referring more particularly to the drawings , fig1 and 2 show the first embodiment of the exercise apparatus 10 according to the present invention . the exercise apparatus 10 comprises a dynamic means 12 , a framework means 14 and a resistance means 16 . the dynamic means 12 comprises an upper frame 40 which is pivotally attached to a lower frame 60 . the dynamic means 12 further comprises arm rests 80 which are attached to lateral members 41 of the upper frame 40 , a seat 50 which is pivotally mounted to a top frame member 62 of the lower frame 60 , and a foot rest 70 . the framework means 14 comprises a vertical frame 20 which is maintained in an upright position by a horizontal frame 30 . horizontal frame 30 is configured to lie on a flat surface . however , there are other ways known in the art to stabilize the dynamic means 12 such as bolting the vertical frame 20 to the ceiling . both the upper frame 40 and the lower frame 60 are pivotally mounted to the vertical frame 20 . additionally , the upper frame 40 is slideably mounted to the vertical frame 20 . as shown in fig3 pivotal attachments 42 on the upper frame 40 are mounted on linear bearings 44 which slide along rods 46 secured to flanges 48 which in turn are secured to the lateral members 24 of the vertical frame 20 . as shown in more detail in fig2 arms 72 of the foot rest 70 are pivotally attached to a cross frame member 32 of the horizontal frame 30 in a manner well known in the art . the components of the present invention are constructed of commercially available materials , the selection of which is within the ability of the ordinary skilled worker . as shown in fig2 and 3 , the arm rests 80 have hand grips 87 attached to elbow rests 83 which in turn are attached to sleeves 84 that fit around and slide along the lateral members 41 of the upper frame 40 , enabling the arm rests 80 to be adjusted to the heights of different users . the arms rests 80 also have adjustment pins 86 which fit through holes 85 of the sleeves 84 and two of a plurality of adjustment holes 88 on the lateral members 41 of the upper frame 40 , thereby securing the arm rests 80 to the upper frame 40 . alternatively , the arm rests may be configured such that the arm rests are connected to each other so that the user need make only one adjustment . as shown in fig2 and 4 , the lower frame 60 has a projecting member 66 attached to a bottom frame member 64 of the lower frame 60 such that the projecting member 66 remains at a fixed angle with respect to the plane defined by the lower frame 60 . rollers 68 attached to the end of the projecting member 66 contact the foot rest 70 such that the pivoting motion of the lower frame 60 with respect to the vertical frame 20 effects a concurrent pivoting motion in the foot rest 70 about the cross frame member 32 . in the embodiment shown in fig1 resistance to both the forward folding movement and the return straightening movement is provided by a fly wheel - fan resistance mechanism 90 which is known in the art . as seen in more detail in fig2 cables 92 are attached to the pair of cable connections 49 attached to each side of the top member 43 of the upper frame 40 . one of the cables 92 runs up to the top member 22 of the vertical frame 20 , within the top member 22 of the vertical frame 20 , then down within the lateral member 24 of the vertical frame 20 to the base of the vertical frame 20 . the other one of the cables 92 runs to the lateral member 24 of the vertical frame 20 to the base of the vertical frame 20 . the cables 92 are guided by a system of pulleys 94 to the fly wheel - fan resistance mechanism 90 having a drum 96 , a shaft 97 and a fly wheel - fan 98 . the cables 92 are wrapped around the drum 96 so that movement of the upper frame 40 causes the cables 92 to rotate the drum 96 . the drum 96 is ratchet mounted on and drives the shaft 97 , which in turn drives resistance means such as the fly wheel - fan 98 . in order to use this apparatus , the user first stands on the foot rest 70 , leans back against the seat 50 and places his arms in the arm rests 80 . as described above , a user may adjust the arm rests 80 along the lateral members 41 of the upper frame 40 to suit his particular height . in addition , the hand grips 87 of the arm rests 80 are curved such that any user may grip the hand grips 87 while resting his elbows in the elbow rests 83 regardless of the length of his forearms . exercise on this apparatus essentially comprises two movements , a forward folding movement as illustrated in fig5 and a return straightening movement as illustrated in fig6 . the angle θ , which is defined by the upper frame 40 and the lower frame 60 as shown in fig5 constantly changes during exercise , decreasing steadily during the forward folding movement and increasing steadily during the return straightening movement . during the forward folding movement , the user exerts his abdominal muscles to pull the arm rests 80 toward the foot rest 70 , thereby rocking or pivoting the upper frame 40 toward the lower frame 60 . as the lower frame 60 pivots , the rollers 68 at the end of the projecting member 66 push against and roll along the foot rest 70 , causing it to pivot about the foot pivots 74 as shown in fig5 and 6 . the pivoting action of the foot rest 70 causes the knees to bend as θ decreases . then during the return straightening movement , the user exerts his back muscles to pull the arm rests 80 away from the foot rest 70 , rocking or pivoting the upper frame 40 away from the lower frame 60 . the apparatus stops as soon as the user stops exerting his muscles . stops 26 may be provided on the vertical frame 20 as shown in fig5 and 6 to control the range of movement of this apparatus . the stops 26 prevent θ from exceeding 180 °, thereby reducing the chance of physical injury to the user by preventing him from extending his pelvic region beyond his feet in a vertical stance . of course , the stops 26 may be designed such that the upper limit of θ is less than 180 ° in a manner known in the art . the cables 92 may also be used to control the range of θ or movement of this apparatus . persons of ordinary skill in the art will appreciate that resistance means other than the fly wheel - fan resistance mechanism described above may be readily adapted to the present invention . for example , as shown in fig7 the apparatus may employ an electro - magnetic resistance mechanism 90a . as seen more fully in fig8 chains 92a , 92b connected to the upper and lower frame 40 , 60 respectively , traverse around sprockets 99a , 99b , which are mounted concentrically with sprocket 99c on shaft 97a . shaft 97a is mounted to the horizontal frame 30 . the chains 92a , 92b then continue in a parallel arrangement around a system of pulleys 94a ( not shown ) to connect with return springs 95a . chain 92c is wound around the associated sprocket of the electromagnetic resistance mechanism 90a , the operation of which is understood by persons skilled in the art . a further alternative embodiment of the present invention is illustrated in fig9 . in this embodiment , resistance is provided only against the forward folding movement , and not against the return straightening movement . in this embodiment , only one cable 92 runs from one cable connection 49 , up to the top member 22 of the vertical frame 20 , within the top member 22 of the vertical frame 20 , then down within the lateral member 24 of the vertical frame 20 to the base of the vertical frame 20 . the cable 92 is guided by pulleys 94 to the fly wheel - fan resistance mechanism 90 having a drum 96 , a shaft 97 and a fly wheel - fan 98 . the fly wheel - fan resistance mechanism 90 functions as previously set forth in connection with the description of the first embodiment . the drum 96 is further provided with torsion springs to rewrap the cable during the return straightening movement . an additional , optional spring , such as extension spring 95 can be provided for greater resistance and faster return . a further alternative embodiment of the present invention is illustrated in fig1 . in this embodiment , resistance is provided only against the return straightening movement , and not against the forward folding movement . the resistance mechanism of this embodiment is the same as the resistance mechanism of the alternative embodiment illustrated in fig7 and 8 except that the former lacks the chain 92b and the sprocket 99b . a weight stack also may be used for resistance in a manner known in the art . fig1 schematically illustrates the apparatus in which resistance against the forward folding movement is provided by a weight stack . cable 92d is secured to upper frame 40 and traverses around pulleys 94b to weight stack 100 . the user may select the amount of weight desired . it is contemplated that a resistance mechanism which employs a weight stack also may be configured by a person of ordinary skill such that resistance may be provided against the return straightening movement . a further alternative embodiment of the present invention is illustrated in fig1 . in this embodiment , the upper frame 40 and the lower frame 60 are pivotally mounted to the vertical frame 20 in a manner well known in the art . in this embodiment , the lower frame 60 is also slideably mounted to the vertical frame 20 . whereas , in the first embodiment of the present invention , the user pulls the arm rests 80 toward the foot rest 70 in order to effect the forward folding movement , in this embodiment , the user pulls the foot rest 70 toward the arm rests 80 to effect the forward folding movement . this embodiment increases the force required by the user &# 39 ; s muscles and provides a more strenuous workout . in this embodiment , the foot rest 70 is additionally provided with foot stirrups 76 . any of the resistance means previously discussed may be easily adapted to this embodiment . in addition , the resistance means may be adapted to provide resistance against both the forward folding movement and the return straightening movement or either of the two . it is also contemplated that each of the embodiments described above will include an adjustment means known in the art for providing varying degrees of resistance . the present invention may be embodied in other forms without departing from its spirit or essential characteristics . the described embodiments are to be considered only as illustrative and not as restrictive . the scope of the invention is , therefore , indicated by the appended claims .
apparatus for exercising a user &# 39 ; s abdominal muscles and / or back muscles . this exercise apparatus includes a dynamic means in the form of an upper frame which is pivotally attached to a lower form . with the use of the user &# 39 ; s abdominal and / or back muscles , the dynamic means produces a forward folding movement and a return straightening movement . a framework means in the form of a vertical frame affixed to a horizontal frame which maintains the vertical frame in an upright position supports the dynamic means . this exercise apparatus also includes a resistance means for opposing the forward folding movement and / or the return straightening movement . various resistant means include fly wheel - fan , electro - magnetic and weight stack .