Patent Publication Number: US-2020289877-A1

Title: Multi-function Exercise Machine and Bench

Description:
FIELD OF USE 
     This invention relates to exercise equipment for strengthening muscles of the human body. 
     BACKGROUND ART 
     Physical exercise is important to the human body. In addition to increasing strength and stamina, physical exercise can increase longevity. Physical exercise commonly make humans feel good physically and mentally. 
     Exercise machines have been developed to enable physical exercising to be done in a time-efficient manner. Some exercise machines target largely only a single feature of the human anatomy such as the legs. 
     Other exercise machines are designed to enable multiple features of the human anatomy, e.g., the legs and arms/shoulders, to be exercised.  FIG. 1  illustrates such a multi-function exercise machine as disclosed in U.S. Pat. No. 6,902,515 B2. The prior art exercise machine of  FIG. 1  consists of base assembly  20 , pedal-revolving pedaling mechanism  22 , seat  24 , seatback  26 , upper-body assembly  28 , and rotational arm-shoulder device  30 . Pedaling mechanism  22  includes a pair of pedals  32 . When actuated by the feet of a person, pedals  32  revolve about an axis to exercise the person&#39;s legs. Ann-shoulder device  30  includes a pair of off-center handles  34  which can similarly be revolved about an axis by the person&#39;s hands to exercise the person&#39;s arms and shoulders. 
       FIGS. 2 a  and 2 b    illustrate two way in which upper-body assembly  28  can be connected to the back of seatback  26  (not shown in  FIG. 2 a    or  2   b ) to enable portion  36  of assembly  28  to be moved in various ways while a person is exercising with the machine of  FIG. 1 . In the embodiment of  FIG. 2 a   , back member  38  of movable portion  36  is connected by pin  40  to seatback  26  for enabling portion  36  to pivot from side to side about axis  42  that extends generally parallel to the length of base assembly  20 . A pair of springs  44  connected between back member  38  and fixed base member  46  of upper-body assembly  28  provide resistance for the side-to-side movement. 
     In the embodiment of  FIG. 2 b   , back member  38  is connected by bearing mechanism  48  to fixed base member  50  of assembly  28  for enabling movable portion  36  to pivot in various manners about bearing mechanism  48  in order to exercise the arms and shoulders. For example, movable portion  36  can pivot from front to back and vice versa about axis  52  that extends generally perpendicular to the length and height of the exercise machine. Movable portion  36  in  FIG. 2 b    can also pivot about axis  54  that extends generally parallel to back member  38 . Coil torsion spring  56  provides resistance to the movement of portion  36  in  FIG. 2 b   . Although seat  24  and seatback  26  can be adjusted horizontally along the length of base assembly  20  to accommodate persons of different size, seat  24  and seatback  26  are substantially stationary during exercising usage when upper-body assembly  28  is implemented as shown in both  FIG. 2 a    and  FIG. 2   b.    
     The abdominal muscles of the human body often need strengthening. While the multi-function exercise machine of  FIG. 1  appears capable of providing the legs and arms/shoulders with good exercise, the machine of  FIG. 1  is not particularly targeted toward the abdominal muscles. It would be desirable to have an exercise machine that can exercise both the legs and abdominal muscles. 
     GENERAL DISCLOSURE OF THE INVENTION 
     The present invention provides such an exercise machine. In accordance with the invention, an exercise machine capable of exercising both the legs and abdominal muscles of a human user contains a frame, a seat situated over the frame, a seatback, a connection mechanism for flexibly and/or adjustably connecting the seatback to the frame or/and the seat, and a pedaling mechanism connectable to the frame. The seat is located laterally between the pedaling and connection mechanisms. The pedaling mechanism has a pair of pedals that can move in various ways. For example, the pedals can revolve generally around a pedaling axis. Alternatively, the pedals can translate (move linearly) back and forth. Actuation of the pedals by the user&#39;s feet causes the user&#39;s legs to be exercised. 
     The connection mechanism can normally turn about a swivel axis that extends generally parallel to the length of the torso of a typical user seated on the seat with the user&#39;s back lying generally against the seatback. This enables the seatback to swivel about the swivel axis, thereby exercising the user&#39;s abdominal muscles. 
     The connection mechanism also preferably adjustably connects the seatback to the frame or/and the seat so that the seatback is adjustably inclinable relative to the seat. Appropriately adjusting the seatback-to-seat incline assists in exercising the user&#39;s abdominal muscles. For instance, reducing the incline so that the seatback slants further downward away from the seat typically increases the exercise of the user&#39;s abdominal muscles. The incline and swiveling of the seatback thereby typically cause the abdominal muscles to be strengthened as the pedaling mechanism exercises the legs. 
     The connection mechanism is preferably implemented with a bar portion, a pair of cross-bar sleeves, and an axial sleeve. The bar portion is formed with a cross bar and an axial bar which extends generally along the axis of the connection mechanism and meets the cross bar between its ends to divide the cross bar into a pair of cross-bar portions. The cross-bar sleeves are connected to the frame or/and the seat and respectively receive the cross-bar portions for enabling the incline of the seatback to the seat to be adjusted. The axial sleeve is connected to the seatback and receives the axial bar for enabling the seatback to swivel about the axis of the connection mechanism. In addition, the connection mechanism preferably includes a support portion for adjusting the seatback-to-seat incline. The support portion is flexibly and/or adjustably connected to the axial bar or/and the seatback and is likewise flexibly and/or adjustably connected to the frame. 
     Another exercise machine in accordance with the invention contains a pedal-translating pedaling mechanism and a pair of handles. The pedaling mechanism has a pair of pedals that translate back and forth. The handles are situated relative to the pedals such that an average-size adult user of the machine is in a crouched or crouched-to-prone position when the user&#39;s feet respectively contact the pedals and the user&#39;s hands respectively hold the handles. In addition to exercising the user&#39;s legs, this exercise machine of the invention exercises the user&#39;s arms as the user&#39;s feet move the pedals. 
     A further exercise machine in accordance with the invention contains support structure and a handle-translating mechanism connectable to the support structure. The handle-translating mechanism has a pair of handles that generally translate back and forth. The support structure is suitable for receiving a user of the machine such that the user&#39;s hands can respectively grip the handles. By actuating the handles, the user exercises the user&#39;s arms. The exercise machine may include a pedaling mechanism having a pair of movable pedals. In that case, the user can exercise the user&#39;s legs by actuating the pedals with the user&#39;s feet. 
     Each of the present exercise machines may include a display for visually presenting exercise information that occurs during machine operation. For example, the readout display can provide the instantaneous cycling rate of the pedaling or handle-translating mechanism, the duration of an exercise period by a user actuating the pedaling or handle-translating mechanism, or/and an estimate of the caloric energy expended by the user during the exercise period. 
     The frame, seat, seatback, and connection mechanism form an exercise bench in accordance with the invention. The exercise bench typically includes one or more pairs of handles variously connected to the frame, the seat, the seatback, or/and the connection mechanism at generally symmetrical locations on opposite sides of the frame, the seat, the seatback, or/and the connection mechanism. A user can exercise on the bench with each of the pedaling and handle-translating mechanisms disconnected from the frame or simply without using any of the pedaling and handle-translating mechanisms. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a conventional multi-function exercise machine for exercising the legs and arms/shoulders of a user. 
         FIGS. 2 a  and 2 b    are perspective views of two respective implementations of the upper-body assembly and rotational arm-shoulder device in the exercise machine of  FIG. 1 . 
         FIGS. 3-5  are respective perspective, side, and top views of a multi-function exercise machine configured according to the invention for exercising the legs and abdominal muscles of a user. 
         FIG. 6  is a top plan view of the frame in the exercise machine of  FIGS. 3-5 ,  FIGS. 11 and 12 , or  FIG. 17 . 
         FIG. 7  is a backside plan view of the seatback and seatback-adjoining portion of the seatback-to-frame/seat connection mechanism in the exercise machine of  FIGS. 3-5 ,  FIGS. 11 and 12 , or  FIG. 17 . The plan view of  FIG. 7  is taken along plane  7 - 7  in  FIGS. 4, 9, 12, and 17 . 
         FIG. 8  is a cross-sectional plan view of the seatback and seatback-adjoining portion of the seatback-to-frame/seat connection mechanism in the exercise machine of  FIGS. 3-5 ,  FIGS. 11 and 12 , or  FIG. 17 . The cross-sectional view of  FIG. 8  is taken along plane  8 - 8  in  FIGS. 4, 9, 12, and 17 . 
         FIG. 9  is an end view of the seatback and seatback-adjoining portion of the seatback-to-frame/seat connection mechanism in the exercise machine of  FIGS. 3-5 ,  FIGS. 11 and 12 , or  FIG. 17 . The end view of  FIG. 9  is taken along plane  9 - 9  in  FIGS. 4, 7, 8, 12, and 17 . 
         FIG. 10  is a side view of an example of how the exercise machine of  FIGS. 3-5  is used according to the invention. 
         FIGS. 11 and 12  are respective perspective and side views of another multi-functional exercise machine configured according to the invention for exercising the legs and abdominal muscles of a user. 
         FIG. 13  is a top view of the pedal-translating mechanism in the exercise machine of  FIG. 11 . 
         FIG. 14  is a side view of an example of how the exercise machine of  FIGS. 11 and 12  is used according to the invention. 
         FIGS. 15 a  and 15 b    are side views of the main assembly (frame, seat, seatback, seatback-to-frame/seat connection mechanism, and handles) in the exercise machine of  FIGS. 3-5 ,  FIGS. 11 and 12 , or  FIG. 17  as implemented with an alternative embodiment of the seatback and seatback-to-frame/seat connection mechanism. 
         FIG. 16  is a cross-sectional end view of the seatback and seatback-adjoining portion of the seatback-to-frame/seat connection mechanism in  FIGS. 15 a  and 15 b   . The cross-sectional view of  FIG. 16  is taken along plane  16 - 16  in  FIGS. 15 a  and 15 b   . The side views of the seatback and seatback-adjoining portion of the seatback-to-frame/seat connection mechanism of  FIGS. 15 a  and 15 b    are taken along plane  15 - 15  in  FIG. 16 . 
         FIG. 17  is a side view of a variation, configured according to the invention, of the multi-function exercise machine of  FIGS. 11 and 12 . 
         FIGS. 18 and 19  are side views of two respective examples of how the exercise machine of  FIG. 17  is used according to the invention. 
         FIG. 20  is a side view of a further example of how the exercise machine of  FIG. 17 , as implemented with the alternative embodiment of the seatback and seatback-to-frame/seat connection mechanism of  FIGS. 15 a  and 15 b   , is used according to the invention. 
         FIG. 21  is a side view of a variation, configured according to the invention, of the multi-function exercise machine of  FIG. 17  as implemented with the alternative embodiment of the seatback and seatback-to-frame/seat connection mechanism of  FIGS. 15 a    and  15   b.    
         FIG. 22  is a top plan view of the frame in the exercise machine of  FIG. 21  or  FIG. 23 . 
         FIG. 23  is a side view of an extension, configured according to the invention, of the multi-function exercise machines of  FIGS. 3-5  and  FIG. 21 . 
         FIG. 24  is a side view of another multi-function exercise machine configured according to the invention for exercising the legs, arms, and abdominal muscles of a user. 
         FIG. 25  is a top view of the handle-translating mechanism in the exercise machine of  FIG. 24 . 
         FIGS. 26 and 27  are side views of two respective examples of how the exercise machine of  FIG. 24  is used according to the invention. 
         FIG. 28  is a side view of a multi-function exercise bench configured according to the invention as a variation of the main assembly in the exercise machine of  FIG. 21, 23 , or  24 . 
         FIGS. 29 a  and 29 b    are side views of another multi-function exercise bench configured according to the invention as a variation of the main assembly in the exercise machine of  FIG. 21, 23 , or  24 . 
         FIGS. 30 a , 30 b , and 30 c    are side views of three respective examples of how the exercise bench of  FIGS. 29 a  and 29 b    is used according to the invention for exercising with the bench&#39;s handles. 
         FIGS. 31 a  and 31 b    are side views of two respective examples of how the exercise bench of  FIGS. 29 a  and 29 b    is used according to the invention for exercising with free weights. 
     
    
    
     Like reference symbols are employed in the drawings and in the description of the preferred embodiments to represent the same, or very similar, item or items. All planes, axes, and reference lines are indicated in dashed line in the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exercise Machines with Pedaling Mechanisms 
       FIGS. 3-5  illustrate a multi-function exercise machine configured in accordance with the invention for enabling a user to exercise the user&#39;s legs and abdominal muscles. The exercise machine of  FIGS. 3-5  consists of a frame  100 , a generally rectangular seat  102 , a seatback  104 , a mechanism  106  for connecting seatback  104  to frame  100  or/and seat  102 , a first pair of handles  108 L and  108 R (collectively “handles  108 ”), a second pair of handles  110 L and  110 R (collectively “handles  110 ”), a pedal-revolving pedaling mechanism  112 , and a visual readout display  114 . Frame  100 , seat  102 , seatback  104 , connection mechanism  106 , first handles  108 , and second handles  110  form a main assembly  116 . 
     The length of the exercise machine of  FIGS. 3-5 , including the length of frame  100  and main assembly  116 , is taken in the horizontal direction in  FIG. 4 . The width of the exercise machine, including the width of each of frame  100 , seat  102 , and seatback  104 , is taken in the vertical direction in  FIG. 5  and thus perpendicular to the plane of  FIG. 4 . 
     Seat  102  is fixedly mounted on frame  100  near the front end of frame  100 . Seatback-to-frame/seat connection mechanism  106  is fixedly connected to frame  100  near the back edge of seat  102 . Connection mechanism  106  can alternatively or additionally be connected to seat  102  along its back edge. In either case, seat  102  is situated laterally between connection mechanism  106  and pedal-revolving pedaling mechanism  112 . Connection mechanism  106  includes a group of outwardly curved attachment brackets  120  that fixedly connect connection mechanism  106  to the back of seatback  104 . Three attachment brackets  120  are so utilized in the example of  FIGS. 3-5 , 
     Seatback-to-frame/seat connection mechanism  106  has a swivel axis  122  that extends generally parallel to the longitudinal centerline  124  (see  FIG. 4 ) of seatback  104  and thus generally perpendicular to the width of seatback  104 . That is, swivel axis  122  extends generally parallel to the length of the torso of a typical user seated on seat  102  with the user&#39;s back lying generally flat against seatback  104 . Consequently, swivel axis  122  lies in a vertical plane which extends approximately through the longitudinal centerline  124  of seatback  104  and thus also approximately through a machine reference line  126  (also see  FIG. 4 ) that extends along the length of the exercise machine through its center widthwise. 
       FIGS. 3-5  depict the situation in which seatback  104  is inclined backward relative to seat  102 . In particular, the incline angle a between swivel axis  122  and machine reference line  126  (again see  FIG. 4 ) is between 0° and 90°. When so oriented, seatback  104  is often referred to here as being in the inclined position. 
     Connection mechanism  106  includes a support rod  128  which is adjustably and flexibly connected to frame  100  so that mechanism  106  can be turned about a connection axis  130  depicted in  FIGS. 3  and.  5 . Connection axis  130 , whose location is indicated by dot  130 X in  FIG. 4 , extends generally parallel to the width of the exercise machine. Connection axis  130  is close to the back of seat  102  and the bottom of seatback  104 . This enables the incline of seatback  104  to seat  102  to be adjusted from an a value close to 0° to an a value in the vicinity of 90°. In other words, the seatback-to-seat incline can be varied between a position in which seatback  104  lies nearly flat on frame  100  and a position in which seatback is nearly perpendicular to frame  100  and seat  102 . As discussed further below, connection mechanism  106  is also configured so that seatback  104  can swivel (revolve, essentially rotate, through some angle) about swivel axis  122  as a user exercises with the machine of  FIGS. 3-5 . 
     First handles  108 , referred to here generally as “seat” handles, are shown in  FIGS. 3-5  as being received by seat  102  at generally opposite locations along the side (longitudinal) edges of seat  102  near its back edge and thus near the bottom of seatback  104 . Seat handles  108  are preferably movable relative to seat  102 . Alternatively, seat handles  108  can be received by frame  100  at corresponding opposite locations below the reception locations shown in  FIGS. 3-5  near the back edge of seat  102 . Seat handles  108  are then preferably movable relative to frame  100 . 
       FIGS. 3-5  show second handles  110 , referred to here generally as “seatback” handles, as being received by seatback  104  at generally opposite locations along the side (longitudinal) edges of seatback  104  near its top edge. Seatback handles  110  are preferably movable relative to seatback  104 . Depending on the configuration of connection mechanism  106 , seatback handles  110  can alternatively be received by connection mechanism  106  at corresponding generally opposite locations close to the reception locations shown in  FIGS. 3-5 . In that case, seatback handles  110  are preferably movable relative to connection mechanism  106 . 
     Handles  108  and  110  can move in various ways. Seat handles  108 L and  108 R can be respectively turned about first handle axes  132 L and  132 R depicted in  FIG. 5 . First handle axes  132 L and  132 R, whose locations are generally indicated by dot  132 X in  FIG. 4 , can be a common first handle axis extending generally parallel to the width of the exercise machine. Seat handles  108  can be rigidly connected together inside or below seat  102 . Handles  108  then turn simultaneously (in synchronism) about the common first handle axis. Alternatively, handles  108 L and  108 R can be respectively turned about first handle axes  132 L and  132 R independently of each other. Handle axes  132  can then be inclined or/and slightly laterally offset from each other. 
     Similar comments apply to seatback handles  110 . Seatback handles  110 L and  110 R can be respectively turned about second handle axes  134 L and  134 R depicted in  FIG. 5 . Second handle axes  134 L and  134 R, whose locations are generally indicated by dot  134 X in  FIG. 4 , can be a common second handle axis extending generally parallel to the width of the exercise machine. Seatback handles  110  can be rigidly connected together inside or behind seatback  104 . Handles  110  then turn simultaneously (in synchronism) about the common second handle axis. Alternatively, handles  110 L and  110 R can be respectively turned about second handle axes  134 L and  134 R independently of each other. In that case, handle axes  134  can be inclined or/and slightly laterally offset from each other. 
     Pedal-revolving pedaling mechanism  112  consists of a pair of foot pedals  140 L and  140 R (collectively “pedals  140 ”), a pair of pedal cranks  142 L and  142 R (collectively “cranks  142 ”), a cycle housing  144 , an internal cycling apparatus (not shown) situated inside cycle housing  144 , a resistance-adjustment knob  146  for adjusting the pedaling resistance, and a group of housing feet  148 . Cycle housing  144  consists of a relatively high upper portion  144 U and a wider lower portion  144 L that provides pedaling mechanism  112  with mechanical stability. The longitudinal sides of lower housing portion  144 L are approximately equidistant from the longitudinal sides of upper housing portion  144 U. 
     Upper housing portion  144 U has a slanted front surface on which resistance-adjustment knob  146  and readout display  114  are situated. Depending on the configuration of the internal cycling apparatus, resistance-adjustment knob  146  can alternatively be located on top of housing  144  or at some other suitable housing location readily accessible to a user. The slanting of the front surface of upper housing portion  144 U makes it easy for the user to read readout display  114  while seated on seat  102 . 
     Pedal cranks  142  are connected to the internal cycling apparatus of pedaling mechanism  112  through respective openings in the sides of upper housing portion  144 U. Foot pedals  140 L and  140 R are respectively connected to pedal cranks  142 L and  142 R so as to allow each pedal  140 L or  140 R to rotate around a portion of that pedal&#39;s crank  142 L or  142 R. Another portion of each pedal crank  142 L or  142 R rotates around a pedaling axis  150  depicted in  FIGS. 3 and 5 . Pedaling axis  150 , whose location is indicated by dot  150 X in  FIG. 4 , extends generally parallel to the width of the exercise machine. As a result, pedals  140  revolve around pedaling axis  150 . 
     The internal cycling apparatus of pedaling mechanism  112  can be implemented in various ways. Similar to what occurs in U.S. Pat. No. 6,902,515 B2 mentioned above, the internal cycling apparatus can include a flywheel and a pulley in which a belt runs around a pair of pulley wheels. One of the pulley wheels is connected to pedal cranks  142  so as rotate around pedaling axis  150 . The other pulley wheel is connected center-to-center to the flywheel. When caused to rotate by the pulley, the flywheel provides cycling resistance. An internal extension of adjustment knob  146  can press on the belt to enable the cycling resistance to be adjusted by turning knob  146 . The pulley wheel connected to pedal cranks  142  is typically of considerably greater diameter than the pulley wheel connected to the flywheel. 
     Housing feet  148  are implemented here as circular cylinders connected to the lower housing portion  144 L along its lower surface so as to extend downward slightly farther than cycle housing  144 . This implementation of housing feet  148  facilitates sliding housing  144  along the underlying surface. Pedaling mechanism  112  has four housing feet  148  in the example of  FIGS. 3-5 . Two of housing feet  148  are on each side of housing  144 . 
     Pedaling mechanism  112  is adjustably connected to the front end of main assembly  116 , specifically the front end of frame  100 , as further described below in connection with  FIG. 6  for enabling the distance from seat  102 , e.g., the back edge of seat  102 , to pedaling axis  150  to be adjusted in order to accommodate the size of the user.  FIGS. 3-5  depict the situation in which pedaling mechanism  112  substantially touches seat  102  and thus the situation in which the distance from seat  102  to pedaling axis  150  is at a minimum value. Pedaling mechanism  112  and seat  102  are spaced apart from each other when the distance from seat  102  to pedaling axis  150  is adjusted to exceed the minimum value. 
     In the example of  FIGS. 3-5 , the distance from seat  102  to pedaling axis  150  is adjusted with a pair of knobs  152 L and  152 R (collectively “knobs  152 ”) situated on lower housing portion  144 L on opposite sides of upper housing portion  144 U. Distance-adjustment knobs  152  are depicted in  FIGS. 3-5  as being close to the back of pedaling mechanism  112  but, depending on how the seat-to-pedaling-axis distance is adjusted, can be closer to the front of pedaling mechanism  112 . Depending on how the seat-to-pedaling-axis distance is adjusted, one or more devices other than distance-adjustment knobs  152  can be utilized to adjust the distance from seat  102  to pedaling axis  150 . 
     Readout display  114  visually presents exercise information that occurs during operation of the exercise machine of  FIGS. 3-5 . Information provided by display  114  typically includes the instantaneous cycling rate, the duration of an exercise period by a user actuating pedaling mechanism  112 , and the estimated caloric energy expended by the user during the exercise period. The instantaneous cycling rate is the number of pedaling cycles per unit time, typically per minute, where each cycle is a full revolution of either of pedals  140 . Display  114  may present the total number of pedaling cycles during the exercise period. Display  114  may also present the user&#39;s pulse rate by way of a device (not shown) which can be attached to an appropriate part of the user&#39;s body to measure the user&#39;s pulse rate. The pulse-rate measuring device can be permanently or detachably connected to display  114 . 
     One or more on/off switches (not separately shown) are provided on readout display  114  for enabling a user to control presentation of certain of the displayed exercise information. For instance, display  114  may present the duration of an exercise period and the user&#39;s estimated caloric energy expended during the exercise period only upon manually turning such an on/off switch on to start the exercise period. The on/off switch can later be manually turned off to stop the exercise period. The on/off switch may also automatically turn off when the instantaneous cycling rate has dropped substantially to zero for a selected period of time, e.g., 5-10 minutes. Display  114  may present the instantaneous cycling rate only when the on/off switch is turned on, or whenever the instantaneous cycling rate is significantly above zero, e.g., at least 5 cycles per minute, for a sufficiently long period, e.g., 10 seconds. 
     The top of seat  102  and the front of seatback  104  typically consist of leather or leather-like material. The insides of seat  102  and seatback  104  typically consist of cushion-like material formed with suitable foam or/and cotton. 
       FIG. 6  particularly illustrates the layout of frame  100 . As shown in  FIGS. 3-6 , frame  100  is an assembly consisting of two straight long longitudinal rails  160 L and  160 R (collectively “long rails  160 ”) extending generally parallel to each other, three straight cross rails  162 A,  162 B, and  162 C (collectively “cross rails  162 ”) extending generally perpendicular to long rails  160 , a pair of straight short longitudinal rails  164 L and  164 R (collectively “short rails  160 ”) extending generally perpendicular to long rails  160 , a straight channel portion  166  extending generally parallel to long rails  160 , and six generally circular frame feet  168 . 
     Long rails  160  are situated on, and rigidly connected to, cross rails  162  at spaced-apart locations along the length of frame  100  from front to back. Short rails  164  (only depicted in  FIG. 6 ) are situated on, and rigidly connected to, front cross rail  162 A at locations between long rails  160  and extend forward beyond long rails  160 . As discussed below in connection with  FIGS. 28, 29   a , and  29   b , short rails  164  can be flexibly connected to cross rail  162 A so that they can be placed in a position in which they do not extend forward beyond long rails  160  when they are not connected to pedal-revolving mechanism  112  or any other such exercise mechanism. Channel portion  166  is situated on, and rigidly connected to, center cross rail  162 B and back cross rail  162 C at locations approximately mid-way between long rails  160 . Two of frame feet  168  are connected to the bottom of each cross rail  162 A,  162 B, or  162 C close to its ends. 
     Rails  160 ,  162 , and  164  typically consist of metal and are illustrated in  FIGS. 3-5  as hollow but can be solid. Channel portion  166  likewise typically consists of metal and is shown in  FIGS. 3, 5, and 6  as being formed with two members of L-shaped cross-section but can be a single member of U-shaped cross-section. In either case, channel portion  166  has an upward-extending channel  170 . A plurality of pairs of oppositely situated horizontal circular openings  172  extend respectively through the side members of channel portion  166 . As further described below, channel portion  166  acts as an interface to connection mechanism  106 . The bottoms of frame feet  168  consist of rubber or/and rubber-like material that helps inhibit feet  168  from sliding on the underlying surface. 
     Frame  100  is preferably of approximately the following dimensions. Long rails  160  are  140 - 145  cm in length,  3  cm in width, and  5  cm in height. The spacing between long rails  160  is 35-40 cm. Cross rails  162  are 60 cm in length, 4 cm in width, and 3 cm in height. The distance between each consecutive pair of cross rails  162  is 55-65 cm. The distance from front cross rail  162 A to the front ends of long rails  160  is 6-10 cm. The distance from back cross rail  162 C to the back ends of long rails  160  is 2-4 cm. Short rails  164  are 40-45 cm in length, 4 cm in width, and 4 cm in height. As a result, short rails  164  typically extend forward 30-35 cm beyond the front ends of long rails  160 . Channel portion  166  is 2-3 cm in width. 
     Standard mechanical connecting elements (not shown) such as bolts, nuts, and screws are used to connect rails  160 ,  162 , and  164  and channel portion  166  to one another and to connect seat  102  to long rails  160 . Metal-fusing techniques such as welding can be used in connecting components  160 ,  162 ,  164 , and  166  to one another. 
     Short rails  164  respectively extend into a pair of openings (not shown) in the back of pedaling mechanism  112  for adjustably connecting mechanism  112  to the front end of frame  100  of main assembly  116  to accommodate the user&#39;s size, primarily the length of the user&#39;s legs. For use in making this adjustable connection, a plurality of vertical circular openings  174 L situated generally in a line extend through short rail  164 L. A like plurality of vertical circular openings  174 R situated generally in a line extend through short rail  164 R. Openings  174 R are respectively situated substantially directly opposite openings  174 L so that openings  174 L and  174 R (collectively “openings  174 ”) are allocated into pairs of oppositely situated openings  174 . 
     Distance-adjustment knob  152 L (see  FIGS. 3-5 ) is situated generally above the line of openings  174 L in short rail  164 L while distance-adjustment knob  152 R (likewise see  FIGS. 3-5 ) is situated generally above the line of openings  174 R in short rail  164 R. Knobs  152  have respective internal extensions (not shown) which respectively pass through a selected one of the pairs of oppositely situated openings  174  thereby connecting pedaling mechanism  112  to the front end of frame  100  of main assembly  116 . The knob extensions also respectively pass through a pair of openings in an underlying piece of material rigidly connected to cycle housing  144  so as to make the connection solid. 
     The connection of pedaling mechanism  112  to the front end of main assembly  116  is adjusted by first pulling distance-adjustment knobs  152  sufficiently upward to release the connection. The depth to which short rails  164  extend into the openings in pedaling mechanism  112  is changed. Knobs  152  are then pushed downward so that the knob extensions respectively pass through another selected pair of oppositely situated openings  174  and through the two openings in the underlying piece of material connected to housing  144 . In addition to being adjustably connected to main assembly  116 , pedaling mechanism  112  can be readily disconnected from assembly  116  to facilitate storing the exercise machine of  FIGS. 3-5  and to enable another exercise mechanism, such as that described below in connection with  FIGS. 11-13  or in connection with  FIG. 24 , to be adjustably connected to the front end of assembly  116  via short rails  164 . 
       FIGS. 7-9  particularly illustrate the structure of the seatback-adjoining portion of seatback-to-frame/seat connection mechanism  106  in conjunction with seatback  104 . In addition to attachment brackets  120  and support rod  128 , connection mechanism  106  includes a T-shaped bar portion  180 , a pair of circular cylindrical cross-bar sleeves  182 L and  182 R (collectively “cross bar sleeves  182 ”), and a circular cylindrical axial sleeve  184 . T-shaped bar portion  180  is formed with a solid axial bar  186  extending generally along swivel axis  122 , a solid circular cylindrical cross bar  188  extending generally along connection axis  130 , and a pair of cross-bar end caps  190 L and  190 R. Axial bar  186  meets cross bar  188  between its ends to divide cross bar  188  into a pair of cross-bar portions  188 L and  188 R of approximately the same length. Cross-bar sleeves  182 L and  182 R are respectively rigidly connected, e.g., welded, to long rails  160 A and  160 B (see  FIGS. 3 and 6 ) and respectively flexibly receive cross-bar portions  188 L and  188 R in such a way that cross bar  188  can turn, i.e., rotate through some angle less than 360°, in sleeves  182 L and  182 R. 
     Cross-bar end caps  190 L and  190 R cover the respectively cover the ends of cross bar  188  as cross-bar portions  188 L and  188 R just respectively protrude out of cross-bar sleeves  182 L and  182 R. This acts to maintain longitudinal centerline  124  of seatback  104  and the longitudinal centerline of the seatback-adjoining portion of connection mechanism  106  in largely the same vertical plane as the longitudinal centerline of frame  100 . Consequently, swivel axis  122  is in largely the same vertical plane as the longitudinal centerline of frame  100 . 
     Axial sleeve  184  is rigidly connected to seatback  104  via attachment brackets  120 . Axial bar  186  is circularly cylindrical for most of its length. Axial sleeve  184  flexibly receives axial bar  186  where it is cylindrical in such a way that axial sleeve  184  can turn, i.e., rotate through some angle less than 360°, around axial bar  186  . 
     The remote end of axial bar  186 , i.e., the end spaced apart from cross bar  188 , splits into a pair of tines through which a pair of oppositely situated circular openings respectively extend. Letting the two ends of support rod  128  (see  FIGS. 3 and 4 ) be respectively referred to as the seatback-associated end and the frame-associated end, a circular opening extends through the seatback-associated end of rod  128 . With the seatback-associated end of support rod  128  positioned between the tines at the remote end of axial bar  186 , support rod  128  is flexibly connected to axial bar  186  via a seatback-associated solid circular cylindrical pin  192  (especially see  FIG. 3 ) that passes through the opening in the seatback-associated end of rod  128  and through the openings in the tines at the remote end of axial bar  186 . Suitable movement-limiting elements (not shown), such as U bolts, cotter pins, or the like, are present at or near the ends of seatback-associated pin  192  to keep it permanently in place. 
     A circular opening also passes through the frame-associated end of support rod  128 . The plurality of pairs of oppositely situated openings  172  in the side members of channel portion  166  of frame  100  define a like plurality of respectively corresponding frame-associated interface connection locations at which the frame-associated end of support rod  128  can be placed in channel  170 . With the frame-associated end of support rod  128  placed at a selected one of those interface connection locations, support rod  128  is flexibly connected to channel portion  166  via a frame-associated solid circular cylindrical pin  194  (especially see  FIG. 3 ) that passes through the opening in the frame-associated end of rod  128  and through the resulting selected pair of oppositely situated openings  172 . Suitable movement-limiting elements (not shown), such as U bolts or the like, are present at or near the ends of frame-associated pin  194  to keep it in place during an exercise period. One of these movement-limiting elements can be readily removed by a person or, while the movement-limiting element stays in contact with pin  194 , can be readily manipulated by a person for removing pin  194  from the exercise machine but otherwise prevents pin  194  from being removed from the machine during the exercise period. 
     Selection of a pair of oppositely situated openings  172  that receive frame-associated pin  194  establishes a particular value for the incline of seatback  104  to seat  102 . The seatback-to-seat incline is adjusted by removing frame-associated pin  194  from the selected pair of openings  172  and from the opening in the frame-associated end of support rod  128 , selecting another pair of oppositely situated openings  172 , and then placing pin  194  through the new selected pair of openings  172  and through the opening in the frame-associated end of rod  128 . This causes T-shaped bar portion  180  to turn about connection axis  130  by an angle typically no more than approximately 90°, thereby changing the seatback-to-seat incline defined quantitatively by angle a between swivel axis  122  and reference line  126 . In particular, cross bar  188  extending along connection axis  130  turns in cross-bar sleeves  182 L and  182 R. Since the frame-associated end of support rod  128  can be flexibly connected to channel portion  166  at any one of the frame-associated interface connection locations defined by the pairs of oppositely situated openings  172 , the frame-associated end of rod  128  is both flexibly and adjustably connected to channel portion  166 . In addition, channel portion  166  acts as an interface portion of frame  100  for enabling the seatback-to-seat incline to be adjusted by selecting different ones of those interface locations. 
     With support rod  128  connected to interface channel portion  166  of frame  100 , axial sleeve  184  of connection mechanism  106  can turn, i.e., rotate through some angle less than 360°, about axial bar  186  of T-bar portion  180  and thus can similarly turn around swivel axis  122 . The turning of axial sleeve  184  around axial bar  186  and swivel axis  122  is indicated by dashed-line curved arrows  196  in  FIG. 3 . In  FIG. 9  where dot  122 X indicates the location of swivel axis  122  because it extends perpendicular to the plane of the figure, curved arrows  196  also indicate how axial sleeve  184  can turn around axial bar  186  and swivel axis  122 . One or more rings of ball bearings (not shown) can be inserted between axial bar  186  and axial sleeve  184  to facilitate the turning of sleeve  184  around bar  186 . Since seatback  102  is rigidly connected to axial sleeve  184 , seatback  102  can swivel about axial bar  186  and therefore also about swivel axis  122 . Arrows  196  in  FIGS. 3 and 9  also indicate the swiveling of seatback  102  about axial bar  186  and swivel axis  122 . 
     The bottom edge of seatback  104  is shaped in such a way as to enable seatback  104  to swivel through a substantial angle about swivel axis  122  depending on the incline of seatback  104  to seat  102 . The angle through which seatback  104  can swivel about swivel axis  122  generally increases as the seatback-to-seat incline, as measured by incline angle a, increases. The maximum seatback swivel thus typically occurs when seatback  104  is approximately perpendicular to seat  102 , i.e., incline angle a is approximately 90°.  FIGS. 5, 7, and 8  illustrate the bottom edge of seatback  104  as being curved in a generally convex manner. However, the bottom edge of seatback  104  can be shaped in other ways for facilitating the seatback swivel. 
       FIG. 10  presents an example of how a typical human adult  200  uses the multi-function exercise machine of  FIGS. 3-5  to exercise in a seated exercise position. In this example, user  200  is seated on seat  102  with user&#39;s back  202  lying generally against seatback  104 . With user&#39;s feet  204  respectively on foot pedals  140 , user  200  pumps pedals  140  respectively with user&#39;s feet  204  to cause pedals  140  to revolve. This exercises user&#39;s legs  206 . While exercising user&#39;s legs  206 , user  200  can check readout display  114  for the various information presented on display  114 , including an estimate of the caloric energy consumed by user  200  as a result of pumping pedals  140 . 
     User  200  exercises the user&#39;s abdominal muscles by swiveling user&#39;s torso  208  about swivel axis  122  while user  200  is in the seated exercise position so as to cause seatback  104  to swivel about axis  122 . The incline of seatback  104  to seat  102  is adjusted prior to an exercise period to adjust the exercise of the user&#39;s abdominal muscles during the exercise period. Reducing the seatback-to-seat incline so that seatback  104  slants further downward away from seat  102  typically increases the exercise of the user&#39;s abdominal muscles. 
     User  200  can pump foot pedals  140  at the same time that user&#39;s torso  208  swivels about swivel axis  122  , thereby simultaneously exercising user&#39;s legs  206  and the user&#39;s abdominal muscles. Alternatively, user  200  can do only one of these two exercising actions during an exercise period. 
     User&#39;s hands  210  can be in various places. For example, user&#39;s hands  210  can respectively grip seat handles  108  as indicated in  FIG. 10 . This may facilitate pumping of foot pedals  140  by user&#39;s feet  204 . User  200  can also move seat handles  108  with user&#39;s hands  210  to exercise user&#39;s arms  212 . Alternatively, user&#39;s hands  210  can respectively grip seatback handles  110  to enhance swiveling user&#39;s torso  208  about swivel axis  122 , thereby increasing the exercise of the user&#39;s abdominal muscles. User&#39;s hands  210  can, of course, grip other parts of the exercise machine or no part(s) of the machine. 
       FIGS. 11 and 12  illustrate another multi-function exercise machine configured in accordance with the invention for enabling a user to exercise the user&#39;s legs and abdominal muscles. The exercise machine of  FIGS. 11 and 12  consists of frame  100 , seat  102 , seatback  104 , mechanism  106  for connecting seatback  104  to frame  100  or/and seat  102 , seat handles  108 , seatback handles  110 , a pedal-translating pedaling mechanism  220 , and a visual readout display  222 . Frame  100 , seat  102 , seatback  104 , seatback-to-frame/seat connection mechanism  106 , and handles  108  and  110  in main assembly  116  of the exercise machine of  FIGS. 11 and 12  are configured, interconnected, and operable the same as in the exercise machine of  FIGS. 3-5 . Readout display  222  in the machine of  FIGS. 11 and 12  provides largely the same exercise information as readout display  114  in the machine of  FIGS. 3-5 . The two exercise machines differ in that pedal-translating mechanism  220  in the exercise machine of  FIGS. 11 and 12  replaces pedal-revolving mechanism  112  in the exercise machine of  FIGS. 3-5 . 
     Pedal-translating pedaling mechanism  220  is further illustrated in  FIG. 13 . With reference to  FIGS. 11-13 , pedaling mechanism  220  consists of a pair of foot pedals  224 L and  224 R (collectively “pedals  224 ”), a pair of pedal connectors  226 L and  226 R (collectively “connectors  226 ”), a translator housing  228 , an internal translating apparatus (not shown) situated inside translator housing  228 , a resistance-adjustment knob  230  for adjusting the pedaling resistance, and a group of housing feet  232 . Translator housing  228  consists of an upper portion  228 U and a wider lower portion  228 L that provides pedaling mechanism  220  with mechanical stability. The longitudinal sides of lower housing portion  228 L are approximately equidistant from the longitudinal sides of upper housing portion  228 U. 
     Upper housing portion  228 U has a slanted front surface on which readout display  222  is situated to make it easy for a user to read readout display  222  while the user is seated on seat  102 . Resistance-adjustment knob  230  is situated on top of translator housing  228  but, depending on the configuration of the internal translator apparatus, can be located at some other suitable housing location readily accessible to the user. 
     Pedal connectors  226  are connected to the internal translating apparatus of pedaling mechanism  220  through two respective generally straight opposing connector slots  234  in the sides of upper housing portion  228 U. Connector slots  234  typically extend largely in the longitudinal direction of the exercise machine of  FIGS. 11 and 12  , i.e., parallel to reference line  126 , but can extend at a small angle to the exercise machine&#39;s longitudinal direction. Connector slots  234  are typically of largely the same length. 
     Foot pedals  224 L and  224 R are respectively connected to pedal connectors  226 L and  226 R so as to allow each pedal  224 L or  224 R to rotate around a portion of that pedal&#39;s connector  226 L or  226 R. Pedal connectors  226  translate (move linearly) back and forth in connector slots  234 . Foot pedals  224  thereby translate back and forth in the direction of connector slots  234  within a distance range slightly less than the lengths of slots  234 . More particularly, foot pedals  224  have a common center of mass that translates back and forth generally in a plane extending through connector slots  234 . Each cycle of the instantaneous cycling rate presented on readout display  222  consists of a full back and forth translation of one of pedals  224 . 
     Foot pedals  224  can translate back and forth in various ways. Pedals  224  are preferably controlled to operate in synchronism so that one of them translates back as the other translates forward. As measured from a position at which pedals  224  are directly opposite (and thus closest to) each other, the amounts (distances) of forward and backward translation are largely equal at any instant of time. In  FIGS. 11 and 13 , this pedal-opposing position is indicated by a translator reference line  236  extending parallel to the width of the exercise machine. Translator reference line  236 , whose location is indicated by dot  236 X in  FIG. 12 , normally lies in the plane through which the common center of mass of pedals  224  translates back and forth. 
     Foot pedals  224  can operate independently of each other. In that case, the internal translating apparatus of pedaling mechanism  220  may automatically causes pedals  224  to translate backward after they have translated forward and foot pressure on pedals  224  has been reduced sufficiently. Consequently, translator reference line  236  generally represents the neutral location for pedals  224  when they are directly opposite each other. 
     The internal translating apparatus of pedaling mechanism  220  can be implemented in various ways. In the preferred embodiment where foot pedals  224  operate in synchronism so that one of them translates back as the other translates forward, the internal translating apparatus can include a pulley arrangement that causes each pedal connector  226 L or  226 R to translate backward as the other pedal connector  226 R or  226 L translates forward. As measured from translator reference line  236  at which pedals  224  are directly opposite each other so that pedal connectors  226  are largely in line with each other, the pulley arrangement causes the amounts of forward and backward translation of pedal connectors  226  to be largely equal. An internal extension of resistance-adjustment knob  230  can press on a belt of the pulley arrangement to enable the translator resistance to be adjusted by turning knob  230 . 
     As with housing feet  148  in the exercise machine of  FIGS. 3-5 , housing feet  232  are implemented here as circular cylinders connected to the lower housing portion  228 L along its lower surface so as to extend downward slightly farther than translator housing  228 . This implementation of housing feet  232  thereby facilitates sliding housing  228  along the underlying surface. Pedaling mechanism  220  has four housing feet  232  in the example of  FIGS. 11-13 . Two of housing feet  232  are on each side of housing  228 . 
     Pedal-translating mechanism  220  is adjustably connected to the front end of frame  100  of main assembly  116  in the same manner as pedal-revolving mechanism  112  in the exercise machine of  FIGS. 3-5 . This enables the distance from seat  102  to translator reference line  236  in the exercise machine of  FIGS. 11 and 12  to be adjusted in order to accommodate the size of the user. In particular, short rails  164  respectively extend into a pair of openings (not shown) in the back of pedaling mechanism  220 . The distance from seat  102  to reference line  236  in the example of  FIGS. 11 and 12  is adjusted with a pair of knobs  238 L and  238 R (collectively “knobs  238 ”) situated on lower housing portion  228 L on opposite sides of upper housing portion  228 U typically close to the back of pedaling mechanism  220 . Distance-adjustment knobs  238  have respective internal extensions and function the same as distance-adjustment knobs  152  in the exercise machine of  FIGS. 3-5 . 
       FIGS. 11 and 12  depict the situation in which pedaling mechanism  220  substantially touches seat  102  and thus the situation in which the distance from seat  102  to translator reference line  236  is at a minimum value. Pedaling mechanism  220  and seat  102  are spaced apart from each other when the distance from seat  102  to reference line  236  is adjusted to exceed the minimum value. Likewise analogous to pedal-revolving mechanism  112 , pedal-translating mechanism  220  can be readily disconnected from main assembly  116  to enable another exercise mechanism, such as pedal-revolving mechanism  112  or that described below in connection with  FIG. 24 , to be connected to the front end of assembly  116  via short rails  164 . 
       FIG. 14  presents an example of how human adult  200  uses the multi-function exercise machine of  FIGS. 11 and 12  in a seated exercise position. As in the seated-position example of  FIG. 10 , user  200  in the example of  FIG. 14  is seated on seat  102  so that user&#39;s back  202  lies generally against seatback  104 . With user&#39;s feet  204  respectively on foot pedals  224 , user  200  pumps pedals  224  respectively with user&#39;s feet  204  to cause pedals  224  to translate back and forth. User&#39;s legs  206  are thereby exercised. Exercise of other parts of the user&#39;s body, including the user&#39;s abdominal muscles, with the exercise machine of  FIGS. 11 and 12  is performed in substantially the way described above in connection with  FIG. 10  for the exercise machine of  FIGS. 3-5 . 
     Upon disconnecting the frame-associated end of connection rod  128  from channel portion  166  of frame  100  in the exercise machine of  FIGS. 3-5  or in the exercise machine of  FIGS. 11 and 12 , seatback  104  can be rotated backward so as to lie flat or nearly flat against frame  100  in order to reduce the space occupied by main assembly  116 . When so oriented, seatback  104  is often referred to herein as being in the flat position. Placing seatback  104  in the flat position facilitates storage of the exercise machine. Storage can be further facilitated by disconnecting pedaling mechanism  112  or  220  from main assembly  116 . When connection rod  128  is so disconnected from frame  100 , the frame-associated end of rod  128  is normally moved backward so as to lie close to the back end of frame  100 . 
     In the earlier drawings depicting the exercise machines of the invention, seatback-to-frame/seat connection mechanism  106  was shown as extending significantly backward beyond the back of seatback  104  in order to facilitate visual illustration of the structure of connection mechanism  106 . Alternatively, the axial section of the seatback-adjoining portion of connection mechanism  106  can be recessed partially or fully into the back of seatback  104 . This enables seatback  104  to lie flatter against frame  100  when the frame-associated end of connection rod  128  is disconnected from channel portion  166 , and seatback  104  is rotated backward toward frame  100 . Main assembly  116  then occupies even less space so as to further facilitate exercise machine storage, especially when pedaling mechanism  112  or  220  is disconnected from main assembly  116 . 
       FIGS. 15 a  and 15 b    (collectively “ FIG. 15 ”) illustrate a version of main assembly  116  in which the axial section of the seatback-adjoining portion of a variation  106 U of seatback-to-frame/seat connection mechanism  106  is, in accordance with the invention, recessed fully into the back of a variation  104 U of seatback  104 .  FIG. 16  cross-sectionally illustrates seatback  104 U and seatback-to-frame/seat connection mechanism  106 U. 
     Seatback-to-frame/seat connection mechanism  106 U is formed with support rod  128 , T-shaped bar portion  180 , cross-bar sleeves  182 L and  182 R, axial sleeve  184 , pins  192  and  194 , and a group of attachment brackets  120 U corresponding to attachment brackets  120  in seatback-to-frame/seat connection mechanism  106 U. As in connection mechanism  106 , T-shaped bar portion  180  in connection mechanism  106 U consists of axial bar  186 , cross bar  188  formed with cross-bar portions  188 L and  188 R, and cross-bar end caps  190 L and  190 R. Components  182 L,  182 R,  184 ,  186 ,  188 L, and  188 R of connection mechanism  106 U are visible in  FIG. 16  but not in  FIG. 15 a    or  15   b.    
     The axial section of the seatback-adjoining portion of connection mechanism  106 U consists of axial sleeve  184  and axial bar  186 . As indicated in  FIG. 16 , axial section  184  and  186  of the seatback-adjoining portion of connection mechanism  106 U is fully recessed into a channel in the back of seatback  104 U. The channel in the back of seatback  104 U typically extends up to its top edge. Attachment brackets  120 U fixedly connect mechanism  106 U, specifically axial sleeve  184 , to the back of seatback  104 U. In contrast to attachment brackets  120  which are curved outward to hold axial sleeve  184  against the back of seatback  104 , attachment brackets  120 U here are typically curved slightly inward but can be largely flat. Three attachment brackets  120 U are shown in  FIGS. 15 a    and  16 . Due to the recessing of the axial section of the seatback-adjoining portion of connection mechanism  106 U into seatback  104 U, the longitudinal centerline  124 U of seatback  104 U is closer to swivel axis  122  than is longitudinal centerline  124  of seatback  104 . 
     Aside from the differences just indicated, seatback  104 U is configured largely the same as seatback  104 . Consequently, the bottom edge of seatback  104 U is shaped generally as shown in  FIGS. 7 and 8  for seatback  104  to avoid inhibiting the swivel of seatback  104 U about swivel axis  122 . Support rod  128 , T-shaped bar portion  180 , cross-bar sleeves  182 , axial sleeve  184 , and pins  192  and  194  in connection mechanism  106 U are respectively configured, interconnected, and operable the same as in connection mechanism  106 . 
       FIG. 15 a    presents an example of how main assembly  116  appears when seatback  104 U is in the inclined position.  FIG. 15 b    shows how main assembly  116  appears when (a) seatback  104 U is in the flat position and (b) the frame-associated end of connection rod  128  has been disconnected from channel portion  166  (not visible in  FIG. 15 b   ) of frame  100 . The top of seat  102  and the front of seatback  104 U are largely coplanar. Support rod  128  (not visible in  FIG. 15 b   ) now lies in the portion of the seatback channel extending up to, or close to, the top edge of seatback  104 U. Seat handles  108  and seatback handles  110  have been arranged in  FIG. 15 b    to be no higher than the top of seat  102  and the front of seatback  104 U. As  FIG. 15 b    indicates, main assembly  116  is of relatively small height in this compressed position so as to facilitate storage of assembly  116 . 
       FIG. 17  illustrates a multi-function exercise machine configured in accordance with the invention for variously exercising the legs, arms, and abdominal muscles of a user using any of several different exercise positions. As a variation of the exercise machine of  FIGS. 11 and 12 , the exercise machine of  FIG. 17  consists of frame  100 , seat  102 , seatback  104 , seatback-to-frame/seat connection mechanism  106 , seat handles  108 , seatback handles  110 , a third pair of handles  240 L and  240 R (collectively “handles  240 ”), a fourth pair of handles  242 L and  242 R (collectively “handles  242 ”), pedal-translating pedaling mechanism  220 , and readout display  222 . Frame  100 , seat  102 , seatback  104 , connection mechanism  106 , and handles  108  and  110  in main assembly  116  of the machine of  FIG. 17  are respectively configured, interconnected, and operable the same as in the machine of  FIGS. 11 and 12  subject to modification of main assembly  116  to receive third handles  240  and fourth handles  242 . 
     Seatback  104  and connection mechanism  106  in main assembly  116 V can be respectively replaced with seatback  104 U and connection mechanism  106 U as described above in connection with  FIGS. 15 and 16 . In either case, the exercise machine of  FIG. 17  can be used to exercise the legs and abdominal muscles of a user utilizing the seated exercise position generally shown in  FIG. 14  as described above for the exercise machine of  FIGS. 11 and 12 . 
     Third handles  240 , referred to here generally as “seat” handles, are shown in  FIG. 17  as being received by seat  102  at generally opposite locations along the side edges of seat  102  near its front edge. Front seat handles  240  are preferably movable relative to seat  102 . Alternatively, frame  100  can receive seat handles  240  at corresponding opposite locations below the reception locations shown in  FIG. 17  near the front edge of seat  102 . In that case, seat handles  240  are preferably movable relative to frame  100 . 
     Fourth handles  242 , referred to here generally as “frame” handles, are shown in  FIG. 17  as being received by frame  100  at generally opposite locations respectively along the longitudinal side edges of long rails  160  roughly halfway along their length. Long rails  160  can alternatively respectively receive frame handles  242  along the top edges of rails  160 , again roughly halfway along their length. In either case, frame handles  242  are located longitudinally somewhat beyond the back edge of seat  102 . Frame handles  242  are preferably movable relative to frame  100 . 
     Similar to what was said above about handles  108  and  110 , handles  240  and  242  can move in various ways. Front seat handles  240  can be respectively turned about a pair of third handle axes whose location is generally indicated by dot  244 X in  FIG. 17 . The third handle axes can be a common third handle axis extending generally parallel to the exercise machine width. Seat handles  240  can be rigidly connected together inside or below seat  102 . Handles  240  then turn simultaneously (in synchronism) about the common third handle axis. Alternatively, handles  240  can be respectively turned about the third handle axes independently of each other as generally indicated in  FIG. 17 . The third handle axes can then be inclined or/and slightly laterally offset from each other. 
     Frame handles  242  can be respectively turned about a pair of fourth handle axes whose location is generally indicated by dot  246 X in  FIG. 17 . The fourth handle axes can be a common fourth handle axis extending generally parallel to the width of the exercise machine. Frame handles  242  can be rigidly connected together so that they turn simultaneously (in synchronism) about the common fourth handle axis. Instead, handles  242  can be respectively turned about the fourth handle axes independently of each other as generally indicated in the example of  FIG. 17 . Accordingly, the fourth handle axes can be inclined or/and slightly laterally offset from each other. 
     As mentioned above, the common center of mass of foot pedals  224  translates back and forth generally in a plane extending in the direction of, and passing through, connector slots  234 . This plane is typically nearly horizontal when the exercise machine of  FIG. 17  is on a horizontal surface. In any event, most of each of frame handles  242  is normally below this plane when pedal-translating pedaling mechanism  220  is oriented such that this plane is nearly horizontal. The same applies to front seat handles  240  and also to back seat handles  108 . 
       FIG. 18  presents an example of how typical human adult  200  uses the multi-function exercise machine of  FIG. 17  to exercise in a crouched exercise position. User&#39;s hands  210  respectively grip front seat handles  240 . User&#39;s feet  204  are placed respectively on foot pedals  224  so that user  200  is crouched with user&#39;s back  202  directed (facing) generally upward. 
     Front seat handles  240  are situated at a suitable average distance to foot pedals  224  such that user  200  is in the indicated severe crouch when user  200  is an average-size adult. This average distance is largely the distance from translator reference line  236 , indicated by dot  236 X in  FIG. 17 , to the third handle axes, generally indicated by dot  244 X in  FIG. 17 . By appropriately adjusting the connection of pedaling mechanism  220  to frame  100 , the average distance from pedals  224  to seat handles  240  can be adjusted to accommodate the size of user  200 .  FIGS. 17 and 18  depict the situation in which pedaling mechanism  220  substantially touches seat  102  and thus the situation in which the average distance from pedals  224  to seat handles  240  is at a minimum value. Pedaling mechanism  220  and seat  102  are spaced apart from each other when the average distance from pedals  224  to seat handles  240  is adjusted to exceed the minimum value. 
     User  200  pumps foot pedals  224  with user&#39;s feet  204  in the exercise position of  FIG. 18  to cause pedals  224  to translate back and forth, thereby exercising user&#39;s legs  206 . The accompanying movement of the user&#39;s body and the weight placed on user&#39;s arms  212  exercises user&#39;s arms  212 . User  200  can move front seat handles  240  to maintain the user&#39;s balance and to further exercise user&#39;s arms  212 . User  200  can look downward and backward (relative to the user&#39;s position on the exercise machine) to check readout display  222  in order to see the exercise information occurring during the exercise period. 
     Rather than gripping front seat handles  240 , user&#39;s hands  210  can grip back seat handles  108  while user  200  is generally in the crouched position with user&#39;s feet  204  on foot pedals  224  and with user&#39;s back  202  generally directed upward. As another alternative, user&#39;s hands  210  can variously grip, e.g. switch back and forth between, seat handles  108  and  240 . Exercising from the crouched position of  FIG. 18  exercises largely all of the user&#39;s major muscle groups, including the user&#39;s abdominal muscles. 
       FIG. 19  presents an example of how human adult  200  uses the exercise machine of  FIG. 17  to exercise in a largely prone, typically somewhat slanted, exercise position. Seatback  104  is set at a suitable incline relative to seat  102 . As necessary, the connection of pedaling mechanism  220  to frame  100  is adjusted so that the average distance from foot pedals  224  to seatback handles  110  is suitable for enabling user  200  to be in the indicated largely prone exercise position. This average distance is largely the distance from translator reference line  236 , indicated by dot  236 X in  FIG. 19 , to the second handle axes, generally indicated by dot  134 X in  FIG. 19 . 
     User&#39;s hands  210  respectively grip seatback handles  110  for the exercise position of  FIG. 19 . User&#39;s feet  204  are placed respectively on foot pedals  224  so that user  200  is largely prone, i.e., user&#39;s back  202  is directed largely upward. The user&#39;s body is relatively straight but, depending on the incline of seatback  104  to seat  102  and on the distance from pedals  224  to seatback handles  110 , is typically slanted somewhat relative to the surface below the exercise machine. 
     In the prone exercise position of  FIG. 19 , user  200  exercises user&#39;s legs  206  by pumping foot pedals  224  with user&#39;s feet  204  to cause pedals  224  to translate back and forth. User&#39;s arms  212  are simultaneously exercised due to the movement of the user&#39;s body and the weight/stress placed on user&#39;s arms  212  to maintain the prone position. User  200  can move seatback handles  110  to maintain the user&#39;s balance and to further exercise user&#39;s arms  212 . Exercising from the prone position of  FIG. 19  exercises largely all of the user&#39;s major muscle groups, including the user&#39;s abdominal muscles. User  200  can again look downward and backward to check readout display  222 . Insofar as front seat handles  240  and frame handles  242  are not used, exercising from the prone position of  FIG. 18  can also be done on the exercise machine of  FIGS. 11 and 12 . 
       FIGS. 18 and 19  and depict situations in which exercise is performed with seatback  104  in the inclined position. Instead seatback  104  can be in the flat position as generally indicated in  FIG. 15 b    for seatback  104 U. This can be facilitated by substituting seatback  104 U and connection mechanism  106 U of  FIGS. 15 and 16  for seatback  104  and connection mechanism  106  in the exercise machine of  FIG. 17 . 
       FIG. 20  presents an example of how human adult  200  uses the exercise machine of  FIG. 17 , as implemented with seatback  104 U and connection mechanism  106 U of  FIGS. 15 and 16 , to exercise in a crouched-to-prone exercise position with seatback  104 U in the flat position. The connection of pedaling mechanism  220  to frame  100  is adjusted, as necessary, so that the average distance from foot pedals  224  to frame handles  242  is suitable for enabling user  200  to be in the indicated crouched-to-prone exercise position. This average distance is largely the distance from translator reference line  236 , indicated by dot  236 X in  FIG. 20 , to the fourth handle axes, generally indicated by dot  246 X in  FIG. 20 . 
     User&#39;s feet  204  are once again placed respectively on foot pedals  224 . User&#39;s hands  210  respectively grip frame handles  242  so that user&#39;s back  202  is generally directed upward. Because frame handles  242  are considerably further away from pedals  224  than are front seat handles  240 , the user&#39;s body is curved upward somewhat rather than being in the severe crouch of  FIG. 18 . 
     User  200  exercises user&#39;s legs  206  in the crouched-to-prone exercise position of  FIG. 20  by pumping foot pedals  224  with user&#39;s feet  204 . User&#39;s arms  212  are simultaneously exercised due to the movement of the user&#39;s body and the accompanying weight placed on user&#39;s arms  212 . User  200  can move frame handles  242  to maintain the user&#39;s balance and to further exercise user&#39;s arms  212 . Exercising from the crouched-to-prone position of  FIG. 19  exercises largely all of the user&#39;s major muscle groups, including the user&#39;s abdominal muscles. Once again, user  200  can look downward and backward to check readout display  222 . 
     Instead of keeping user&#39;s hands  210  solely on frame handles  242 , user&#39;s hands  212  can respectively switch to gripping back seat handles  108  or front seat handles  240  so that user  200  is generally in the crouched exercise position of  FIG. 18 . User  200  can thereby switch back and forth between the crouched-to-prone exercise position of  FIG. 20  and the crouched exercise position of  FIG. 18 . With seatback  104 U in the flat position, user&#39;s hands  210  may also be able to respectively switch to gripping upper seatback handles  110  so that user  200  is a prone exercise position analogous to that of  FIG. 19 . As a result, user  200  may be able to variously switch between crouched, crouched-to-prone, and prone exercise positions. 
       FIG. 21  illustrates a multi-function exercise machine configured in accordance with the invention for exercising the legs and arms of a user in a crouched or crouched-to-prone exercise position. As a variation of the exercise machine of  FIG. 17 , the exercise machine of  FIG. 21  consists of frame  100 , seat  102 , seatback  104 U, seatback-to-frame/seat connection mechanism  106 U, back seat handles  108 , seatback handles  110 , front seat handles  240 , frame handles  242 , an optional fifth pair of handles  250 L and  250 R (collectively “handles  250 ”), pedal-translating pedaling mechanism  220 , and readout display  222 . Frame  100 , seat  102 , seatback  104 U, connection mechanism  106 U, and handles  108 ,  110 ,  240 , and  242  in main assembly  116  of the machine of  FIG. 21  are respectively configured, interconnected, and operable the same as in the machine of  FIG. 17  subject to (a) substitution of seatback  104 U and connection mechanism  106 U respectively for seatback  104  and connection mechanism  106 , (b) modification of main assembly  116  to receive fifth handles  250 , and (c) modification of frame  100  as described below in connection with  FIG. 22 . Seatback  104 U and connection mechanism  106 U in the machine of  FIG. 21  can be respectively replaced with components  104  and  106 . 
       FIG. 21  shows fifth handles  250 , referred to here generally as “seatback” handles, as being received by seatback  104 U at generally opposite locations along the side edges of seatback  104 U closer to its bottom edge than to its top edge. Lower seatback handles  250  are preferably movable relative to seatback  104 U. Depending on the configuration of seatback-to-frame/seat connection mechanism  106 U, seatback handles  250  can alternatively be received by connection mechanism  106 U at corresponding generally opposite locations close to the reception locations shown in  FIG. 21 . In that case, seatback handles  250  are preferably movable relative to connection mechanism  106 U. 
     Analogous to what was said above about upper seatback handles  110 , lower seatback handles  250  can move in various ways. Seatback handles  250  can be respectively turned about a pair of fifth handle axes whose location is generally indicated by dot  252 X in  FIG. 21 . The fifth handle axes can be a common fifth handle axis extending generally parallel to the width of the exercise machine. Handles  250  can be rigidly connected together inside or behind seatback  104 U. Handles  250  then turn simultaneously (in synchronism) about the common fifth handle axis. Alternatively, handles  250  can be respectively turned about the fifth handle axes independently of each other as generally indicated in the example of  FIG. 21 . The fifth handle axes can then be inclined or/and slightly laterally offset from each other. 
     Referring to  FIG. 22 , frame  100  in the exercise machine of  FIG. 21  is an assembly consisting of long rails  160 , cross rails  162 , short rails  164 , channel portion  166 , frame feet  168 , and a further pair of short longitudinal rails  260 L and  260 R (collectively “short rails  260 ”) extending generally parallel to long rails  160 . Long rails  160 , cross rails  162 , short rails  164 , channel portion  166 , and frame feet  168  in frame  100  of the machine of  FIG. 21  are respectively configured and interconnected the same as in the exercise machine of  FIG. 17 . 
     Further short rails  260  are situated on, and rigidly connected to, back cross rail  162 C in the exercise machine of  FIG. 21  at locations between long rails  160  and extend backward beyond long rails  160 . In particular, short rails  260  typically extend backward beyond long rails  160  approximately the same distance that short rails  164  extend forward beyond long rails  160 . Short rails  260  typically consist of metal and are typically hollow but can be solid. As discussed below in connection with  FIGS. 28, 29   a , and  29   b , short rails  260  can be flexibly connected to cross rail  162 C so that they can be placed in a position in which they do not extend backward beyond long rails  160  when they are not connected to pedaling mechanism  220  or another such exercise mechanism. 
     Returning to  FIG. 21 , pedaling mechanism  220  is adjustably connected to the back end of frame  100  of main assembly  116  in largely the same manner that pedaling mechanism  220  is adjustably connected to the front end of frame  100  of assembly  116  in the exercise machine of  FIG. 17 . In particular, short rails  260  respectively extend into the above-mentioned pair of openings (again not shown) in the back of pedaling mechanism  220 . A plurality of vertical circular openings  262 L situated generally in a line extend through short rail  260 L. A like plurality of vertical circular openings  262 R situated generally in a line extend through short rail  260 R. Openings  262 R are respectively situated substantially directly opposite openings  262 L. Openings  262 L and  262 R (collectively “openings  262 ”) are thereby allocated into pairs of oppositely situated openings  262 . 
     Distance-adjustment knob  238 R (see  FIGS. 11-13 and 21 ) is situated generally above the line of openings  262 R in short rail  260 L while distance-adjustment knob  238 L (likewise see  FIGS. 11-13 and 21 ) is situated generally above the line of openings  262 L in short rail  260 R. The internal extensions (not shown) of knobs  238  respectively pass through a selected one of the pairs of oppositely situated openings  262  thereby connecting pedaling mechanism  220  to the back end of frame  100 . The knob extensions also respectively pass through a pair of openings in an underlying piece of material rigidly connected to translator housing  228  to make the connection solid. 
     To adjust the connection of pedaling mechanism  220  to the back end of main assembly  116 , distance-adjustment knobs  238  are first pulled sufficiently upward to release the connection. The depth to which short rails  260  extend into the openings in pedaling mechanism  220  is appropriately changed. Knobs  238  are then pushed downward so that the knob extensions pass through another selected pair of oppositely situated openings  262  and through the two openings in the underlying piece of material connected to housing  228 . In addition to being adjustably connected to main assembly  116 , pedal-translating mechanism  220  can be readily disconnected from assembly  116  to facilitate exercise machine storage and to enable another exercise mechanism, such as pedal-revolving mechanism  112  or that described below in connection with  FIG. 24 , to be adjustably connected to the back end of assembly  116 . 
     Seatback  104  is normally in the flat position when a user actuates pedals  224  in exercising with the multi-function exercise machine of  FIG. 21 . In light of the explanation below of how a user utilizes the exercise machine of  FIG. 21  to exercise in a crouched position, the average distance from foot pedals  224  to upper seatback handles  110  can be adjusted to accommodate the user&#39;s size for exercising in the crouched position. This distance is largely the distance from translator reference line  236 , indicated by dot  236 X in  FIG. 21 , to second handle axes  134 L and  134 R (see  FIG. 5 ), indicated by dot  134 X in  FIG. 21 . 
       FIG. 21  depicts the situation in which pedaling mechanism  220  touches or nearly touches the back ends of long rails  160  of frame  100  and thus the situation in which the average distance from foot pedals  224  to upper seatback handles  110  is at a minimum value. Alternatively or additionally, pedaling mechanism  220  can touch or nearly touch the top edge of seatback  104 U when the average distance from foot pedals  224  to seatback handles  110  is at the minimum value. Pedaling mechanism  220  is spaced apart from the back ends of long rails  160  or/and the top edge of seatback  104 U when the average distance from foot pedals  224  to seatback handles  110  is adjusted to exceed the minimum value. 
     A user utilizes the exercise machine of  FIG. 21  to exercise in a crouched position similar to that of user  200  in  FIG. 18  except that the user&#39;s body relative to main assembly  116  in  FIG. 21  is generally oriented in the opposite direction to that of the user&#39;s body relative to assembly  116  in  FIG. 18 . More particularly, the user&#39;s hands respectively grip upper seatback handles  110 . The user&#39;s feet are placed respectively on foot pedals  224  so that the user is crouched with the user&#39;s back generally directed upward. The average distance from pedals  224  to seatback handles  110  is chosen so that the user is in a severe crouch when the user is an average-size adult. 
     The user pumps foot pedals  224  respectively with the user&#39;s feet to exercise the user&#39;s legs and arms as described above in connection with  FIG. 18 . The user can move upper seatback handles  110  to maintain the user&#39;s balance and to further exercise the user&#39;s arms. Instead of gripping seatback handles  110 , the user&#39;s hands can grip lower seatback handles  250  or frame handles  240  while in the crouched position. The user&#39;s hands can also variously grip, e.g. switch back and forth between, seatback handles  110  and lower seatback handles  250  or frame handles  242 . The user can look downward and backward to check readout display  222  for exercise information. 
     Similar opposite-orientation comments apply to use of the exercise machine of  FIG. 21  for exercising in a crouched-to-prone position. In particular, a user utilizes the exercise machine of  FIG. 21  to exercise in the crouched-to-prone position similar to that for user  200  in  FIG. 20  except that the user&#39;s body relative to main assembly  116  is generally oriented in the opposite direction to that of the user&#39;s body relative to assembly  116  in  FIG. 20 . The user&#39;s hands respectively grip back seat handles  108  or front seat handles  240 . The user&#39;s feet are placed respectively on foot pedals  224  so that the user&#39;s back is generally directed upward. 
     For exercising in the crouched-to-prone position with the exercise machine of  FIG. 21 , the average distance from pedals  224  to back seat handles  108  or front seat handles  240  is chosen so that the user&#39;s body is curved somewhat upward similar to what is illustrated in  FIG. 20  for user  200 . The average distance from pedals  224  to back seat handles  108  is largely the distance from translator reference line  236  (dot  236 X in  FIG. 21 ) to first handle axes  132 L and  132 R (see  FIG. 5 ), indicated by dot  132 X in  FIG. 21 . Similarly, the average distance from pedals  224  to front seat handles  240  distance is largely the distance from translator reference line  236  (again dot  236 X in  FIG. 21 ) to the third handle axes indicated by dot  244 X in  FIG. 21 . 
     Foot pedals  224  are pumped with the user&#39;s feet to exercise the user&#39;s legs and arms as described above in connection with  FIG. 20 . Depending on whether the user&#39;s hands are gripping back seat handles  108  or front seat handles  240 , the user can move seat handles  108  or  240  to maintain the user&#39;s balance and to further exercise the user&#39;s arms. While in the crouched-to-prone exercise position, the user&#39;s hands can switch to gripping lower seatback handles  250  or frame handles  240 . In fact, the user can switch back and forth between the crouched-to-prone and crouched exercise positions. The user can again look downward and backward to check readout display  222 . 
       FIG. 23  illustrates a multi-function exercise machine configured in accordance with the invention for variously exercising the legs, arms, and abdominal muscles of a user using any of a number of different exercise positions. As an extension of the exercise machines of  FIGS. 3-5  and  FIG. 21 , the machine of  FIG. 23  is formed with main assembly  116 , pedal-revolving mechanism  112 , pedal-translating mechanism  220 , and readout displays  114  and  222  where main assembly  116  here includes seatback  104 U and seatback-to-frame/seat connection mechanism  106 U rather than components  104  and  106 . Frame  100 , seat  102 , seatback  104 U, connection mechanism  106 U, and handles  108 , 110 ,  240 ,  242 , and  250  in main assembly  116  of the machine of  FIG. 23  are respectively configured, interconnected, and operable as described above for the exercise machine of  FIG. 21 . 
     Pedal-translating mechanism  220  in the exercise machine of  FIG. 23  is adjustably connected to the back end of frame  100  as described above for the exercise machine of  FIG. 21 . Pedal-revolving mechanism  112  in the machine of  FIG. 23  is adjustably connected to the front end of frame  100  as described above for frame  100  in the exercise machine of  FIGS. 3-5 . Both of pedaling mechanisms  112  and  220  can be disconnected from frame  100  to facilitate exercise machine storage. 
       FIG. 23  depicts the situation in which seatback  104 U is in the flat position. A user can then utilize the multi-function exercise machine of  FIG. 23  to exercise in the crouched and crouched-to-prone positions with pedal-translating mechanism  220  as described above in connection with the exercise machine of  FIG. 21  and thus similar to what is shown in  FIGS. 18 and 20 . With seatback  104 U in the inclined position, the user can utilize the machine of  FIG. 23  to exercise in the seated position with pedal-revolving mechanism  112  as generally shown in  FIG. 10  except that seatback  104 U and connection mechanism  106 U replace components  104  and  106 . 
     Pedal-revolving mechanism  112  can be disconnected from main assembly  116  in the exercise machine of  FIG. 23  to produce the exercise machine of  FIG. 21  for which a user can exercise in the crouched and crouched-to-prone positions using pedal-translating mechanism  220 . On the other hand, pedal-translating mechanism  220  can be disconnected from main assembly  116  in the machine of  FIG. 23  to produce a variation of the exercise machine of  FIGS. 3-5  in which frame  100  includes short rails  260  and in which components  104 U and  106 U replace components  104  and  106 . The user can then exercise in the seated position using pedal-revolving mechanism  112  as generally shown in  FIG. 10 . 
     Pedal-translating mechanism  220  can be disconnected from the back end of main assembly  116  in the exercise machine of  FIG. 23  and, after disconnecting pedal-revolving mechanism  112  from assembly  116 , can be connected to the front end of assembly  116  to produce a variation of the exercise machine of  FIGS. 11 and 12  in which frame  100  again includes short rails  260  and in which components  104 U and  106 U again replace components  104  and  106 . A user can utilize the resulting exercise machine to exercise in the seated position with pedal-translating mechanism  220  as described above in connection with  FIG. 14 . 
     Disconnection of pedal-revolving mechanism  112  from the front end of main assembly  116  and transference of pedal-translating mechanism  220  from the back end of assembly  116  to the front end of assembly  116  produces a variation of the exercise machine of  FIG. 17  in which frame  100  once again includes further short rails  260  and in which components  104 U and  106 U once again replace components  104  and  106 . In addition to exercising in the seated position with pedal-translating mechanism  220  as described above in connection with  FIG. 14 , a user can exercise in the crouched, crouched-to-prone, and largely prone positions with pedal-translating mechanism  220  as described above in connection with  FIGS. 18-20 . If desired, pedal-revolving mechanism  112  can be connected to the back end of main assembly  116  via short rails  260 . 
     In short, pedaling mechanisms  112  and  220  in the machine of  FIG. 23  can be connected to main assembly  116  in various ways. This enables a user to exercise variously in the crouched, crouched-to-prone, and largely prone positions with pedal-translating mechanism  220  and in the seated position with pedal-revolving mechanism  112  or pedal-translating mechanism  220 . 
     Exercise Machine with Handle-Translating Mechanism 
       FIG. 24  illustrates a multi-function exercise machine configured in accordance with the invention for enabling a user to exercise the user&#39;s legs, arms, and abdominal muscles. The exercise machine of  FIG. 24  is formed with main assembly  116 , pedal-translating mechanism  220 , a handle-translating mechanism  270 , readout display  222 , and another visual readout display  272  where main assembly  116  here includes seatback  104 U and seatback-to-frame/seat connection mechanism  106 U rather than components  104  and  106 . Frame  100 , seat  102 , seatback  104 U, connection mechanism  106 U, and handles  108 ,  110 ,  240 ,  242 , and  250  in main assembly  116  of the machine of  FIG. 24  are configured, interconnected, and operable as described above for the exercise machine of  FIG. 21 . Readout display  272  provides largely the same exercise information as readout display  222  and thus largely the same exercise information as readout display  114 . 
     Pedaling mechanism  220 , with on-board readout display  222 , is adjustably connected to the front end of frame  100  of main assembly  116  in the same way that pedaling mechanism  220  is adjustably connected to the front end of frame  100  in the exercise machine of  FIG. 17 . Similarly, handle-translating mechanism  270  is adjustably connected to the back end of frame  100  of main assembly  116  in the same way that pedaling mechanism  220  is adjustably connected to the back end of frame  100  in the exercise machine of  FIG. 21 . 
     Handle-translating mechanism  270 , further illustrated in  FIG. 25 , consists of a pair of translatable handles  274 L and  274 R (collectively “handles  274 ”), a pair of handle connectors  276 L and  276 R (collectively “connectors  276 ”), a translator housing  278 , an internal translating apparatus (not shown) situated inside translator housing  278 , a resistance-adjustment knob  280  for adjusting the handle-translating resistance, and a group of housing feet  282 . Handle connectors  276 , translator housing  278 , resistance-adjustment knob  280 , and housing feet  282 , are configured, interconnected, and operable the respectively the same as pedal connectors  226 , translator housing  228 , resistance-adjustment knob  230 , and housing feet  232  in pedal-translating mechanism  220 . The same applies to the internal translating apparatus inside translator housing  278 . 
     Translator housing  278  consists of an upper portion  278 U and a wider lower portion  278 L that provides pedal-translating mechanism  270  with mechanical stability. Readout display  272  is situated on the slanted front surface of upper housing portion  278 U. Resistance-adjustment knob  280  is illustrated in  FIG. 24  as being situated on top of housing  278  but can be located elsewhere on housing  278 . Handle connectors  276  are connected to the internal translating apparatus of handle-translating mechanism  270  through two respective generally straight opposing connector slots  284  in the sides of upper housing portion  278 U. Connector slots  284  are configured the same as connector slots  234  in pedal-translating mechanism  220 . 
     Translatable handles  274 L and  274 R are respectively connected to handle connectors  276 L and  276 R so as to allow each handle  274 L or  274 R to rotate around a portion of that handle&#39;s connector  276 L or  276 R. Because the internal translating apparatus inside translator housing  278  is configured and operable the same as the internal translating apparatus inside translator housing  228  of pedal-translating mechanism  220 , handle connectors  276  translate back and forth in connector slots  284  in the same way that pedal connectors  226  translate back and forth in connector slots  234  of pedal-translating mechanism  220 . Handles  274  thus translate back and forth in the direction of connector slots  284  in the same way that foot pedals  224  translate back and forth in the direction of connector slots  234 . In fact, pedal-translating mechanism  220  can be converted into handle-translating mechanism  270  by substituting handles  274  respectively for pedals  224 . Each cycle of the instantaneous cycling rate presented on readout display  272  consists of a full back and forth translation of one of handles  272 . 
     Item  286  in  FIG. 25  is a translator reference line that generally represents the neutral location for translatable handles  274  when they are directly opposite each other. Translator reference line  286  for the handle-opposing position extends parallel to the width of the exercise machine and normally lies in the plane through which the common center of mass of handles  274  translates back and forth. In  FIG. 24 , dot  286 X indicates the location of reference line  286 . The longitudinal distance from handles  274 , i.e., reference line  286 , to another exercising part of the exercise machine of  FIG. 24  is adjusted with a pair of knobs  288 L and  288 R (collectively “knobs  288 ”) situated on lower housing portion  288 L on opposite sides of upper housing portion  288 U typically close to the back of handle-translating mechanism  270 . Distance-adjustment knobs  288  have internal extensions and function the same as distance-adjustment knobs  238  on pedal-translating mechanism  220 . 
     With pedal-translating mechanism  220  connected to the front end of main assembly  116  in the multi-function exercise machine of  FIG. 24 , a user can utilize pedaling mechanism  220  to exercise with the machine of  FIG. 24  in any of the ways described above for exercising with the exercise machines of  FIGS. 11 and 17  in which pedaling mechanism  220  is similarly connected to the front end of assembly  116 . For instance, the user can exercise with the machine of  FIG. 24  using the seated, crouched, largely prone but somewhat slanted, and crouched-to-prone exercise positions of  FIGS. 14 and 18-20 . 
       FIG. 26  presents an example of how user  200  utilizes the exercise machine of  FIG. 24  to exercise in a nearly fully prone exercise position with pedal-translating mechanism  220  and handle-translating mechanism  270 . As necessary, the connection of pedal-translating mechanism  220  or/and handle-translating mechanism  270  to frame  100  is adjusted so that the average distance from foot pedals  224  to translatable handles  274  is suitable for enabling user  200  to be in the indicated prone position. This average distance is largely the distance from translator reference line  236 , indicated by dot  236 X in  FIG. 26 , to translator reference line  286 , generally indicated by dot  286 X in  FIG. 26 . 
     User&#39;s hands  210  respectively grip translatable handles  274  for the exercise position of  FIG. 26 . User&#39;s feet  204  are placed respectively on foot pedals  224  so that user  200  is nearly fully prone, i.e., user&#39;s back  202  is directed nearly fully upward. In this exercise position, user  200  exercises user&#39;s legs  206  by pumping foot pedals  224  with user&#39;s feet  204  to cause pedals  224  to translate back and forth. User  200  exercises user&#39;s arms  212  by pressing laterally on handles  274  with user&#39;s hands  210  to cause handles  274  to translate back and forth. User&#39;s arms  212  can be so exercised at the same time as user&#39;s legs  206  or at different times. User  200  can look downward and backward to check readout display  222  for information on the exercise of user&#39;s legs  206 . User  200  can also look generally downward to check readout display  272  for information on the exercise of user&#39;s arms  204 . 
     Exercising using the prone position of  FIG. 26  can be done with the locations of pedal-translating mechanism  220  and handle-translating mechanism  272  reversed. That is, handle-translating mechanism  270  can be connected to the front end of main assembly  116  while pedal-translating mechanism  220  is connected to the back end of assembly  116 . 
       FIG. 27  presents an example of how user  200  utilizes the exercise machine of  FIG. 24  to exercise user&#39;s arms  204  with seatback  104 U in the flat position. In this example, user  200  is seated on the back of seatback  104 U. User&#39;s hands  210  respectively grip translatable handles  274 . User&#39;s legs  206  extend respectively to the sides of the exercise machine. User&#39;s feet  204  may touch the surface on which the exercise machine is situated. User&#39;s hands  210  press laterally on handles  274  to cause them to translate back and forth, thereby exercising user&#39;s arms  212 . By looking generally downward, user  200  can check readout display  272  for exercise information. 
     As with the prone exercise position of  FIG. 26 , exercising using the seated position of  FIG. 27  can be done with the locations of pedal-translating mechanism  220  and handle-translating mechanism  272  reversed. In that case, the user sits on seat  102 . Seatback  104 U can be in the flat or inclined position. The exercise position of  FIG. 27  can also be done with pedal-translating mechanism  220  disconnected from main assembly  116 . In the example shown in  FIG. 27  and in these variations, main assembly  116  serves as a support structure for seatably receiving the user, i.e., on which the user sits. 
     Exercise Benches 
     Main assembly  116 , variously including pairs of handles  108 ,  110 ,  240 ,  242 , and  250 , serves as an exercise bench in accordance with the invention regardless of whether pedal-revolving mechanism  114 , pedal-translating mechanism  220 , handle-translating mechanism  270 , or a similar exercise mechanism is, or is not, connected to the front or back end of assembly  116 . A user can utilize handles  108 ,  110 ,  240 ,  242 , and  250  variously provided on exercise bench  116  to do various exercises without actuating mechanism  114 ,  220 , or  270  or a similar exercise mechanism. The user can also do exercises on bench  116  without employing any of handles  108 ,  110 ,  240 ,  242 , and  252 . 
       FIG. 28  illustrates a variation  116 V of main assembly  116  configured in accordance with the invention. Main assembly  116 V can be substituted for main assembly  116  in any of the exercise machines of the invention. In addition, main assembly  116 V is particularly suitable for use as an exercise bench. 
     Main assembly  116 V consists of frame  100 , seat  102 , seatback  104 U, connection mechanism  106 U, and handles  108 ,  110 ,  240 ,  242 , and  250  respectively configured, interconnected, and operable as described above except for the connections of short rails  164  and  260  respectively to cross rails  162 A and  162 C in frame  100 . Short rails  164  at the front end of frame  100  are flexibly connected to front cross rail  162 A for enabling short rails  164  to be placed in a retracted (or non-use) position in which they do not extend forward beyond long rails  160 . Short rails  260  at the back end of frame  100  are likewise flexibly connected to back cross rail  162 C for enabling short rails  260  to be placed in a retracted (or non-use) position in which they do not extend backward beyond long rails  160 . Placement of short rails  164  and  260  in their retracted positions facilitates use of main assembly  116 V as an exercise bench. 
       FIG. 28  depicts the situation in which flexibly connected short rails  164  and  260  are in their retracted positions. Because short rails  164  and  260  are thereby hidden by long rails  160  when main assembly  116 V is viewed from the side, short rails  164  and  260  do not appear in the side view of  FIG. 28 . Short rails  164  are in an extended (or use) position when they extend fully forward beyond the front ends of long rails  160 . Short rails  260  are similarly in an extended (or use) position when they extend fully backward beyond the back ends of long rails  160 . When short rails  164  and  260  are in their extended positions, frame  100  of main assembly  116 V appears substantially as shown in  FIG. 22  except for the elements that flexibly connect short rails  164  and  260  respectively to cross rails  162 A and  162 C. 
     The flexible connection of short rails  164  to front cross rail  162 A can be implemented by slidably connecting short rails  164  to front cross rail  162 A so that they can slide in sliding members rigidly connected to cross rail  162 A. The flexible connection of short rails  260  to back cross rail  162 C can likewise be implemented by slidably connecting short rails  260  to cross rail  162 C so that they can slide in sliding members rigidly connected to cross rail  162 C. Pushing short rails  164  and  260  so that they slide to locations fully between long rails  160  places short rails  164  and  260  in their retracted positions. In their retracted positions as viewed from above (or below) frame  100 , most of each of short rails  164  lies between front cross rail  162 A and middle cross rail  162 B while most of each of short rails  260  lies between back cross rail  162 C and middle cross rail  162 B. 
     The flexible connection of short rails  260  to back cross rail  162 C can alternatively be implemented by hingably connecting short rails  260  to cross rail  162 C. When seatback  104 U is turned sufficiently upward, short rails  260  can be rotated upward around respective hinges attached to back cross rail  162 C and then downward so that they end up in a retracted position largely between cross rails  162 C and  162 B as viewed from above frame  100 . If seat  102  can be readily removed from frame  100 , the flexible connection of short rails  164  to front cross rail  162 A can likewise alternatively be implemented by hingably connecting short rails  164  to cross rail  162 A. Short rails  260  can then be rotated upward around respective hinges attached to front cross rail  162 A and downward so that they similarly end up in a retracted position largely between cross rails  162 A and  162 B as viewed from above frame  100 . 
     Regardless of how short rails  164  and  260  are respectively flexibly connected to cross rails  162 A and  162 C, locking members hold short rails  164  and  260  in place when they are in their extended and retracted positions. When short rails  164  or  260  are locked in their extended positions, main assembly  116 V is suitable for receiving pedal-revolving mechanism  112 , pedal-translating mechanism  220 , handle-translating mechanism  270 , or another exercise mechanism at the front or back end of frame  100  to produce variations of the present exercise machines. 
       FIGS. 29 a  and 29 b    (collectively “ FIG. 29 ”) illustrate another variation  116 W of main assembly  116  configured in accordance with the invention. As with main assembly  116 V, main assembly  116 V can be substituted for main assembly  116  in any of the present exercise machines. Additionally, main assembly  116 W is especially suitable for use as an exercise bench whose upper surface is in the vicinity of 30-50 cm above the surface on which assembly  116 W is situated. 
     Main assembly  116 W consists of frame  100 , seat  102 , seatback  104 U, connection mechanism  106 U, and handles  108 ,  110 ,  240 ,  242 , and  250  respectively configured, interconnected, and operable as in main assembly  116 V subject to modification of frame  100  to include a set of retractable frame legs that enable the top of seat  102  to be roughly 30-0.50 cm above the underlying surface when the legs are in their extended (or use) positions.  FIG. 29  illustrates two such retractable frame legs  290 A and  290 B (collectively “legs  290 ”). Each of frame legs  290  is shaped generally like a “U” with a generally straight cross member connecting the two side members of the “U”. The two side members of leg  190 A are respectively flexibly connected, typically by hinges (not shown), to the bottoms of long rails  160  near front cross rail  162 A. The two side members of leg  190 B are respectively flexibly connected, likewise typically by hinges (also not shown), to the bottoms of long rails  160  near back cross rail  162 C. 
       FIG. 29 a    depicts how main assembly  116 W appears when frame legs  290  are in their retracted (or non-use) positions so that the two side members of each of legs  290  respectively lie against, or nearly against, long rails  160 . Frame feet  168  extend further downward than legs  290  when they are in their retracted positions. Legs  290  are switched to their extended positions by rotating them approximately 90° downward away from middle cross rail  162 B.  FIG. 29 b    depicts how assembly  116 W appears when legs  290  are in their extended positions so that the two side members of each of legs  290  extend downward approximately perpendicular to long rails  160 . The bottoms of the cross members of legs  290  may be configured to inhibit legs  290  from slipping on the underlying surface. Locking members (not shown) hold legs  290  in place when they are in their retracted and extended positions. 
     When main assembly  116 V or  116 W serves as an exercise bench, a user can utilize exercise bench  116 V or  116 W in performing various exercises. More particularly, the user can utilize handles  108 ,  110 ,  240 ,  242 , and  250  to do various exercises in which user&#39;s hands respectively grip handles  108 ,  110 ,  240 ,  242 , or  250 . Seatback  104 U can be in the inclined or flat position. When seatback  104 U is in the inclined position, the user can be seated on bench  116 V or  116 W with the user&#39;s back lying against seatback  104 U so that the user&#39;s abdominal muscles are exercised by swiveling seatback  104 U about swivel axis  122 . One or more of the pairs of handles  108 ,  110 ,  240 ,  242 , and  252  may also be readily removed from bench  116 V or  116 W to facilitate doing exercises which do not involve those particular handles  108 ,  110 ,  240 ,  242 , or/and  250 . 
       FIGS. 30 a -30 c    illustrate three examples of exercises performed with exercise bench  116 W while seatback  104 U is in the flat position and short rails  164  and  260  and legs  290  are in their respective retracted positions. In the exercise of  FIG. 30 a   , user  200  is in a crawl position with the lower parts of user&#39;s legs  206  on top of bench  116 W. User  200  moves upper seatback handles  110  with user&#39;s hands  210  to exercise user&#39;s arms  212 . The exercise of  FIG. 30 b    involves moving front seat handles  240  while user&#39;s back  202  is top of bench  116 W with user&#39;s legs  206  above user&#39;s torso  208 . The exercise of  FIG. 30 c    is the same as that of  FIG. 30 b    except that user&#39;s legs  206  move back and forth. The exercises of  FIGS. 30 b  and 30 c    exercise user&#39;s arms  212 , user&#39;s legs  206 , and the user&#39;s abdominal muscles. User  200  can perform the exercises of  FIGS. 30 a -30 c   , or exercises similar to those of  FIGS. 30 a -30 c   , by gripping others of handles  108 ,  110 ,  240 ,  242 , and  252  than those gripped in  FIGS. 30 a -30 c    and/or with the user&#39;s body oriented opposite to what is shown in  FIGS. 30 a   - 30   c.    
     A user can also utilize exercise bench  116 V or  116 W to do exercises that do not involve moving any of handles  108 ,  110 ,  240 ,  242 , and  252 .  FIGS. 31 a  and 31 b    examples of such exercises performed with exercise bench  116 W while short rails  164  and  260  are in their retracted positions and frame legs  290  are in their extended positions. In the exercise of  FIG. 31 a   , user&#39;s back  202  is on top of bench  116 W while seatback  104 U is in the flat position. In the exercise of  FIG. 31 b   , seatback  104 U is in the inclined position with user  200  seated on bench  116 W so that user&#39;s back  202  lies against seatback  104 U. User&#39;s hands  212  move free weights  290  of the dumbbell type in both exercises to exercise user&#39;s arms  212 . 
     Variations 
     While the invention has been described with reference to particular embodiments, this description is solely for the purpose of illustration and is not to be construed as limiting the scope of the invention as claimed below. For instance, the openings in the tines at the remote end of axial bar  186 , the openings at the ends of support rod  128 , and openings  172  in frame channel portion  166  that adjustably and flexibly receives the frame-associated end of rod  128  in seatback-to-frame/seat connection mechanism  106  or  106 U need not be circular. In that case, pins  192  and  194  need not be circular cylinders. 
     Channel portion  166  of frame  100  can be replaced with a further rail having a plurality of openings respectively corresponding to the pairs of oppositely situated openings  172  in portion  166 . The openings in the further rail define corresponding interface connection locations at which the frame-associated end of support rod  128  can be adjustably and flexibly connected to the rail via a frame-associated pin, such as pin  194 , that passes through the opening in the frame-associated end of rod  128  and through any selected one of the openings in the rail. Similar to how the remote end of axial bar  186  is configured, the frame-associated end of support rod  128  can also split into a pair of tines through which a pair of oppositely situated openings respectively extend. In that case, support rod  128  is adjustably and flexibly connected to the further rail via a pin that passes through both openings in the frame-associated end of rod  128  and through one of the openings in the rail. 
     The roles of the ends of support rod  128  in regard to how they are connected to axial bar  186  and frame  100  can be reversed. That is, the seatback-associated end of rod  128  can be adjustably and flexibly connected to axial bar  186  by configuring bar  186  so that its remote end can flexibly receive the seatback-associated end of rod  128  at any one of a plurality of seatback-associated flexible connection locations. This can be achieved by providing the remote end of axial bar  186  with a plurality of openings respectively corresponding to the connection locations. Alternatively, the remote end of axial bar  186  can be configured as a channel member, similar to channel portion  166 , having a plurality of pairs of oppositely situated openings where each pair of the oppositely situated openings defines a different one of the connection locations. 
     When the connection roles of the ends of support rod  128  are reversed, rod  128  is flexibly connected to axial bar  186  at any selected one of the seatback-associated connection locations via a pin the passes through the opening in the frame-associated end of rod  128  and through one of the openings in the remote end of bar  186  or, if its remote end is configured as the just-mentioned channel member, through one of the pairs of oppositely situated openings in the channel member. If the remote end of axial bar  186  simply has a plurality of openings corresponding to the connection locations, the seatback-associated end of support rod  128  can alternatively split into a pair of tines through which a pair of oppositely situated openings respectively extend. Support rod  128  is then adjustably and flexibly connected to axial bar  186  via a pin that passes through both openings in the seatback-associated end of rod  128  and through one of the openings in bar  186 . 
     A ball-joint arrangement can be used in place of seatback-associated pin  192  for flexibly connecting support rod  128  to axial bar  186  when rod  128  is to be flexibly connected to bar  186  at only one location. Likewise, a ball-joint arrangement can be used in place of frame-associated pin  194  for flexibly connecting support rod  128  to frame  100  when rod  128  is to be flexibly connected to frame  100  at only one location. 
     The seatback-associated end of support rod  128  can be adjustably and flexibly connected to axial bar  186  at any one of a plurality of seatback-associated flexible connection locations while the frame-associated end of rod  128  is adjustably and flexibly connected to frame  100  at any one of a plurality of frame-associated flexible connection locations. These adjustable and flexible connections for both ends of support rod  128  can be done in any of the ways described above. 
     Instead of adjustably connecting pedaling mechanism  112  or  220  or handle-translating mechanism  270  to main assembly  116 ,  116 V, or  116 W via openings  174  in short rails  164  or via openings  262  in short rails  260 , one side of each short rail  164  or  260  can be provided with teeth. The tooth-containing sides of short rails  164  or  260  can, for example, be the sides facing away from the longitudinal center of frame  100 . Distance-adjustment knobs  152 ,  238 , or  288  then have internal extensions provided with respective cog wheels whose cogs engage the teeth of short rails  164  or  260 . Knobs  152  ,  238 , or  288  are turned to turn the cog wheels for adjusting the connection of pedaling mechanism  112  or  220  or handle-translating mechanism  270  to frame  100  of main assembly  116 ,  116 V, or  116 W. The connection is adjusted while knobs  152  ,  238 , or  288  are pulled upward slightly. For any selected adjustment, the connection is locked by pressing knobs  152  ,  238 , or  288  downward sufficiently to engage a locking mechanism. 
     In the examples of handles  108 ,  110 ,  240 ,  242 , and  250  shown in the drawings, each of handles  108 ,  110 ,  240 ,  242 , and  250  is open-ended and generally shaped like an “L”. One leg of each of handles  108 ,  110 ,  240 ,  242 , and  250  extends approximately along its handle axis (See  FIGS. 5, 17, and 23 ) and thus rotates about that axis. Instead of being turned about handle axes, seat handles  108  and  240  can pivot about respective ball joints (not shown) connected to seat  102  or/and frame  100 . Similarly, frame handles  242  can pivot about respective ball joints connected to frame  100  rather than being turned about handle axes. Seatback handles  110  and  250  can pivot about respective ball joints connected to seatback  104  or  104 U or/and connection mechanism  106  or  106 U instead of being turned about handle axes. 
     Handles  108 ,  110 ,  240 ,  242 , and  250  can have other shapes and can be positioned differently than described above. For instance, some or all of handles  108 ,  110 ,  240 ,  242 , and  250  can be closed-ended. Seatback handles  110  can be received along the top edge of seatback  104  or  104 U or/and along the top of connection mechanism  106  or  106 U. 
     For the situation in which seatback handles  110 , seat handles  240 , or frame handles  242  turn around axes, the average distance from handles  110 ,  240 , or  242  to another exercise machine part has been described above as being measured from those axes. More generally, the average distance from handles  110 ,  240 ,  242  to another exercise machine part is measured from the average location of the common center of mass of handles  110 ,  240 , or  242  to that other exercise machine part. These two ways of measuring distance from handles  110 ,  240 , or  242  produce largely the same distance value when handles  110 ,  240 , or  242  turn about axes. 
     Similar generalizations apply to the above statement that the average distance from foot pedals  140  to another exercise machine part is measured from pedaling axis  150 , to the above statement that the average distance from foot pedals  224  to another machine part is measured from translator reference line  236 , and to the above statement that average distance from translatable handles  274  is measured from translator reference line  286 . That is, the average distance from pedals  140  or  224  to another exercise machine part is more generally measured from the average location of the common center of mass of pedals  140  or  224  to that other exercise machine part. The average distance from handles  274  to another exercise machine part is likewise more generally measured from the average location of the common center of mass of handles  274  to that other exercise machine part. 
     The dimensions of frame  100  may be adjusted to better accommodate users of varying heights or to accommodate users considerably shorter or taller than typical adult users. For instance, short rails  164  can be in the vicinity of 60 cm long so that they extend forward approximately 50 cm beyond the front ends of long rails  160 . The length of short rails  260  can be increased similarly. 
     Structures other than frame legs  290  of “U” shape can be used to enable the top of seat  102 U to be in the vicinity of 30-50 cm above the underlying surface when main assembly  116 W serves as an exercise bench. For instance, the cross member of each frame leg  290  can be deleted so that the two side members become a pair of separate legs. Alternatively, each frame leg  290  can be furnished with one or more additional cross members that connect the leg&#39;s side members. Frame feet  168  can be provided with legs that collapse when suitable leg-locking members are released. Frame feet  168  and frame legs  290  can be viewed as separate elements from frame  100 . 
     Frame legs  290  can be replaced with adjustable retractable legs that enable the top of seat  102  to be placed at any of two or more distances above the surface underlying main assembly  116 W. Since the top of seat  102  is at a further distance above the underlying surface when the adjustable retractable legs are fully retracted, the combination of frame feet  168  and the adjustable retractable legs enables the top of seat  102  to be placed at any of three or more distances above the underlying surface. Frame legs  290  can also be replaced with legs that are readily removable from frame  100 . 
     A user can exercise in the crouched, crouched-to-prone, and largely prone positions using pedal-revolving mechanism  112  similar to how user  200  respectively exercises in those positions using pedal-translating pedaling mechanism  220 . Various modifications and applications may thus be made by those skilled in the art without departing from the true scope of the invention as defined in the appended claims.