assembly to a neutral position when the user applies weight to foot plate  136 . 
     As in the  FIG. 1 ,  FIG. 2 , and  FIG. 4  embodiments, the right and left side pivotal linkage assemblies may be cross coupled so that the right and left foot plates  136  move in opposition. Also as in  FIG. 1 ,  FIG. 2 , and  FIG. 4  embodiments, additional braking systems may be included to resist horizontal movement of the foot plates. 
       FIG. 6  is an illustration of exemplary method  600  adapted according to an embodiment of the invention. Method  600  may be performed, for example, by a user of a system, such as that shown in  FIGS. 1 ,  2 ,  4 , and  5 . 
     In step  601 , alternating vertical forces are applied to the right and left foot support members, changing the distance between the coupling locations of the flexible element to the frame and the crank system thereby rotating the crank shaft. Similarly, in step  602 , alternating front-to-back forces are applied to the foot support members, so that the right and left foot support members trace substantially closed paths. 
     In step  603 , one or more of the forces are changed, thereby varying a length of the substantially closed paths. Some embodiments include arcuate motion members for a user to grasp and to make forward and backward motions therewith. In such embodiments, step  604  includes alternatingly moving the left and right arcuate motion members. 
     Method  600  is shown as a series of discrete steps. However, other embodiments of the invention may add, delete, repeat modify and/or rearrange various portions of method  600 . For example, steps  601 - 604  may be performed continuously for a period of time. Further, steps  601 - 604  will generally be performed simultaneously during the user&#39;s striding motion. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.