Patent Publication Number: US-9901774-B2

Title: Elliptical exercise device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of international patent application Serial No. PCT/US2015/034146, filed Jun. 4, 2015, which claims priority from U.S. patent application Ser. No. 14/643,587, filed Mar. 10, 2015 and U.S. patent application Ser. No. 14/643,522, filed Mar. 10, 2015, both of which claim priority to U.S. provisional patent application Ser. No. 62/086,470 filed Dec. 2, 2014. In addition, application Serial No. PCT/US2015/034146 claims priority to U.S. provisional patent application Ser. No. 62/086,470, filed Dec. 2, 2014. The contents of all of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to elliptical exercise devices in which the path of travel of a user&#39;s foot is generally elliptical. 
     BACKGROUND OF THE INVENTION 
     There are a number of exercise devices that operate to allow a user to implement a foot action following a generally closed, curved path of travel, simulating running and/or walking. These devices are generally referred to as “elliptical” exercise devices. Many such elliptical exercise devices are large, complicated, costly, and/or have undesirable characteristics related to the motion of the user&#39;s feet. 
     U.S. Pat. No. 5,518,473 to Miller shows an early design for an elliptical exercise device. The device provides a path of travel that simulates running and/or walking but is quite large and does not provide for arm exercise. 
     U.S. Pat. No. 5,611,756 to Miller discloses an elliptical exercise device with arm and leg movement. A pair of guide links are pivotally supported on a frame and a foot engaging link is supported at the lower end of each guide link. An intermediate link connects each guide link to crank. A control link joins each foot link to the corresponding intermediate link to vary the angle of the foot link relative to the guide link. 
     U.S. Pat. No. 6,045,487 to Miller discloses an elliptical exercise device having a pair of guide links pivotally supported on a frame and a foot link supported at the lower end of each guide link. An intermediate link connects each guide link to a crank of a crank system. A flexible control member engages each foot link and extends up and over a pulley located at the guide link pivot axis. The control members connect to a reciprocating assembly for moving the foot links up and down as the guide links pivot back and forth. 
     U.S. Pat. No. 7,708,668 to Rodgers, Jr. shows several embodiments of an exercise device having flexible elements coupling left and right foot support members to a crank system. The exercise device allows for a variable stride length and decouples the vertical and horizontal components of foot travel. 
     U.S. Pat. No. 7,556,591 to Chuang et al. discloses an exercise device with cranks mounted to an upper portion of a frame. Two handles are pivoted to the frame forward of the cranks. Foot supports are pivotally coupled to the lower ends of the handles. Pivot rods extend between each foot support and one of the cranks. Additional links connect each handle with the same cranks as the respective pivot rod. 
     SUMMARY OF THE INVENTION 
     The present invention provides multiple embodiments of exercise devices. According to one embodiment, an elliptical exercise device has a frame configured to be supported on a horizontal surface, the frame having a first pivot axis defined thereon. A first and a second guide link each has a first and a second attachment point defined thereon. Each guide link is pivotally attached, through its first attachment point, to the frame at the first pivot axis thereof. A first and a second foot support link each has a foot receiving area configured to support a user&#39;s foot thereupon. Each foot support link is pivotally connected to the second attachment point of a respective one of the guide links so that when the guide links pivot relative to the frame, they each cause the respective foot receiving area to move in a path of travel having a horizontal component of motion. A cam system has a horizontal control cam portion supported for rotation about a cam axis, the horizontal control cam portion having a first and second offset horizontal drive portion. A horizontal follower support is disposed on the frame and has a horizontal follower pivot axis defined thereon. A first and a second horizontal control follower are pivotally connected to the horizontal follower support at the horizontal follower pivot axis. Each horizontal control follower has a control portion and a cam engagement portion, the cam engagement portion having a cam engagement surface engaging a respective one of the offset horizontal drive portions of the horizontal cam portion such that as the horizontal cam portion rotates about the cam axis, the offset horizontal drive portions cause the horizontal control followers to pivot back and forth about the horizontal follower pivot axis thereby causing the control portions to oscillate back and forth. A first and a second mechanical horizontal control coupling each couples a respective one of the guide links to the control portion of a respective one of the horizontal control followers such that as the horizontal cam portion rotates about the cam axis, the mechanical horizontal control couplings pivot the guide links about the first pivot axis, thereby moving the foot receiving areas of the foot support links in a path of travel having a horizontal component of motion. A vertical drive system is mechanically coupled to the foot support links so as to move the foot receiving areas of the foot support links in a path of travel having a vertical component of motion. Movement of each foot receiving area in the path of travel having a vertical component of motion is generally out of phase with the movement in the path of travel having a horizontal component of motion such that when the horizontal component of motion of each foot receiving area is at its forwardmost or rearwardmost limit, the vertical component of motion of the same foot receiving area is approximately midway between its uppermost and lowermost limit. The foot receiving area of each foot support link moves in a generally elliptical path when the cam portion rotates about the cam axis. 
     In some versions, the horizontal follower support is a movable support operable to move the horizontal follower pivot axis relative to the cam axis so as to alter a range of travel of the control portion of the horizontal control followers, thereby altering a range of the path of travel having a horizontal component of motion. A horizontal control actuator is operable to move the movable horizontal control follower support. 
     In certain versions, the horizontal follower support is a horizontal follower support link having a frame end pivotally connected to the frame and a follower end defining the horizontal follower pivot axis. The horizontal follower support link is pivotable about the frame end so as to move the horizontal follower pivot axis relative to the cam axis. In other versions, the horizontal follower support is linearly displaceable on the frame. 
     In some versions, the vertical drive system has a crank supported for rotation about a crank axis and a first and a second mechanical vertical control coupling each coupling a respective one of the foot support links to the crank such that as the crank rotates about the crank axis, the mechanical vertical control couplings move the foot receiving areas of the foot support links in the path of travel having the vertical component of motion. The cam system may include a crank portion defining the crank and the crank axis may be the cam axis. The first and second mechanical vertical control couplings may be flexible couplings each having one end coupled to the crank and an opposite end coupled to the respective foot support link, each flexible coupling having a midportion extending over a guide disposed on the frame rearward of the first pivot axis. 
     The horizontal control followers may be elongated elements. In one version, each has one end pivotally connected to the horizontal follower support, an opposite end defining the control portion, and a midportion defining the cam engagement portion. In a second version, each has one end pivotally connected to the horizontal follower support, an opposite end defining the cam engagement portion, and a midportion defining the control portion. In a third version, each has one end defining the cam engagement portion, an opposite end defining the control portion, and a midportion pivotally connected to the horizontal follower support. The cam engagement portion of each elongated horizontal control follower may be a slot defined in the elongated element. 
     In some versions, the first and second mechanical horizontal control couplings are horizontal control links each having one end coupled to the control portion of the respective one of the horizontal control followers and a second end connected to a respective one of the guide links. 
     In some versions, each of the guide links further includes a hand portion extending upwardly from the first attachment point. 
     In certain versions, the device includes an adjustable resistance element coupled to the cam system. 
     According to another embodiment of the present invention, an elliptical exercise device has a frame configured to be supported on a horizontal surface with a first pivot axis defined on the frame. A first and a second guide link each has a first and a second attachment point defined thereon, each guide link being pivotally attached, through its first attachment point, to the frame at the first pivot axis thereof. A first and a second foot support link each has a foot receiving area configured to support a user&#39;s foot thereupon. Each foot support link is pivotally connected to the second attachment point of a respective one of the guide links so that when the guide links pivot relative to the frame, they each cause the respective foot receiving area to move in a path of travel having a horizontal component of motion. A cam system has a vertical control cam portion and a horizontal control cam portion, the cam portions supported for rotation about cam axes. The vertical control cam portion has a first and a second offset vertical drive portion. The horizontal control cam portion has a first and second offset horizontal drive portion. A vertical follower support is disposed on the frame and has a vertical follower pivot axis defined thereon. A first and a second vertical control follower are each pivotally connected to the vertical follower support at the vertical follower pivot axis. Each vertical control follower has a control portion and a cam engagement portion. The cam engagement portion has a cam engagement surface engaging a respective one of the offset vertical drive portions of the vertical cam portion such that as the vertical cam portion rotates about the respective cam axis, the offset vertical drive portions cause the vertical control followers to pivot back and forth about the vertical follower pivot axis thereby causing the control portions to oscillate back and forth. A first and a second mechanical vertical control coupling each couples a respective one of the foot support links to the control portion of a respective one of the vertical control followers such that as the vertical cam portion rotates about the respective cam axis, the mechanical vertical control couplings move the foot receiving areas of the foot support links in a path of travel having a vertical component of motion. A horizontal follower support is disposed on the frame, the horizontal follower support having a horizontal follower pivot axis defined thereon. A first and a second horizontal control follower are each pivotally connected to the horizontal follower support at the horizontal follower pivot axis. Each horizontal control follower has a control portion and a cam engagement portion. The cam engagement portion has a cam engagement surface engaging a respective one of the offset horizontal drive portions of the horizontal cam portion such that as the horizontal cam portion rotates about the respective cam axis, the offset horizontal drive portions cause the horizontal control followers to pivot back and forth about the horizontal follower pivot axis thereby causing the control portions to oscillate back and forth. A first and a second mechanical horizontal control coupling each couples a respective one of the guide links to the control portion of a respective one of the horizontal control followers such that as the horizontal cam portion rotates about the respective cam axis, the mechanical horizontal control couplings pivot the guide links about the first pivot axis, thereby moving the foot support areas of the foot support links in a path of travel having a horizontal component of motion. Movement of each foot receiving area in the path of travel having a vertical component of motion is generally out of phase with the movement in the path of travel having a horizontal component of motion such that when the horizontal component of motion of each foot receiving area is at its forwardmost or rearwardmost limit, the vertical component of motion of the same foot receiving area is approximately midway between its uppermost and lowermost limit. As such, the foot receiving area of each foot support link moves in a generally elliptical path when the cam portions rotate about the cam axes. 
     In some versions, the cam system is a single cam with the vertical control cam portion and the horizontal cam portion each forming part of the single cam and the cam axes are a common axis defined on the frame. In some alternatives, the first offset vertical drive portion and the first offset horizontal drive portion are generally coaxial and the second offset vertical drive portion and the second offset horizontal drive portion are generally coaxial. 
     In some versions, the vertical control followers are disposed generally perpendicular to the horizontal control followers. 
     In some versions, the vertical follower support is a movable support operable to move the vertical follower pivot axis relative to the respective cam axis so as to alter a range of travel of the control portion of the vertical control followers, thereby altering a range of the path of travel having a vertical component of motion. A vertical control actuator may move the movable vertical control follower support. 
     In certain versions, the vertical follower support is a vertical follower support link having a frame end pivotally connected to the frame and a follower end defining the vertical follower pivot axis, the vertical follower support link being pivotable about the frame end so as to move the vertical follower pivot axis relative to the respective cam axis. A vertical control actuator may pivot the vertical follower support link. In other versions, the vertical follower support is linearly displaceable on the frame. 
     In some versions, the horizontal follower support is a movable support operable to move the horizontal follower pivot axis relative to the respective cam axis so as to alter a range of travel of the control portion of the horizontal control followers, thereby altering a range of the path of travel having a horizontal component of motion. A horizontal control actuator may move the movable horizontal control follower support. 
     In certain versions, a follower support rocker is pivotally interconnected with the frame. The rocker has a first arm defining the vertical follower support, an outer end of the first arm defining the vertical follower pivot axis. The rocker also has a second arm defining the horizontal follower support, an outer end of the second arm defining the horizontal follower pivot axis. A control actuator pivots the rocker about the rocker pivot thereby moving the vertical and horizontal pivot axes relative to the respective cam axes. 
     In some versions, the followers are curved. 
     In certain versions, the first and second mechanical vertical control couplings are flexible couplings each having one end coupled to the control portion of the respective vertical control follower and an opposite end coupled to the respective foot support link. Each flexible coupling has a midportion extending over a guide disposed on the frame rearward of the first pivot axis. The vertical control followers may have a lower end pivoted to the frame and an upper end defining the control portion. The one end of each flexible coupling is coupled to the upper end of the respective vertical control follower and extends generally rearwardly to the guide on the frame. 
     In certain alternatives, each of the guide links has a guide length defined between the first and second attachment point and each of the flexible couplings has a foot support portion extending between a coupling point on the respective foot support link and the guide on the frame. The foot support portion is generally parallel to the respective guide link throughout the motion of the device and the foot support portion has a length that is similar to the guide length when the respective foot support link is at a midpoint of vertical travel. The respective first attachment point, second attachment point, guide on the frame and coupling point on the foot support portion generally define a parallelogram when the respective foot support link is at the midpoint of vertical travel. 
     In some versions, the first and second mechanical vertical control couplings are vertical control links each having one end connected to the control portion of a respective one of the vertical control followers and a second end connected to a respective one of the foot support links forward of the second attachment point. 
     The vertical control followers may be elongated elements. In one version, each has one end pivotally connected to the vertical follower support, an opposite end defining the control portion, and a midportion defining the cam engagement portion. In a second version, each has one end pivotally connected to the vertical follower support, an opposite end defining the cam engagement portion, and a midportion defining the control portion. In a third version, each has one end defining the cam engagement portion, an opposite end defining the control portion, and a midportion pivotally connected to the vertical follower support. 
     In some versions, each of the guide links further includes a hand portion extending upwardly from the first attachment point. 
     In certain versions, the device has an adjustable resistance element coupled to the cam system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic showing a cam and follower arrangement for use with some embodiments of the present invention; 
         FIG. 1B  is a schematic similar to  FIG. 1A  in which the support for the follower is moved closer to the cam in order to alter the range of travel of a control portion of the follower; 
         FIG. 2A  is a schematic of an alternative cam and follower arrangement; 
         FIG. 2B  is a schematic of a further alternative cam and follower arrangement; 
         FIG. 3  is a side view of a first embodiment of an exercise device in accordance with the present invention; 
         FIG. 4  is a side view of a second embodiment of an exercise device in accordance with the present invention; 
         FIG. 5  is a side view of a third embodiment of an exercise device in accordance with the present invention; 
         FIG. 6  is a side view of a portion of the exercise device of  FIG. 5  with the horizontal and vertical linkage assemblies removed; 
         FIG. 6A  is a view taken along line  6 A- 6 A of  FIG. 6 , showing a construction of the cam; 
         FIG. 7  is a side view of a portion of the exercise device of  FIG. 5 , showing only the horizontal control portion; 
         FIG. 8  is a side view of a fourth embodiment of an exercise device in accordance with the present invention; 
         FIG. 9  is a side view of the exercise device of  FIG. 8  showing the vertical drive system; 
         FIG. 9A  is a view taken along lines  9 A- 9 A of  FIG. 9  showing the horizontal cam portion and vertical drive; 
         FIG. 10  is a side view of a fifth embodiment of an exercise device in accordance with the present invention; 
         FIG. 11  is a side view of a sixth embodiment of an exercise device in accordance with the present invention; 
         FIG. 12  is a side view of a seventh embodiment of an exercise device in accordance with the present invention; 
         FIG. 13  is a side view of a portion of an exercise device showing a horizontal coordination mechanism that may be used with some embodiments of the present invention; 
         FIG. 13A  is a view taken along lines  13 A- 13 A of  FIG. 13  showing the coordination linkage; 
         FIG. 14  is a side view of an exercise device showing a flywheel and resistance mechanism which may be used with embodiments of the present invention; 
         FIG. 15  is a side view of a portion of an exercise device in accordance with an eighth embodiment of the present invention; 
         FIG. 16  is a side view similar to  FIG. 15  with the follower support in a different position; 
         FIG. 17  is a side view of a portion of an exercise device in accordance with a ninth embodiment of the present invention, showing the horizontal control portions; 
         FIG. 18  is a side view of the ninth embodiment of an exercise device showing the vertical control portions; 
         FIG. 19  is a front view of a portion of the ninth embodiment showing the relationship between the horizontal and vertical control portions; 
         FIG. 20  is a side view of a tenth embodiment of an exercise device in accordance with the present invention; and 
         FIG. 21  is a side view of an eleventh embodiment of an exercise device in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be explained with reference to several particular embodiments, including variations and optional features of these embodiments. It is to be understood that yet other embodiments, modifications, and variations thereof will be apparent to those of skill in the art in view of the teaching presented herein. Further, features and elements of certain embodiments may be combined with each other in combinations other than those illustrated and variations and optional features may be used with any of the embodiments. 
     The present invention relates to exercise devices which are often referred to as elliptical exercise devices. An elliptical exercise device is designed to be used by a user placing their feet on respective foot receiving areas and then moving their feet along a generally elliptical path. This path will have horizontal and vertical components. The term “elliptical exercise device” is used herein in its broad sense to include both free stride exercise devices and fixed path exercise devices. 
     In a free stride exercise device, the motion of the foot receiving areas along a path of travel having a horizontal component of motion is generally decoupled from motion of the foot receiving areas along a path of travel having a vertical component of motion. Typically, a free stride exercise device will allow a user to alter the length of the horizontal path of travel by exerting more or less fore-aft force to the foot receiving areas or associated hand grip areas. Typically, such a device will have a coordination linkage that coordinates the horizontal travel such that as one foot receiving area moves rearwardly, the other foot receiving area moves forwardly by an equal amount. Typically, a resistance element is also provided to provide resistance to the horizontal motion, though this is not mandatory. In a free stride device, the vertical motion is typically controlled by some type of vertical drive system that is coupled to the foot receiving areas and causes the foot receiving areas to oscillate upwardly and downwardly by a predetermined amount. The height of the vertical travel may or may not be adjustable. In some free stride devices, the path of travel may be adjusted so as to be primarily horizontal so as to mimic a striding or cross-country skiing motion, primarily vertical so as to mimic a climbing motion, or a combination of horizontal and vertical such that the foot receiving areas travel along a curved generally elliptical path. The term “generally elliptical” is intended to mean any curved path and is not limited to a strictly mathematical ellipse. 
     A fixed path elliptical exercise device is one in which the foot receiving areas travel along a path that is determined by the device rather than by the amount of force applied by the user. The amount of horizontal or vertical travel may be non-adjustable such that the foot receiving areas travel through a single predetermined path. Alternatively, the horizontal or the vertical travel, or both, may be adjustable so as to change the length, height, and/or shape of the elliptical path. In some embodiments, the present invention may also be useful as a stepper or striding type exercise device that may not typically be considered an elliptical exercise device. 
     Embodiments of the present invention make use of a cam and follower arrangement to control horizontal and/or vertical motion of the foot receiving areas of the exercise device. A “cam” is defined herein as an element that rotates about a cam axis and has one or more portions that are offset from the cam axis. As such, as the cam rotates about the cam axis, a follower contacting the offset portion at a particular radial position would be moved inwardly and outwardly relative to the cam axis. Such an offset portion may take the form of a cam lobe or an eccentric disk such as a round shaft with a central axis that is offset from the cam axis. In the present invention, a follower is typically a pivoting elongated element with a portion that contacts the offset portion of the cam. The cam follower is pivotally attached to a follower support and has a cam engagement portion spaced from the pivot that contacts the offset portion of the cam. The follower further has a control portion that is caused to oscillate back and forth as the cam rotates about the cam axis. A cam may be referred to herein as a cam system, with the cam system consisting of one or more cams each with one or more offset portions. Embodiments of the present invention couple the control portion of followers to elements that cause horizontal or vertical motion of the foot receiving areas such that as the cam or cam system rotates, the control portions of the followers oscillate back and forth causing reciprocal horizontal and/or vertical motion of the foot receiving areas. 
     Referring now to  FIG. 1A , a generic cam and follower arrangement will be discussed. The cam and follower arrangement  10  includes a cam  12  that is rotatable about a cam axis  14 . In  FIG. 1A , the cam  12  has an offset portion  16  in the form of a round shaft with a central axis  18  offset from the cam axis  14 . The cam  12  is illustrated with the offset portion  16  at a 12:00 position and also illustrated with the offset portion at a 6:00 position shown in phantom lines. As will be clear to those of skill in the art, the offset portion  16  rotates about the cam axis  14  as the cam  12  rotates. A follower support  20  is spaced from the cam  12  and has a follower pivot axis  22  defined thereon. A follower  24  has a pivot end  26  pivotally attached to the follower pivot axis  22  and an opposite control end or portion  28 . A mid portion  30  of the follower  24  extends between the ends  26  and  28  and defines a cam engagement portion with a cam engagement surface in contact with the outer surface of the offset portion  16  of the cam  12 . The follower  24  is shown in solid lines in contact with the offset portion  16  in the 12:00 position and in phantom lines in contact with the offset portion  16  in the 6:00 position. As is clear from the figure, as the cam  12  rotates about the cam axis  14 , the control end  28  of the follower  24  will oscillate up and down and travel along a distance labeled as D 1 . 
     In certain embodiments of the present invention, horizontal and/or vertical motion is adjustable by adjusting the relative distance between the follower pivot axis and the cam. The cam and follower arrangement  10  is shown in  FIG. 1B  with the follower support  20  moved closer to the cam  12 . As shown, this reduces the distance between the follower pivot axis  22  and the cam axis  14 . Because the cam  12  is now closer to the pivot end  26  of the follower  24  the control end  28  is caused to travel or oscillate through a distance labeled as D 2  which is greater than D 1 . 
     As will be clear to those of skill in the art, a cam follower arrangement may take a variety of forms.  FIG. 2A  illustrates an alternative in which a follower support  32  is pivotally attached to one end of a follower  34  while the offset portion  36  of a cam  38  engages an engagement portion  40  of the follower that is at an end opposite the pivot end  42 . In this arrangement, the control portion  44  is a mid portion of the follower  34 . Some type of control element or coupling  46  may be attached to the control portion  44  of the follower  34 . 
       FIG. 2B  illustrates a further alternative arrangement in which the follower support  48  is pivotally attached to a mid portion of the follower  50 , a cam  52  engaging one of the ends  54  of the follower  50 , and the other end  56  defining the control portion. In each of these arrangements, the distance between the pivot axis on the follower support and the cam may be adjusted so as to adjust the amount of travel of the control portion of the follower. Certain embodiments of the present invention are illustrated with one type of cam and follower arrangement. Those of skill in the art will recognize that other arrangements may be substituted. 
     Referring now to  FIG. 3 , a first embodiment of an exercise device in accordance with the present invention is shown generally at  100 . The illustrated device is a free stride type device in which the extent of horizontal motion is controlled by the user. However, the device  100  may be modified to include a horizontal control system from one of the other embodiments in order to convert the device into a fixed path device. The illustrated device  100  includes a frame  102  which is configured and operative to retain and support the various other components of the device on a horizontal surface such as a floor. The frame  102  is typically fabricated from metal and/or composite materials, but any material may be used. The frame  102  has an upper portion  104  and a lower portion  106 . The lower portion  106  is configured to contact the horizontal surface while the upper portion  104  supports several components of the device. A first pivot axis  108  is defined in a middle area of the upper portion  104  of the frame  102 . The frame  102  may be said to have a forward portion forward of the first pivot axis  108 , which is to the left in the view of  FIG. 3 , and a rearward portion rearward of the first pivot axis  108 , which is to the right in the view of  FIG. 3 . As will be clear to those of skill in the art, exercise devices such as those described herein include left and right elements for supporting the respective left and right feet of the user. The right and left components of the device are typically substantially the same, though the machine may be constructed such that the two foot receiving areas are 180 degrees out of phase. That is, when one foot receiving area is moving forwardly and/or downwardly, the other foot receiving area is moving rearwardly and/or upwardly. The embodiments of the present invention will be described primarily with reference to only one set of components, with it being understood that the corresponding components of the other half of the device are constructed similarly.  FIG. 3  shows a side view of the device  100  with the left elements most visible. 
     A pair of guide links are pivotally interconnected with the frame so as to be pivotal about the first pivot axis  108 . The left guide link  110  is shown at the midpoint of its travel with the right guide link hidden behind it. All left and right components may alternatively be referred to as first and second components for ease of description. The guide link  110  may be said to have a first attachment point  112  towards its upper end and a second attachment point  114  at its lower end. The guide link  110  is pivotally interconnected with the first pivot axis  108  of the frame  102  at its first attachment point  112 . In the illustrated embodiment, the guide link  110  further includes a hand portion  116  that extends upwardly from a first attachment point  112 . Each guide link  110  has a corresponding foot support link  118  pivotally connected thereto. In the illustrated embodiment, the foot support link  118  has a forward end  120  that is pivotally interconnected with the second attachment point  114  of the guide link  110 . The foot support link  118  further has a foot receiving area  122  defined at its rearward end. A cam system  124  is pivotally interconnected with the frame  102  such that a cam system  124  rotates about a second pivot axis  126  defined on the frame  102 . The second pivot axis  126  also serves as the cam axis. In this embodiment, the cam system  124  is at the upper portion  104  of the frame  102  and forward of the first pivot axis  108 . The second pivot axis  126  is below the first pivot axis  108 . The cam system  124  is similar to the cam system illustrated in  FIGS. 1A and 1B , having an offset portion  128  for controlling vertical motion of the left foot support link  118 . The offset portion  128  is shown at a 6:00, or downward, position. An alternative position with the crank system  124  rotated 180 degrees is shown in phantom lines at  130 . This offset portion  130  may alternatively represent the offset portion for controlling the vertical motion of the right foot support link. A follower support is shown at  132 . The follower support  132  is referred to as a vertical follower support because it supports followers  134  and  136  that are responsible for vertical motion of the foot support links. 
     In this embodiment, the follower support takes the form of a follower support link  132  having a frame end  138  pivotally connected to the frame  102  and a follower end  140  defining the vertical follower pivot axis  144 . The frame  102  may be said to have a third pivot axis  142  to which the vertical follower support link  132  is pivotally attached. By pivoting the vertical follower support link  132  about the axis  142 , the follower end  140  and associated vertical follower pivot axis  144  is moved closer to or further from the cam axis  126 . An actuator  146  may be provided for pivoting the vertical follower support link  132  about the axis  142 . In the illustrated embodiment, both the left vertical control follower  134  and right vertical control follower  136  are pivoted to the follower end  140  of the vertical follower support link  132 . Alternatively, separate links may be used. 
     The left vertical control follower  134  has a control portion  148  that moves upwardly and downwardly as the cam system  124  rotates about the cam axis  126 . A mid portion  150  of the follower  134  acts as a cam engagement portion with a surface that presses against the offset portion  128  of the cam system  124 . A mechanical vertical control coupling  152  couples the control portion  148  of the follower  134  to the respective foot support link  118  such that rotation of the cam system  124  causes the foot receiving area  122  of the foot support link  118  to move upwardly and downwardly, which is a path of travel having a vertical component of motion. The mechanical vertical control coupling may take a variety of forms. In the illustrated embodiment, the control coupling  152  is a flexible element such as a cable or strap having one end connected to the control portion  148  of the follower  134 , an opposite end connected to a mid portion of the foot support link  118 , forward of the foot receiving area  122 , and a mid portion that passes over a pair of guide pulleys on the frame  102 . A forward guide pulley  154  is disposed on the upper portion  104  of the frame  102  forward of the first pivot axis  108  and generally directly above the control portion  148  of the follower  134 . A rear guide pulley  156  is disposed on the upper portion  104  of the frame  102  rearward of the first pivot axis  108  and generally directly above the coupling point  158  where the flexible element is connected to the foot support link  118 . 
     The illustrated configuration provides a parallelogram-type configuration. The flexible coupling  152  may be said to have a foot support portion  160  extending between the coupling point  158  and the rear guide pulley  156 . This foot support portion  160  is generally parallel to the respective guide link  110  at all times. Further, the guide link  110  may be said to have a guide length defined between the first attachment point  112  and second attachment point  114 . The length of the foot support portion  160  of the flexible coupling  152  varies with the position of the foot support link  118 . In  FIG. 3 , the foot support link  118  is shown in an upper position. The right foot support link  119  is shown in the downward position. As will be clear from the figure, the length of the foot support portion  160  of the flexible coupling  152  when the foot support link is at a midpoint of its vertical travel is similar to or generally the same as the guide length of the guide link  110 . As such, the first attachment point  112 , second attachment point  114 , rear guide pulley  156 , and coupling point  158  generally define a parallelogram when the foot support link  118  is at a midpoint of its vertical travel. This parallelogram-type configuration provides a desirable motion profile. 
     As mentioned previously, the illustrated embodiment of the exercise device  100  is a free stride type device. This means that horizontal travel of the foot support portions depends on how much fore-aft force is applied to the foot receiving areas or hand portions by the user. Horizontal travel occurs as the guide links  110  pivot about the first pivot axis  108 . Alternatively, the exercise device  100  may be a fixed path device by providing a drive mechanism for horizontal motion. The guide links  110  are shown having an attachment portion  162  extending forwardly from the remainder of the guide link. A horizontal drive apparatus may be attached to the attachment portion  162  for providing pivoting motion of the guide links and therefore movement of the foot receiving areas  122  in a path of travel having a horizontal component of motion. 
     As will be clear from the earlier discussion of  FIGS. 1A and 1B , the range of vertical motion of the foot receiving areas  122  may be altered by vertical follower support link  132  so as to move the pivot  144  closer to or further from the cam axis  126 . As the link  132  pivots counterclockwise, the follower support pivot  144  moves closer to the cam axis  126  causing increased travel of the control portions  148  of the followers and thereby increased travel of the flexible coupling  152  and associated foot support link  118 . One or more sensors may be provided on the exercise device, such as pivot sensor  109 , to sense the amount of horizontal travel and/or the position of the guide links. This allows several options. The amount of vertical travel may be increased or decreased depending on the length of the horizontal stride. For example, the vertical travel may be decreased as horizontal stride length increases. The position of the guide links and/or the rate at which they pivot may be used to determine the cam position or rate of rotation in order to maintain a desired coordination between horizontal and vertical travel. 
     Referring now to  FIG. 4 , a second embodiment of an exercise device in accordance with the present invention is shown generally at  200 . Much of the structure is similar to the first embodiment, including a frame  202  having a first pivot axis  208  and a guide link  210  connected to the first pivot axis at its first attachment point  212 . A first foot support link  218  is connected to a second attachment point  114  of the guide link  210 . Unlike the first embodiment, the foot support link  218  is pivotally connected to the second attachment point  214  at a mid portion of the link  218  with a rearward end of the link  218  defining the foot receiving area  222  and a forward end  223  coupled to the cam and follower system. The cam and follower system is similar to the first embodiment, including a cam system  224  pivotally attached to a second pivot axis on the frame at a cam axis  226 . A vertical follower support link  232  is pivoted to the frame at  242  and vertical control followers  234  and  236  are pivotally attached to the upper follower end  240  of the vertical follower support link  232 . In this embodiment, the mechanical vertical control couplings take the form of vertical control links  252 . An upper end of the vertical control link  252  is pivotally attached to the control portion  248  of the follower  234  and the lower end of the vertical control link  252  is pivotally connected to the forward end  223  of the foot support link  218 . As will be clear from the figure, rotation of the cam system  224  about the cam axis  226  causes the control portion  248  of the follower  234  to oscillate upwardly and downwardly, thereby causing the foot receiving area  222  to oscillate upwardly and downwardly, along a path of travel having a vertical component of motion. Again, the amount of vertical travel may be adjusted by adjusting the position of the vertical follower support link  232 , such as by using actuator  246 . As with the first embodiment, the embodiment  200 , as illustrated, is a free stride type exercise device, but may be configured as a fixed path device by providing a horizontal drive mechanism for pivoting the guide links with respect to the frame. 
     Referring now to  FIGS. 5-7 , a third embodiment of an exercise device in accordance with the present invention will be discussed.  FIG. 3  shows a complete exercise device  300  with a cam and follower arrangement controlling both horizontal and vertical motion of the foot receiving areas.  FIG. 6  provides a view of just a portion of the exercise device  300 , with the horizontal and vertical control portions removed for ease of description.  FIG. 7  is a view similar to  FIG. 6  but with the horizontal follower support link and horizontal follower included. Beginning with  FIG. 6 , the exercise device  300  includes a frame  302  with an upper portion  304  for supporting components of the exercise device and a lower portion  306  for contacting the horizontal support surface. A first pivot axis  308  is defined on the upper portion  304  of the frame  302 . A guide link  310  is pivotally attached to the first pivot axis  308  at a first attachment point  312  and a foot support link  318  is pivotally attached to a second attachment point  314  on the guide link  310 . A cam system  324  is pivotally attached to the upper portion  304  of the frame  302  at a second pivot axis  326 , also defining a cam axis. 
     The cam system  324  is shown in more detail in  FIG. 6A . In this embodiment, the cam system comprises a single cam. The cam  324  has a portion that may be referred to as a horizontal control cam portion for controlling horizontal motion of the foot receiving areas and a portion that may be referred to as a vertical control cam portion for controlling the vertical motion of the foot receiving areas. In this embodiment, the vertical control cam portion includes the inner offset drive portions  325   a  and  325   b  and the horizontal control cam portion includes the outer offset drive portions  327   a  and  327   b . As shown, these offset portions may be circular with a central axis that is offset from the cam axis  326 . In some embodiments, the control cam portions may take the form of a roller bearing or other type of surface. As shown, the vertical control cam portion  325   a  for the left half of the machine and the horizontal control cam portion  327   a  for the left side of the machine share a common axis. Likewise, the vertical control cam portion  325   b  for the right half of the machine and the horizontal control cam portion  327   b  for the right half of the machine share a common axis. The portions  325   a  and  327   a  are offset 180 degrees from the portions  325   b  and  327   b , thereby placing the right and left halves of the machine 180 degrees out of phase with one another. 
     Referring now to  FIG. 7 , a portion of the exercise device  300  is shown with the horizontal control portions included. A horizontal follower support link  370  has a frame end  373  pivoted to the frame  302  at a pivot axis  372 . The axis  372  is rearward and below the first pivot axis  308 . The horizontal follower support link  370  has an opposite follower end  374  to which a lower end of a horizontal control follower  376  is pivotally attached. The horizontal control follower  376  has an upper end  378  that serves as a control portion and is pivotally interconnected with an attachment portion  362  of the guide link  310  by a horizontal control link  380 . A mid portion of the horizontal control follower, serving as a cam engagement portion, has a slot  382  defined therein. The left offset drive portion  327   a  of the cam system  324  is received in the slot  382  such that as the cam  324  rotates about the cam axis, the control portion  378  of the horizontal control follower  376  is moved fore and aft, thereby causing the guide link  310  to pivot about the first pivot axis  312 , causing the foot receiving areas to move in a path of travel having a horizontal component of motion. The horizontal control follower  376  in this embodiment uses the slot  382  as a cam engagement portion so that the horizontal control follower can both push and pull on the guide link  310 . As will be clear to those of skill in the art, the cam engagement surface in this embodiment will be both sides of the slot  382 , since the offset portion engages both sides of the slot. In an alternative approach, the follower may have a side surface that contacts the offset portion, instead of the slot, and a biasing member such as a spring can keep the follower in contact with the offset portion. Other approaches may also be used for causing the follower motion to be controlled by the offset portion. 
     Referring now to  FIG. 5 , a more complete illustration of the exercise device  300  is provided, including both vertical and horizontal control. As shown, an actuator  384  may be provided for controlling the position of the horizontal follower support link  370 , thereby controlling the range of horizontal travel. 
     A vertical follower support link  332  is also pivotally attached to the pivot axis  372  on the frame  302  and extends upwardly to a follower end  340  to which vertical control followers  334  and  336  are pivotally attached at axis  344 . An actuator  346  controls the position of the vertical follower support link  332 . The vertical control system is structured similar to the embodiment of  FIG. 4 , with the mid portion of the follower  334  serving as a cam engagement portion and engaging the offset vertical control portion  325   a  of the cam  324 . The follower  334  has a forward end  348  that acts as a control portion and is linked to a forward end  323  of the foot support link  318  by vertical control link  352 . In the illustrated embodiment, the horizontal follower support link  370  and the vertical follower support link  332  are separately pivotable such that the range of horizontal and vertical motion may be individually adjusted. Alternatively, the follower support  370  and the follower support  332  may be part of a single structure such that they pivot together such that one actuator may adjust both follower supports. Alternatively, the two follower supports may be interconnected by a linkage or gear mechanism to allow coordinated adjustment. 
     It is noted that in this embodiment the horizontal control followers and vertical control followers are disposed generally perpendicular to each other, with the vertical control followers extending generally horizontally between their pivot ends and control portions and the horizontal control followers extending generally vertically between their pivot ends and control portions. The horizontal follower support link and vertical follower support link are also generally perpendicular to each other, with the horizontal follower support link extending generally horizontally and the vertical follower support link extending generally vertically. The followers extend generally perpendicularly from their respective follower support links. This overall arrangement allows the use of a single cam wherein the left offset portions  325 A and  327 A of the vertical and horizontal control cam portions share a common axis and the right offset portions  325 B and  327 B also share a common axis. In an alternative approach, the vertical and horizontal control followers may be more parallel to each other, necessitating a cam system with horizontal and vertical drive portions offset from one another. 
       FIGS. 8 and 9  illustrate a fourth embodiment of an exercise device in accordance with the present invention.  FIG. 8  illustrates the horizontal control portions and  FIG. 9  illustrates the vertical control portions. As with earlier embodiments, the device  400  includes a frame  402  with an upper portion  404 , a lower portion  406 , and a first pivot axis  408  defined on the upper portion. Left guide link  410  is pivotally attached to the axis  408  at a first attachment point  412  and a foot support link  418  has a forward end  420  attached to a second attachment point  414  on the guide link  410 . A foot receiving area  422  is defined at the rearward end of the foot support link  418 . A cam system  424  is pivotally attached to the frame  402  at a second pivot axis  426 , also defining the cam axis. The cam axis  426  is below and forward of the first pivot axis  408 . A horizontal follower support link  470  is pivotally attached to the frame at pivot axis  472 . A horizontal control follower  476  is pivotally supported to a follower end  474  of the follower support link  470  and has a cam engagement slot  482  engaging the offset horizontal drive portion of the horizontal control cam portion of the cam system  424 . A control portion  478  of the horizontal control follower  476  is linked to the guide link  410  by a horizontal control link  480 . An actuator  484  may be used to adjust the position of the horizontal follower support link  470  so as to adjust the range of horizontal travel. 
     Referring to  FIG. 9 , the vertical control system will be described. The exercise device  400  differs from earlier embodiments in that a cam and follower arrangement is not used to control the vertical travel of the foot receiving areas  422 . Instead, a flexible element  452  has one end connected to a portion of the cam system  424  that serves as a crank, an opposite end coupled to the foot support link  418  at coupling point  458 , and a mid portion that passes over a forward guide pulley  454  and a rearward guide pulley  456 .  FIG. 9A  shows a detail of part of the crank system  424  including the offset horizontal drive portion  427  and the attachment of the flexible coupling  452  that acts as a crank arm  453 . As will be clear to those of skill in the art, as the cam system  424  rotates about the cam axis  426 , the crank arm portion  453  pulls on the flexible coupling  452  causing oscillation of the foot support link  418 . This arrangement for vertical control may be referred to as a vertical drive system that is mechanically coupled to the foot support links. 
     Referring now to  FIG. 10 , a fifth embodiment of an exercise device in accordance with the present invention is shown generally at  500 . As with earlier embodiments, the device  500  includes a frame  502  with a first pivot axis  508 ; a guide link  510  having a first attachment point  512  attached to the first pivot axis  508  and a second attachment point  514 ; and a foot support link  518  having a forward end  520  pivotally attached to the second attachment point  514  of the guide link  510  and a foot receiving area  522  at a rearward end of the foot support link  518 . A vertical follower support link  532  and a horizontal follower support link  570  are both pivotally attached to a third pivot axis  572  of the frame  502 , with the vertical follower support link extending upwardly and the horizontal follower support link  570  extending forwardly. A vertical control follower  534  is pivotally attached to a follower end  540  of the follower support link  532  and extends forwardly to a control portion  548 . A mid portion  550  of the vertical control follower  534  serves as a cam engagement portion and engages the offset portion  530  of the cam system  524 . A flexible element  552 , serving as a mechanical vertical control coupling, has one end coupled to the control portion  548  of the follower  534  and a second end  558  coupled to a mid portion of the foot support link  518 . A mid portion of the flexible element  552  passes over a forward guide pulley  554  and a rearward guide pulley  556 . As discussed with respect to an earlier embodiment, this embodiment has a parallelogram-type arrangement of the foot support portion  560  of the flexible coupling  552  and the guide link  510 . 
     A horizontal control follower  576  is pivotally attached to a follower end of the horizontal follower support link  570  and extends upwardly to a control portion  578 . A mid portion of the follower  576  has a slot  582  defined therein that serves as an engagement portion for engaging the offset portion  530  of the cam system  524 . A horizontal control link  580  couples the control portion  578  of the horizontal control follower  576  to the guide link  510 . As will be clear from a review of the figures, as the cam system  524  rotates about the cam axis  526 , the offset portion  530  acts as both a horizontal control portion and a vertical control portion of the cam system and causes both the followers  534  and  576  to oscillate such that the foot receiving area  522  is caused to travel along a generally elliptical path. The cam system may take a form similar to in  FIG. 6A . The actuators  546  and  584  may be used to adjust the position of the vertical follower support link  532  and the horizontal follower support link  570 , respectively, so as to adjust the range of vertical and horizontal travel. Alternatively, the vertical follower support link  532  and horizontal follower support link  570  may be interconnected as one element or interlinked in a variety of ways so as to allow coordinated adjustment. 
     Referring now to  FIG. 11 , a sixth embodiment of an exercise device in accordance with the present invention is shown generally at  600 . The device has a frame  602  with a first pivot axis  608  defined thereon, a guide link  610  with a first attachment point  612  pivotally attached to the first axis  608  and a second attachment point at its lower end, a foot support link  618  having a forward end  620  pivotally attached to the second attachment point  614  and a rearward end defining a foot receiving area  622 . The device  600  is a free stride type device wherein horizontal motion depends on the user. The device  600  includes a simplified vertical control system having a cam  624  attached to a second pivot axis on a frame at cam axis  626 . The cam has a vertical control portion with offset portion  630 . In this embodiment, the vertical follower support takes the form of a linearly movable follower support  633  mounted to the frame  602 . The follower support  633  may be moved upwardly and downwardly on the frame by actuator  646 . A vertical control follower  634  is pivotally attached to the follower support  633  and extends upwardly to an upper end that acts as a control portion  648 . A mid portion  650  serves as a cam engagement portion and engages the offset portion  630 . The control portion  648  is coupled to the foot support link  618  by a mechanical vertical control coupling, taking the form of flexible element  652 . As with earlier embodiments, the flexible element  652  has a foot support portion  660  that is generally parallel to the guide link  610  and forms a parallelogram-type arrangement. The flexible element  652  is coupled to the foot support link  618  at coupling point  658 . As will be clear to those of skill in the art, as the cam system  624  rotates about the cam axis  626 , the foot receiving area  622  will be caused to move along a path of travel having a vertical component of motion. The exercise device of  FIG. 11  may be made into a fixed path device by adding a horizontal control portion, such as those shown in  FIG. 7 or 8 . Alternatively, the cam and follower arrangement, and flexible element routing, of  FIG. 11  may be substituted into other embodiments, such as the embodiments of  FIGS. 4-10 . Further combinations will be clear to those of skill in the art. 
     Referring now to  FIG. 12 , portions of a seventh embodiment of an exercise device in accordance with the present invention are schematically illustrated at  700 . The device  700  includes a guide link  710  with a first attachment point  712  that is pivotally attached to a frame, not shown, and a second attachment point  714  at its lower end. A foot support link  718  is pivotally attached to the second attachment point  714  at a mid portion thereof and has a foot receiving area  722  defined at a rearward end and an opposite forward end  723 . In this embodiment, the horizontal and vertical aspects of the cam system are divided into two portions. A horizontal control cam portion is shown at  724   a  and a vertical control cam portion is shown at  724   b , with each portion being rotatable about its own cam axis. The two portions  724   a  and  724   b  may be interconnected by a belt, chain, or other means so that they rotate in synchrony, or they may be uncoupled to allow independent rotation. Such a separated version of a cam system may be used with any embodiment of the present invention. In this embodiment, the vertical follower support takes the form of a linearly movable support  733  that may be mounted to the frame, not shown. A vertical control follower  734  is pivotally attached to the support  733  and has a control portion  740  at an opposite end and a mid portion  750  that engages the offset portion  730   b  of the cam portion  724   b . A vertical control link  752  interconnects the control portion  740  of the follower  734  with the forward end  723  of the foot support link  718  such that rotation of the vertical control cam portion  724   b  causes motion of the foot receiving area  722  along a path of travel having a vertical component of motion. In this embodiment, the horizontal follower support takes the form of a linearly movable support  771  mounted to the frame, not shown. An actuator  784  may be used to adjust the position of the support  771  relative to the horizontal cam portion  724   a . A horizontal control follower  776  is pivotally attached to the support  771  and has an opposite end serving as a control portion  778  and a mid portion with a cam engagement slot  782 . The horizontal control cam portion  724   a  has an offset portion  730   a  that engages the slot  782  such that rotation of the horizontal control cam portion  724   a  causes the control portion  778  of the horizontal control follower  776  to move upwardly and downwardly. The guide link  710  has an attachment portion  762  with a slot  763  defined therein. The control portion  778  of the horizontal control follower  776  has a pin  779  extending therefrom that engages the slot  763  in the attachment portion  762  of the guide link  710 . As such, the motion of the control portion  778  of the horizontal control follower  776  is translated into the guide link  710  being pivoted about the first attachment point  712 , causing the foot receiving area  722  to move along a path of travel having a horizontal component of motion. As shown, the length of the slot  782  and slot  763  may be chosen such that the horizontal follower support  771  may be moved relative to the horizontal control cam portion  724   a  to allow adjustment in the range of horizontal travel. 
     As will be clear to those of skill in the art, it is desirable in a free stride type exercise device to coordinate the movement of the foot receiving areas such that as one area moves rearwardly, the other area moves forwardly by an equal amount.  FIGS. 13 and 13A  illustrate one version of a horizontal coordination linkage  790  for providing such coordinated movement. The linkage  790  has a cross member  791  with a mid portion pivotally attached to the frame at  792 . One end of the cross member  792  is interconnected with the left guide link  710  by a left link  793  and the other end is interconnected with the right guide link by a right link  794 . It may also be desirable to provide resistance to this horizontal travel. Resistance may be provided in a variety of ways, such as a resistance element at the pivotal connection  792 . An additional resistance element may be interconnected with the coordination linkage or with the individual guide links in other ways. A coordination linkage such as  790 , or of other types, may be used with any embodiment of the present invention in which this type of coordination is desirable, typically a free stride type device. Resistance for horizontal motion may also be added to any embodiment. 
     Referring now to  FIG. 14 , a resistance and flywheel system is generally shown at  795 . A cam system  796  has a resistance wheel  797  attached thereto, to which resistance may be applied magnetically, electrically, or frictionally. A flywheel  798  is interconnected with the resistance wheel  797  by a belt but may be interconnected in other ways, or integrated with the resistance wheel. Other types of resistance may also be used. The remainder of the device shown in  FIG. 14  is provided just for reference. The resistance and flywheel system  795 , or other types of resistance and flywheel systems, may be used with any embodiment of the present invention. 
     Referring now to  FIGS. 15 and 16 , portions of an eighth embodiment of the present invention are shown generally at  800 . As with earlier embodiments, the device  800  includes a frame  802  that pivotally supports a guide link  810  and a foot support link  818  pivotally attached to the lower end of the guide link  810 . A crank system  824  is shown pivotally supported on the frame midway between the upper and lower ends of the frame. A horizontal follower support link  870  is pivoted to the frame at  872  and extends generally downwardly to a follower end. Horizontal control followers  876   a  and  876   b  are pivotally interconnected with the lower end of the follower support link  870  and extend rearwardly so as to engage the cam system  824 . The follower  876   a  represents the left follower and follower  876   b  represents the right follower. Alternatively, the illustrated followers  876   a  and  876   b  may represent the upper and lower positions of the follower resulting from rotation of the crank system  824 . The followers have a cam engagement slot  882  engaging an offset portion  830  of the cam system  824 . Comparing  FIGS. 15 and 16 , the follower end of the follower support link  870  is moved closer to the cam system  824  in  FIG. 16  than in  FIG. 15  resulting in increased travel of the control portion  878  of the horizontal control follower  876 . In  FIG. 15 , the control portion  878  would travel from the position marked as A 1  to the position marked as A 2 . Though not shown, the guide link  810  would have an attachment portion that extends forwardly and a horizontal control link would extend between the control portion  878  of the horizontal control follower  876  and this attachment portion. Such a link would extend between the location marked A 1  and B 1  or between position A 2  and B 2  depending on the position of the horizontal control follower  876 . The movement of the attachment portion of the guide link  810  between positions B 1  and B 2  would cause the lower end of the guide link to move between the positions marked as C 1  and C 2 . Referring now to  FIG. 16 , the control portion  878  of the horizontal control link  876  now travels between the positions marked as D 1  and D 2 , and a link interconnecting D 1  and E 1  or D 2  and E 2  would cause the lower end of the guide link to swing between the positions marked as F 1  and F 2 . It can be seen that this arrangement allows significant adjustability in the range of horizontal travel. While the embodiment of  FIGS. 15 and 16  illustrates only an apparatus for controlling horizontal travel, similar apparatus may be provided instead for vertical travel, or for both horizontal and vertical travel. It is noted that the horizontal control follower  876  and the cam engagement slot  882  are both curved along the length of the follower. 
     Referring now to  FIGS. 17 and 18 , components of a ninth embodiment of an exercise device in accordance with the present invention are shown generally at  900 . Many components are not illustrated in order to simplify the figures.  FIG. 17  shows a guide link  910  and associated foot support link  918 . The guide link has a forwardly extending attachment portion  962 . This embodiment has a follower support rocker  986  that is shaped generally like an inverted V with the top end of the follower pivotally interconnected to the frame, not shown, at  987 . The rocker  986  has a forward arm  970  that serves as a horizontal follower support link and a rear arm  932  that serves as a vertical follower support link. A horizontal control follower  976  has a forward end pivotally interconnected to the lower end of the horizontal follower support link  970  and extends rearwardly to a rearward end that serves as a control portion  978 . A mid portion has a cam engagement slot  982  that engages the offset drive portion  930  of the cam system  924 . A horizontal control link  980  links the control portion  978  of the horizontal control follower  976  to the attachment portion  962  of the guide link  910 . Thereby, rotation of the cam system  924  causes pivotal movement of the guide link  910  and movement of the associated foot receiving area along a path of travel having a horizontal component of motion.  FIG. 18  illustrates the vertical control portions of this embodiment. The follower support rocker  986  is now illustrated without the horizontal control follower. Instead, a vertical control follower  934  is pivotally connected to the lower end of the vertical follower support link  932  and extends forwardly to a control portion  940 . A mid portion of the follower  934  engages the offset portion of the cam system  924 . A flexible element  952  couples the control portion  940  of the vertical follower  934  to the respective foot support link  918  such that rotation of the cam system  924  causes movement of the foot receiving area along a path of travel having a vertical component of motion. An actuator  946  is attached to the rocker  986  so as to pivot the rocker and change the distance between the follower support links and the cam system  924 , causing adjustment in both horizontal and vertical travel. 
     Referring now to  FIG. 19 , portions of the horizontal and vertical controls are schematically illustrated to show the relationship between the cam system and the flexible elements and links. The cam system is shown at  924  and has two offset drive portions for controlling horizontal motion, which may be considered a horizontal control portion of the cam system. The cam system  924  further has two offset drive portions for vertical control, which may be considered a vertical control portion of the cam system. A portion of a flexible element is shown at  952  positioned above one of the outboard offset drive portions for vertical motion control and the horizontal control link  980  is shown positioned above one of the offset portions for horizontal motion control. As shown earlier, the link  980  and flexible element  952  are connected to followers, not directly to the cam system. Comparing the embodiment of  FIGS. 17-19  with the embodiment of  FIGS. 5-7 , it can be seen that the cam system in the embodiment of  FIGS. 17-19  is more complex in that the vertical and horizontal control portions are offset from one another by 90 degrees. In the embodiment of  FIGS. 5-7 , the horizontal and vertical control portions of the cam system for the left side of the machine are aligned with one another and the horizontal and vertical control portions for the right side are offset by 180 degrees with respect to the left side and are aligned with one another. 
     Referring now to  FIG. 20 , a tenth embodiment of an exercise device in accordance with the present invention is shown generally at  1000 . This embodiment is somewhat similar to the embodiment of  FIGS. 17-19 , but has a flexible element  1052  directly connected to a portion of the cam system  1024  rather than using a cam and follower arrangement.  FIG. 11  illustrates an alternative version of the embodiment of  FIG. 20 , in which the flexible element  1052  is connected to a crank  1025  that is offset from the remainder of the crank system  1024  and interconnected by a drive chain. 
     As will be clear to those of skill in the art, the embodiments of the present invention illustrated and discussed herein may be altered in various ways without departing from the scope or teaching of the present invention. Also, elements and aspects of one embodiment may be combined with elements and aspects of another embodiment. It is the following claims, including all equivalents, which define the scope of the present invention.