Patent Publication Number: US-10786705-B2

Title: Exercise machines for leg strengthening

Description:
FIELD 
     The present disclosure relates to exercise machines for leg strengthening, and particularly to exercise machines for strengthening a user&#39;s leg muscles, including but not limited to the user&#39;s hamstring muscles. 
     BACKGROUND 
     Conventional exercise machines for strengthening the hamstring muscles include machines where the user&#39;s hip angle remains fixed, for example seated leg curl machines, lying leg curl machines, kneeling leg curl machines, and variations thereof. 
     The following U.S. patents are incorporated herein by reference: 
     U.S. Pat. No. 9,604,090 discloses a weight stack assembly for an exercise apparatus. The weight stack assembly comprises a plurality of primary weights and a plurality of secondary weights that are located next to the plurality of primary weights. A head plate is on the plurality of primary weights. A primary weight selector mechanism is on the head plate and is configured to couple a user force receiving member to one or more of the plurality of primary weights. A secondary weight selector mechanism is on the head plate and is configured to couple the head plate to a first secondary weight in the plurality of secondary weights, and to couple the head plate to a second secondary weight in the plurality of secondary weights. The secondary weight selector mechanism is configured to engage with the first secondary weight so that the first secondary weight remains balanced in the horizontal direction when a force is applied to the user force receiving member. The secondary weight selector mechanism is further configured to engage with the second secondary weight so that the first and second secondary weights remain balanced in the horizontal direction when the force is applied to user force receiving member. 
     U.S. Pat. No. 6,676,574 discloses an adjustment system for positioning a pad on a user arm for an exercise machine. The user arm is coupled to a rotating cam which is attached to one end of a cable. The other end of the cable is attached to a weight system which pulls the rotating cam to bias the user arm in one position. The adjustment system has a selector hub mounted on one end of the user arm. The selector hub has an arcuate surface having a plurality of holes. A pull pin assembly is rotatably positioned around the selector hub. The pull pin assembly includes a pin which may be inserted in the plurality of holes to lock the pin assembly in a fixed position. A linkage bar has one end pivotably mounted to the pull pin assembly and an opposite end pivotably attached to one end of a support linkage bar. The support linkage bar is rotatably mounted on the user arm. The opposite end of the support linkage bar is coupled to a perpendicular rod with a pad. The perpendicular rod and pad are fixed in position relative to the user arm when the pin is inserted in one of the plurality of holes. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     In certain non-limiting examples, an exercise machine is for leg strengthening. The exercise machine has a stationary frame; and a thigh support member and an ankle support member coupled to the frame and configured to support a user&#39;s thigh and ankle, respectively, during a hamstring curl exercise motion. The thigh support member and the ankle support member are each movable with respect to the stationary frame during the hamstring curl exercise motion, thus facilitating contraction and extension of both of a hamstring and glute of the user during the hamstring curl exercise motion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is described with reference to the following Figures. The same numbers are used throughout the Figures to reference like features and like components. Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale. 
         FIG. 1  is a front perspective view of an exercise machine for leg strengthening, particularly enabling a hamstring curl exercise motion. 
         FIG. 2  is a rear perspective view of the exercise machine. 
         FIG. 3  is an exploded view of the exercise machine. 
         FIG. 4  is an exploded view of a linkage that couples an ankle support member and a hamstring support member to a stationary frame of the exercise machine. 
         FIG. 5  is a side view of the exercise machine depicting the ankle support member and hamstring support member in a raised position, prior to performance of a hamstring curl exercise motion. 
         FIG. 6  is a side view of the exercise machine depicting the ankle support member and hamstring support member upon initial contraction of the user&#39;s hamstring during the hamstring curl exercise motion. 
         FIG. 7  is a side view of the exercise machine depicting the ankle support member and hamstring support member after initial contraction of the user&#39;s hamstring and glute during the hamstring exercise motion. 
         FIG. 8  is a side view of the exercise machine depicting the ankle support member and hamstring support member after contraction of the user&#39;s hamstring and glute during the hamstring curl exercise motion. 
         FIG. 9  depicts a platform frame and platform for supporting a user with respect to the exercise machine. 
         FIG. 10  depicts the platform as it is being raised with respect to the platform frame. 
         FIG. 11  depicts the platform after it has been raised with respect to the platform frame. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described below. 
     During research and development with exercise equipment, the present inventors identified a frequent occurrence of hamstring injuries in athletes, particularly high performance athletes such as professional soccer players. The present inventors have realized and believe that many of these injuries could have been avoided with improved strength training, and specifically strength training that better simulates the actual motion of a running stride. The present inventors are not aware of any prior art exercise machines for leg training that accomplish this objective. For example, the present inventors are not aware of any prior art that recognizes this issue, and also are not aware of any prior art that facilitates, for example, a contralateral, standing, single leg motion resembling a running stride. The present disclosure is a result of the inventors recognition of this problem, and unique ways to solve the problem, and provides results of the present inventors efforts to provide such strength training. 
       FIGS. 1-3  depict an exercise machine  20  for leg strengthening. The exercise machine  20  has a stationary frame  22  with a number of rigid frame members that support the exercise machine  20  with respect to a ground surface. The type and configuration of the stationary frame  22  shown in the drawings is merely exemplary and can vary. In the illustrated example, the stationary frame  22  includes a base beam  24  that is raised above and extends generally parallel to the ground surface. The base beam  24  is connected at its rearward and forward ends to generally vertically extending rearward and forward support columns  26 ,  28 . Each of the rearward and forward support columns  26 ,  28  has a foot pedestal  30  consisting of a generally flat plate that engages the ground surface. The base beam  24  extends between the rearward and forward support columns  26 ,  28  and is connected thereto at a location slightly above the foot pedestals  30  so that the base beam  24  is spaced from the ground surface. Pairs of angular supporting legs  32  extend transversely downwardly from a lower portion of the rearward and forward support columns  26 ,  28  and have foot pedestals  30  for engaging the ground surface. The angular supporting legs  32  thus provide lateral support to the stationary frame  22 . 
     An intermediate support column  34  extends generally vertically upwardly from the base beam  24  between the rearward and forward support columns  26 ,  28 . A top beam  36  is connected to the tops of the rearward and intermediate support columns  26 ,  34 . Together, the rearward portion of the base beam  24 , the rearward support column  28 , the intermediate support column  34  and the top beam  36  define a surrounding frame for supporting portions of a resistance mechanism, which will be further described herein below. 
     The stationary frame  22  also includes first and second opposing frame arms  38 ,  40  that extend angularly upwardly from a middle portion of the intermediate support column  34  towards the forward support column  28 . The first opposing frame arm  38  is fixed at opposite ends to a side surface of the intermediate support column  34  and a side surface of the forward support column  28 . The second opposing frame arm  40  is fixed at its rearward end to a front side surface of the intermediate support column  34 . The forward end of the second opposing frame arm  40  is cantilevered from the intermediate support column  34  and is laterally spaced apart from the forward support column  28 . A cross brace  50  ( FIG. 3 ) laterally extends between the first and second opposing frame arms  38  and  40  providing rigidity to the assembly. A third frame arm  52  extends between the intermediate support column  34  and the forward support column  28  and is located above the first and second opposing frame arms  38 ,  40 . The third frame arm  52  is fixed at its rearward end to the side surface of the intermediate support column and at its forward end to the rear side surface of the forward support column  28 . 
     A handle frame  54  extends upwardly and laterally from the forward support column  28 . The handle frame  54  has a support beam  55  with a first end attached to an upper portion of the forward side surface of the forward support column  28 , and a second end that is cantilevered transversely outwardly relative to the forward support column  28 , so that the second end extends perpendicularly relative to the forward support column  28 . The support beam  55  is generally L-shaped so as to facilitate the perpendicular orientation of the cantilevered second end relative to forward support column  28 . A generally L shaped cross-brace  59  has a first end fixed to an intermediate portion of the third frame arm  52  between its opposite ends, and a second end fixed to an intermediate portion of the support beam  55 , thus providing rigidity and strength to the cantilevered handle frame  54 . An elongated handle bar  60  is fixed to the second end of the support beam  55  for grasping by a user while standing and operating the exercise machine  20 , as further described herein below. 
     Referring to  FIGS. 1-3 , the exercise machine  20  also has a platform  66  on which the user stands while performing an exercise motion using the exercise machine  20 , as will be described further herein below. The platform  66  includes a planar tread member  69  having raised and/or lowered treads for encouraging a secure frictional engagement between the user&#39;s feet and the planar tread member  69 . The height of the platform  66  above the ground surface is adjustable. The platform  66  thus may be raised and lowered, depending upon the height of the user. In particular, a platform frame  68  supports the platform  66  and facilitates positioning of the platform  66  in a variety of fixed positions with respect to the stationary frame  22 . The platform frame  68  has opposed supporting beams  70  that extend parallel to each other and have foot pedestals  30  that engage the ground surface and support the opposed supporting beams  70  above the ground surface. Generally L-shaped support bars  72  are attached at their forward end to the respective opposed supporting beams  70  and extend upwardly and rearwardly above the opposed supporting beams  70 . A pair of angular rear supporting columns  74  have lower ends connected to the opposed supporting beams  70  and extend forwardly at an angle. The upper ends of the angular rear supporting columns  74  are fixed to the L-shaped supporting bars  72 , thus providing rigidity and support to the platform frame  68 . 
     Positioning plates  75  are located on the sides of opposing forward portions of each of the L-shaped support bars  72 , and each has an angled slot  76  with a series of stepped recesses  78  extending from and below the angled slot  76 . The number of stepped recesses  78  can vary from what is shown. In the illustrated example, there are three stepped recesses  78 , each corresponding to a different fixed height of the platform  66 . A lift handle  80  extends from one side of the platform  66  and through the angled slot  76 . The lift handle  80  can be manually raised and lowered along the angled slot  76 , as shown by comparison of  FIGS. 9-11 , to adjust the height of the platform  66 . In particular, the lift under force of gravity, lift handle  80  is engageable with the platform frame  68  by manually releasing the lift handle  80  so that it becomes seated in one of the stepped recesses  78 . 
     Comparison of  FIGS. 9-11  shows a progression of lifting the lift handle  80  from the lowermost stepped recess  78  and moving the lift handle  80  upwardly along the angled slot  76 , and then releasing the lift handle  80  so that it becomes seated under force of gravity in the uppermost stepped recess  78 . A pin  81  ( FIG. 2 ) extends from the platform  66  into the angled slot on the opposite side of the platform frame  68  relative to the lift handle  80 . The pin  81  engages with the stepped recesses on the opposite side, when the lift handle  80  is manually released and seated in the stepped recesses  78  on the side shown in  FIGS. 9-11 . A gas cylinder  82  is located below the platform  66  and assists movement and positioning of the platform  66  with respect to the platform frame  68 . The gas cylinder  82  is transversely oriented with respect to the platform  66  and has a first end coupled to the platform  66  at a pivot point (not shown) and a second end coupled to the platform frame  68  at a pivot point (not shown). The gas cylinder  82  provides an assistance force on the platform  66  to assist the user with lifting the platform  66  via the lift handle  80 . The gas cylinder  82  also provides a force on the platform  66  that prevents the platform  66  from free-falling when the lift handle  80  is removed from the stepped recesses  78 . 
     The rear of the platform  66  is pivotably coupled to the platform frame  68 . In particular, opposing slide bars  88  are fixed to and angularly extend between the opposed supporting beams  70  and the rear ends of the L-shaped support bars  72 . The rear of the platform  66  is pivotably connected by pivot joints  90  to sleeves  92  that slide up and down along the opposing slide bars  88  as the lift handle  80  is raised and lowered along the angled slot  76 . The angle of the slide bars  88  allows the sleeves  92  to frictionally engage with and retain the platform  66  with respect to the platform frame  68  when the lift handle  80  is manually released and gravity allows the lift handle  80  to seat in one of the stepped recesses  78 , thus retaining the platform  66  in a horizontal position. 
     Referring now to  FIGS. 1-4 , the exercise machine  20  has a unique linkage  100  that couples a thigh support member  102  and an ankle support member  104  to the stationary frame  22 . The thigh support member  102  is for supporting a user&#39;s thigh during a hamstring curl exercise motion, and includes a cantilevered arm  106  that supports a resilient pad  108 , having a top surface that is sized and shaped to comfortably support the bottom of a user&#39;s thigh. The ankle support member  104  is for supporting the user&#39;s ankle during the hamstring curl exercise motion, and includes a cantilevered arm  110  and a resilient pad  112 , which is tubular and sized and shaped to comfortably support the bottom of a user&#39;s ankle along the lower calf. As described herein below, advantageously, the thigh support member  102  and ankle support member  104  are each movable with respect to the stationary frame  22  during the hamstring curl exercise motion, thus facilitating contraction and extension of both of the user&#39;s thigh and ankle. In particular, as described further herein below, contraction and extension of both of the user&#39;s hamstring and glute during the hamstring curl exercise motion causes each of the thigh support member  102  and ankle support member  104  to pivot, respectively, with respect to the stationary frame  22 . 
     The type and configuration of the linkage  100  can vary from what is shown. Referring particularly to  FIGS. 4-8 , the linkage  100  is a four-bar linkage; however other configurations could instead be employed. The linkage  100  is configured such that that contraction and extension of the user&#39;s hamstring and glute during the hamstring exercise motion causes the thigh support member  102  to pivot about a rear fixed pivot axis  116 , which remains stationary with respect to the stationary frame  22 . In particular, the linkage  100  has a rear pivot arm  118  that couples the thigh support member  102  to the stationary frame  22  such that the rear pivot arm  118  and the thigh support member  102  pivot together about the rear fixed pivot axis  116 . The rear pivot arm  118  is an elongated member having a rearward end  120  that is coupled to the stationary frame  22  by opposing axle ends  122  that transversely extend from opposite sides of the rearward end  120  of the rear pivot arm  118  and are supported by the stationary frame  22 , and particularly (returning to  FIG. 3 ) extending into a bearing  124  supported in an intermediate portion of the first opposing frame arm  38  and extending into a bearing  126  supported in a stanchion  128  extending upwardly from the second opposing frame arm  40 . The opposing axle ends  122  thus extend along and define the rear fixed pivot axis  116 . The rear pivot arm  118  has a forward end  130  that is parallel to the rearward end  120 , and a middle portion  131  that is angular relative to the forward and rearward ends  120 ,  130 . The cantilevered arm  106  of the thigh support member  102  is attached to the forward end  130  of the rear pivot arm  118  and extends transversely outwardly relative to the rear pivot arm  118  into a position for support of the user&#39;s thigh. 
     The linkage  100  also includes a forward pivot arm  132  that couples the ankle support member  104  to the rear pivot arm  118  at a first movable pivot axis  134  (see  FIG. 5 ), which as described further herein below, pivots about the rear fixed pivot axis  116  along with the rear pivot arm  118 . The forward pivot arm  132  has a rearward end  136  and a forward end  138 . A pivot axle  141  transversely extends from the rearward end  136  into a bearing  143  on the forward end  130  of the rear pivot arm  118 . The pivot axle  141  thus extends along and defines the first movable pivot axis  134  and is carried by the rear pivot arm  118  as it pivots with respect to the rear fixed pivot axis  116 . The cantilevered arm  110  of the ankle support member  104  is coupled to and extends transversely from the forward end  138  of the forward pivot arm  132 , such that the ankle support member  104  extends transversely relative to the forward pivot arm  132  into a position for supporting the user&#39;s ankle. The ankle support member  104  is coupled to the forward pivot arm  132  by an ankle support member adjustment device  140  that facilitates adjustment of the ankle support member  104  into and between multiple (a plurality of) fixed positions relative to the forward pivot arm  132 . The ankle support member adjustment device  140  includes a fixed plate  142  extending upwardly from the forward end  138  of the forward pivot arm  132  and a spring-loaded pin  144  mounted on a support bracket  146  extending upwardly from the cantilevered arm  110  of the ankle support member  104 . The cantilevered arm  110  has a crank arm  148  on its inward end that is rotatably engaged with a pivot axle  149  extending through a boss  150  on the side of the forward end  138  of the forward pivot arm  132 . The spring-loaded pin  144  can be selectively engaged with each of multiple (a plurality of) holes  153  to thereby fix the ankle support member  104  into each of the fixed positions relative to the forward pivot arm, thus allowing for adjustment of the ankle position of the user. 
     The linkage  100  further includes an intermediate pivot arm  152  that couples the forward pivot arm  132  to the stationary frame  22  at a forward fixed pivot axis  154  (see  FIG. 5 ), which remains stationary with respect to the stationary frame  22 , and such that, as described further herein below, contraction and extension of the user&#39;s hamstring during the hamstring exercise causes the ankle support member  104 , forward pivot arm  132 , and intermediate pivot arm  152  to pivot about the forward fixed pivot axis  154 . The intermediate pivot arm  152  has a forward end  160 , a rearward end  162 , and an intermediate portion  164  that extends between the forward and rearward ends  160 ,  162 . A pivot axle  170  extends through the intermediate portion  164  via a throughbore  166  and is supported on opposite sides of the intermediate portion  164  with respect to the stationary frame  22  by bearings  172  (see  FIG. 3 ) supported in the forward support column  28  and second opposing frame arm  40 . The pivot axle  170  thus extends along and defines the forward fixed pivot axis  154 . The intermediate pivot arm  152  is fixed to the pivot axle  170  so that the two components pivot together with respect to the forward fixed pivot axis  154 . The rearward end  162  of the intermediate pivot arm  125  extends rearwardly with respect to the forward fixed pivot axis  154 . 
     The first movable pivot axis  134  is located at the forward end  160  of the intermediate pivot arm  152  (and at the rearward end  136  of the forward pivot arm  132 , as previously discussed). The intermediate pivot arm  152  is coupled to an intermediate portion  156  of the forward pivot arm  132 , between the forward and rearward ends  136 ,  138 , at a second movable pivot axis  158  (see  FIG. 5 ) that is located forwardly of the first movable pivot axis  134  along the forward pivot arm  132 . The intermediate pivot arm  152  is coupled to the forward pivot arm  132  by opposing axle ends  167  that extend laterally outwardly from opposite sides of the forward end  160  of intermediate pivot arm  152  and are supported by bearings  168  of a supporting frame  169  on the inward side of the forward pivot arm  132 . As such, contraction and extension of the user&#39;s hamstring and glute during the hamstring curl exercise causes the second movable pivot axis  158  to pivot about the first movable pivot axis  134  and causes the first movable pivot axis  134  to pivot about the rear fixed pivot axis  116 , as will be further described herein below with reference to  FIGS. 5-8 . 
     Referring to  FIGS. 1 and 2 , the exercise machine further includes a resistance mechanism  180  that resists pivoting movement of the thigh support member  102  and ankle support member  104 , respectively, during the hamstring curl exercise motion. The type and configuration of the resistance mechanism can vary from what is shown, with suitable examples disclosed in the above-incorporated U.S. Pat. No. 9,604,090. In the illustrated example, the resistance mechanism  180  a weight stack having a number of resistance weights  184  that are supported by slide bars  186  extending between the base beam  24  and top beam  36 . A conventional bayonet (not shown) extends into a centerhole through the weight stack and is engageable by a selector pin  188  ( FIG. 5 ) for engaging a particular number of resistance weights  184  with the bayonet. An elongated pulley member  190  has a first end that is attached to the bayonet via a head plate  192 . The pulley member  190  is a belt, however in other examples it could be a cable and/or the like. The pulley member  190  is trained around a pair of pulley wheels  193  located on the top beam  36  and has a second end that is coupled to the linkage  100 , particularly to a cam plate  194 , which will be described further herein below. 
     Referring to  FIG. 4 , the cam plate  194  is fixed to and rotates with the pivot axle  170  with respect to the forward fixed pivot axis  154 . The cam plate  194  has a radially outer cam surface  197  with a curved profile along which the pulley member  190  engages when the cam plate  194  is rotated. Thus, as can be seen by comparison of  FIGS. 5-8  that pivoting motion of the intermediate pivot arm  152  causes rotation of the pivot axle  170 , which in turn causes rotation of the cam plate  194 . Rotation of the cam plate  194  in one direction pulls on the pulley member  190 , against resistance from the resistance weights selected by the selector pin  188 . Rotation of the cam plate  194  in the opposite direction releases the pulley member  190  and is assisted by the resistance weights selected by the selector pin  188 . The outer profile of the cam plate  194  can be intentionally contoured to provide a certain resistance profile to the user. 
     Referring to  FIG. 4 , a resistance member adjustment device  196  facilitates angular positioning of the intermediate pivot arm  152  about the forward fixed pivot axis  154  with respect to the cam plate  194 . In particular, the resistance member adjustment device  196  facilitates user selection of one of multiple (a plurality of) angular positions of the intermediate pivot arm  152  to adjust the start position of the user&#39;s ankle and thigh. The resistance member adjustment device  196  includes a spring-loaded pin  198  mounted to the rearward end  162  of the intermediate pivot arm  152 , and multiple (a plurality of) holes  200  formed in the cam plate  194 . Engagement of the spring-loaded pin  198  in each of the holes  200  fixes the intermediate pivot arm  152  into a different angular position with respect to the cam plate  194 , thus affecting the starting position. 
     Referring now to  FIGS. 5-8 , operation of the exercise machine  20  will be further described. As shown in  FIG. 5 , the user stands on the platform  66  and raises one leg up onto the exercise machine  20  so that the user&#39;s thigh  300  rests on the thigh support member  102  and the user&#39;s ankle  302  rests on the ankle support member  104 . As needed to achieve a comfortable fit, the height of the platform  66  can be adjusted via the lift handle  80 , as described herein above with reference to  FIGS. 9-11 . As needed, the position of the thigh support member  102  can be adjusted via the resistance member adjustment device  196 , as described herein above. As needed, the position of the ankle support member  104  can be adjusted via the ankle support member adjustment device  140 , as described herein above.  FIG. 5  depicts the user in dash-and-dot lines and the exercise machine  20  adjusted to suit the size of the user, as described herein above. Although not shown, referring briefly to  FIGS. 1 and 2 , the elongated handle bar  60  is positioned above the user&#39;s lower body for grasping by the user for added stability. 
       FIGS. 6-8  sequentially depict exemplary positions of the exercise machine  20  as the user&#39;s hamstring and glute is contracted to perform a hamstring curl exercise motion. Comparison of  FIGS. 5 and 6  illustrates the initial pivoting movement of the forward pivot arm  132  and intermediate pivot arm  152  as the user&#39;s ankle is curled downwardly. The forward pivot arm  132  is caused to pivot downwardly about the first movable pivot axis  134 . The intermediate pivot arm  152  is also caused to pivot downwardly about the forward fixed pivot axis  154 . This movement is resisted by the resistance mechanism  180 , as the cam plate  194  is caused to rotate with the intermediate pivot arm  152  about the forward fixed pivot axis. The pulley member  190  is wrapped onto the outer radius of the cam plate  194  and the selected resistance weights  184  are raised from the remainder of the weight stack  182 . The rear pivot arm  118  is also caused to pivot downwardly about the rear fixed pivot axis  116 , as shown. The thigh support member  102  thus begins to pivot downwardly along with the rear pivot arm  118 . So both the thigh support member  102  and the ankle support member  104  pivot downwardly with respect to the stationary frame  22 . 
     A comparison of  FIGS. 6 and 7  illustrates the exercise machine  20  as the user&#39;s hamstring and glute are further contracted during the hamstring curl exercise motion.  FIG. 7  depicts the ankle support member  104  pivoted downwardly beneath the thigh support member  102 . The forward pivot arm  132  is further pivoted about the first movable pivot axis  134  and the intermediate pivot arm  152  is further pivoted about the forward fixed pivot axis  154 . The rear pivot arm  118  is further pivoted downwardly about the rear fixed pivot axis  116 , and so the thigh support member  102  is further pivoted downwardly. 
     A comparison of  FIGS. 7 and 8  illustrates the exercise machine  20  as the user&#39;s hamstring and glute are further contracted during the hamstring curl exercise motion.  FIG. 8  depicts the ankle support member  104  pivoted rearwardly of the thigh support member  102 , about the first movable pivot axis  134 . The rear pivot arm  118  is further pivoted downwardly about the rear fixed pivot axis  116 , and so the thigh support member  102  is also further pivoted downwardly. 
     A comparison of  FIGS. 8-5  depicts the exercise machine  20  during subsequent extension of the user&#39;s hamstring and glute. 
     Referring to  FIGS. 2 and 4 , the linkage  100  further includes a manual assist lever  114  that is coupled to the pivot axle  170  on an opposite side of the stationary frame  22  relative to the rest of the linkage  100 . The manual assist lever  114  is configured for a second user to manually assist the hamstring curl exercise motion, for example when the user&#39;s strength is depleted, or otherwise to modify the resistance level provided by the resistance mechanism  180 . Grasping and rotating the manual assist lever  114  relative to the rear fixed pivot axis  116  rotates the pivot axle  170 , which in turn rotates the cam plate  194  relative to the rear fixed pivot axis  116 . A fixed assist lever  176  is fixed to the handle frame  54  so that the second user can place the other hand on the fixed assist lever  176  for stability. 
     The present disclosure thus provides examples of leg exercise machines having features intended for eccentric overload training of a user&#39;s leg muscles. In certain examples, the exercise machine advantageously strengthens the muscles involved in a running motion during the exercise. In addition, in certain examples, a handle is provided for a third party to assist the user during the concentric phase of the repetition when the user has exhausted their concentric strength, but still has eccentric strength remaining in the muscle. When exercising the hamstring on prior art exercise machines, the knees are usually the only joint rotating while the hips are fixed. Thus certain examples disclosed herein are improved over the prior art in that they facilitate a compound movement from both the hip and knee joint. 
     Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Other technical advantages may become readily apparent to one of ordinary skill in the art after review of the following figures and description. Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set. 
     To aid the Patent Office and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim.