Stairclimber apparatus pedal mechanism

[0001] This is a continuation of U.S. patent application Ser. No. 10/183,605, filed Jun. 28, 2002, now U.S. patent Ser. No. 6,905,441; which in turn is a continuation-in-part of U.S. Pat. application No. 09/903,967, filed Jul. 12, 2001, now U.S. Pat. No. 6,855,093.

[0002] The present invention relates to exercise equipment and more particularly to exercise equipment which simulates aerobic stair climbing.

[0003] Stair climbing is recognized as a particularly effective type of aerobic exercise, and as a result, exercise machines facilitating this type of exercise are popular for both home and health club use.

[0004] There have been a variety of approaches taken in designing stair climbing apparatus, including the simulation of an actual staircase as illustrated in U.S. Pat. Nos. 3,497,215 and 4,687,195. Another approach has been to simulate the action of stair climbing by using a pair of reciprocating pedals.

[0005] As exemplified by U.S. Pat. No. 5,135,447, reciprocating pedal machines include a pair of pedals which are adapted for vertical reciprocating motion to provide a user who is standing on the pedals with a simulated climbing exercise. The vertical reciprocating motion is typically translated into a rotary motion by a suitable system of belts, gears and clutches, for example. The rotary motion (which may be imparted to a shaft, flywheel or the like) is opposed by a variable source of resistance force, typically an alternator, eddy current break or the like. The alternator is responsive to a control signal for selectively varying the level of resistance.

[0006] Other previous attempts at simulating stair climbing exercisers, such as Potts, Re. 34,959, feature independently oscillating pedals wherein the speed may be controlled and monitored by the operator, or may be preselected, controlled and monitored by computer control programs. Some such apparatuses produce an unnatural heel to toe flexure that reduces exercise efficiency. As will be appreciated, in the present invention, the foot pedal assembly remains parallel to a support surface throughout its entire range of motion, as the foot pedal assembly travels from its upper position to its lower position, thereby producing a more natural heel to toe flexure which increases exercise efficiency, making it easier and more enjoyable to exercise.

[0007] Additionally, the Potts disclosure simulates stair climbing through the utilization of a four-bar linkage pedal system and a frame plate. Such four-bar linkage pedal systems with frame plates tend to be noisy, have numerous pinch points, and substantially increase manufacturing and repair expense. As a result, it is desirable to decrease the manufacturing expense, improve the smoothness of pedal motion and decrease noise of stair climbing apparatuses.

[0008] In general, the objective of these systems is to simulate stair climbing. Stair climbing is characterized by its uniform, repetitive nature. Ideally, stair climbing apparatuses would provide a more dynamic climbing simulation to increase user interest. A need therefore exists for an improved stair climbing apparatus.

[0009] It is, therefore, a principal object and purpose of the present invention to provide an exercise apparatus that accurately and dynamically simulates stair climbing and is of a light weight and simple design.

[0010] It is an additional principal object and purpose of the present invention to provide a stair climbing exercise apparatus that maintains its pedal assembly in a level position, parallel to a support surface, throughout its entire range of motion, as the pedal assembly travels from its upper position to its lower position.

[0011] It is another object and purpose of the present invention to provide a stair climbing exercise apparatus that simulates a natural heel to toe flexure and thereby promotes exercise efficiency.

[0012] It is still another object and purpose of the present invention to provide a stair climbing exercise apparatus wherein the two pedals operate independently of each other. Each pedal is connected to the transmission by a separate belt drive.

[0013] It is an additional object and purpose of the present invention to provide a stair climbing exercise apparatus that is less stressful on the user's body ligaments than running, aerobic dancing or other aerobic exercises since it eliminates jarring of the body.

[0014] These and other objectives and advantages are provided by the present invention which is directed to a stair climbing exercise apparatus that maintains the user's feet parallel to a support surface throughout the apparatus' entire range of motion. It should be noted, however, that the exercise apparatus can also maintain the user's feet at an angle to the support surface if that proves desirable. The stair climbing exercise apparatus includes a frame that is adapted for placement on the floor, a resistance member which provides a resistive force to pedal assemblies, a transmission including a pair of one way clutches, a drive belt supported by the frame, independently operating right and left pedal assemblies including pedals, and a track. The track is secured to the frame and engages the right and left pedal assemblies such that the pedal assemblies move in a linear reciprocating path throughout their entire range of motion, as the pedal assemblies travel from their upper position to their lower position. Consequently, as the pedal assemblies move in their linear reciprocating path, the pedals remain parallel to a relatively fixed plane, such as the floor.

[0015] A second embodiment of the invention includes a frame, a resistance member which provides a resistive force to pedal assemblies, a transmission including a pair of one way clutches, a drive belt supported by the frame, independently operating right and left pedal assemblies including pedals, and an arcuate track. The track is secured to the frame and engages the right and left pedal assemblies such that the pedal assemblies move in an arcuate reciprocating path throughout their entire range of motion, as the pedal assemblies travel from their upper position to their lower position. Consequently, as the pedal assemblies move in their arcuate reciprocating path, the pedals remain parallel to a relatively fixed plane, such as the floor.

[0016] A third embodiment of the invention includes a frame that is adapted for placement on the floor, a resistance member which provides a resistive force to pedal assemblies, a transmission including a pair of one way clutches, a drive belt supported by the frame, independently operating right and left pedal assemblies including pedals, and a pair of linear tracks. The tracks are secured to the frame and engage the right and left pedal assemblies which have a pair of parallel support rollers that support the pedal assemblies on the tracks such that the pedal assemblies move in a linear reciprocating path throughout their entire range of motion, as the pedal assemblies travel from their upper position to their lower position. Consequently, as the pedal assemblies move in their linear reciprocating path, the pedals remain parallel to a relatively fixed plane, such as the floor.

[0017] A fourth embodiment of the invention includes a frame, a resistance member which provides a resistive force to pedal assemblies, a transmission including a pair of one way clutches, a drive belt supported by the frame, independently operating right and left pedal assemblies including pedals, and a pair of linear tracks. The tracks are secured to the frame and engage the right and left pedal assemblies utilizing linear bearings such that the pedal assemblies move in an arcuate reciprocating path throughout their entire range of motion, as the pedal assemblies travel from their upper position to their lower position. Consequently, as the pedal assemblies move in their arcuate reciprocating path, the pedals remain parallel to a relatively fixed plane, such as the floor.

[0018] The above embodiments of the invention can also include a data input means and a control means. The data input means permits the user to input control signals. The control means responds to the input control means to control the resistance member and apply a braking force to the pedal assemblies. The user can thus control the amount of resistance offered by the pedal assemblies and so can vary the degree of effort required to move the pedals. The invention thus can accommodate the individual needs and desires of different users.

[0031] Referring to the drawings in detail, FIGS. 1 and 2 show a stair climbing-type exercise apparatus 10 that includes a tubular frame 12, a control panel 14, a right pedal assembly 16 including a pedal 17 and a left pedal assembly 18 including a pedal 19. The frame 12 acts as the supporting structure for the stair climbing-type exercise apparatus 10 and can be of any suitable construction. In the illustrated embodiment, the frame 12 includes a generally U-shaped support member 20, a longitudinal support member 22 secured to the U-shaped support member 20, a cross member 24 secured to the longitudinal support member 22, a generally curved support member 26 secured to the longitudinal support member 22, a first vertical support member 28 secured to the curved support member 26, a second vertical support member 30 secured to the curved support member 26 and the longitudinal support member 22, and a cross member 32 secured to the second vertical support member 30. The first vertical support member 28 provides support for the control panel 14. Additionally, handrails 31, including handgrips 33, are rigidly secured to the U-shaped support member 20.

[0032] The U-shaped support member 20, the longitudinal support member 22 and the cross member 24 are configured for placement on a floor 34. Levelers 36 are provided on the U-shaped support member 20 so that if the floor 34 is uneven, the U-shaped support member 20 can be raised or lowered such that the U-shaped support member 20, the longitudinal support member 22 and the cross member 24 are substantially level. Rollers 38 are provided on the cross member 24 so that the stair climbing-type exercise apparatus 10 can be easily moved from one location to another.

[0033] The stair climbing-type exercise apparatus 10 includes a right cover 40 and a left cover (not shown) to protect and shield from view the internal components of the stair climbing-type exercise apparatus 10. The central location of the internal components, between the legs of the user, provides stability to the stair climbing-type exercise apparatus 10 and allows for a lightweight and simple design.

[0034] As described above, the pedal assemblies 16 and 18 oscillate independently of each other. As a result, when the right pedal 17 moves, it is not necessary that the left pedal 19 be also in motion. It should be noted that the pedals 17 and 19 remain essentially parallel to the floor or, in this case, the longitudinal support member 22 throughout the substantially vertical reciprocating motion of the pedals 17 and 19 with the longitudinal axis of the pedals 17 and 19 parallel to the longitudinal support axis 22. The operation of the right pedal assembly 16 is similar to the operation of the left pedal assembly 18. Thus, the operation of only the left pedal assembly 18 will be described. The left pedal assembly 18 is connected to a drive belt 42. The drive belt 42 can be connected to the left pedal assembly 18 in any way suitable to fixedly secure the drive belt 42 to the left pedal assembly 18. For example, the drive belt 42 can be connected to the left pedal assembly 18 by a winglet or a leaf spring. In the preferred embodiment, the drive belt 42 is secured to the left pedal assembly 18 by a U-shaped belt clamp 44 and bolt (not shown) which permits rapid and convenient release of the drive belt 42.

[0035] As illustrated in FIG. 2, once connected to the left pedal assembly 18, the drive belt 42 first engages a smooth idler pulley 46 rotatably mounted to the second vertical support member 30 by any suitable mounting means such as a shaft. Thereafter, the drive belt 42 continues down and engages a grooved clutch pulley 48. The grooved clutch pulley 48 is rotatably mounted to the second vertical support member 30 through a shaft 50. A second smooth idler pulley 52 operates to maintain the drive belt 42 in engagement with the grooved clutch pulley 48. The second smooth idler pulley 52 is located in close proximity-to the grooved clutch pulley 48 and is rotatably mounted to a shaft 54 by any suitable mounting means. The shaft 54 is in turn secured to the second vertical support member 30. With continued reference to FIG. 2, the drive belt 42 is also connected to a return spring 56 by a connector 58. The connector 58 can be any suitable connector known in the art. In the preferred embodiment, the connector 58 is a bolt and clamp arrangement. The return spring 56 travels over a guide sheave or pulley wheel 60 rotatably mounted to a shaft 62 by any suitable mounting means. The shaft 62 is in turn secured to the curved support member 26 in close proximity to the first vertical support member 28. Thereafter, the end of the return spring 56 is secured to the longitudinal support member 22 by any suitable securing means known in the art. In the preferred embodiment, the end of the spring 56 is hooked over a post 64 mounted to the longitudinal support member 22. The spring 56 has sufficient tension to return the left pedal assembly 18 to an upper position as illustrated in FIG. 2. When the user steps on the left pedal 19, the return spring 56 will extend so as to allow the end of the drive belt 42 attached to the spring 56 to move downward towards the floor 34. When the user's foot is lifted, the spring 56 will cause the left pedal assembly 18 to return to the upper position as illustrated in FIG. 2. The weight of the user, thus activates the pedal assemblies 16 and 18. Again, the operation of the right pedal assembly 16 is similar to the operation of the left pedal assembly 18.

[0036] In order to regulate the rate at which the right pedal assembly 16 and the left pedal assembly 18 can be moved and thus control the rate of simulated stair climbing, a variable source of resistance force is provided. Preferably, the variable source of resistance force is an alternator 66 and its associated combined flywheel and pulley 68 secured to the curved support member 26 as illustrated in FIG. 2. Rotational resistance is applied from the alternator 66 to the combined flywheel and pulley 68 and then to the drive belt 42 by a double reduction transmission 70. The double reduction transmission 70 includes the combined flywheel and pulley 68, a belt 74 connected to the combined flywheel and pulley 68 and a pulley 76 coupled to a rotatable shaft 78, a second pulley 80 coupled to the pulley 76 which is mounted on the shaft 78, and a drive belt 82 connecting the second pulley 80 to a third pulley 84 which is in turn coupled to the shaft 50. The belt 74 and the drive belt 82 can be any type of belt which promotes quiet operation of the stair climbing-type exercise apparatus 10, or drive chains, or any other type of flexible power transmitting device.

[0037] In addition, a pair of one way clutches 86, which are commonly known in the art, are utilized to connect each grooved clutch pulley 48 to the shaft 50. The function of the one way clutches 86 is to ensure that the shaft 50 and hence the alternator 66 can only rotate in one direction even though each grooved clutch pulley 48 will be rotating in both directions due to the reciprocating motion of the right pedal assembly 16 and the left pedal assembly 18.

[0038] As illustrated in FIGS. 2 and 3, the stair climbing-type exercise apparatus 10 further includes a right linear track member 88 and a left linear track member 90. The right linear track member 88 and the left linear track member 90 are secured to the U-shaped support member 20 at a bottom portion thereof and the cross member 32 at a top portion thereof by any suitable securing means.

[0039] With reference to FIG. 4, the right pedal assembly 16 and the left pedal assembly 18 will be described in further detail. As with the operation, the description of the right pedal assembly 16 is similar to the description of the left pedal assembly 18. Thus, the description of only the right pedal assembly 16 will be discussed. The right pedal assembly 16 includes the pedal 17, a track engaging bracket 94 and a support bracket 96 which supports and connects the pedal 17 to the track engaging bracket 94.

[0040] The pedal 17 includes a pad portion 98 which forms the tread portion of the right pedal assembly 16 and a U-shaped foot retaining wall 100 which aids in keeping the user's foot within the pad portion 98. The track engaging bracket 94 is generally U-shaped, and includes a flange portion 102 and a drive belt retaining portion 104. The drive belt retaining portion 104 is generally taller than the flange portion 102 and is located in close proximity to the second vertical support member 30. A set of rollers 106 are rotatably mounted to an inner surface 108 of the track engaging bracket 94. A roller 110 is rotatably mounted to the flange portion 102. A roller 112 is rotatably mounted to the drive belt retaining portion 104. Rollers 106, 110 and 112 are mounted by any suitable mounting means. In the preferred embodiment, as shown in FIG. 4, the rollers 106, 110 and 112 are mounted to the track engaging bracket 94 through apertures 114 by use of a nut 116 and a bolt 118 arrangement. The location of the rollers 106 and the roller 110 are adjustable so as to provide the maximum amount of contact with the right linear track member 88. As previously described, the drive belt retaining portion 104 includes the U-shaped belt clamp 44 which secures the drive belt 42 to the right pedal assembly 16.

[0041] As illustrated in FIG. 3, the right linear track member 88 and the left linear track member 90 each include a right track portion 120 and a left track portion 122. The right track portion 120 includes a track 124 which is generally hexagonal in shape. The left track portion 122 includes a track 126 which is generally rectangular in shape. With continued reference to FIGS. 2 and 3, during operation, rollers 106 ride within hexagonally shaped track 124 and rectangularly shaped track 126. For the right pedal assembly 16, roller 112 rides primarily on the left track portion 122 while roller 110 rides primarily on the right track portion 120. In this regard, the left pedal assembly 18 is a mirror image of the right pedal assembly 16. Thus, for the left pedal assembly 18, roller 112 rides primarily on the right track portion 120 while roller 110 rides primarily on the left track portion 122.

[0042] In order to operate the stair climbing-type exercise apparatus 10, the user will grasp the handgrips 33 and step up onto both the right pedal 17 and the left pedal 19. Under the weight of the user, the pedal assemblies 16 and 18 will move downward to their lowermost position near the floor 34. The user will then press the start/enter key on the control panel 14, which will prompt the user to enter the required information and to select among the various programs. First, the user is prompted to enter the user's weight. The control panel 14 then lists the various exercise programs and prompts the user to select a program. Once a program is chosen, the control panel 14 prompts the user to provide program-specific information. After the user has entered all the program-specific information, the user is prompted to specify the goal type (time or calories), to specify the desired exercise duration in either total time or total calories, and to chose between one of the numerous exercise levels. Once the user has entered all the required parameters, a microprocessor implements the chosen exercise program based on the information provided by the user. The user will then begin the simulated stair climbing exercise, adjusting his or her stride to a comfortable one. When the user then operates the right pedal assembly 16 and the left pedal assembly 18 in the previously described manner, the right pedal assembly 16 moves along the right linear track member 88 while the left pedal assembly 18 moves along and the left linear track member 90, in a linear path that simulates a natural heel to toe flexure that minimizes or eliminates stresses due to unnatural foot flexures since the pedal assemblies remain parallel to a relatively fixed plane, such as the floor 34 throughout their entire range of motion, as the pedal assemblies 16 and 18 travel from their upper position to their lower position. It should be noted, however, that the right pedal 17 and the left pedal 19 can be set at an angle to the floor 34 if such a position should prove desirable. The stair climbing-type exercise apparatus 10 thus provides a wide variety of exercise programs that can be tailored to the specific needs and desires of individual users, and consequently, enhances exercise efficiency and promotes a pleasurable exercise experience.

[0043] FIG. 5 illustrates a second general embodiment 150 of a stair climbing-type exercise apparatus pedal mechanism according to the invention. As noted previously, the second embodiment 150 of the invention includes a second type of pedal assembly and a second type of track, but still exhibits the desired parallel relationship between the pedal assemblies and a relatively fixed plane, such as a floor. As with the previous embodiment 10, the stair climbing-type exercise apparatus 150 includes, but is not limited to, the frame 12, the control panel 14, the drive belt 42, and the various motion controlling components, such as the alternator 66, the double reduction transmission 70, the combined flywheel and pulley 68, the belt 74, the drive belt 82 and the one way clutches. 86. The stair climbing-type exercise apparatus 150 differs primarily from the previous embodiment 10 in the nature and construction of the pedal assemblies and the track.

[0044] The stair climbing-type exercise apparatus 150 includes a right pedal assembly 152, a left pedal assembly (not shown) and an arcuate track member 154. As with the previous embodiment 10, the operation and description of the right pedal assembly 152 is similar to the operation and description of the left pedal assembly (not shown). Thus, the operation and description of only the right pedal assembly 152 will be discussed.

[0045] The right pedal assembly 152 of the stair climbing-type exercise apparatus 150 includes a lever arm 156 and a pedal 158. The drive belt 42 is connected to the lever arm 156 by a connector 160. The connector 160 can be any suitable connector as previously discussed or known in the art. The lever arm 156 is pivotably coupled to the longitudinal support member 22 at a pivot point 162. Likewise, the pedal 158 is pivotably coupled to the lever arm 156 at a pivot point 164. The pedal 158 includes a foot pad portion 166 which forms the tread portion of the pedal 158 and side walls 168. A roller 170 is rotatably mounted to an inner surface of the side walls 168 by any suitable mounting means.

[0046] With continued reference to FIG. 5, the arcuate track member 154 is centrally located between the right pedal assembly 152 and the left pedal assembly (not shown). The arcuate track member 154 is secured to the longitudinal support member 22 and to the first vertical support member 28 by any suitable securing means. The arcuate track member 154 also includes a centrally located slot 172 formed therein. As such, the roller 170, mounted to the pedal 158, rides within the slot 172 formed in the arcuate track member 154 during the pedal's entire range of motion, from its upper position to its lower position.

[0047] FIGS. 6 and 7 illustrate a third, and preferred, embodiment 172 of a stair climbing-type exercise apparatus pedal mechanism 172 according to the invention. This pedal mechanism 172 is similar to the first embodiment shown in FIGS. 2–4 as described above and the same reference numerals are used for like components of the third pedal mechanism 172. For simplicity, only the left pedal mechanism 172 is shown in FIGS. 6–7 and it will be understood that a right pedal mechanism would, preferably, be similar in construction. In this pedal mechanism 172, a track member 174 serves the same basic purpose as the track members 88 and 90 of the first embodiment. For reasons of cost and simplicity of manufacture, the preferred embodiment of the track member 174 is a hollow linear member having a square or rectangular cross section shown at a reference number 176 and is composed of a front support surface 178, a rear support surface 180, a right guide surface 182 and a left guide surface 184. The orientation of the track member 174 is generally vertical but with a small angular tilt forward similar to the orientation of the track members 88 and 90 shown in FIG. 2 so as to provide a realistic stepping experience for a user. A bracket assembly 186 including a bracket 188 is used to support the pedal 19 such that the pedal 19 stays generally horizontal or parallel with the plane of the floor as the bracket assembly 186 moves up and down the track member 174. Normally, a user will place his left foot on the pedal 19 longitudinally along the pedal axis indicated by a line 190 which also corresponds to the longitudinal axis of the apparatus 12 with his toes toward the forward end of the pedal 19 toward the track member 174 and his heel placed toward the after end of the pedal 19. Also, as shown in FIGS. 6 and 7, a protective shield 192 is secured over the front support surface 178. And, in similarity with the first embodiment of the invention, the drive belt 42 is clamped to the bracket 188 by a clamp 194 that includes a portion of a toothed gear 196 having its teeth engaged with the teeth on the belt 42.

[0048] FIGS. 8 and 9 provide detailed depictions of the bracket assembly 186 where for clarity the track member 174 is omitted. Primary support for the bracket 186 on the track member 174 is provided by a first support roller 198 and a second support roller 200. The support rollers 198 and 200 are mounted for rotation on the bracket 188 by a pair of axles indicated generally at 202 and 204. Preferably the support roller 198 is mounted on the lower part of the bracket 188 perpendicular to the pedal axis 190 and the second support roller is mounted on the upper portion of the bracket 188 as shown in FIGS. 8 and 9. Thus, the first support roller 198 will abut and roll along the front support surface 178 of the track member 174 and the second support roller will abut and roll along the second support surface 180 in parallel with the first support roller 198. This offset arrangement of the support rollers 198 and 200 where the first support roller 198 is located in parallel with and below the second support roller 200 serves to transmit the longitudinal forces generated when a user steps on the pedal 19 to the track member 174.

[0049] In order to aid in maintaining said pedal 19 in a horizontal position with respect to said track member 174, a positioning roller 206 is rotatably mounted on an axle, indicated generally at 208, which in turn in secured to the bracket 188 above the first support roller 198. The positioning roller 206 serves to prevent the pedal 19 from rotating with respect to the track member 174 when weight is removed from the pedal 19. In addition, at least one pair of guide rollers 210 and 212 mounted for rotation on a pair of axles 214 and 216 secured to each side of the bracket 188 can be used to provide lateral alignment of the bracket 188 on the track member 174. In this embodiment, the guide rollers 210 and 212 extend through the bracket 188, as indicated in FIG.9 by an opening 218, and roll vertically along said third and fourth guide surfaces 182 and 184 respectively of the track member 174. Additional guide rollers such as a third guide roller 220, as shown in FIGS. 6 and 7, can be used to aid in the lateral alignment of the bracket 188 on the track member 174.

[0050] FIG. 10 provides an exploded view of the preferred embodiment of said first support roller 198. The second support roller 200 is of substantially the same construction. In this embodiment of the invention, since the support rollers 198 and 200 bear most of the forces generated by the user it is preferable that the support rollers 198 and 200 be of robust construction. Here, the support roller 198 includes a cylinder 222 with a pair needle bearings 224 and 226 inserted with a press fit into each end 228 and 230 of the cylinder 220. The bearings 224 and 226 ride on the axle 202 which is not shown in FIG. 10. To provide for smooth and quiet operation, a sleeve 232 made of an elastomeric material such as rubber is placed over most of the surface of the cylinder 220.

[0051] FIG. 11 illustrates a fourth embodiment of a stair climbing-type exercise apparatus pedal mechanism 234 according to the invention. For simplicity, only the right pedal mechanism 234 is shown in FIG. 11 and it will be understood that a left pedal mechanism would be of similar in construction. In this embodiment, a linear bearing assembly, indicated generally at 236, is essentially substituted for the bracket assembly 186 of the third embodiment 172. Also, a vertical track or support member 238 serves the same purpose as the vertical track 174 in the pedal mechanism 172 in that it provides support for the linear bearing assembly 236 including the pedal 17 as it moves in a substantially vertical direction. Attached to the bearing assembly 236 is a bracket 240 to which the pedal 17 is secured. The linear bearing assembly 236 includes a rail 242 that is secured to a front surface of the vertical track 244 and a carriage 246 that is engaged with the rail 242. There are a number of commercially available linear bearing assemblies that can be used with a pedal mechanism of the type 234 including the Model No. SHS35LV1SS+600L which can be obtained from THK LTD. In this case, the bracket 240 is attached to the carriage 246. Also, as shown in FIG. 11, a protective shield 248 is secured to the vertical track 238 over the rail 242.

[0052] In second, third and fourth embodiments, the stair climbing-type exercise apparatus can use the same programs as the previously describes in connection with the apparatus 10 of the first embodiment. When the user then operates the stair climbing-type exercise apparatus 150 as described above, the pedal assemblies move along the arcuate track member 154 in an arcuate path that simulates a natural heel to toe flexure that minimizes or eliminates stresses due to unnatural foot flexures since the pedal assemblies remain parallel to a relatively fixed plane, such as the floor 34 throughout their entire range of motion, as the pedal assemblies travel from their upper position to their lower position.

[0053] Although the present invention has been described with reference to specific embodiments thereof, it will be understood that various changes and modifications will be suggested to one skilled in the art and it is intended that the invention encompass such changes and modifications as fall within the scope of the appended claims.