Abstract:
An exerciser including a movable body support mounted on an exerciser frame for movement along tracks provided by the frame. A movable foot support extends from the exerciser frame. The movable foot support is adapted to be engaged by the user&#39;s feet to absorb the energy of movement in a first direction and to provide the user with a bouncing movement, which the user may translate into a movement of the movable body support in the opposite direction. The movable foot support may be provided as an attachment and retrofitted to existing exercisers, and, in some embodiments, may comprise independently movable foot supports for each foot. The exerciser may include a resilient resistance system coupled to the movable body support and a set of pull lines with user grips trained over pulleys carried by the exerciser frame. Also disclosed are methods for enabling users to exercise.

Description:
RELATED APPLICATIONS 
     This application is based on U.S. Provisional Application No. 60/668,970 filed Apr. 7, 2005, the entire contents of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to methods of exercising and to exercise apparatuses for carrying out those methods. 
     2. Description of Related Art 
     One of the consistent challenges in the fitness industry is devising exercise methods and apparatuses that allow the user to achieve maximum, diverse fitness effects by performing exercises in comfortable positions. For example, a type or set of exercises may be particularly attractive and beneficial to the user if it provides strengthening, toning and cardiovascular benefits. Exercise equipment used to perform fitness exercises should ideally be relatively simple in construction, flexible in the types of exercises allowed, and adaptable to a wide range of resistances and levels of exertion. 
     A popular type of exercise equipment provides a pair of generally parallel tracks, on which a carriage is mounted for sliding or rolling movement along the tracks. Depending on the particular variation, the carriage may be connected to a resistance system including one or more resilient members, such as springs or bungee cords, which bias the carriage towards a particular position. The carriage may also be connected to pull cords that are trained over a pulley system, allowing the user to move the carriage by pulling the pull lines. The user exercises with such an apparatus by using the arms or legs to move the carriage along the tracks. 
     Sliding-carriage multi-function exercise equipment of this type also typically includes a foot rest or foot bar which extends in a direction generally perpendicular to the rails. The foot rest or foot bar is operationally fixed in position, and allows a user to control the movement of the carriage by exerting his or her leg muscles against it. A foot rest typically includes a set of frame members or frame portions that are adapted to connect at a first end to either the rails of the apparatus or other appropriate structures provided for that purpose. At their respective second ends, the frame members are attached to a rigid member, such as a board. The board is typically covered with a layer of foam or other cushioning material, which may be enclosed in a layer of outer material, such as vinyl. The foam and outer material cushion the user&#39;s feet to some degree and provide traction. 
     A foot bar is a generally U-shaped and typically hollow bar that is adapted to be connected to the exercise apparatus at its ends. The top portion of the foot bar is covered with a traction/cushioning material. The user typically places his or her hands or feet on the cushioned portion of the foot bar to control the movement of the carriage. 
     One variation of the above-described type of exercise apparatus is disclosed in U.S. Pat. No. 5,967,955, which is incorporated herein by reference in its entirety. The disclosed apparatus includes a movable carriage mounted on generally parallel tracks and a foot rest of the type described above. The apparatus does not use resilient members to provide resistance; instead, resistive bias is provided by inclining the tracks at one of a number of angular orientations, thereby allowing the user to move the carriage by working against a corresponding fraction of his or her own weight bias under the influence of gravity using a pulley system that is coupled to the carriage. As the angular orientation of the carriage changes, the fraction of the user&#39;s weight bias changes correspondingly, such that at greater inclinations, the weight bias that the user works against is greater. 
     Another variation of the above-described type of exercise apparatus is that sold under the general name Pilates Performer™ (Stamina Products, Inc., Springfield, Mo., United States) for use with the Pilates exercise system. An apparatus of this type is shown in U.S. Pat. No. D. 382,319 to Gerschefske et al., the contents of which are incorporated by reference in their entirety. The apparatus includes a frame having a pair of generally parallel tracks that support a movable carriage which is mounted on the tracks with rollers for rolling horizontal movement along the tracks. A set of tensile resilient resistance elements is connected to the frame at one end and to the carriage at the other, thereby biasing the carriage towards a particular position. A pulley system and associated pull lines are coupled to the carriage, such that the carriage may be moved by application of force to the pull lines. A foot bar is provided at one end of the frame, and shoulder blocks are provided at one end of the carriage, allowing the user to position him or herself in a supine position to move the carriage against the resilient bias provided by the tensile resilient resistance elements using the muscles of either the legs or the arms. 
     There have been proposed in the prior art other types of exercisers that provide support for the user in a fixed seated position with a movable back support. See, for example, U.S. Pat. Nos. 5,215,511 and 5,897,459. Still others provide for fixed support of the user while on his or her back. See, for example, U.S. Pat. Nos. 6,206,809 and 6,500,099. U.S. Pat. No. 5,445,583 discloses two different exercisers. The  FIG. 1-8  embodiment provides support for the user in a fixed seated position with a tiltingly adjustable back support. The  FIG. 9-11  embodiment provides three modes of operation, one of which is seat supportive as in the  FIG. 1-8  embodiment. The other two modes of operation include (1) a standing mode and (2) a “floating” mode where the user&#39;s seat is unsupported enabling the user to “float” while his or her back is supported on an inclined freely movable back rest and his feet push against movable foot pedals. 
     The present invention relates to a combination of method steps and exerciser components which co-act together to enable a user to perform cardiovascular friendly aerobic exercises while movably supported in a supine position. The exercises can be said to simulate running in soft sand. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention relates to a method of enabling a person to exercise comprising the following steps. Providing a movable body support for the exercising person which supports the seat and back of an exercising person in a supine position which allows the body of the exercising person while in supported relation to move with the movable body support with the feet of the exercising person free to be moved with respect to the movable body support. Providing a movable foot assembly separate from said body support in a position to be engaged by the feet of the exercising person supported on the movable body support. Providing for the absorption of the energy of the movement of the movable body support in a first direction away from the movable foot assembly by the exercising person supported thereon and the conversion of the absorbed energy to a movement of the movable body support with the exercising person supported thereon in a second direction toward the movable foot assembly. Providing for the damped resiliently resisted movement of the movable foot assembly caused by the engagement thereof by the feet of an exercising person moving with the movable body support in said second direction. Establishing as a result of the damped resiliently resisted movement of the movable foot assembly in said second direction, a damped resilient return movement by the movable foot assembly in the first direction, which the exercising person can translate into a movement of the movable body support in the first direction, the arrangement being such that the exercising person can control the repetition and magnitude of the movements of the movable body support by flexure of the legs at the knees. 
     Another aspect of the present invention relates to an exerciser comprising the following combination of components. A frame assembly. A movable body support disposed on the frame assembly and constructed and arranged to support the seat and back of an exercising person in a supine position which allows the body of the exercising person while in supported relation to move with the movable body support with the feet of the exercising person free to be moved with respect to said movable body support. A movable foot assembly coupled to the frame assembly and constructed and arranged to be engaged by the feet of the exercising person supported on said movable body support. The movable body support being mounted on said frame assembly for movement in a first direction away from said movable foot support and a second direction toward said movable foot support and being constructed and arranged to absorb the energy of a movement thereof in the first direction by a user supported thereon and to convert the absorbed energy into a movement thereof with the user supported thereon in the second direction. The movable foot assembly being constructed and arranged to yield resiliently with a damping action in response to the engagement of the feet of the exercising person moving with the movable body support in the second direction and to establish, as a result of the damped resilient yielding, a resiliently damped movement return by the movable foot assembly in the first direction which can be translated by the exercising person into a movement of the movable body support in the first direction. 
     Other aspects of the invention will become apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the following drawings, in which like numerals represent like features throughout the figures, and in which: 
         FIG. 1  is an exploded perspective view of one embodiment of an exerciser embodying the principles of the present invention; 
         FIG. 2  is a side elevational view of the exerciser of  FIG. 1 ; 
         FIG. 3  is a fragmentary elevational view of the foot end of the exerciser of  FIG. 1 ; 
         FIG. 4  is a view similar to  FIG. 3  showing a variation in the construction of the movable foot assembly embodying the principles of the present invention; 
         FIG. 5  is a perspective view of another embodiment of an exerciser embodying the principles of the present invention; 
         FIG. 6  is a side elevational view of the exerciser of  FIG. 5  in a first operative position; 
         FIG. 7  is a side elevational view of the exerciser of  FIG. 5  in a second operative position; 
         FIG. 8  is a perspective view of an exerciser according to a further embodiment of the invention; 
         FIG. 9  is a perspective view of the underside of a portion of the exerciser of  FIG. 8 , illustrating the movable foot assembly of the exerciser; and 
         FIG. 10  is a longitudinal cross-sectional view of a spring and shock absorber unit suitable for use in the exerciser of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a perspective view of an exerciser, generally indicated at  10 , according to one embodiment of the invention. The exerciser  10  is generally of the type shown in U.S. Pat. Des. 382,319, which was incorporated by reference above. The exerciser  10  includes a frame assembly, generally indicated at  12 , a movable body support, generally indicated at  14 , disposed on the frame structure  12  in a position to support the seat and back of the user in a position which allows the body of the user while in supported relation to move with the movable body support  14  with the feet of the user free to be supported with respect to the movable body support  14 , and a movable foot assembly, generally indicated at  16 , constructed and arranged to be mounted on the frame structure  12  in a position to be engaged by the feet of the user while movably supported on the movable body support  14 . 
     The frame assembly  12  includes a frame  18 , which is adapted to support the movable body support  14 , with the user supported thereon. The frame  18  also includes a stand  20 , which is adapted to connect to the frame  18  to hold the frame  18  in a generally horizontal plane above floor level. As is shown in  FIG. 1 , an exploded perspective view of the exerciser  10 , the stand  20  comprises a plurality of legs  22  connected at respective upper ends thereof by cross bars  24 , such that the stand portion  20  is comprised of generally rectangular or trapezoidal segments having legs  22  disposed at the corners of the segments. End caps  26  of a rubber or other non-skid material may be provided at floor-contacting ends of the legs  22 . Upper receptacle sections  28  of the stand  20  are adapted to receive corresponding mating structures provided on the underside of the frame  18  (not shown in the Figures), so as to operatively secure the frame  18  to the stand  20 . The legs  22  of the stand  20  may be of any length that provides a convenient user height for the frame portion  18 . 
     Depending on the embodiment, the frame  18  and stand  20  may be separable, so that the exerciser  10  can be stored easily. Additionally, the stand  20  may be omitted or sold separately, particularly if the height provided by the stand  20  is not required for the exercises that are to be performed. Moreover, it may be desirable to construct the stand  20  such that one end is wider than the other. A stand  20  with one wider end and one narrower end may be desirable if one end of the exerciser  10  requires a broader base of support to prevent lateral tipping, or if the exerciser  10  is constructed such that the stand  20  will only mate with the frame  18  if the frame  18  is in a particular orientation. 
     The frame  18  is comprised of two generally parallel support tracks  30 , connected and braced by a number of cross members. Each of the support tracks  30  has a generally C-shaped cross-section, such that each support track  30  defines an interior track  32 , in the shape of a channel, which is adapted to receive engaging portions of the movable body support  14 . The engaging portions of the movable body support  14  in this embodiment are rollers  33  (shown in phantom in  FIG. 2 ) that rollingly engage interior tracks  32 . The rollers  33  are mounted to the underside of the movable body support  14  on appropriately-sized lateral projections, and allow the movable body support  14  to roll along the support tracks  30  between limiting portions of the support tracks  30 . The limiting portions of the support tracks  30  define the extent of travel for the movable body support  14 . In the exerciser  10 , one of the limiting portions is a crossbar  34  that extends between the two support tracks  30 ; the other limiting portion is defined by an endpiece  36  of the frame portion  18 . Alternatively, the limiting portions may simply be the ends of the grooves  32  in the support tracks  30 . 
     Although rollers  33  are used in the illustrated embodiment, a number of bearings and other movement support structures are known in the art, and any one of these known types of bearings may be used in place of the rollers. For example, instead of rollers, blocks of low-friction material may be used, and the inside tracks  32  in the support tracks  30  may be lubricated in order to facilitate sliding movement with reduced friction. 
     The support tracks  30  may be continuous bars that run the length of the exerciser, or they may be comprised of sets of shorter bars which are secured together by welds or fasteners. As shown in  FIG. 2 , each support track is comprised of two shorter support bars  38 ,  40 . At one end, each shorter support bar  38 ,  40  connects to an endpiece  36 ,  37  to form an end of the frame  18  of the exerciser  10 . (The endpieces  36 ,  37  of the illustrated embodiments are bars covered with decorative plastic moldings, but they may be made in other configurations.) At the other ends of the shorter support bars  38 ,  40 , cooperating hinge structure  42  is provided, such that the shorter support bars  38 ,  40  may be hingedly connected together in a manner which allows the exerciser  10  to be folded when not in use. 
     In alternative embodiments of the invention, the support tracks may have a substantially rectangular cross section, and a movable body support with rollers or other movement support structures may be configured so as to rest on top of the support tracks, rather than engaging inside tracks defined within them. The precise manner of engagement of the movable body support and the support tracks is not critical. 
     Several body-engaging components are mounted on the movable body support  14  so as to facilitate the body positioning of the user. Two padded shoulder blocks  44 , one on each side of the body support  14 , extend vertically, and are positioned so as to engage the upper portion of the user&#39;s torso (i.e., at the collarbone or shoulder region) when the user is lying prone or supine on the movable body support  14 , so as to prevent the user from sliding relative to the movable body support  14  in a direction away from the foot support  16 . The shoulder blocks  44  may be removably attached to the movable body support  14 , for example, by a threaded connection. 
     A padded head rest  46  is also mounted on the movable body support  14 . In the position illustrated in  FIGS. 1 and 2 , the head rest  46  is positioned such that its user-contacting surface is generally horizontal and co-planar with those of the movable body support  14 . However, the head rest may be mounted on a multi-position bracket, such that its angular position may be adjusted relative to that of the movable body support so as to support the user&#39;s head in an inclined position. In addition to the head rest  46 , torso pad  48  is mounted on the movable body support  14  so as to cover a substantial portion of the movable body support  14  to provide traction and comfort. 
     When the user is lying on the movable body support  14  in a supine position with his or her head on the head rest, the user&#39;s feet are free from the movable body support  14 , and extend in a direction toward the movable foot assembly  16 . As can be seen in  FIGS. 1-3 , in one example, the movable foot assembly  16  includes a foot contact portion  404  connected to a vertically extending support  406  by compression springs  408  and a piston and cylinder damper unit  409 . The foot contact portion  404  extends horizontally forward from the vertically extending support  406 . Several variations of this are possible: in the top plan view of  FIG. 4 , a movable foot assembly  402  has two foot contact portions  410 , each foot contact portion  410  being sized to accommodate one of the user&#39;s feet, whereas in the top plan view of  FIG. 3  and in  FIGS. 1 and 2 , the foot contact portion  404  is a unitary structure sized to accommodate both feet. In each case, the foot contact portions  404  and  410  would be provided with a layer of foam or other padding material  414  to provide comfort and traction for the user&#39;s feet. Those of skill in the art will note that the exercising motion enabled by the foot support  402  is similar to the exercising motion enabled by the foot support  16 . 
     The movable foot assembly  16  and movable foot assembly  402  are both in a position to be engaged by the feet of an exercising person supported on the movable body support  14 . The body support  14  is mounted so as to absorb the energy of the movement of the movable body support  14  in a first direction away from the movable foot assembly  16 ,  402  by the exercising person supported thereon and to convert the absorbed energy to a movement of the movable body support  14  with the exercising person supported thereon in a second direction toward the movable foot assembly  16 ,  402 . The movable foot support  16 ,  402  provides for the damped resiliently resisted movement of the movable foot assembly  16 ,  402  caused by the engagement thereof by the feet of an exercising person moving with the movable body support  14  in the second direction and establishes as a result of the damped resiliently resisted movement of the movable foot assembly  16 ,  402  in the second direction; a damped resilient return movement by the movable foot assembly  16 ,  402  in the first direction. The exercising person can translate this movement into a movement of the movable body support  14  in the first direction, enabling the exercising person to control the repetition and magnitude of the movements of the movable body support  14  by flexure of the legs at the knees. The movable foot assembly  16  is intended to be moved by both feet whereas the movable foot assembly  402  can be moved by either foot acting alone or both together. 
       FIG. 5  is a perspective view of an exerciser  500  embodying the principles of the present invention. The exerciser  500  includes a frame, generally indicated at  502 . The frame  502  comprises two generally parallel frame members  504  joined at respective ends by front and rear crossmembers  506  and  508 . The frame members  504  define interior tracks  510  in the form of channels that extend substantially the entirety of the length of the frame members  504 . A movable body support  512  is mounted for movement in the tracks  510  by means of rollers (not shown in  FIG. 5 ). The movable body support  512  includes padded shoulder blocks  514  that extend perpendicular to the movable body support  512  and are contoured and arranged to contact the shoulder/clavicular region of the user during exercise motions. A lumbar support  513  is provided as a gently upwardly sloped portion of the movable body support  512 . An adjustable head rest  516  forms a segment of the movable body support  512  beyond the shoulder blocks  514 . In addition, the movable body support  512  provides two fixed L-shaped members  515  that are secured to its underside and extend outwardly and upwardly therefrom. Upper portions of the L-shaped members  515  may be used as hand grips. 
     Toward the front crossmember  506 , an intermediate crossmember  518  extends between the two parallel frame members  504  and limits the motion of the movable body support  512  by acting as a motion stop. In accordance with the principles of the present invention, a movable foot assembly generally indicated at  520 , is mounted between the two parallel frame members  504  and includes a mounting member in the form of a bolt  522  extending through each of the tracks  510  and secured in place by a nut. 
     The movable foot assembly  520  also includes left and right support posts  524  pivotally mounted on the bolt  522  so as to rotate about a pivotal axis extending in a transverse horizontal direction. Typically, the support posts  524  would include apertures of sufficient size to allow the bolt  522  to pass through them such that the support posts  524  are mounted for rotation about the bolt  522 . 
     Each of the support posts  524  includes an upper transversely-extending portion  526 , which would typically be welded or otherwise fixedly secured to the rest of the support post  524 . Pivotally mounted on the transversely-extending portions  526  are the individual left and right foot support pieces  528 , which rotate about pivotal axes defined by the transversely-extending portions  526 . 
     The exerciser  500  is of the type that provides one foot support piece  528  for each foot, which would allow the user to exercise each one of his or her legs individually or in combination, in synchronized, alternating, or random fashion. A shift in weight or pressure from one leg to the other is possible during the exercising motions. Because the individual support pieces  528  are pivotally mounted on the transversely-extending portions  526 , they can assume whatever angle is required to establish or maintain contact with the user&#39;s feet. 
     In accordance with the principles of the present invention, the movable foot assembly  520  provides for the movement of the foot support pieces  528  to be yieldingly resisted with a damping action capable of effecting a resiliently damped return movement when the moving pressure is released by the user. The resiliency is provided by two torsion coil springs  530 , each of which is mounted on the bolt  522  adjacent to one of the support posts  524 . As best shown in  FIG. 5 , a first arm  532  of each torsion spring  530  is received in a channel  534  on the support post  524 ; a second arm  536  of each torsion spring  530  is received in a receiving member  540  that is mounted on the front crossmember  506 . With this mounting arrangement, motion of the support posts  524  in a direction toward the front crossmember  506  is resiliently opposed by the torsion springs  530 . In the absence of any user-applied forces, the support posts  524  are resiliently biased toward the position shown in  FIG. 5  by the torsion springs  530 . The damping associated with each resiliently resisted user movement and resilient return movement is provided by left and right piston and cylinder damper units  541 . As best shown in  FIGS. 6 and 7 , the damper units  541  are connected between lower free ends of the left and right posts  524  and undersides of a forward portion of the frame  502 . 
     The exerciser  500  is supported on a horizontal surface such that it can be inclined at a plurality of angles. Arcuate rocker feet  542  extend on the underside of the frame  502  between the front crossmember  506  and the intermediate crossmember  518 . Each rocker foot  542  can provide good contact with a horizontal surface, such as the floor or a mat, at a plurality of angles. Typically, the rocker feet  542  would be covered with a non-skid material, such as a rubber, to prevent the exerciser  500  from skidding or sliding along the horizontal surface while in use. 
     Two pivotable frame supports  544  support the frame  502  proximate to the rear crossmember  508 . Each frame support  544  is essentially triangular with a rounded bottom portion  546  that is adapted to contact the horizontal surface. The frame supports  544  and rocker feet  542  can be seen more clearly in the side elevational view of  FIG. 6 . Each frame support  544  can pivot about a horizontal pivotal axis defined by a hinge pin  548  supported in a bracket  550  on the underside of the frame  502 . However, in the position illustrated in  FIGS. 5 and 6 , the frame supports  544  are fixed in their illustrated, relatively upright position by a threaded rod that passes through the rear crossmember  508  and releasably engages a crossbar  552  that extends between the two frame supports  544  and secures them relative to one another. A user-accessible knob  553  attached to the threaded rod allows the user to remove it from or insert it into the crossbar  552 , thereby securing or releasing the two frame supports  544 . Once the two frame supports  544  have been released, they can be pivoted counterclockwise (with respect to the coordinate position of  FIGS. 5 and 6 ) to assume the position shown in  FIG. 7 , another side elevational view of the exerciser  500 . 
     As shown in  FIG. 7 , the angle between the frame  502  and the horizontal surface on which it rests has decreased. Additionally, the portions of the frame supports  544  and the rocker feet  542  that engage the horizontal surface have changed. The position of the exerciser  500  shown in  FIG. 7  is a stable position and a user may exercise in it. 
     The exerciser  500  also includes a set of wheels  554  rotatably mounted on wheel extensions  556  that extend forwardly from the front crossmember  506 . In the positions illustrated in  FIGS. 6 and 7 , the wheels  554  are not in contact with the horizontal surface and do not allow the exerciser  500  to be moved. However, if the user tilts the exerciser  500  so that the wheels  554  are in contact with the horizontal surface, the wheels  554  allow for easy movement of the exerciser  500 . 
     The angle between the frame  502  and the horizontal surface on which it rests determines the degrees to which the energy of the user movement of the movable body support  512  in a direction away from the movable foot assembly  520  is absorbed and then converted into a movement of the movable body support  512  in the opposite direction toward the movable foot assembly  520 . The angle adjustment system described provides for two different absorption and conversion levels. Other adjusting systems may be provided instead which provide for a multiplicity of adjusted positions within a range of positions. In the two level system described, the energy of user movement is absorbed and converted into a return movement by gravity acting on the users weight supported by the movable body support  512 . Preferably, this gravitational action is supplemented by a resilient multiple removable bungee cord system of the type well known in pilates exercisers. Such a system is shown in  FIGS. 5 and 8  as embodying four bungee cords  558  of different resilient resistance removably connected to the frame cross member  518  and to the movable body support  512 . While both adjustments are preferred, it is within the contemplation of the present invention to utilize either without the other. 
     As was noted above, the resiliency of the foot supports of exercisers according to the present invention may be created in a variety of ways.  FIG. 8  is a perspective view of an exerciser  600  according to another embodiment of the present invention. Many of the components of the exerciser  600  are identical to those found in the exerciser  500 ; therefore, the description above will suffice for those components which are designated by the same reference numerals. 
     The primary difference between the exerciser  500  and the exerciser  600  is in the resilient damping system connected to the support posts  624 . Instead of torsion springs  530  and damper units  541 , the exerciser  600  uses two combination spring and damper units  630  mounted on the underside of the front crossmember  606 .  FIG. 9  is a perspective view of the underside of the exerciser  600  proximate to the front crossmember  606 , showing the units  630  and their attachment in more detail. As before, the piston rods  631  of the units  630  are pivotally connected to short lever arms  632 , forming lower free ends of the support posts  624 . 
     With the units  630  connected to the lever arms  632  below the foot support mount member  520  (about which the support posts  624  pivot), the overall arrangement is such that a movement of the support posts  624  forward (clockwise with respect to  FIG. 8 ) results in an extension of the piston rods  631  of the units  630 . The action of the units  630  is such that resilient restorative force is provided to retract the shaft  631  of the unit  630  and thereby to return the support post  624  to its original position (i.e., that illustrated in  FIG. 8 ) when the shaft  631  of the unit  630  is extended. 
     As those of skill in the art will appreciate, spring and shock absorber units  630  could also be attached to points on the support posts  624  that are above the foot support mount member  520 , in which case the “sense” of the motion would be reversed and the shaft of the unit would need to retract upon forward motion of the support post  624  and resiliently extend to return the support post  624  to its original position. Other types of connections between the support posts  624  and the units  630  may also necessitate motion of the “sense” opposite that illustrated in  FIGS. 8 and 9 . 
     The particular type and internal arrangement of the units  630  is not critical to the invention. Many types of spring and shock absorber units are known in the art and may be used or adapted for use in exercisers according to the present invention. For example, U.S. Pat. Nos. 5,622,527 and 5,071,115 disclose exemplary types of hydraulic cylinders that may be used as shocks in exercisers according to the present invention, and the disclosure in those two references that pertains to hydraulic cylinders is hereby incorporated by reference. 
     The units  630  of the exerciser  600  would generally comprise a damper (i.e., hydraulic or gas cylinder with restricted orifices to control the flow between chambers in the cylinder or across the piston) in parallel with a conventional compression or tension spring. The spring may be placed inside or outside of the cylinder. If the spring is outside of the cylinder, it may be axially coextensive with the cylinder. 
       FIG. 10  is a longitudinal cross-sectional view of one suitable type of unit  630  that may be used in the exerciser  600  of the present invention. The unit  630  combines resistive structure and biasing structure in a single cylinder having a central axis  632 . The unit  630  holds a compressible coil spring  634  between the piston  636  and the cylinder end piece  638  of the cylinder  640 , which biases the shaft  631  to resiliently retract and return to the position shown in  FIG. 19  when extended. 
     Piston  636  is shown as having a peripheral shoulder  642  within which spring  634  is registered to maintain its alignment within cylinder  640 . The piston  636  includes a peripheral O-ring  644  for sealing the piston within the cylinder  640 . The piston  636  is shown fixed to a threaded  646  reduced diameter portion  648  of shaft  631  by a locknut  650 . A collar  652  is fitted on reduced diameter portion  652 , and retains a check valve spring  654  on the reduced end  656 . The spring  654  holds washer  656  against the piston  636  to overcover the orifices  658 , preventing oil flow through the orifices  658  when the pressure on the washer side  660  of the piston is higher than the pressure on the opposite side  662 . Orifices  664  permit fluid flow in both directions. 
     Cylinder end piece  666  is attached to the cylinder  640  as by welding. The end piece  666  is shown with a circular slot  668  in its exterior face into which seal spring  670  fits. Seal spring  670  maintains pressure on shaft seal  672  to prevent leakage from the outer chamber  674 . An orifice  676  in the end piece  638  permits pressure equalization across the end piece  638  so that seal  672  does not become overpressurized. An orifice  678  in cylinder  640  permits pressure equalization between the cylinder  640  and chamber  674 . 
     The exercisers  500 ,  600  illustrated in  FIGS. 5-9  are of the sort that might be used primarily in the home, because they are relatively lightweight, simple in construction, and capable of being moved and stored. However, certain adaptations to the exercisers  500 ,  600  are advantageous if the exercisers are to be used in a professional setting. For example, in a professional setting, it is advantageous if the damping/resistance provided by the units  630  can be user controlled so as to provide a more or less intense workout depending on the user&#39;s fitness level. This may be accomplished, for example, using the type of unit shown in U.S. Pat. No. 5,071,115. In more “advanced” embodiments, the variable restriction valve or other control structure within the unit  630  could be placed under computer control and manipulated electrically (e.g., in the case of a solenoid valve) or electromechanically/hydraulically (e.g., in the case of a traditional restricted orifice). In either case, an interface would be provided, allowing the user to select the amount of resistance. Additionally, instead of the two position frame supports  544 , the exercisers  500 ,  600  could include supports that are hydraulically or electromechanically controllable to produce a user desired incline angle from a continuous range of possible incline angles. If the exerciser  500 ,  600  includes both variably adjustable resistance levels and a variably adjustable incline, the controls and interface for the two features, as well as the control lines or hydraulic fluid lines may be integrated into one set of controls and conduits. 
     The exercisers according to the present invention provide several advantages. First, the user can perform exercises in a supine or prone position, which is usually at least perceived to be more comfortable by the user. Second, the type of exercises that can be performed on exercisers according to the invention may have cardiovascular, strength, and flexibility benefits. Third, as was described above, certain known types of exercises, such as Pilates exercises, may be performed on exercisers according to the invention, if desired by the user. 
     Although the invention has been described with respect to certain embodiments, those of ordinary skill in the art will realize that modifications may be made within the scope of the invention.