Patent Publication Number: US-10322310-B2

Title: Abdominal exercise apparatus

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 14/995,513 filed Jan. 14, 2016, which is a continuation of PCT/US2015/019866, filed Mar. 11, 2015 which claims the benefit of priority to U.S. Provisional Application No. 61/951,011 filed Mar. 11, 2014 and U.S. Provisional Application No. 61/951,059 filed Mar. 11, 2014 and U.S. Provisional Application No. 61/951,026 filed Mar. 11, 2014 and U.S. Provisional Application No. 61/951,034 filed Mar. 11, 2014 and U.S. Provisional Application No. 61/951,046 filed Mar. 11, 2014 the disclosures of all of which are incorporated herein by reference in their entirety as if fully set forth herein. 
     This application incorporates by reference the disclosures of all of the following in their entirety as if fully set forth herein: U.S. Pat. Nos. 7,717,831, 4,725,054, 7,666,123, 8,070,658, 7,278,955, 8,025,609, 7,727,128, 486,535, 490,127, U.S. Patent Publication No. 2003/0092541, U.S. Patent Publication No. 2007/0173384, U.S. Patent Publication No. 2006/0270531, U.S. Patent Publication No. 2008/0167169, U.S. Patent Publication No. 2010/0204021. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to physical exercise machines and more particularly to an exercise apparatus that enables users to perform an abdominal muscle exercise that is resisted by one or more resistance mechanisms. 
     BACKGROUND OF THE INVENTION 
     Exercise machines for exercising abdominal muscles are known and used for directing movement of a user upper torso by forcing the user to use the user&#39;s abdominal muscles against a weight resistance. In such machines the force that the user is required to exert typically starts at zero and increases at a very high rate of increase immediately upon engagement by the user with the assembly, arm or the like that is interconnected to the weight resistance. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention there is provided an exercise apparatus  10  for performing a back extension exercise by a user  5  having a lower back  7 , legs  11  and a trunk T 1 , T 2 , T 3 , that has a longitudinal trunk axis LA and a trunk weight, the apparatus  10  comprising: 
     a frame  12 , 
     a seat  16  having a seating surface PS and a pelvic stabilization pad  18  having a lower back engagement surface ES, 
     the seating surface PS and the pelvic stabilization pad  18  being mounted, adapted and arranged on the frame in a disposition relative to each other such that the user  5  can simultaneously sit on the seating surface PS and engage the user&#39;s lower back  7  against the lower back engagement surface ES, 
     an input arm assembly  30  interconnected by a first interconnection  47 ,  60 ,  70  to a first resistance mechanism  43  and by a second interconnection  48 ,  50  to a second manually selectively adjustable fixed weight resistance mechanism  42 , 
     the input arm assembly  30  including a manually graspable mechanism  30   h  and being arranged on the apparatus  10  such that the input arm assembly is pivotable beginning from a start motionless position SMP along a path of travel PT forwardly away from the pelvic stabilization pad  18  under resistance R 1 , R 2  exerted by one or both of the resistance mechanisms  42 ,  43 , 
     the input arm assembly being arranged on the apparatus such that when the user ( 5 ) is seated on the seating surface and the user&#39;s lower back  7  is engaged against the lower back engagement surface ES, the seat  16  and the pelvic stabilization pad position  18  dispose the user in a position in which the user can manually engage ME the manually graspable mechanism  30   h  and exert a forwardly directed pushing force F on the input arm assembly beginning from the start motionless position continuing along the path of travel PT, PT 2  against resistance R 1 , R 2  exerted by one or both of the first  43  and second  42  resistance mechanisms. 
     The first resistance mechanism is adapted to increase resistance as the degree of pivoting of the input arm assembly increases along the path of travel PT, PT 2  away from the start motionless position SMP toward the pelvic stabilization pad. 
     The seat and the pelvic stabilization pad are arranged on the apparatus such that when the user is seated on the seat with the user&#39;s lower back engaged against the lower back engaging surface and the input arm assembly is disposed in the start motionless position, the user&#39;s trunk axis LA is disposed at a generally vertical VP disposition when the user manually engages the manually graspable mechanism and wherein the user&#39;s trunk axis is disposed at a forwardly angled disposition relative to vertical leaning forwardly away from the pelvic stabilization pad  18  when the user manually engages ME the manually graspable mechanism  30   h  and pushes the input arm assembly forwardly away from the pelvic stabilization pad. 
     The seat and the pelvic stabilization pad are arranged on the apparatus such that when the user manually engages ME and pushes the input arm assembly from the start motionless toward the pelvic stabilization pad, the user&#39;s trunk axis LA pivots forwardly from the generally vertical VP disposition and travels PT from the generally vertical disposition toward a forwardly angled disposition, the user&#39;s lower back  7  being assisted by more force from the trunk weight and opposed by more resistance R 1  from the first resistance mechanism  43  as the user&#39;s trunk axis travels forwardly toward a more forwardly angled disposition. 
     The first resistance mechanism can comprise an extendable spring that increases in resistance as the spring is increasingly extended, the spring being interconnected to the input arm assembly in an arrangement such that movement of the input arm assembly along the path of travel toward the pelvic stabilization pad increasingly extends the spring and movement toward the start motionless position reduces extension of the spring. 
     Alternatively, the first resistance mechanism can comprise an enclosed cylinder having a piston slidably mounted within the cylinder forming opposing fluid sealed chambers within the piston, the piston being interconnected to a rod that extends outside the enclosed cylinder for driving the piston, the chambers containing a selected compressible fluid, the rod being interconnected to the input arm assembly and driven by movement of the input arm assembly from the start motionless position toward the pelvic stabilization pad to cause fluid in at least one of the chambers to compress and increase resistance against movement of the input arm assembly with an increase in the degree of compression of the fluid. 
     The seating surface (PS) is preferably generally disposed in a plane disposed at a downwardly sloping angle relative to horizontal, the seat having a downwardly disposed front end and an upwardly disposed rear end, the pelvic stabilization pad being mounted such that the lower back engagement surface is disposed at the upwardly disposed rear end of the seating surface in an arrangement that engages the user&#39;s lower back when the user is seated on the seating surface and pushing the user&#39;s lower back toward the pelvic stabilization pad with the user&#39;s legs. 
     The apparatus preferably includes a foot pad  20  mounted forwardly relative to the seat, the foot pad being arranged on the apparatus such that the user can engage the foot pad with the user&#39;s foot and push on the foot pad with the user&#39;s leg to push the user&#39;s lower back into engagement with the lower back engagement surface while seated on the seat. 
     The lower back engagement surface is typically generally circular CES, RA, CD,  FIG. 4 , in radial cross-section. 
     The input arm assembly  32  is preferably interconnected to the first resistance mechanism  43  by a cable  70 , the arm assembly being interconnected to a cam  60  having a receiving groove CP that receives the cable, the cam  60  being interconnected to the arm assembly such that the cam rotates together with pivoting of the input arm assembly, the receiving groove having a profile CP 1 , CP 2  selected to create a lesser torque force F 1   a  against the user&#39;s pulling force F 1  when the user starts pulling the arm assembly from the start motionless position and gradually increase torque force F 2   a  against the user&#39;s pulling force F 2  as the user continues to pull the input arm assembly rearwardly. 
     In another aspect of the invention there is provided a method of performing a back extension exercise using the apparatus of claim  1  comprising the user&#39;s: 
     seating the user&#39;s trunk on top of the seat of the apparatus of claim  1 , 
     pushing the user&#39;s lower back into engagement against the lower back engaging surface while seated on the seat, 
     manually engaging the manually graspable mechanism, 
     pivoting the user&#39;s trunk forwardly such that the user&#39;s trunk axis is disposed at a forward angle sufficient to push the input arm assembly from the start motionless position forwardly away from the pelvic stabilization pad. 
     In another aspect of the invention there is provided An exercise apparatus for performing a back extension exercise by a user having a lower back, legs and a trunk that has a longitudinal trunk axis and a trunk weight, the apparatus comprising: 
     a frame, 
     a seat  16  having a seating surface PS and a pelvic stabilization pad  18  having a lower back engagement surface ES, 
     the seating surface and the pelvic stabilization pad being mounted, adapted and arranged on the frame in a disposition relative to each other such that the user can simultaneously sit on the seating surface and engage the user&#39;s lower back against the lower back engagement surface, 
     an input arm assembly  30  interconnected by a first interconnection to a first resistance mechanism and by a second interconnection to a second manually selectively adjustable fixed weight resistance mechanism, 
     the input arm assembly including a manually graspable mechanism and being arranged on the apparatus such that the input arm assembly is pivotable beginning from a start motionless position along a path of travel forwardly away from the pelvic stabilization pad under resistance exerted by one or both of the resistance mechanisms, 
     wherein the first resistance mechanism is adapted to increase resistance as the degree of pivoting of the input arm assembly increases along the path of travel forwardly away from the pelvic stabilization pad. 
     In such an apparatus the input arm assembly is preferably arranged on the apparatus such that when the user is seated on the seating surface and the user&#39;s lower back is engaged against the lower back engagement surface, the seat and the pelvic stabilization pad position the user in a position at which the user can manually engage the manually graspable mechanism to push the input arm assembly forwardly beginning from the start motionless position away from the pelvic stabilization pad along the path of travel against resistance exerted by one or both of the first and second resistance mechanisms. 
     The seat and the pelvic stabilization pad are preferably arranged on the apparatus such that when the user is seated on the seat with the user&#39;s lower back engaged against the lower back engaging surface and the input arm assembly is disposed in the start motionless position, the user&#39;s trunk axis is disposed in a generally vertical disposition and the user&#39;s trunk is disposed at a forwardly angled position away from the stabilization pad when the user manually engages the manually graspable mechanism and pushes the input arm assembly forwardly. 
     The seat and the pelvic stabilization pad are preferably arranged on the apparatus such that when the user manually engages and pushes the input arm assembly from the start motionless forwardly away from the pelvic stabilization pad, the user&#39;s trunk axis pivots forwardly from the generally vertical disposition and travels toward a forwardly angled disposition, the user&#39;s lower back being opposed by less force from the trunk weight and more resistance from the first resistance mechanism as the user&#39;s trunk axis travels forwardly away from the vertical disposition. 
     The first resistance mechanism typically comprises an extendable spring that increases in resistance as the spring is increasingly extended, the spring being interconnected to the input arm assembly in an arrangement such that movement of the input arm assembly along the path of travel toward the pelvic stabilization pad increasingly extends the spring and movement toward the start motionless position reduces extension of the spring. 
     Alternatively, the first resistance mechanism can comprise an enclosed cylinder having a piston slidably mounted within the cylinder forming opposing fluid sealed chambers within the piston, the piston being interconnected to a rod that extends outside the enclosed cylinder for driving the piston, the chambers containing a selected compressible fluid, the rod being interconnected to the input arm assembly and driven by movement of the input arm assembly from the start motionless position toward the pelvic stabilization pad to cause fluid in at least one of the chambers to compress and increase resistance against movement of the input arm assembly with an increase in the degree of compression of the fluid. 
     The seating surface PS is typically generally disposed in a plane disposed at a downwardly sloping angle relative to horizontal, the seat having a downwardly disposed front end and an upwardly disposed rear end, the pelvic stabilization pad being mounted such that the lower back engagement surface is disposed at the upwardly disposed rear end of the seating surface in an arrangement that engages the user&#39;s lower back when the user is seated on the seating surface and pushing the user&#39;s lower back toward the pelvic stabilization pad with the user&#39;s legs. 
     The apparatus preferably includes a foot pad mounted forwardly relative to the seat, the foot pad being arranged on the apparatus such that the user can engage the foot pad with the user&#39;s foot and push on the foot pad with the user&#39;s leg to push the user&#39;s lower back into engagement with the lower back engagement surface while seated on the seat. 
     The lower back engagement surface is typically generally circular in radial cross-section. 
     In another aspect of the invention there is provided a method of performing a back extension exercise using the apparatus described immediately above comprising the user&#39;s: 
     seating the user&#39;s trunk on top of the seat of the apparatus, 
     pushing the user&#39;s lower back into engagement against the lower back engaging surface while seated on the seat, 
     manually engaging the manually graspable mechanism, 
     pivoting the user&#39;s trunk forwardly such that the user&#39;s trunk axis is disposed at a forward angle sufficient to push the input arm assembly from the start motionless position forwardly away from the pelvic stabilization pad. 
     In another aspect of the invention there is provided an exercise apparatus for performing a back extension exercise by a user having a lower back, legs and a trunk that has a longitudinal trunk axis and a trunk weight, the apparatus comprising: 
     a frame, 
     a seat  16  having a seating surface PS and a pelvic stabilization pad  18  having a lower back engagement surface ES, 
     the seating surface and the pelvic stabilization pad being mounted, adapted and arranged on the frame in a disposition relative to each other such that the user can simultaneously sit on the seating surface and engage the user&#39;s lower back against the lower back engagement surface, 
     an input arm assembly  30  interconnected by a first interconnection to a first resistance mechanism, 
     the input arm assembly including a manually graspable mechanism and being arranged on the apparatus such that the input arm assembly is pivotable beginning from a start motionless position along a path of travel forwardly away from the pelvic stabilization pad under resistance exerted by one or both of the resistance mechanisms, 
     wherein the first resistance mechanism is adapted to increase resistance as the degree of pivoting of the input arm assembly increases along the path of travel forwardly away from the pelvic stabilization pad. 
     Such an apparatus preferably includes a second interconnection to a second manually selectively adjustable fixed weight resistance mechanism. 
     The input arm assembly is preferably arranged on the apparatus such that when the user is seated on the seating surface and the user&#39;s lower back is engaged against the lower back engagement surface, the seat and the pelvic stabilization pad position the user in a position at which the user can manually engage the manually graspable mechanism to pull the input arm assembly beginning from the start motionless position forwardly away from the pelvic stabilization pad along the path of travel against resistance exerted by one or both of the first and second resistance mechanisms. 
     The seat and the pelvic stabilization pad are preferably arranged on the apparatus such that when the user is seated on the seat with the user&#39;s lower back engaged against the lower back engaging surface and the input arm assembly is disposed in the start motionless position, the user&#39;s trunk axis is disposed in a generally vertical disposition and the user&#39;s trunk is disposed in a forwardly angled disposition when the user manually engages the manually graspable mechanism and pushes the input arm assembly forwardly. 
     The seat and the pelvic stabilization pad are preferably arranged on the apparatus such that when the user manually engages and pushes the input arm assembly from the start motionless forwardly away from the pelvic stabilization pad, the user&#39;s trunk axis pivots forwardly from the generally vertical disposition forwardly toward a forwardly angled disposition, the user&#39;s lower back being opposed by less force from the trunk weight and more resistance from the first resistance mechanism as the user&#39;s trunk axis pivots more forwardly. 
     The first resistance mechanism preferably comprises an extendable spring that increases in resistance as the spring is increasingly extended, the spring being interconnected to the input arm assembly in an arrangement such that movement of the input arm assembly along the path of travel toward the pelvic stabilization pad increasingly extends the spring and movement toward the start motionless position reduces extension of the spring. 
     Alternatively, the first resistance mechanism can comprise an enclosed cylinder having a piston slidably mounted within the cylinder forming opposing fluid sealed chambers within the piston, the piston being interconnected to a rod that extends outside the enclosed cylinder for driving the piston, the chambers containing a selected compressible fluid, the rod being interconnected to the input arm assembly and driven by movement of the input arm assembly from the start motionless position toward the pelvic stabilization pad to cause fluid in at least one of the chambers to compress and increase resistance against movement of the input arm assembly with an increase in the degree of compression of the fluid. 
     The seating surface (PS) is preferably generally disposed in a plane disposed at a downwardly sloping angle relative to horizontal, the seat having a downwardly disposed front end and an upwardly disposed rear end, the pelvic stabilization pad being mounted such that the lower back engagement surface is disposed at the upwardly disposed rear end of the seating surface in an arrangement that engages the user&#39;s lower back when the user is seated on the seating surface and pushing the user&#39;s lower back toward the pelvic stabilization pad with the user&#39;s legs. 
     The apparatus typically includes a foot pad mounted forwardly relative to the seat, the foot pad being arranged on the apparatus such that the user can engage the foot pad with the user&#39;s foot and push on the foot pad with the user&#39;s leg to push the user&#39;s lower back into engagement with the lower back engagement surface while seated on the seat. 
     The lower back engagement surface is preferably generally circular in radial cross-section. 
     In another aspect of the invention there is provided a method of performing a back extension exercise using the apparatus described immediately above comprising the user&#39;s: 
     seating the user&#39;s trunk on top of the seat of the apparatus, 
     pushing the user&#39;s lower back into engagement against the lower back engaging surface while seated on the seat, 
     manually engaging the manually graspable mechanism, 
     pivoting the user&#39;s trunk forwardly such that the user&#39;s trunk axis is disposed at a forward angle sufficient to push the input arm assembly from the start motionless position forwardly away from the pelvic stabilization pad. 
     In another aspect of the invention there is provided an exercise apparatus for performing a back extension exercise by a user comprising: 
     a frame, 
     an input arm assembly being interconnected by a first interconnection to a spring resistance mechanism 
     the input arm assembly being interconnected by a second interconnection to a manually selectively adjustable weight resistance mechanism, 
     a seat having a generally planar seating surface PS and pelvic stabilization pad having a lower back engagement surface ES having a central radial axis RA, the seating surface PS being generally disposed in a plane disposed at a downwardly sloping angle relative to horizontal, 
     the seating surface and the lower back engagement surface being mounted, adapted and arranged relative to each other such that the seating surface and the central radial axis are disposed at an obtuse angle relative to each other, 
     wherein the input arm assembly is mounted, arranged and adapted to enable the user to manually push on the arm assembly to perform a pushing exercise while seated on the seat with the user&#39;s lower back engaged against the lower back engagement surface. 
     The input arm assembly of such an apparatus is typically mounted to the frame to be rotatable around a pivot axis and the input arm assembly is interconnected to the spring resistance mechanism such that when the user pulls on the arm in a direction that causes the arm to rotate, the arm pulls on the spring which exerts an opposing resistance force against the exercise force of the user. 
     The lower back engagement surface is preferably generally circular in cross-section, the central radial axis RA extending from or intersecting the center of a circle in which the circular circumference is disposed through the center or half way around the circumference of the generally circumferential surface ES. 
     The input arm assembly  32  is preferably interconnected to the first resistance mechanism  43  by a cable  70 , the arm assembly being interconnected to a cam ( 60 ) having a receiving groove CP that receives the cable, the cam  60  being interconnected to the arm assembly such that the cam rotates together with pivoting of the input arm assembly, the receiving groove having a profile CP 1 , CP 2  selected to create a lesser torque force F 1   a  against the user&#39;s pushing force F 1  when the user starts pushing the arm assembly from the start motionless position and gradually increase torque force F 2   a  against the user&#39;s pushing force F 2  as the user continues to push the input arm assembly forwardly 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: 
         FIG. 1  is a top side-front perspective view of a back extension and abdominal exercise apparatus according to the invention with the input arm assembly in a start, motionless position. 
         FIG. 2  is a view of the  FIG. 1  apparatus showing the input arm assembly in a forwardly disposed position relative to its starting position. 
         FIG. 2A  is a view similar to  FIG. 2  apparatus showing the input arm assembly in its start motionless position. 
         FIG. 2AA  is a rear perspective view of the  FIG. 1  apparatus. 
         FIG. 3  a side view of the  FIG. 1  apparatus showing a user seated on the seat leaning slightly rearwardly grabbing the handles of the input arm assembly at the start of an exercise. 
         FIG. 4  is a side view of the  FIG. 1  apparatus showing a user having pushed the input arm assembly to a forwardly angled position with the user&#39;s torso or trunk having been pivoted forwardly to a position where the longitudinal axis of the user&#39;s torso has travelled past vertical to a forwardly angled position. 
         FIG. 5  is a schematic side view of a user&#39;s body in various angular orientations when seated in proper position on the seat of an apparatus of  FIGS. 1-4  for performance of a back extension exercise using an apparatus of  FIGS. 1-4 . 
         FIG. 6  is a side view of certain of the components of the apparatus in particular showing the pivoting arm of the input arm assembly from a generally vertical to a forwardly angled position together with the cam and spring components. 
         FIG. 6A  is a side enlarged view of the arm, cam, cable, pulley and pivot components associated with operation of the input arm assembly disposed in the start motionless position of the arm assembly. 
         FIG. 6B  is a side enlarged view of the arm, cam, cable, pulley and pivot components associated with operation of the input arm assembly disposed in a forwardly angled disposed position relative to the start motion position. 
         FIG. 7  is an enlarged side view of the arm and pivot components of an apparatus according to the invention in an alternative embodiment where the arm assembly is interconnected to increasing force resistance mechanism comprised of a fluid cylinder and piston-rod assembly. 
     
    
    
     DETAILED DESCRIPTION 
     The present state of the art in back extension weight training machines allows for movement of the torso in a rotational pattern against some sort of variable resistance (typically from a weight stack). As the torso moves through its normal range of motion, gravity also has a variable effect on the torque developed around the axis of rotation. The more horizontal the torso is to the ground, the greater the effective moment arm which defined as the horizontal distance from the center of gravity to the instant center of rotation of the spine. The problem is created in the present art due to the difference in these two resistive loads (the resistance from the weight stack and the resistance from gravity) and how they vary based on the user capability. It is possible to have a user with a large heavy torso that has limited muscular capacity to create a high torque load around the spine, or a light small framed user that has a high capacity to create a high torque load around the spine. This would create a situation where the variation in the resistance would create the need for a completely different cam shape based on what the difference was in frame size and muscle capacity. One way to solve this problem is to create two different resistance sources. One to counterbalance the torso and the other to provide resistance for the abdominal muscles to work against as the trunk rotates anteriorly around the instant center of rotation in spinal flexion. In preferred embodiments, there is a spring that is connected through a flexible link to a main exercise engagement input arm via a variable ratio cam such that it is designed to apply a varying torque to the arm as it travels through its normal range of motion during the exercise. This allows a separate resistance source, the intensity of which can be selected by the user to be proportional to their muscular capacity, to be applied directly to the user&#39;s back. 
     The weight of the trunk creates a significant independent torque load from gravity as it moves through the range of motion to train spinal extension around an instant rotation axis about the lumbar spine. To address this, a separate resistance source originating from a spring or other force increasing mechanism can be provided to act directly on the input arm to effectively offset the gravity effect on the trunk. The highest trunk gravity effect is when the user&#39;s trunk is disposed at its most horizontal disposition relative to the ground in an anterior flexed posture or posterior extension posture. Unlike an abdominal configuration, the apparatus cannot be counterbalanced in the same way since without the user on the machine, the counterbalance would lift the arm up to the start. For that reason, instead of applying a load to make the trunk lighter as it moves forward into flexion, the apparatus applies a higher resistive load at the end of the range of the exercise in the same direction as the main resistive load of fixed weight, as the trunk moves rearward where gravity has less effective torque. Although it works opposite of an abdominal machine, the effect of offsetting gravitational torque effects though use of a separate spring or other force increasing based resistive source is the same. 
     In an exemplary embodiment of the invention, as shown in  FIGS. 1, 2, 3  a back extension machine  10  includes a support frame  12  on which a user support structure  14  is mounted. The user support structure  14  includes a seat  16  having a seat surface PS and a pelvic stabilizer pad  18  having a lower back engaging surface ES. The seat  16  is mounted on and supported by the forwardly facing upper portion  12   a  of the support frame  12  which is disposed at an angle X to horizontal H (greater than 90 degrees) to orient the seating surface PS at an angle X to horizontal H as well as to orient the tangent T of the pelvic stabilizer pad  18  at its own angle, typically an increased angle over angle X, relative to horizontal H. The seat  16  is positioned such that the user&#39;s lower back  7  and pelvic region abuts and engages the engaging surface ES of the pelvic stabilizer pad  18  and the user&#39;s legs  11  extend forwardly FW and downwardly relative to the trunk T 1 , T 2 , T 3 . The pelvic stabilizer pad  18  is affixed to an upper end portion  12   b  of the support frame  12 , is inclined rearwardly, and is curved CES in its forwarding facing surface CES in a substantially curved configuration, such as partially-circular CES in shape to accommodate for and engage with the user&#39;s lower back  7 . 
     An adjustable footrest  20  is attached to the front of the support frame  12 , where the oblique angle A of the seat  16  substantially directs the seat  16  down towards footrest  20 . The footrest  20  is positioned so the user can apply a force using the leg muscles to push the pelvis an lower back  7  rearwardly RW away from the user input arm  30  into engagement with the pelvic stabilization pad  18 . The footrest  20  can be adjusted or pivioted back and forth (forward and backward) and up and down (vertically) with a footrest adjustment mechanism  22  to accommodate users of varying heights. When a user&#39;s feet are positioned on the footrest  20 , the footrest  20  is typically adjusted such that the user&#39;s thighs are disposed in a position that is substantially parallel with the ground as shown in  FIG. 3 . Additionally, the seat  16 , pad  18 , footrest  20  are arranged, mounted and adapted such that the user&#39;s knees are preferably disposed in a flexion position of between about 10 degrees knee flexion to about 30 degrees knee flexion. This spatial arrangement of the pelvic stabilizer pad  18 , seat  16 , and footrest  20  combination effectively immobilize the user&#39;s pelvic area, preventing it from rotating in either the anterior or posterior direction. 
     An input assembly  24  comprised of a user engagement arm  30  is mounted to the frame, arranged, adapted and interconnected to a weight resistance (in this embodiment a weight stack  42  and a spring  43 ) with an input  30  that is positioned forwardly of the seat  16 . The arm  30  is adapted and mounted to the support frame  12  for pivoting arcuate rotation about a horizontal axis AA. The horizontal arm  30  is pivotable about axis AA for arcuate front to back FW-RW movement by forcible pushing F on the handles  30   h  interconnected to the arm  30  starting from the start motionless position SMP of the arm  30  while the user  5  is properly seated on seat surface PS facing forwardly with the user&#39;s lower back  7  engaged against the engagement surface ES of the pelvic stabilization pad  18 . The horizontal arm  30  is attached to a curved offset arm  32  that is attached to a bushing  33  that is rotatably CC mounted to the frame. As shown,  FIGS. 1-7 , arm  32  is attached via a link  39  to bracket  37  on which a pulley  37   p  is mounted around which a cable  48  is wound, one end of the cable  48  being interconnected to frame bracket  12   d , the other end of cable  48  being interconnected to the lifting post  50 . Bracket  37  and its associated pulley  37   p  are pivotably rotatable CC together with arm  32  around axis AA. As arm  32  is pivoted forwardly FW, cable  48  is concomitantly pushed forwardly FW around the pulley  37   p  thus lifting post  50  and however many fixed weight plates  42   w  are attached to the post  50  via pin  42   p . As bracket  37  and its associated pulley  37   p  are pivoted forwardly, resistance force R 2  is exerted by fixed weights  42   w  against the pulling force F exerted by the user  5 . 
     Similarly as arm  32  is pivoted CC forwardly beginning from the start motionless position SMP to a forward position  32   us ,  32   f , the spring  43  is pulled into an extended disposition by a second cable  70  interconnected between the arm  32  and the spring  43 . As shown in  FIGS. 3-6B , the cable  70  is interconnected to the arm  32  via an attachment member  63  disposed at the base of a cam mechanism  60 . The cable  70  is routed through the profiled groove CP of the cam mechanism  60  which is fixedly connected to the arm  32  in a manner such that the cam  60  rotates or pivots CC around axis AA together with pivoting PT, PT 3  of the arm  32 . The cam  60  is provided with a circumferential cable receiving groove CP,  FIG. 6A  around which the cable  70  is routed. The cable  70  is further routed around a pulley  67   p  that is rotatably mounted on a bracket  67  that is fixedly attached to the frame  12 . The distal end of the second cable  70  is fixedly interconnected to a bracket  47 ,  47   a ,  47   b  that is connected to the proximal end of the spring  43 . 
     In a preferred embodiment, the circumferential groove CP in the cam member  60  is contoured and configured with a profile CP 1 , CP 2  to control the degree of torque force exerted by the user against the spring according to the degree of rotation of the arm  32  such that the user feels a more smooth transition of force exertion F 1 ,  FIG. 5, 6A, 6B , beginning from a start  32   r  no force position SMP further along to the force F 2  needed at a more forwardly pivoted position  32   f  when and while the user continues to push F 2  on the arms  30 ,  32 ,  FIGS. 6A, 6B . At the start position SMP,  32   f , the radius L 1  of the cam profile CP 1  is lower than the radius L 2  at the cam profile position CP 2  such that the leverage force F 1  required to overcome the torque force resistance TF 1  of the spring  43  and rotate the arm  32  at the beginning of the exercise is less than the leverage force F 2  required to overcome the torque force resistance TF 2  of the spring  43  when the cam  60  has been rotated PT 2  to a position where the radius L 2  of the profile CP 2  is greater than the initial radius L 1 . Thus the user  5  is thus required to exert less force torque force F 1  at the beginning of the exercise starting from the start motionless position SMP. As shown in  FIG. 6 , when the arm  32  is pivoted PT 2  forwardly FW, the spring  43  extends by an extension distance ED to the XT 2  position. The larger the extension distance ED, the larger the resistance force R 1  will be exerted against the user&#39;s pushing force. 
     A selected number of incremental weights  42   w  making up a weight stack  42  are selectively interconnectable via a pin  42   p  to the pivoting arm  30 ,  32  via connection of one end of a cable  48  to a manifold or lifting post  50  that is selectively interconnectable to a selected number of the incremental weights by inserting a pin  42   p  in one of a plurality of holes provided in a lifting post  50  that passes vertically through the incremental weights or plates  42   w , as is well known in the art. For example, the weight stack  42  is formed by a stack of rectangular, brick-shaped plates. Each plate  42   w  typically has at least one horizontal channel or hole, wherein the pin  42   p  may be disposed to slidably engage any of a series of horizontal channels which are vertically spaced on the lifting post  50  to match the vertical spacing of the stacked weight plates  52 . The pin thereby engages a portion of the stack of weight plates  52 , such that when vertical force is applied to the lifting post  50  via the cable that is interconnected to pivotable arm  30 ,  32 , the selected stack of weight plates  52  is moved upwards to create a resistance. Typically, the weight stack  42  apparatus is oriented such that the further down the pin is entered into the lifting post  50 , the greater the number of plates  52  are engaged, thereby increasing the resistance R 2  of the weight stack  42  machine. 
     In the present invention the apparatus includes a second cable  70 , one end of which is connected to the input arm assembly, the cable  70  being mounted within the outer circumferential groove of a guide cam member  60 . The opposite end of the cable  70  is connected to an increasing force resistance mechanism such as a spring  43 . The cable  70 , spring  43 , arms  30 ,  32  and cam  60  are arranged, interconnected and adapted such that when the arms  30 ,  32  are forcibly pushed by the user in a clockwise direction CL, the cable  70  pulls on a connector  47  attached to the end of the spring  43  which exerts an opposing resistance force to whatever pulling force F is applied to arms  30 ,  32  by the user or otherwise. The circumferential groove CP 1  in the cam member  60  is contoured and configured to control the degree of force exerted by the user against the spring such that the user feels a more smooth transition of force exertion from a start, no force position and an operational position when the user starts pulling F on the arms  30 ,  32 . 
       FIGS. 1, 4  show the seat  16  having a generally planar seating surface PS that lies generally in a plane P at an obtuse angle X relative the central radial axis of the lower back engagement surface ES of the back pelvic stabilization pad  18 , the pelvic stabilization pad  18  having a lower back engagement surface ES having a central radial axis RA. The seating surface PS being generally disposed in a plane P that is disposed at a downwardly and forwardly sloping angle X relative to horizontal H, the seating surface PS and the lower back engagement surface ES being mounted, adapted and arranged relative to each other such that the seating surface PS and the central radial axis RA are disposed at an obtuse angle A relative to each other. As shown, the lower back engagement surface ES is preferably generally circular in cross-section, the central radial axis RA extending from or intersecting the center of a circle COC in which the circular circumference is disposed and also through the center CES or half way around the cross-section circumferential distance CD of the generally circumferential surface ES. 
     In performing a typical abdominal exercise, the user  5 ,  FIGS. 3, 5 , initially seats themselves on the sloped seat surface PS and engages at least one foot  9  on the foot pad or foot support  20  which is stationarily mounted to the frame  12 ,  FIGS. 1-4 . The user  5  then pushes with their legs and knees  11  against the stationarily mounted foot support  20  to force the user&#39;s trunk rearwardly RW toward the pad  18  to a degree or length such that the user&#39;s lower back  7  is pushed into engagement with the lower back engagement surface ES of the pelvic stabilization pad  18 . Once the user&#39;s lower back  7  is engaged with the surface ES, the user then typically leans rearwardly at a relatively small angle EXT rearwardly RW such that the longitudinal axis LA of the user&#39;s trunk T 1  is in an angled backward position ABP at which the user can manually extend the user&#39;s arm  13  forwardly FW and manually engage and hold ME the handles  30   h  of the pivoting arm  30  with or via the user&#39;s hand  17 . Next the user exercises the user&#39;s abdominal  19  and lower back  7  muscles to move the user&#39;s trunk forwardly from the start trunk position T 1  toward or to the generally vertical VP position T 2  while holding the handles  30   h  thus pushing the arm  30  from the rest or start motionless position SMP through an arcuate path of travel PT against the opposing force R 1 , R 2  of either or both of the force resistance mechanisms  42 ,  43 . As the user pushes the arm  30  from the seated user position T 1  to T 2 , at least one of the resistance mechanisms exerts an increasing amount of force R 1  that increases with the degree of forward FW movement of the arm  30  from its starting position  32   f  to or toward its rearward more vertical position  32   v . When the user&#39;s trunk is disposed in the starting position T 1 , the weight of the user&#39;s trunk T 1  exerts its own torque force TF 1  around the user&#39;s lower back  7  as a result of torque around the user&#39;s lower back  7  on the user&#39;s abdominal muscles  19  and lower back  7  muscles. The torque force TF 1  is in the same direction against the lower back  7  as and adds to the resistance forces R 1 , R 2  that are exerted by the mechanisms  42 ,  43  when the user&#39;s trunk is between the positions T 1  and T 2 . 
     With reference to  FIGS. 3, 5 , as the user&#39;s trunk travels further forwardly FW from the vertical position T 2  toward the more forwardly angled position, the inherent weight of the user&#39;s trunk increases the opposition to the resistance forces R 1 , R 2  thus assisting the user  5  in pushing F 2  the arm  30  forwardly from the vertical position  32   v  to the most forward  32   f  position where the weight of the user&#39;s trunk exerts the maximum amount of weight assisted torque force TF 2  in opposition to the weight resistance mechanism  42 ,  43  forces R 1 , R 2 . Thus the increasing force R 1  exerted by the mechanism  43  as the arm moves from position  32   r  to  32   v  to  32   f  serves to counterbalance the increasing torque force TF 2  exerted by the weight of the user&#39;s trunk when travelling from the T 2  position to the T 3  position. 
     As shown in the embodiment of  FIGS. 1-6, 6A, 6AA , the increasing force mechanism is comprised of a spring  43  that is adapted not to exert any force R 1  when the arm  30  is in the start motionless position SMP,  FIG. 1 . When the arm  30  is moved from the start motionless position SMP forwardly to a forward angled position PT, PT 2  such as shown, the spring  43  is extended from an initial, typically relaxed, position XT 0  to an extended position, XT 1 , XT 2 , as shown in  FIGS. 2, 4, 6  to exert a force R 1  that opposes or resists the user&#39;s pushed force F, the spring force R 1  increasing as the spring is increasingly extended such as between the arm positions  32   v ,  32   f  because the spring  43  has been increasingly extended as a result of the increased angular movement of arm  30  from angle PT to angle PT 2 . 
       FIG. 7  illustrates in schematic an alternative increasing force resistance mechanism  43   a  which is comprised of an enclosed cylinder  200  having a piston  202  slidably mounted within the cylinder forming opposing fluid sealed chambers  200   a ,  200   b  within the cylinder  200 , the piston  202  being interconnected to a rod  204  that extends outside the enclosed cylinder for driving the piston  202  from an initial start position  202  to a resistance position  202   a , the chambers  200   a ,  200   b  containing a selected compressible fluid, the rod being interconnected to the input arm assembly  30  and driven by movement of the input arm assembly from the start motionless position,  32   f , SMP toward the pelvic stabilization pad  18  to cause fluid CF in at least one of the chambers to compress and increase in resistance force R 1   a  against movement PT 3  of the input arm assembly with an increase R 1  in the degree of compression of the fluid CF on continued movement of the piston  202   a  to a position where the fluid CF is more compressed. As shown, the rod  204  is pivotably interconnected to arm  32  and the cylinder is interconnected to the frame member  12   e  such that as arm  32  is pivoted forwardly PT 3  the rod  204  and its interconnected piston  202  are driven forwardly FW reducing the volume of chamber  200   a  and compressing the fluid CF which increases R 1  as the degree of forward travel of arm  204  increases. 
     In alternative embodiments, other mechanisms for providing increasing resistance R 1 , such as friction fittings, springs, elastic bands, pneumatic, hydraulic or electromagnetic resistance, or an air resistance fan could be employed (either alone or in combination) and still practice the invention.