SYSTEMS AND METHODS FOR ADJUSTING A STIFFNESS OF FITNESS MACHINES

Abstract

A system for adjusting a stiffness of a fitness machine having a base and a mobile portion that moves relative to the base. A resilient body that resists movement of the mobile portion towards the base in a height direction. The resilient body has a length defined in a length direction perpendicular to the height direction, which increases when the mobile portion moves towards the base. An end stop prevents the length from increasing beyond a set maximum, the end stop being fixed relative to the base in the length direction. An actuator is operable to adjust the set maximum at which the end stop prevents the length of the resilient body from increasing. Resistance provided by the resilient body to resist movement of the mobile portion towards the base is unaffected by operation of the actuator when the length of the resilient body is less than the set maximum.

Claims

1. A system for adjusting a stiffness of a fitness machine operable by a user, the fitness machine having a base and a mobile portion that moves relative to the base during operation of the fitness machine, the system comprising: a resilient body that resists movement of the mobile portion towards the base in a height direction, wherein the resilient body has a length defined in a length direction that is perpendicular to the height direction, and wherein the length of the resilient body increases when the mobile portion moves towards the base; an end stop that prevents the length of the resilient body from increasing beyond a set maximum, the end stop being fixed relative to the base in the length direction; and an actuator operable to adjust the set maximum at which the end stop prevents the length of the resilient body from increasing, wherein a resistance provided by the resilient body to resist movement of the mobile portion towards the base is unaffected by operation of the actuator when the length of the resilient body is less than the set maximum.

2. The system according to claim 1, wherein the resilient body has a parabolic shape.

3. The system according to claim 2, wherein the mobile portion is supported at least in part by a vertex of the parabolic shape of the resilient body.

4. The system according to claim 1, wherein the mobile portion includes a running deck supporting a belt on which the user may run, wherein the belt moves parallel to the length direction of the resilient body during use of the fitness machine, and wherein operating the actuator moves the resilient body in the length direction.

5. The system according to claim 1, wherein the resilient body is coupled to the actuator via an arm, wherein the arm is configured such that moving the actuator in a first direction causes the resilient body to move in a second direction opposite the first direction.

6. The system according to claim 1, wherein the resilient body is coupled to the actuator via an arm, wherein the mobile portion includes a running deck supporting a belt on which the user may run, and wherein the arm has an opening through which the belt extends without contacting the arm.

7. The system according to claim 1, wherein the resilient body is coupled to the actuator via an arm, wherein the resilient body is coupled to a first pivot point of the arm, the actuator is coupled to a second pivot point of the arm different than the first pivot point, and wherein operating the actuator causes the arm to pivot about a third pivot point of the arm that is different than the first pivot point and the second pivot point of the arm.

8. The system according to claim 7, wherein the first pivot point is positioned between the second pivot point and the third pivot point such that the arm acts as a class 2 lever between the actuator and the resilient body.

9. The system according to claim 7, wherein the arm is positioned such that the mobile portion is between the resilient body and the third pivot point in the height direction.

10. The system according to claim 1, wherein the resilient body is a first resilient body, the length is a first length, the end stop is a first end stop, and the set maximum is a first set maximum, further comprising: a second resilient body functionally equivalent to the first resilient body, wherein the resilient body has a second length defined in the length direction; and a second end stop that prevents the second length of the resilient body from increasing beyond a second set maximum; wherein the actuator is operable to adjust the second set maximum at which the second end stop prevents the second length of the second resilient body from increasing, wherein a resistance provided by the second resilient body to resist movement of the mobile portion towards the base is unaffected by operation of the actuator when the second length of the resilient body is less than the second set maximum.

11. The system according to claim 10, wherein the first resilient body and the second resilient body are offset from each other in a width direction perpendicular to the length direction and perpendicular to the height direction.

12. The system according to claim 1, wherein the resilient body resists the mobile portion moving towards the base in a first phase and in a second phase, wherein in the first phase the mobile portion moves towards the base principally via bending of the resilient body, and wherein in the second phase the mobile portion moves towards the base principally via compression of the resilient body.

13. The system according to claim 12, wherein operating the actuator to adjust the set maximum at which the end stop prevents the length of the resilient body from increasing changes when the resilient body changes resistance from the first phase to the second phase.

14. The system according to claim 1, wherein the fitness machine is a treadmill and the mobile portion is a running deck supporting a belt on which the user may run.

15. The system according to claim 1, wherein the actuator comprises a lever manually moveable to adjust the set maximum at which the end stop prevents the length of the resilient body from increasing.

16. The system according to claim 15, wherein the actuator is configured to be retained in at least a first position and a second position, and wherein the actuator is moved between the first position and the second position by pivoting via the lever.

17. The system according to claim 16, wherein the lever pivots about a pivot axis, wherein the actuator is retained in the first position and in the second position via a spring, and where the spring moves from a first side of the pivot axis to a second side of the pivot axis when the actuator is moved from the first position to the second position.

18. The system according to claim 16, wherein the mobile portion includes a running deck supporting a belt on which the user may run, wherein the belt moves parallel to the length direction of the resilient body during use of the fitness machine, wherein the lever pivots in a plane parallel to the length direction.

19. The system according to claim 15, wherein the resilient body is coupled to the actuator via an arm, and wherein the lever is pivotally coupled to the arm via a linkage therebetween.

20. A method for adjusting a stiffness of a fitness machine operable by a user, the fitness machine having a base and a mobile portion that moves relative to the base during operation of the fitness machine, the method comprising: resisting via a resilient body movement of the mobile portion towards the base in a height direction, wherein the resilient body has a length defined in a length direction that is perpendicular to the height direction, and wherein the length of the resilient body increases when the mobile portion moves towards the base; preventing the length of the resilient body from increasing beyond a set maximum via an end stop that is fixed relative to the base in the length direction; and operating an actuator to adjust the set maximum for which the length of the resilient body may extend during operation of the fitness machine, wherein a resistance provided by the resilient body to resist movement of the mobile portion towards the base is unaffected by operating the actuator when the length of the resilient body is less than the set maximum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present disclosure is described with reference to the following drawing.

[0051] FIG. 1 is a rear perspective view of a fitness machine incorporating an exemplary adjustable shock absorption system according to the present disclosure.

[0052] FIG. 2 is a side view of a lower portion of a fitness machine having adjustable shock absorption.

[0053] FIG. 3 is a close-up side view of the embodiment similar to that of FIG. 2.

[0054] FIG. 4 is a top-down view of the lower portion of the fitness machine of FIG. 2.

[0055] FIG. 5 is an exploded perspective view depicting a system similar to that of FIG. 2.

[0056] FIG. 6 is a close-up view of the system of FIG. 5.

[0057] FIG. 7 is a perspective view of an exemplary resilient body such as may be incorporated within an adjustable shock absorbing system according to the present disclosure.

[0058] FIG. 8 depicts exemplary data for adjustable shock absorption systems according to the present disclosure, particularly the stiffness versus gap size between a resilient body and an end stop.

[0059] FIGS. 9A-9D depict further exemplary data for testing adjustable shock absorption systems according to the present disclosure.

[0060] FIG. 10 depicts an exemplary control system for operating adjustable shock absorption systems according to the present disclosure.

[0061] FIG. 11 is a close-up perspective view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0062] FIGS. 12A-12C are close-up side views of an arm from an adjustable shock absorption system such as that of FIG. 11 in three different positions.

[0063] FIG. 13 is a close-up perspective view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0064] FIG. 14 is a close-up perspective view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0065] FIG. 15 is a close-up top view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0066] FIG. 16 is a close-up side view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0067] FIG. 17 is a close-up side view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0068] FIG. 18 is a close-up side view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0069] FIG. 19 is a close-up side view of part of another embodiment of an adjustable shock absorption system according to the present disclosure.

[0070] FIG. 20 is a rear perspective view of another fitness machine incorporating an exemplary adjustable shock absorption system according to the present disclosure.

DETAILED DISCLOSURE

[0071] The present disclosure generally relates to systems and methods for providing shock absorption for fitness machines, including systems in which the amount of shock absorption is adjustable. FIG. 1 depicts an exemplary embodiment of a fitness machine 1 incorporating an adjustable shock absorption system 40 according to the present disclosure. In the illustrated embodiment, the fitness machine 1 is a treadmill having a belt 2 that is rotated such that a user may run or walk on the belt 2. FIGS. 1 and 2 show the belt 2 having a running upper strand 3 and a returning lower strand 4 that continuously cycle about belt rollers 6 in a conventional manner. While the present disclosure principally discusses embodiments in which the fitness machine 1 is a treadmill having a motor that rotates the belt 2, it should be recognized that the present disclosure equally applies to treadmills in which forces by the user rotate the belt 2, as well as to fitness machines 1 other than treadmills (e.g., stair climbers).

[0072] The fitness machine 1 of FIGS. 1 and 2 is supported on a base 20 having a front 21 and rear 22 (also referred to as extending a length direction or longitudinal direction therebetween), left 23 and right 24 (also referred to as extending in a width direction or transverse direction therebetween), and top 25 and bottom 26 (also referred to as extending in a height direction therebetween). Operation of the fitness machine 1 is controlled by a console 10 in a manner known in the art, which for example controls the speed of the belt 2, an incline of the belt 2 relative to a horizontal plane (e.g., via a height adjustment system 30 in a manner known in the art), resistance levels (for example with bicycles, rowers, elliptical trainers, and/or treadmills in which the user rotates the belt), and/or other functions customary for operating fitness machines 1, as known in the art. The base 20 of the fitness machine 1 is supported on feet 14 and casters 12. As will be discussed below, manual controls 116 for adjusting the stiffness may be provided. The manual controls 116 may be moveable by the user in a manner similar to systems known in the art (e.g., here, selectable among 4 stiffness settings). However, as will become apparent, the presently disclosed systems and methods effectuate this stiffness adjustment in a completely different manner.

[0073] Through experimentation and development, the present inventors have identified that fitness machines presently known in the art typically have a fixed or minimally adjustable stiffness. In the case of treadmills, this may mean the stiffness of the running surface, for example. Even in fitness machines that do include some degree of adjustable stiffness (for example, the Life Fitness T5 Treadmill), existing systems do not provide a sufficient range of adjustability for the level of stiffness experienced by the user. Likewise, the present inventors have identified that with systems presently known in the art, some users (e.g., light weight users) have a difficult time detecting changes in stiffness, for example between medium and soft settings. Additionally, some users of fitness machines require an especially soft stiffness. The present inventors have found that this is not accomplished by fitness machines that also provide a traditional stiffness, requiring dedicated equipment (and thus increasing the cost for a facility to offer such workout regimens). As such, the present inventors have recognized an unmet need for a fitness machine that offers a full range of stiffness settings, for example from a stiffer setting corresponding to running on concrete down to a very-soft setting corresponding to sand, a gymnastics floor, or a pool springboard, for example.

[0074] FIGS. 2-3 depict two exemplary systems 40 for providing shock absorption, and in these examples systems 40 in which the shock absorption is adjustable to provide a range of stiffness selections. In each example the fitness machine 1 includes a base 20 and a mobile portion 42 that is engageable by the user, which consequently moves relative to the base 20 during operation of the fitness machine 1. The mobile portion 42 shown is a running deck that supports the belt 2 in a conventional manner, which moves up and down relative to the base 20 from the impact of the user running or walking thereon.

[0075] The system 40 include one or more resilient bodies, for example leaf springs 50, that resist movement of the mobile portion 42 towards the base 20, particularly in a height direction HD. In certain embodiments, the leaf spring 50 is made of an elastomeric material, such as rubber, polyurethane, and/or other polymers.

[0076] The embodiments shown in FIGS. 2-4 each include four distinct and separate leaf springs 50 that work independently. These leaf springs 50 are each configured to function in the same or in a similar manner as the others. Thus, for simplicity, the leaf spring 50 and corresponding function are presently discussed singularly. Likewise, the leaf spring 50 described herein may be used in combination with one or more other shock absorbing devices presently known in the art.

[0077] FIG. 7 depicts a close-up view an exemplary leaf spring 50 as incorporated within the system 40 of FIGS. 2-4. The leaf spring 50 is a resilient body that extends between a first end 51 and second end 52. A length L is defined between the first end 51 and the second end 52 in a length direction LD that is perpendicular to the height direction HD. The leaf spring 50 has a parabolic shape that opens downwardly and supports the mobile portion 42 at or near a vertex 54 of the parabolic shape. In the example shown, the mobile portion 42 rests on the leaf spring 50 without being coupled to the mobile portion 42. For simplicity, the fitness machine may also be referred to as having a length direction and a height direction that unless otherwise stated may be substantially parallel to those of the resilient bodies 50.

[0078] A first pin hole 55 extends transversely through the leaf spring 50 at the first end 51, and in certain embodiments a second pin hole 57 also extends transversely through the leaf spring at the second end 52. The first pin hole 55 (and second pin hole 57 when present) are each configured to receive a pin such as first pin 66 therethrough, as discussed below. The first end 51 and second end 52 have a substantially circular side profile that is thicker in the height direction HD than the resilient body therebetween for added strength. The first pin hole 55 and second pin hole 57 each also have substantially circular side profiles that are approximately centered within the circular profiles of the first end 51 and the second end 52. However, this is merely an exemplary configuration for the leaf spring 50, which may be configured to have differing side profiles between the first end 51 and the second end 52 to alter the characteristics of the shock absorption provided by the leaf spring 50, for example.

[0079] FIGS. 3 and 5-6 depict how these leaf springs 50 may be coupled between the base 20 and the mobile portion 42, shown here for an adjustable shock absorption system 40 similar to that of FIG. 2. The first end 51 of the leaf spring 50 is pivotally coupled to the base 20 via a bracket 60. The bracket 60 includes a plate 62 with a bottom segment 197 extending perpendicularly away from the plate 62. The plate 62 is coupled to the inside of the base 20, for example via welding, fasteners (e.g., nuts and bolts), or other methods presently known in the art. Two ears 195 extend upwardly from the bottom segment 197 and are substantially parallel to the plate 62. A first pin hole 53 extends through each of the cars 195, the interiors of the first pin holes 53 being smooth or threaded depending on the first pin 66 to be received. The first pin holes 53 are configured to receive a first pin 66, where the first pin 66 is also being received through the first pin hole 55 in the first end 51 of the leaf spring 50 to therefore pivotally couple the leaf spring 50 to the bracket 60.

[0080] Returning to FIG. 7, an exemplary first pin 66 is shown extending between a head 143 and tip 141 with a smooth shaft therebetween. An opening 145 is defined near the tip 141 for receiving a cotter pin 147 after the first pin 66 has been received through the bracket 60 (and through the first end 51 of the leaf spring 50). It should be recognized that the bracket 60 depicted in FIG. 7 is shown as only a partial view so as to not obscure the first pin hole 55, omitting the cars 195, for example. Other types of fasteners known in the art may also or alternatively be used as the first pin 66, including those with set screws, threads (e.g., engaging with a nut 67 as shown in FIG. 3), or press fits, those integrated with the leaf spring 50 (e.g., via over-molding), those welded to the bracket 60, and/or those used in conjunction with cars 195 of the bracket 60 that prevent lateral translation of the first pin 66, for example. These same examples for the first pin 66 also apply to a second pin 82 for the second end 52 of the leaf spring 50, which is discussed below.

[0081] In this manner, the leaf spring 50 is permitted to freely rotate about the first pin 66, but the first end 51 is prevented from translating in the length direction LD or in the height direction HD relative to the base 20.

[0082] As shown in FIGS. 5-6, the systems 40 further include end stops 70 that are fixable relative to the base 20, in some embodiments in an adjustable manner. A separate end stop 70 is shown provided for each leaf spring 50 in a similar manner as the brackets 60. However, other configurations are also contemplated. For simplicity, the end stops 70 are principally discussed singularly. In the embodiment of FIGS. 5-6, each end stop 70 extends from a top 156 to bottom 158 with a vertical segment 162 therebetween. Holes 160 are provided through the bottom 158 of the end stop 70 for mounting the end stop 70 to the base 20, specifically via a frame 100 to be discussed further below. The holes 160 receive threaded studs 166 that extend upwardly from the frame 100, in this example four threaded studs 166 for each end stop 70. Nuts 168 engage the threaded studs 166 to retain the end stops 70 on the frame 100. It should be recognized that other methods may be used for coupling the end stops 70 to the frame 100, including welding, other types of fasteners, and/or the like.

[0083] For each end stop 70, a floor 164 extends perpendicularly from the vertical segment 162, which intersects at a front end to a stop wall 80 connecting the floor 164 to the top 156. In the embodiment of FIGS. 5-6, the stop wall 80 is concaved such that a lip 154 extends rearwardly from the top 156 where the top 156 meets the stop wall 80. The contour of the stop wall 80 is configured in this manner to correspond with the contour of the second end 52 of the leaf spring 50, for example having a same approximate diameter. The second end 52 of the leaf spring 50 can thus slide forwardly along the floor 164 of the end stop 70 in the length direction LD until it engages the stop wall 80. The lip 154 that extends rearwardly from the top 156 is thus configured to prevent the second end 52 of the leaf spring 50 from moving upwardly in the height direction HD upon contacting the stop wall 80. It should be recognized that the lip 154 is not required and other forces such as the weight of the moving portion 42 and the user also act to prevent movement of the second end 52 upwardly in the height direction HD.

[0084] Certain embodiments of systems 40 provide that the position each end stop 70 is adjustable in the length direction LD relative to the base 20, which as will become apparent provides adjustability of the stiffness for the fitness machine 1. As shown in FIGS. 3 and 7, a gap G exists between the second end 52 of the leaf spring 50 (or in certain embodiments discussed below, a second pin 82 extending therethrough) and the stop wall 80 of the end stop 70. This gap G is greater when the user is not generating any force on the mobile portion 42, for example when the user is mid-air while running on a treadmill. Since the stop wall 80 limits the forward translation of the second end 52 of the leaf spring 50, the gap G between the second end 52 and the stop wall 80 can be adjusted to modify the amount and/or characteristics of shock absorption being provided by the leaf spring 50.

[0085] The position of the stop wall 80 for an end stop 70 is adjustable by moving the support frame 100 to which the end stop 70 is coupled, as described above. As shown in FIGS. 4-5, the support frame 100 includes cross members 104 extending between a first end 125 and a second end 127 that run perpendicular to the length direction LD, as well as side members 102 extending between a first end 121 and second end 123 and a mid-support 103 extending between a first end 131 and second end 133 that all run parallel to the length direction LD. The cross members 104, side members 102, and mid-support 103 may vary in number from that shown and may be coupled together and/or integrally formed, for example. The end stops 70 are coupled to the support frame 100 such that when multiple leaf springs 50 are provided, one or more leaf springs 50 (and therefore the gaps G associated therewith) are adjustable together.

[0086] With reference to FIGS. 4-6, the support frame 100 is translatable relative to the base 20 in the length direction LD via engagement within a track system 90. In this embodiment, support beams 196 extend inwardly from the base 20, each of which having a hole 198 in the height direction HD. A base 188 rests on the top of the support beam 196. In the example shown, the base 188 includes a plate 190 that rests on the top of the support beam 196, and wall 192 extending perpendicularly downwardly from the plate 190. The wall 192 engages with an inside edge of the support beam 196 to prevent rotation of the base 188 relative to the support beam 196.

[0087] An elongated hole 194 is provided through the plate 190 of base 188. An elongated standoff 184 having an exterior shape substantially matching the interior shape of the elongated hole 194 is received in part within the elongated hole 194. A hole 186 is defined through the elongated standoff 184 in the height direction HD, which in the present example has a circular cross section. As shown in FIG. 6, the elongated standoff 184 is also received in part within a slot 170 defined within the support frame 100, specifically through the side members 102 in close proximity to the mounting location of each end stop 70. The exterior shape of the elongated standoff 184 is also configured to have a width 187 corresponding to a width of the slot 170 in the support frame 100. In the example shown, a top of the elongated standoff 184 is substantially flush with a top for the side member 102 of the support frame 100 when assembled.

[0088] A flanged coupler 172 has a flange top 176 with a barrel 174 extending downwardly therefrom. A hole 178 is defined through the flanged coupler 172. The barrel 174 is configured to have an outer diameter corresponding to the interior diameter of the hole 186 in the elongated standoff 184 such that the barrel 174 is received therein. When assembled, the underside of the flange top 176 is approximately flush with the top of the side member 102, preventing movement in the height direction HD. A fastener 180 (e.g., a bolt) having a head 182 is received through the flanged coupler 172, the elongated standoff 184, the plate 190, and the hole 198 in the support beam 196 and threadingly engages a nut 183 on the opposite side of the support beam 196. It should be recognized that alternate methods of fastening known in the art may also be used. Once coupled together in this manner, the support frame 100 is translatable in the length direction LD by the elongated standoff 184 sliding within the slot 170, but prevented from rotating (i.e., due to like-engagement between the support frame 100 and other support beams 196 of the base 20), moving transversely, or moving in the height direction HD.

[0089] It should be recognized that other embodiments are contemplated in which there are multiple, separate support frames 100 for changing the positions of one or more leaf spring 50 separately from other leaf springs 50. For example, leaf springs 50 could be adjusted independently, all together, or in subgroups. In certain embodiments, two support frames 100 may be provided to enable separate adjustment between front and rear pairs of leaf springs 50. This separation of adjustability enables one set of leaf springs 50 to travel a greater distance than another set of leaf springs 50, for example.

[0090] The support frame 100 and particularly its position in the length direction LD may be moved and locked in place using various forms of hardware known in the art. For example, a manual adjustment mechanism may be provided, such as a threaded hand crank or fasteners coupling the support frame 100 to discrete openings within the base 20 (e.g., the manual controls 116 of FIG. 1 in a manner known in the art). Alternatively, cam locks as presently known in the art may be used to lock the support frame 100 to the base 20 once in the desired position, for example. The locking hardware may be electrically actuated, including electrically actuated cams.

[0091] With reference to FIG. 3-5, the support frame 100 is moveable via an actuator 110, which may be operated via electrical momentary switches, a control system 200 as discussed below (including via the console 10), or other methods known in the art. The actuator may be an electrical, pneumatic, and/or hydraulically actuator known in the art. For example, a mechanism similar to a conventional height adjustment mechanism 30 (see FIG. 1) for a treadmill could be employed to move the support frame 100. One such commercially available height adjustment mechanism is Treadmill incline motor lift actuator 0K65-01192-0002/CMC-778, produced by P-Tech USA. The actuator 110 may also itself provide the locking function for the positioning of the support frame 100.

[0092] The actuator 110 is coupled between the base 20 and a front end 101 of the support frame 100 to translate the support frame 100 relative to the base 20 in the length direction LD. Specifically, a first end of the actuator 110 is coupled to a cross member 126 of the base 20 with brackets 119 and fasteners 117, such as bolts, pins, and/or the like. An opposite end of the actuator 110 is coupled to the support frame 100, also via a bracket 119 and fastener 117 in a conventional manner, which may be the same bracket 119 and/or fastener 117 provided between the actuator 110 and the cross member 126 as described above. It should be recognized that the actuator 110 may be coupled between the base 20 and support frame 100 in alternate positions as well. Likewise, other types of actuators 110, including scissor-type actuators, rack and pinion actuators, and/or other configurations known in the art may also be used.

[0093] The exemplary actuator 110 of FIGS. 4-5 includes a motor 112 that rotatably engages with a gearbox 113. Rotation of the motor 112 extends or retracts a rod 114 relative to a housing 115 of the gearbox 113 in the length direction LD. Specifically, rotation of the motor 112 in a first direction causes rotation of the rod 114 through the gearbox 113, where a threaded engagement between the outer diameter of the rod 114 and the interior of the housing 115 causes the rod 114 to extend or retract in the length direction LD relative to the housing 115 as the motor 112 rotates. In contrast, rotation of the motor 112 in an opposite direction causes retraction of the rod 114 in the opposite manner. It should be recognized that either the rod 114 or the housing 115 may be coupled to the support frame 100 (with the other to the base 20), depending on the configuration of the actuator 110. In this manner, operating the actuator 110 causes movement of the support frame 100 relative to the base 20. This movement of the support frame 100 consequently adjusts the gap G between the leaf springs 50 and the stop walls 80 of the corresponding end stops 70, as discussed above. In the example shown, all leaf springs 50 are adjusted simultaneously and equivalently (i.e., a same distance in the length direction LD).

[0094] With reference to FIGS. 3-4, it should be recognized that the length L between the first end 51 and the second end 52 of the leaf spring 50 is caused to increase when the mobile portion 42 moves towards the base 20 during operation of the fitness machine 1. In other words, the parabolic shape of the leaf spring 50 is caused to flatten during use. However, the length L of the leaf spring 50 may be constrained by engagement between the second end 52 and the stop wall 80 of the end stop 70. Once the length L can no longer increase, the leaf spring 50 may further resist movement of the mobile portion 42 towards the base 20, but now through a different mechanism, namely, compression of its resilient material. Therefore, adjusting the gap G between the leaf spring 50 and the stop wall 80 of the end stop 70 adjusts the allowable length L of the leaf spring 50, and thus the profile of resistance provided by the system 40, which consequently adjusts the stiffness of the fitness machine 1.

[0095] The resistance provided by the system 40 varies depending upon whether the second end 52 of the leaf spring 50 is engaging the stop wall 80, creating two or more distinct phases. In an initial phase referred to as first phase P1 (discussed further below and shown in FIG. 6), the resistance provided by the leaf spring 50 against movement between the mobile portion 42 and the base 20 is primarily provided via bending deformation of the leaf spring 50. In other words, the length L of the leaf spring 50 may change, increasing as the mobile portion 42 moves towards the base 20. However, once the second end 52 engages with the stop wall 80 of the end stop 70 (or second pin 82 extending therethough for an embodiment discussed further below), which is been fixed relative to the base 20, a second phase P2 begins in which a length L of the leaf spring 50 can no longer change. At this stage, further movement of the mobile portion 42 towards the base 20 is resisted by the leaf spring 50 primarily by compressing the leaf spring 50, rather than by bending the leaf spring 50 as provide during phase 1 P1. In other words, the parabolic shape can no longer get wider longer, and thus the leaf spring 50 starts to compress. In certain embodiments, the term primarily with respect to the basis for resistance means the basis has a greater contribution than any other basis (i.e., bending contributing to the resistance more than compressing contributes to the resistance). In certain embodiments, the basis having the greatest contribution provides more than 50% of the total resistance. In certain configurations, approximately 50%, 70%, 80%, 90%, 95%, or other portions of the stiffness is provided in phase 2 P2.

[0096] As shown in FIGS. 8 and 9A-9D, the resistance provided by the leaf spring 50, also referred to as spring stiffness, is thereby provided as a function of whether the resistance is in phase one P1 or phase two P2. Likewise, the selection of when a transition T from phase one P1 to phase two P2 occurs (i.e., the position of the mobile portion 42 relative to the base 20) is based upon the gap G provided between the second end 52 of the leaf spring 50 and the stop wall 80. In certain embodiments, the leaf spring 50 is selected such that the resistance provided in phase one P1 is substantially lower than the resistance provided in phase two P2. For example, in certain cases the spring stiffness in phase one P1 is no more than 50 percent of the spring stiffness in phase two P2. In further examples, the spring stiffness in phase one P1 is no more than 10 percent of the spring stiffness in phase two P2, or one order lower.

[0097] It should be recognized that while the present disclosure generally refers to the leaf spring 50 providing a resistance in each of the phases, here phase one P1 and phase two P2, the resistance may also be considered a resistance profile. For example, the resistance need not be constant, nor linear within a given phase (such as in phase two P2 of FIG. 8). It should also be recognized that the larger the gap G between the second end 52 of the leaf spring 50 and the stop wall 80, the greater the deflection of the mobile portion 42 relative to the base 20 before phase 2 P2 is entered. In other words, a larger gap G provides for more deflection within the softer stiffness of phase one P1. As discussed above, the systems 40 and methods presently disclosed allow the user to fully configure the stiffness of the shock absorption for the fitness machine 1, and specifically when this greater resistance of phase two P2 is felt by the user.

[0098] It should be recognized that additional phases may also be provided by the system 40. For example, instead of pivotally fixing the first end 51 of the leaf springs 50 to the bracket 60, the first end 51 may also be translatable in the length direction LD in a similar or same manner as the second end 52. An example of this configuration is shown in FIG. 3, specifically for the forward-most bracket 60 shown. A stop wall 81 is integral with or coupled to the bracket 60, which provides a limit for the first end 51 of the resilient body 50 moving rearwardly. The stop wall 81 thus prevents translation of the first end 51 of the leaf spring 50 without the use of a first pin 66. Other features may also be included to restrict movement of the first end 51 in the height direction HD, for example, such as the slot 74 discussed for the end stop 70 discussed above. In this embodiment, the first end 51 has a gap G2 of travel before being constrained by stop wall 81, thereby changing the overall resistance profile for the system 40 relative to the pivoting embodiment of the rear-most bracket 60 shown. Additional phases or impacts to the overall resistance profile may be provided by controlling one or more leaf springs 50 separately from others, such as having a gap G (and/or gap G2) that is greater for rear leaf springs 50 relative to forward leaf springs 50, for example.

[0099] It will also be understood that the leaf spring 50 need not be shaped as shown in the figures, which may also or alternatively vary in number and/or position relative to the base 20 and mobile portion 42 of the fitness machine 1. The positions of the leaf springs 50 relative to the base 20 may also be adjustable in ways other than adjusting the gap G between the leaf spring 50 and the stop wall 80 (and/or gap G2 for stop wall 81). Similarly, the end stops 70 may be adjustable in the height direction HD in addition to, or in the alternative to in the length direction LD, further modifying the manner in which the adjustments change the resistance profiles of the leaf springs 50.

[0100] Additional testing results for a fitness machine 1 and system 40 as shown in FIGS. 2-4 are provided in FIGS. 9A-9D, which were tested on a hydraulic MTS test system in which the leaf springs 50 were compressed for 0.45 inches in the height direction HD in 2 Hz and 5 Hz sinusoidal motion-controlled mode. In the plots, the horizontal axes represent the amount of compression (the same for the four plots), while the vertical axes represent the applied forces to reach the corresponding deformations. The scale of the vertical axes is kip, or 1000 lbf.

[0101] The curves demonstrate that there was little difference between responses under the two tested frequencies. FIG. 9D depicts the results when the leaf spring 50 was constrained at the original length L (no gap G to the stop wall 80), whereby the resultant force reached about 500 lbf at 0.45 inch vertical travel. FIG. 9C was tested with 25% gap G (the percentage compared to the maximum gap, or equivalently the gap G needed to let the leaf spring 50 free bend into a straight beam. In this case, 25% was about 2.8 mm, where the peak loading reached about 400 lbf. FIG. 9B was tested at 50% gap G (about 5.6 mm), where about 250 lbf was needed to compress the spring down by 0.45 inch. FIG. 9A was tested at 75% gap G, with maximum force of about 120 lbf. Collectively these results demonstrate how the stiffness of the fitness machine 1 can be effectively controlled using the system 40.

[0102] FIGS. 2-3 depict an alternative configuration for an end stop 70, which may be used alone or in conjunction with the end stop 70 discussed above for the system 40 of FIGS. 5-6. In this embodiment, the stop wall 80 is formed at the end or termination of a slot 74 defined within the sides of the end stop 70. Specifically, the end stop 70 has a top 71 with two arms 73 that extend rearwardly from a front 76 to finger tips 77. In the example shown, the finger tips 77 extend from the front 76 of the end stop 70 approximately the same distance as do base tips 79 such that a slot 74 is formed between the finger tip 77 and base tip 79 on each side of the end stop 70. As shown in the top-down review of FIG. 4, providing two arms 73 for each end stop 70 allows the leaf spring 50 to be positioned between the arms 73, which retains the leaf spring 50 in position relative to the left 23 and right 24 of the fitness machine 1.

[0103] This embodiment of end stop 70 is configured such that a second pin 82 extending through the second pin hole 57 in the second end 52 of the leaf spring 50 is translatable in the length direction LD within the slot 74. The second pin 82 is insertable into the slot 74 at least via the open end 75 opposite a stop wall 80 and front 76. The clearance C of the slot 74 is selected based on the diameter of the second pin 82 such that no movement is permitted in the height direction HD. Forward translation of the second end 52 of the leaf spring 50 may thus be prevented by engagement between the stop wall 80 and the second pin 82 extending through the second end 52, and/or engagement between the stop wall 80 and the second end 52 itself.

[0104] With continued reference to FIGS. 2-3, the second pin 82 may be the same or similar to the first pin 66, or be formed of other hardware known in the art. In certain examples, the second pin 82 and/or first pin 66 are rods retained in place via cotter pins and/or the like. In another example, the second pin 82 and/or first pin 66 are over-molded to be retained on the leaf spring 50 to extend outwardly therefrom, for example. Whether or not first pins 66 and/or second pins 82 are used, the leaf spring 50 may also or alternatively be coupled to the mobile portion 42, for example at the vertex 54.

[0105] The present disclosure also anticipates differing configurations for the support frame 100 being translatably moveable relative to the base 20 in the length direction LD. FIG. 3 depicts an embodiment of a system 40 providing this adjustment via engagement via a different track system 90 than discussed above. This track system 90 includes a sliding track 92 that is coupled to the base 20 via track mounts 91. Specifically, a track riding bracket 94 is coupled to the support frame 100, for example on the side members 102. The track riding bracket 94 slideably engages with the sliding track 92, which may function similarly to a conventional drawer slide having roller bearings, incorporate a rack and pinion engagement, and/or other sliding mechanisms known in the art. The support frame 100 may then be locked relative to the base 20 in a manner known in the art and as discussed above.

[0106] Certain embodiments of system 40 for adjusting the stiffness of fitness machine 1 incorporate the use of a control system 200. FIG. 10 depicts an exemplary control system 200 for adjusting the stiffness for a fitness machine 1, which may be manually operated by the user and/or automatically selected or modified according to a given program controlled by the console 10. The control system 200 in certain embodiments automatically modifies the stiffness according to a changing program or other factors such as user's body weight or fitness levels. For example, the stiffness may be automatically modified when a program for the fitness machine 1, such as a treadmill, transitions from simulating running on a trail versus running on a road (here, transitioning from soft to firm stiffnesses), for example.

[0107] Certain aspects of the present disclosure are described or depicted as functional and/or logical block components or processing steps, which may be performed by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, certain embodiments employ integrated circuit components, such as memory elements, digital signal processing elements, logic elements, look-up tables, or the like, configured to carry out a variety of functions under the control of one or more processors or other control devices. The connections between functional and logical block components are merely exemplary, which may be direct or indirect, and may follow alternate pathways.

[0108] In certain examples, such as shown in FIG. 10, the control system 200 communicates with each of the one or more components of the system 40 via a communication link CL, which can be any wired or wireless link. The control system 200 is capable of receiving information and/or controlling one or more operational characteristics of the system 40 and its various sub-systems by sending and receiving control signals via the communication links CL. In one example, the communication link CL is a controller area network (CAN) bus; however, other types of links could be used. It will be recognized that the extent of connections and the communication links CL may in fact be one or more shared connections, or links, among some or all of the components in the fitness machine 1. Moreover, the communication link CL lines are meant only to demonstrate that the various control elements are capable of communicating with one another, and do not represent actual wiring connections between the various elements, nor do they represent the only paths of communication between the elements. Additionally, the system 40 may incorporate various types of communication devices and systems, and thus the illustrated communication links CL may in fact represent various different types of wireless and/or wired data communication systems.

[0109] The control system 200 may be a computing system that includes a processing system 210, memory system 220, and input/output (I/O) system 230 for communicating with other devices, such as input devices 199 and output devices 201, either of which may also or alternatively be stored in a cloud 202. The processing system 210 loads and executes an executable program 222 from the memory system 220, accesses data 224 stored within the memory system 220, and directs the system 40 to operate as described in further detail below.

[0110] The processing system 210 may be implemented as a single microprocessor or other circuitry, or be distributed across multiple processing devices or sub-systems that cooperate to execute the executable program 222 from the memory system 220. Non-limiting examples of the processing system include general purpose central processing units, application specific processors, and logic devices.

[0111] The memory system 220 may comprise any storage media readable by the processing system 210 and capable of storing the executable program 222 and/or data 224. The memory system 220 may be implemented as a single storage device, or be distributed across multiple storage devices or sub-systems that cooperate to store computer readable instructions, data structures, program modules, or other data. The memory system 220 may include volatile and/or non-volatile systems, and may include removable and/or non-removable media implemented in any method or technology for storage of information. The storage media may include non-transitory and/or transitory storage media, including random access memory, read only memory, magnetic discs, optical discs, flash memory, virtual memory, and non-virtual memory, magnetic storage devices, or any other medium which can be used to store information and be accessed by an instruction execution system, for example. An input/output (I/O) system 230 provides communication between the control system 200 and peripheral devices, such as input devices 199 and output devices 201, which are discussed further below. In practice, the processing system 210 loads and executes an executable program 222 from the memory system 220, accesses data 224 stored within the memory system 220, and directs the system to operate as described in further detail below.

[0112] Through experimentation and development, the present inventors have determined that in some cases certain tradeoffs arise with implementing adjustable stiffness systems for fitness machines, and particularly those in which adjustments are made by moving an end stop that limits the length of a resilient body. For example, moving the end stops via a carriage or track system (which may include features similar to the track system 90 of FIG. 3), provides for smooth translation in the length direction of the treadmill, but includes a complex arrangement of components, which can be costly and time consuming to produce. Moreover, such carriages or track systems may require relatively tight tolerancing. This can lead to an increased risk of carriage binding if proper maintenance is not performed to maintain alignment, lubricate the components, etc. Furthermore, carriages or track systems may be relatively wide, which can increase an overall width of the fitness machine, take up more area in a workout facility, and increase costs of the fitness machine.

[0113] In further examples, moving the end stop requires the longitudinal position, the vertical position, and the orientation (rotation in the vertical plane) of that end stop to be accurately controlled. If the longitudinal position, the vertical position, or the orientation of the end stop are not as intended, the spring rate of the resilient body can be inconsistent, and the resilient body can provide a resistance that is other than intended. For example, a misaligned end stop may not only limit the resilient body to the wrong length, but the end stop may introduce additional resistance even before the resilient body reaches the end stop (e.g., the end stop not being level and forming an upward ramp that increases resistance before the end stop is reached).

[0114] In contrast, the present inventors have recognized that there are benefits to moving a pivotally coupled end of the resilient body to adjust a set maximum length for the resilient body rather than moving the end stop. For example, moving the resilient body requires control over longitudinal position without further control over orientation. In particular, because the resilient body is pivotably connected, the orientation does not impact resistance. Due to the arc shape of the resilient body 50, the vertical position of the pivotally coupled end has relatively little impact on the performance or spring rate of the resilient body 50. The presently disclosed systems and methods therefore simplify the design and control scheme for adjusting stiffness, which also increasing robustness and the adjustment range for which stiffness may be controlled.

[0115] In view of these findings, the present inventors have developed new systems and methods in which stiffness adjustments may be made for configurations having end stops, but without moving these end stops. It should be recognized that while the systems and methods described below largely relate to concepts that do not include carriage or track type systems for making adjustments, using such carriages and track systems to move the resilient body rather than the end stop are also contemplated by the present disclosure.

[0116] FIG. 11 discloses a system 300 for adjusting a stiffness of a fitness machine operable by a user, such as may be implemented with the fitness machine 1 of FIG. 1 (e.g., a treadmill). In particular, the system 300 is configured to provide for adjusting stiffness for a fitness machine 301 that has a base 20 and a mobile portion 42 that moves relative to the base 20 during operation of the fitness machine. For brevity, similar reference numbers are used to describe parts of the fitness machine shown in FIG. 11 as those used to describe fitness machines above, to the extent that these parts could be reused for the fitness machine 301.

[0117] The system 300 may include a same or similar resilient body 50 as other fitness machines and systems discussed above, whereby the resilient body 50 resists movement of the mobile portion 42 towards the base 20 in a height direction HD. FIG. 11 provides a close-up view of the system 300 with only one resilient body 50 shown. However, it should be recognized that there may be multiple resilient bodies that provide shock absorption for the fitness machine, and that multiple resilient bodies may be configured for adjusting the stiffness thereof.

[0118] The resilient body 50 has a length defined between a first end 51 and a second end 52 in a length direction LD that is perpendicular to the height direction HD. The length of the resilient body 50 increases when the mobile portion 42 moves towards the base 20, similar to embodiments described above. As with other systems discussed above, the resistance provided by the resilient body 50 may depend upon whether the resilient body 50 is allowed to elongate in the length direction LD (also referred to as being in a first phase in which the resilient body is principally bending), or is prevented from extending in the length direction LD (also referred to as being in a second phase in which the resilient body is principally compressing). The resistance provided by the resilient body, and also the transition point at which the resilient body shifts from acting in the first phase to acting in the second phase, is adjustable by operation of an actuator 110 coupled to the fitness machine (e.g., via a clevis bracket 330 coupled to a cross-member 126 of the base 20 as shown in FIG. 4). It should be recognized that the actuator 110 is coupled such that a housing 115 of the actuator 110 is generally translationally fixed relative to the base 20, pivotably in certain embodiments, with a rod 114 extending and retracting from the housing 115 through operation. Operation of the actuator 110 may be controllable as discussed above in relation to FIG. 10. The actuator may be a commercially available electromechanical and/or manually actuated device, which may be controlled via levers, pedals, etc.

[0119] The resilient body 50 is coupled to the actuator 110 via an arm 310. The arm 310 extends from a first end 312 to a second end 314 (in certain cases referred to as a height), between an inner side 316 and an outer side 318 generally extending from the first end 312 to the second end 314 (in certain cases referred to as a depth or thickness), and between opposing transverse sides 320 that generally extend from the first end 312 to the second end 314 and from the inner side 316 to the outer side 318. Openings 322 extend through the arm 310 between the inner side 316 and the outer side 318, which form a first pivot axis PA1, a second pivot axis PA2, and a third pivot axis PA3, respectively. By way of example, the arm 310 may be made of cast or forged metals such as steel.

[0120] The first end 51 of the resilient body 50 is pivotally coupled to the arm 310 so as to be pivotable about the first pivot axis PA1. By way of example, this coupling may be similar to the manner in which the resilient body 50 is coupled to the bracket 60 as shown in FIG. 5, such as via a fastener like the pin 66. In the embodiment shown of FIG. 11, two fingers 313 are provided at the first end 312 of the arm 310 to form a clevis, wherein the opening 322 in the first end 312 extends through both fingers 313. The first end 51 of the resilient body 50 is positioned between the two fingers 313 and pivotally coupled thereto via a pin 66 or another fastener, such as a clevis pin extending through the openings 322 in the fingers 313, and also through the first end 51 of the resilient body 50 therebetween. Other configurations are also contemplated by the present disclosure, such as the first end 51 of the resilient body 50 having two fingers with a notch therebetween so as to form a clevis, whereby the arm 310 is then received within the notch and pivotally coupled to the fingers.

[0121] With continued reference to FIG. 11, the arm 310 is pivotally coupled to the base 20 so as to pivot about the second pivot axis PA2, such as via a pin 66 (e.g., a press-fit pin, a pin with a set screw or cotter pin for locking purposes, etc.) or other fastener extending through the corresponding opening 322 in the arm 310 and into the base 20. In other examples, the arm 310 may be pivotally coupled to the base 20 via a shaft welded in place, or a bolt with a head that prevents the arm 310 from being removed from the base 20 when pivotally coupled thereto. Other mechanisms known in the art may alternatively be used to retain the arm 310 relative to the base 20 while allowing the arm 310 to pivot relative thereto. It should further be recognized that where two elements are referenced as being coupled together, this may be indirectly, through other intermediate elements.

[0122] The arm 310 is also pivotally coupled to the actuator 110, in this case via a fastener 117 extending through the opening 322 corresponding to the third pivot axis PA3, and likewise through the rod 114 of the actuator 110. As with the first end 312 of the arm 310, two fingers 315 are provided at the second end 314 to form a clevis, whereby a portion of the actuator 110 is positioned and coupled therebetween via the fastener 117 as a clevis pin. In other examples, the actuator 110 has two fingers and the second end 314 of the arm 310 is positioned therebetween.

[0123] It should be recognized that by virtue of the couplings described above, the first end 51 of the resilient body 50 is therefore coupled to the base 20 via the arm 310, the first end 51 being substantially moveable along an arc centered at the second pivot axis PA2. In this manner, pivoting the arm 310 about the second pivot axis PA2 moves the first end 51 of the resilient body 50 substantially in the length direction LD (noting that there may be movement of the first end 51 in the height direction HD as well, see FIGS. 12A-12C). This movement may be referred to as being in the length direction even if not exclusively in the length direction. In certain embodiments, the movement in the length direction is greater than any movement in the height direction and is thus referred to as moving primarily in the length direction. The present inventors have recognized that the system 300 is uniquely able to adjust the stiffness by moving the resilient body in the length direction, despite also potentially moving in the height direction, due to the shape of the resilient body 50 (here being a parabolic shape). As such, moving the first end 51 of the resilient body 50 in the height direction HD, despite the second end 52 remaining unchanged in the height direction HD, is not detrimental to providing resistance for the mobile portion 42 as contact is still made at a first point on the resilient body 50 between the first end 51 and the second end 52 and a second point on the mobile portion 42. Additionally, this change in orientation still advantageously allows the resilient body 50 to act in the first and second phases in providing resistance discussed above.

[0124] For the configuration of FIG. 11, the arm 310 is configured such that the second pivot axis PA2 is positioned between the first pivot axis PA1 and the third pivot axis PA3 along the length of the arm 310 between the first end 312 and the second end 314 thereof. Since the arm 310 is pivotally coupled to the base 20 so as to rotate about the second pivot axis PA2, the actuator 110 moving one end of the arm 310 in one direction (substantially parallel to the length direction LD) thereby causes the opposite end of the arm 310, and thus the first end 51 of the resilient body 50, to move in an opposite direction. In this manner, the arm 310 for the system 300 of FIG. 11 acts as a first class lever to couple the actuator 110 to the resilient body 50. Other types of levers are also contemplated and discussed further below.

[0125] The present inventors have recognized that using a rotating lever provides a mechanical advantage and applies a lower load to the actuator (whether electromechanical or manual), which increases case of operation and reduces wear. This also improves the reliability and/or requirements for the actuator, permitting a lower capacity device to be used and thereby saving cost and weight. In certain embodiments, the required translation for the resilient body is relatively small, which is difficult to accurately measure and control for the carriage or track system (e.g., the track system 90 of FIG. 3). It is noteworthy that the present inventors have determined that users can detect stiffness changes of the fitness machine based on relative minute position changes of the resilient body, and thus accuracy and precision are critical. Thus, the mechanical advantage the lever provides increases movement of the actuator relative to the movement of the spring, which increases actuator travel and allows for more precise control of the system.

[0126] The present inventors have further recognized that using a pivoting lever arrangement as disclosed herein can provide more flexibility in where the actuator is positioned and how it can travel. For example, since the variable stiffness system is positioned under the deck, excess vertical translation of the mobile portion 42 can result in undesired contact with the mechanism, or completely flattening the resilient range of the resilient body. The lever arm can be positioned such that at the softer settings, the coupled end of the resilient body pivots downward and away from the deck, increasing clearance in the stiffness range where clearance is needed. Thus, while performance and spring rate of the resilient body 50 are relatively unaffected by the vertical position of the first end 51, such vertical movement provides additional clearance for the mobile portion 42 to deflect downward.

[0127] In certain embodiments, such as that shown in FIG. 11, the arm 310 has a notch 324 that extends inwardly from the inner side 316. The notch 324 is positioned between the openings 322 for the first pivot axis PA1 and the second pivot axis PA2 along the length of the arm 310 between the first end 312 and the second end 314. However, other configurations are contemplated. The notch 324 is configured such that a portion of the fitness machine may extend therethrough without contacting the arm 310 in use. In the example shown, the mobile portion 42 is a running deck of a treadmill that supports a belt 2 on which the user may run. This belt 2, and particularly a lower strand 4 thereof, extends through the notch 324 in the arm 310 while the belt 2 is rotating. This allows the resilient body 50 to be positioned between the mobile portion 42 and the lower strand 4, while also advantageously allowing the actuator 110 to be positioned below the lower strand 4. This also reduces the required space between an upper strand 3 and the lower strand 4 of the belt 2 and/or provides more space for the actuator 110, its motion (e.g., extension and retraction), and the connections thereto. The notch 324 also permits the width of the system 300 in a width direction WD (roughly perpendicular to both the length direction LD and the height direction HD of the fitness machine discussed above) to be reduced over a configuration in which the actuator 110 is not positioned, or is positioned to a lesser extent, under the belt 2 in the width direction WD.

[0128] The notch 324 in the arm 310 is FIG. 11 has a height and depth configured to avoid any contact with the belt 2 during use of the fitness machine, including as the mobile portion 42 moves up and down. For clarity, the height of the notch 324 may be defined in the direction between the first end 312 and the second end 314 of the arm 310, and likewise the depth being the perpendicular distance from the inner face 316 inwardly. The height and depth also prevent contact between the belt 2 and the arm 310 when the arm 310 is pivoted about the second pivot axis PA2 as the actuator 110 moves between being fully extended and fully retracted. Additionally, the arm 310 is configured such that an upper face 326 and a lower face 328 forming the notch 324 are each rounded. This accommodates the pivoting nature of the arm 310 relative thereto to ensure clearance remains at the extreme angles of the arm 310. This also helps to prevent damage or wear to the belt 2 if accidental contact is made with the arm 310 on occasion, such as the belt 2 becoming loose.

[0129] With continued reference to FIG. 11, the system 300 further includes an end stop 70 with a stop wall 80, which may be similar to that described above. The position of the end stop 70, and particularly the stop wall 80, establishes a set maximum for which the length of the resilient body 50 may increase in the length direction LD, including due to downward movement of the mobile portion 42. However, unlike some of the embodiments discussed above, the set maximum for the length of the resilient body 50 imparted by the end stop 70 is not adjusted by moving the end stop 70, but rather by moving the resilient body 50 closer or father from the end stop 70 in the length direction (e.g., in the manner described above via pivoting of the arm 310). In particular, the end stop 70 is non-moveable relative to the base 20, for example by being coupled thereto via welds or fasteners such as screws or bolts. For example, the end stop 70 may be coupled to the base 20 so as to be cantilevered from an inner side of the base 20, similar to the bracket 60 of FIG. 4. However, it should be recognized that other mechanisms for fixing the end stop 70 to the base 20 are also contemplated.

[0130] Since the end stop 70 is non-moveable relative to the base in the length direction LD, it follows that a gap 332 between the second end 52 of the resilient body 50 and a stop wall 80 of the end stop 70 therefore varies as the resilient body 50 bends and/or as the first end 51 of the resilient body 50 is moved in the length direction LD. As discussed above, the first end 51 is moveable by the actuator 110 and arm 310 to thereby adjust the set maximum at which the end stop 70 prevents the length of the resilient body 50 from increasing, which is essentially a distance substantially parallel to the length direction LD between the first end 51 and the stop wall 80. Advantageously, the resistance provided by the resilient body 50 to resist movement of the mobile portion 42 towards the base 20 remains unaffected by operation of the actuator 110 when the length of the resilient body 50 is less than or equal to the set maximum. Therefore, the system 300 still allows the resilient body 50 to act in first and second phases corresponding to bending and compressing, as discussed above.

[0131] FIGS. 12A-12C show the arm 310 in three different positions. More specifically, the examples of FIGS. 12A-12C show the outer side 318 the arm 310, whereby an opening (e.g., the notch 324) through which the belt extends in the manner described above is present but not visible. FIG. 12A shows the resilient body before its length is limited by the end stop, which may be considered a soft setting. A gap G is visible between the stop wall 80 of the end stop 70 and the resilient body 50, as discussed above. FIG. 12B shows the arm 310 rotated such that the resilient body 50 is just contacting the stop wall 80 of the end stop 70, but without substantial lateral force therebetween, which may be considered a medium setting. In both FIG. 12A and FIG. 12B, the length of the resilient body 50 is shown as L1. FIG. 12C shows the arm 310 being rotated further such that the resilient body 50 is limited in length by the stop wall 80 of the end stop 70 with opposing forces being present between the stop wall 80 and the resilient body 50. As such, the length L2 of the resilient body 50 is less in FIG. 12C than in FIGS. 12A and 12B. The resilient body 50 is therefore shown in a pre-flexed or pre-compressed state, which may be considered a stiff setting. Based on the geometry of the resilient body 50, a height H2 of the resilient body 50 in the vertical direction is greater in FIG. 12C than a height H1 thereof in FIGS. 12A and 12B due to the pre-compression of the resilient body 50.

[0132] It should therefore be recognized that the system 300 provides adjustment of the set maximum at which the end stop 70 prevents the length of the resilient body 50 from increasing in a much simpler and more robust manner than previously known. Rather than the actuator 110 translating a track system or carriage, the actuator 110 simply rotates the arm 310 about its second pivot axis PA2 to change the set maximum for the resilient body 50. This reduces the time, cost, and space of assembly and also reduces the frictional forces (and thus, lubrication needs) to only a small number of pivot points.

[0133] As discussed above, there may be multiple resilient bodies 50 that work together to provide adjustable stiffness for the fitness machine. In certain embodiments, each is adjustable independently, having its own arm and actuator that operate in the manner described above. In other embodiments, multiple resilient bodies 50 may be adjusted via a shared actuator, which may be in series (offset in the length direction), in parallel (offset in the width direction), and/or offset in the height direction via different lengths or arms or configurations of resilient bodies.

[0134] FIG. 13 shows another system 350 having some common features to the system 300 of FIG. 11. Among the changes is a different type of arm 310. In particular, it should be noted that the arm 310 is not linear between the first end 312 and the second end 314, but has a curved profile. The present inventors have recognized that different shapes can not only provide flexibility for the location of the actuator 110, but also mechanical advantages during use.

[0135] FIG. 14 depicts a system 400 having some common features to the system 300 of FIG. 11. Among the differences is that a single actuator 110 operates to pivot not only a single resilient body 50 and arm 310 pair, but two resilient bodies 50 with two corresponding arms 310. In this case, the arms 310 may be the same as those described above.

[0136] The resilient bodies 50 in the system 400 of FIG. 14 are referred to as being in series. The system 400 includes a link 170 that extends between a first end 172 and a second end 174. The first end 172 of the link 170 is pivotally coupled to one arm 310, and the second end 174 of the link 170 is pivotally coupled to the other arm 310. More specifically, the link 170 is pivotally coupled to the second ends 314 of the arms 310 to adjust two or more resilient bodies 50 in a serial orientation (e.g., like a cross-member 502 of FIG. 15, but with the arms 310 being in series rather than parallel). Furthermore, the first end 172 of the link 170 is pivotally coupled to the rod 114 of the actuator. Thus, the link 170 is pivotable about the third pivot axes PA3 of both arms 310. With the arms 310 coupled to the link 170 in this manner, the actuator 110 can pivot either of the arms 310 (as discussed above) and/or move the link 170 to pivot both arms 310 together simultaneously. In short, this serial configuration would function like a 4-bar linkage system (e.g., 4-bar linkage system 701 of FIG. 17) with both resilient bodies 50 moving in the same direction.

[0137] Other example systems with resilient bodies 50 arranged in series are also contemplated. For example, the system can include second class levers rather than the first class levers (see FIG. 18). Furthermore, more than two resilient bodies 50 can be arranged in series to provide support to more areas of the moveable portion 42. In some examples, the link 170 includes a single bar made of cast metal material (e.g., steel, etc.). However, the link 170 can also include two parallel bars that are each positioned adjacent to the inner and outer sides 316, 318 of the arms 310, respectively. One or more additional bars or linkages can also be pivotally coupled to the link 170 and/or the arm(s) 310 to more efficiently apply leverage or force for pivoting the arms 310.

[0138] FIG. 15 shows part of a system 500 in which a single actuator 110 is operable to adjust multiple resilient bodies 50 that are offset from each other parallel to the length direction LD (also referred to as being a parallel configuration). In this example, the belt and mobile portion of the fitness machine are removed for clarity, as well as one of the resilient bodies 50. First ends 51 of the resilient bodies 50 are pivotally coupled to first ends 312 of corresponding arms 310, which may be in the manner described above. The second ends (not visible in FIG. 15) of the arms 310 are each coupled to a common cross-member 502. One end of the actuator 110 is coupled to the cross-member 502 extending between the arms 310. In this embodiment, the cross-member 502 is received in an open end 508 of the rod 114 of the actuator 110 and coupled thereto via a fastener 506 such as a carriage bolt. The actuator 110 may be coupled to the cross-member 502 in other manners known in the art, such as via clamps or clevis brackets. The other end of the actuator 110, here the housing 115, is coupled to a cross-member 510 that is part of the base 20. Additional struts 512 may also be coupled between the cross-member 510 and the side members of the base 20 (or elsewhere) for strength and/or to prevent torsion. In this manner, operation of the actuator 110 causes the second ends of the arms 310 to move in the length direction LD, which as discussed above causes the arms 310 to pivot about the second pivot axis PA2 and thus the first ends 312 of the arms 310 to move in an opposing direction to the second ends in the length direction LD. This motion thereby moves the first ends 51 of the resilient bodies 50 coupled to the first ends 312 of the arms 310. This in turn changes the starting positions of the second ends 52 (and thus, the first ends 51) of the resilient bodies 50 relative to an end stop 570 and stop wall 580, similar to other embodiments discussed above. In the embodiment shown, a single end stop 570 and stop wall 580 extends laterally across the base 20, doubling as a strut to provide further rigidity for the fitness machine. In this manner, the system 500 thus adjusts the stiffness of the fitness machine by moving the fixed first ends 51 of the parallel resilient bodies 50, simultaneously.

[0139] FIG. 16 shows another system 600 having some common features to the system 300 of FIG. 11. Among the differences is that the system 600 incorporates a class 2 lever for pivoting moving the resilient body 50, rather than using the class 1 lever of arm 310 in FIG. 11. In particular, the system 600 includes an arm 610 that extends between a first end 612 and a second end 614 and has openings 622 therethrough to form a first pivot axis PA1, a second pivot axis PA2, and a third pivot axis PA3. The second pivot axis PA2 is defined to be between the first pivot axis PA1 and the third pivot axis PA3 along the length between the first end 612 and the second end 614. Like the arm 310, the arm 610 is pivotally coupled the actuator at the third pivot axis PA3. However, unlike the arm 310, the arm 610 is pivotally coupled to the base 20 at the first pivot axis PA1 rather than at the second pivot axis PA3. Similarly, the arm 610 is pivotally coupled the first end 51 of the resilient body 50 at the second pivot axis PA2. The present inventors have recognized that this configuration, which functions as a class 2 lever to transmit force from the actuator 110 to move the resilient body 50, provides further mechanical advantage over a class 1 lever. This improves stability and/or permits a smaller actuator to be employed. The system also advantageously provides flexibility for where the arms may be pivotally coupled to the base 20 (e.g., the position of the first pivot axis PA1).

[0140] Since the resilient body 50 is coupled to rotate about the second pivot axis PA2, which is between the first pivot axis PA1 and the third pivot axis PA3, in certain embodiments it is advantageous to provide the first pivot axis PA1 above the belt 2 (e.g., to minimize the distance between the upper strand 3 and the lower strand 4 of the belt 2). In this case, the present inventors have recognized that the arm 610 requires two notches 624A, 624B rather than the single notch 324 of the arm 310. In particular, the lower notch 624B accommodates the lower strand 4 of the belt 2 running therethrough, as with the arm 310. Additionally, the upper notch 624A is provided to accommodate the upper strand 3 of the belt 2, as well as the mobile portion 42.

[0141] Another system 601 similar to those of FIGS. 14 and 16 is shown in FIG. 18, which has a single actuator 110 configured to move two (or more) arms 610 together in series. The system 601 includes the link 170 (see FIG. 14) that extends between the first end 172 and the second end 174. The first end 172 of the link 170 is pivotally coupled to one arm 610 and the second end 174 of the link 170 is pivotally coupled to the other arm 610. The link 170 may be coupled to the arms 610 at the second pivot ends 614 of the arms 610, including being pivotable about the same third pivot axis PA3 at which the actuator 110 is coupled to one of the arms 610. While coupling at the second ends 614 provides the greatest mechanical advantage, other pivot locations for coupling the link 170 are also contemplated.

[0142] FIG. 17 depicts another system 700 having some common features to the system 300 of FIG. 11. The system 700 includes a 4-bar linkage system 701 for moving the first end 51 of the resilient body 50 in the length direction LD. A first bar 702, a second bar 704, and a third bar 706 each extend between a first end 708, 710, 712 and a second end 714, 716, 718 thereof. The first end 708 of the first bar 702 and the third end 718 of the third bar 706 are pivotally coupled to the base 20. The second end 714 of the first bar 702 is pivotally coupled to the first end 710 of the second bar 704 and the second end 716 of the second bar 704 is pivotally coupled to the first end 712 of the third bar 706. The first end 710 of the second bar 704 is also pivotally coupled to the first end 51 of the resilient body 50. The different pivotable couplings may be made via pins, axles, fasteners, or other mechanisms known in the art, as discussed above.

[0143] The actuator 110, here the rod 114 thereof, is pivotally coupled to the first bar 702 at a pivot point 720. The other end of the actuator 110 is coupled to the base 20 in a similar manner to other embodiments discussed above. In use, the operation of the actuator 110 moves the first bar 702, which by virtue of the 4-bar linkage system 701 moves the second bar 704 and the third bar 706. Moving the second bar 704 moves the resilient body 50 to adjust the stiffness of the fitness machine as discussed above.

[0144] In certain examples, the lower strand of the belt 2 (not shown here) may run below the actuator 110 and/or below the 4-bar linkage system 701. In other cases, the first bar 702 and the third bar 706 may have openings therein that are similar to the notch 324 in the arm 310 of FIG. 11 to accommodate the belt 2 running therethrough. In this configuration, the actuator 110 and/or portions of the first bar 702 and the third bar 706 may be positioned below the lower strand of the belt 2 in the height direction HD. This provides flexibility for the placement of the actuator 110, which is highly advantageous in providing a compact, durable, and easy to assemble fitness machine. For example, the first end 51 of the resilient body 50 can be positioned further toward the center of the four-bar linkage 701 to more evenly distribute the load on the first and third bars 702, 706. This location can also help reduce overall movement of the first end 51 and the linkage 701.

[0145] It should be recognized that the systems for adjusting the stiffnesses of fitness machines disclosed herein may be positioned differently than expressly shown relative to these fitness machines. By way of example, the system 700 of FIG. 17 shall also be interpreted as disclosing additional embodiments in which the resilient body 50 elongates in the lateral or width direction WD, rather than in the longitudinal or length direction LD (e.g., the longitudinal direction LD in the axis labels may be replaced with the width direction WD, with the belt 2 now moving into and out of the page in use). Oblique orientations are also contemplated.

[0146] FIG. 19 depicts another system 800 having some common features to the system 300 of FIG. 11, which as with other embodiments discussed above, may re-use reference numbers where the same or similar components may be used for brevity. The system 800 provides for adjusting the stiffness of a fitness machine, specifically via a manual actuator 802 as the actuator that moves the resilient body 50, in this embodiment by moving an arm 310 that moves the resilient body 50 in the manner discussed above. The system 800 includes lever 804 that extends along a first axis 806 from a first end 808 to a second end 810, with an extension 812 extending along a second axis 814 perpendicular to the first axis 806 from a third end 814 to a fourth end 818. The lever 804 is pivotally coupled to the base 20 of the fitness machine at a first pivot point 820, which in the embodiment shown is near the second end 810 of the lever 804 and positioned approximately along the first axis 806. A handle 822 or grip is positioned at the first end 808 of the lever 804 and is configured to be gripped by a user for manually pivoting the lever 804 between two or more positions.

[0147] FIG. 19 depicts the lever 804 in a first position shown in solid lines and a second position shown in dotted lines. The lever 804 is pivotally coupled to the base 20 at the first pivot point 820 (as well as other pivot points to be discussed below) via a pin, axle, or other type of fastener similar to the pin 66 discussed above (see e.g., FIG. 11) extending through an opening in the lever 804. A second pivot point 824 is provided near the fourth end 818 of the lever 804 and is positioned approximately along the second axis 814, which may also be configured as an opening through the lever 804 that receives a pin, axle, or other fastener therethrough. In the embodiment shown, the second pivot point 824 is offset from the first pivot point 820 both in a direction parallel to the first axis 806 and in a direction parallel to the second axis 814, which in the orientation shown, is also the case in the height direction HD and in the length direction LD. It should be recognized that other arrangements are contemplated, including the entire system 800 being oriented differently with respect to the mobile portion 42 of the fitness machine (e.g., rotating 90 degrees such that the resilient body 50 extends in a width direction rather than in the length direction).

[0148] The system 800 further includes a linkage 830 that extends between a first end 832 and a second end 834, which is a rigid member comprising aluminum, steel, and/or another material. The first end 832 of the linkage 830 is pivotally coupled to the second end 314 of the arm 310, specifically at the third pivot axis PA3 of the arm 310 discussed above. This pivotal coupling may be via an axle that extends from the linkage 830 and is received through an opening in the arm 310, vice versa, a pin 66 extending through openings in both the linkage 830 and the arm 310, and/or other techniques. The second end 834 of the linkage 830 is similarly pivotally coupled to the lever 804, specifically at the second pivot axis 824 near the fourth end 818 of the lever 804.

[0149] In this manner, moving the handle 822 of the lever 804 causes the lever 804 to rotate about the first axis 820 thereof, which moves the linkage 830 to thereby cause rotation of the arm 310. In the configuration shown, rotating the lever 804 in a first direction (e.g., clockwise from a first position to a second position) causes the arm 310 to rotate in an opposite second direction (e.g., counterclockwise from a first position to a second position). However, other configurations are contemplated. For example, pivotally coupling the first end 832 of the linkage 830 to the first pivot point PA1 of the arm 310, or other locations on the arms side of the second pivot point PA2 in which the arm 310 pivots relative to the base 20, would cause the lever 804 and the arm 310 to rotate in primarily like directions. The movements may also be referred to with respect to non-rotational movement, such as moving in the height direction HD and/or the length direction LD. In these cases, movements may optionally be referred to as being primarily in a referenced direction since pivoting rotation is not limited to being purely in the height direction HD or the length direction LD.

[0150] In the orientation of FIG. 19, rotating the lever 804 clockwise from the first position to the second position causes the arm 310 to rotate counterclockwise, moving the second end 52 of the resilient body 50 close to the stop wall 80 of the end stop 70 and thus reducing the set maximum in which the length of the resilient body 50 may increase in use of the fitness machine. In other words, rotating the lever 804 clockwise would increase the stiffness of the fitness machine (e.g., from a soft or moderate setting to a moderate or firm setting, respectively). End stops 805, 807 (e.g., pins, blocks welded or otherwise coupled to the base 20, or other components) prevent further rotation of the lever 804 in either direction. The stops 805, 807 may comprise a cushioning material to prevent noise during use of the fitness machine (e.g., comprising Delrin, having foam, and/or the like).

[0151] The system 800 further includes a biasing device to assist in retaining the selected position of the lever 804 (and thus the arm 310 and the resilient body 50) during use of the fitness machine to prevent unintentional changes to stiffness. In particular, the embodiment shown includes a spring 836 that extends from a first end 838 to a second end 840. Other types of biasing members are also contemplated, such as elastomeric bands, gas springs, and/or the like. The first end 838 of the spring 836 is pivotally coupled to the base 20, here at a position below the first pivot point 820 of the lever 804 in the height direction HD, and also closer to the resilient body 50 than the first pivot point of the lever 804 is to the resilient body 50 in the length direction LD. The first end 838 of the spring 836 may be pivotally coupled to the base 20 in a manner similar to that discussed above for other pivotal couplings, such as via a pin 66. The second end 840 of the spring 836 is similarly pivotally coupled to the lever 804, here via a pin 66 coupled within the extension 812 portion of the lever 804.

[0152] The present inventors have advantageously configured the system 800 to utilize over-center arrangements to retain the position of the lever 804, the arm 310, and the first end 51 of the resilient body 51 during use of the fitness machine. In the embodiment shown, the second end 840 is pivotally coupled to the lever 804 at a position that is between the first pivot axis 820 and the second pivot axis 824, both in a direction parallel to the first axis 816 and in a direction parallel to the second axis 814. Therefore, the spring 836 moves from a first side (here, to the left in the length direction LD) of the first pivot axis 820 of the lever 804 to a second side (to the right) of the first pivot axis 820 when the lever 804 is moved from the first position (solid lines) to the second position (dotted lines) in an over-center arrangement. In other words, a length of the spring 836 between the first end 838 and the second end 840 is shorter when in the lever 804 is in the first position and in the second position as compared to when rotating therebetween. In this manner, the spring 836 biases the lever 804 to remain in the first position or in the second position upon selection by the user, whereby the user must overcome this spring force to change between positions.

[0153] The present inventors have also advantageously configured the system 800 to provide mechanical advantages for which use of the fitness machine helps prevent changes in the stiffness setting selected by the lever 804 as the actuator. In the configuration shown in FIG. 19, the arm 310 functions in an over-center arrangement such that downward forces from the mobile portion 42 of the fitness machine on the resilient body 50 act in a manner that does not change the position of the arm 310 or lever 804. For example, downward forces on the resilient body 50 when the arm 310 is in the first position as shown in FIG. 19, a relatively softer setting, encourages clockwise rotation of the arm 310 and thus tension on the linkage 830. However, the lever 804 cannot be further rotated via such tension, being limited by the end stop 805 as discussed above. In contrast, when the lever 804 is rotated to the second position, which rotates the arm 310 into its second position providing for further stiffness by the resilient body 50, downward forces on the resilient body 50 encourage clockwise rotation of the arm 310, resulting in tensile forces on the lever 804 via the linkage 830. However, the lever 804 cannot further rotate, being stopped by the end stop 807 as discussed above. As such, once the user selects the stiffness setting for the system 800, use of the fitness machine does not risk drifting from this stiffness setting, but only further prevents the stiffness setting from unintentionally changing. Additionally, this configuration puts many elements of the mechanism (e.g., elements 310, 804, 830) into a pre-loaded state from the spring 836 and resilient body 50 back-driving the mechanism, which is beneficial for preventing noise (rattling, shaking, clicking, etc.)

[0154] In certain embodiments, the locations of the end stops 805, 808 are adjustable to change the stiffnesses selectable in each position of the lever 804. For example, as shown for the end stop 807, the end stop 807 may include a threaded opening therethrough that receives a fastener such as a bolt 809 therein. Rotating the bolt 809 in a first direction reduces the pivotal range of the lever 804, and rotating the bolt 809 in an opposite direction increases the pivotal range of the lever 804 (e.g., until stopped by the end stop 807 itself). Other mechanisms for adjusting the locations of the end stops 805, 807 are also contemplated, such as the end stops being couplable to the base 20 within different openings throughout, the end stops themselves being pins (e.g., pins 66) receivable in the different openings 811 (e.g., similar to selecting a pin location in a conventional weight stack of a fitness machine), or other techniques.

[0155] In addition, or as an alternative, to allowing the end stops 805, 807 to move based on user preferences, the end stop locations may be chosen based on user weight, fitness machine setup, and/or the like to ensure consistent stiffness performance across users or machines, and/or to prevent bottoming out of the mobile portion 42 in use. For example, a heavier user may be instructed to select a stiffer location for positioning the end stop 805 since this lighter resistance setting for the resilient body 50 allows more movement of the mobile portion 42.

[0156] It is beneficial to prevent bottoming out of the mobile portion 42 in all stiffness settings; however, there is a greater likelihood of bottoming out in softer settings. The presently disclosed systems and methods advantageously provide that as the arm rotates clockwise into softer settings, the controlled end of the resilient body begins to reduce in elevation, moving itself further from incidental contact risk (or, bottoming out). In certain embodiments, the system is further configured to prevent bottoming out by control systems preventing softness settings below a particular stiffness, which may be controlled as a function of other variables such as weight or running speed (since footfall force is proportional, for a range).

[0157] It should be recognized that the embodiment of FIG. 19 shows a configuration in which the system 800 provides resistance in two phases when the lever 804 is in the first position shown in solid lines, and in only one phase when the lever 804 is in the second position shown in dotted lines. However, the present disclosure contemplates other configurations, including those in which both lever 804 positions provide two phases of resistance, or both provide one phase of resistance (in which case the second position provides further pre-loading or compression to increase stiffness further than in the first position).

[0158] It should further be recognized that the manual actuator 802 of FIG. 19 may be implemented in other configurations of systems according to the present disclosure. For example, the same lever 804 may control the set maximum of multiple resilient bodies, whether in parallel (e.g., FIG. 15) and/or in series (e.g., FIG. 14). The manual actuator 802 may also be used with arms 310 having notches 324 through which a belt 2 extends (e.g., FIG. 19), or those that do not (e.g., FIG. 17). Likewise, where the resilient body is moved by moving a lever, manual actuators may be used for different types or classes of levers. Furthermore, as with the other embodiments discussed herein, the present disclosure contemplates uses for adjustable stiffness other than with respect to treadmills.

[0159] The present disclosure also contemplates arrangements in which a manual actuator may be positioned in more than two positions. For example, a tension screw or other locking mechanism may be employed to retain a lever such as the lever 804 in FIG. 19, in one or more intermediate positions between the first position and the second position, providing intermediate stiffness levels. In another example, the lever 804 may be moveable similar to a conventional deck-height adjustment mechanism for a riding lawn tractor, whereby the lever is moved perpendicularly to the pivot axis (e.g., first pivot axis 820) to disengage a locking member from a toothed rack, then moved back into engagement within the toothed rack after pivoting to the desired angle. For brevity, this well-known mechanism is not shown, but may be configured like the deck-height adjustment mechanism of a John Deere S120 Lawn Tractor.

[0160] The present disclosure also contemplates positioning the lever 804 in different positions relative to the fitness machine to be accessible to the user for adjusting the stiffness thereof. By way of example, FIG. 20 shows a system 800 having two separate levers 804 for adjusting the stiffness. While a given system may have more than one lever (e.g., to adjust front versus rear stiffness), the system 800 of FIG. 20 is shown for the purpose of example only. A first lever 804 is shown on the left side 23 of the fitness machine, adjustable by pivoting the lever 804 in the length direction LD. A second lever 804 is shown at the front 21 of the fitness machine within a second system 801 similar to the system 800, being adjustable by rotating in the width direction WD. In the embodiment shown, an arc 844 is also provided at the front 21 such that the lever 804 is pivotable therein, preventing accidental contact with the lever 804. In certain examples, the levers are aligned with the direction in which the corresponding resilient bodies extend in use. However, other configurations are contemplated.

[0161] The different embodiments disclosed herein advantageously provide for adjustment of the stiffness for fitness machines, but without the downsides of moving ends stops discussed above. Moreover, the different embodiments provide this functionality while also providing further mechanical advantage (e.g., implementing a class 2 lever), reduced space requirements (e.g., the openings 324 in arms 310), and other benefits described above.

[0162] The functional block diagrams, operational sequences, and flow diagrams provided in the Figures are representative of exemplary architectures, environments, and methodologies for performing novel aspects of the disclosure. While, for purposes of simplicity of explanation, the methodologies included herein may be in the form of a functional diagram, operational sequence, or flow diagram, and may be described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance therewith, occur in a different order and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology can alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all acts illustrated in a methodology may be required for a novel implementation.

[0163] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. Certain terms have been used for brevity, clarity, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have features or structural elements that do not differ from the literal language of the claims, or if they include equivalent features or structural elements with insubstantial differences from the literal languages of the claims.