PATENT DOCUMENT

Abstract:
A ski exercising apparatus has a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the track, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one articulated footpad mounted to the wheeled carriage, and at least one power band providing constraint for the wheeled carriage as it rides on the track. A variety of improvements in such an exercising apparatus are taught and claimed.

Full Description:
CROSS-REFERENCE TO RELATED DOCUMENTS  
       [0001]     The present application claims priority as a divisional of patent application Ser. No. 10/447,014 file on May 27, 2003 which is a continuation in part application of application Ser. No. 09/533,614, filed Mar. 22, 2000 (now U.S. Pat. No. 6,569,064 issued on May 27, 2003. The present application is also related in part to U.S. Pat. No. 5,147,257 issued on Sep. 15, 1992 and filed on Sep. 4, 1990, which is a divisional of U.S. Pat. No. 4,953,853 issued on Sep. 4, 1990 and filed on Apr. 6, 1988, which is a continuation-in-part of U.S. Pat. No. 4,743,014 issued on May 10, 1988 and filed on Jul. 30, 1987. The present application is also related to U.S. Pat. No. 5,020,793 issued on Jun. 4, 1991 filed on Oct. 24, 1989, which is also a continuation-in-part of U.S. Pat. No. 4,743,014. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to exercising apparatus for a user to simulate the motions, exertions and techniques involved in skiing, and for rehabilitation that simulates the range of motion and balance required in many sports, while providing modality for dynamic balance and functional rehabilitation, thereby increasing the user&#39;s strength and skill, and more particularly to improvements in such apparatus.  
       BACKGROUND OF THE INVENTION  
       [0003]     Apparatus for use by skiers on which they may simulate the motions, exertions and techniques required in skiing has been built and sold for several years. In particular U.S. Pat. No. 3,524,641 was issued to Robert J. Ossenkop on Aug. 18, 1970, for a device comprising a movable carriage on a set of rails. The carriage of that device is constrained in its movement on the rails by flexible members attached to both the carriage and to transverse members between the rails near each end of the set of rails, and a user can move the carriage from side to side on the rails to simulate the Wedeln or “parallel” technique of skiing.  
         [0004]     U.S. Pat. No. 3,547,434 was issued to the same inventor on Dec. 15, 1970. This later patent is for a device similar to the first device, but comprising a number of improvements, such as movable footrests on the carriage whereby a user may simulate turning and edging techniques in addition to parallel skiing; and, in some embodiments may also move the feet relative to one another.  
         [0005]     The inventions referenced above each include a safety strap attached to a transverse member between the parallel rails and to the carriage on the rails in addition to the flexible member by which the carriage is constrained to travel on the rails. The purpose of the safety strap is to provide for a situation in which the aforementioned flexible member might rupture on one side of the carriage, providing a sudden force urging the carriage to the side where the flexible member remains unruptured, which sudden force could dislodge a user and perhaps cause serious injury. The safety strap in such instance provides a restoring force toward the center tending to lessen the amplitude of carriage displacement that might otherwise occur.  
         [0006]     In U.S. Pat. No. 4,743,014, to which this case is related, and by the same inventor, an exerciser is disclosed having a pair of spaced-apart rails, a platform for riding on the rails, a first resilient element providing a first restoring force on the platform, and a second resilient element providing a second restoring force on the platform. The second resilient element has an adjustment element contacting the second resilient element in at least three points.  
         [0007]     In the latter exerciser, the rails are held in a spaced-apart relationship by a brace element in the center, which is fastened to the rails by screw-type fasteners, and by transverse elements fastened at the ends of the rails. The transverse elements at the ends are tubular in form, and the rails pass through openings in the tubular transverse elements, fastening to a bracket internal to each tubular transverse element. This joining arrangement is illustrated by  FIG. 1A  and  FIG. 1B  of the referenced patent. As shown in these figures rails  301  and  303  pass through holes  305  and  307  respectively into tubular transverse element  309 . Inside, the rails are fastened to a bracket  311  by screw fasteners  313  and  315 . Rubber-like end caps  317  and  319  close the ends of the tubular transverse element after assembly and act as non-skid pads in contact with the floor in operation. The end caps are of molded rubber-like material, and disk-like pieces carrying designs and lettering are added for identification and aesthetic effect. This particular method of joining and spacing the rails has not proved entirely satisfactory in terms of cost and ease of assembly, and in terms of strength and rigidity of assembly, and the multiple-piece construction of the end caps has also proved to be relatively expensive.  
         [0008]     In U.S. patent application Ser. No. 09/533,614, (hereinafter &#39;614), to which the present application is related, a ski-exercising machine is provided comprising a set of at least two parallel rails joined to cross members at the ends, the cross members providing support on a horizontal support surface, and joined to a central frame structure extending from the horizontal surface near the center to the rails, the rails extending from each cross member at each end upward at an acute angle with the horizontal rising to a maximum height in the center; a wheeled carriage riding on the rails; at least one articulated footpad mounted to the wheeled carriage; and a set of three power bands each anchored at both ends by a clamp to a bottom surface of the frame structure beneath the wheeled carriage, passing over separate roller sets, with one or more of the power bands anchored to the wheeled carriage and one or more passing over a roller anchored to the wheeled carriage.  
         [0009]     Although related U.S. patents issued to the inventor address the above problem and other problems related to construction and function of various components of the parent ski exerciser, there are still non-obvious improvements desired in several areas related to construction or assembly techniques, profile, materials, operation and longevity of the apparatus. For example, in U.S. Pat. No. 5,147,257 (hereinafter &#39;257), in  FIG. 5A and 5B , a ski exerciser is illustrated both in an elevation view ( FIG. 5A ), and in a plan. view (overhead  FIG. 5B ). Arcuate rails  15  comprise tubing structures having a continuous arc or bow over their entire length.  
         [0010]     Additionally, further non-obvious improvements are desired in several areas related to tension adjustability of the power bands, band roller operation, positioning of individual footpads on the wheeled carriage, simulation of actual skiing movements and dynamics, as well as rehabilitation and versatility of the skiing apparatus to simulate range of motion and balance required in many sports other than downhill skiing. Still further improvements are desired in areas relating to safety aspects of apparatus to minimize the possibility of injury to the user.  
         [0011]     It has been discovered partly through empirical methods that an even better action may be simulated with rails shaped somewhat differently than in the prior art. Firstly, the arcuate portions of the parallel rails can be shortened, and the straight portions lengthened to provide more intensity in the simulation of the skiing action. Secondly, the inventor has discovered that further adjustability of the power bands, in addition to footpad positioning, pivoting and sliding action, provide more accurate skiing motion simulation than the apparatus in the referenced prior art.  
         [0012]      FIG. 5A  in &#39;257 illustrates roller assemblies housing rollers such as rollers  25  and  27  which are identical in size and construction with other illustrated rollers which make rolling contact with resilient members  23  and  59 . The diameter of the aforementioned rollers is disclosed as approximately 1 inch, and the rollers are generally cylindrical. It has been discovered that larger rollers, also crowned have a beneficial effect in smoother power band operation. The crowned rollers keep the belts better centered on the rollers.  
         [0013]     The present inventor has also determined that improvements may be made in the positioning of wheels for the wheeled carriage, and in the form of the rails and how the wheels interface to the rails.  
         [0014]      FIG. 16  in &#39;614 illustrates a ski exercising apparatus  301  according to an embodiment of the present invention having an optional third power band assembled between the first, or outer power band, and the second, or inner, power band, and a pair of tensioning structures ( 303  and  304 ), each having a single roller assembly rotatably mounted to the tensioning structure such that consistent tension is provided to the wheeled carriage assembly given a specific range of motion of the carriage assembly.  
         [0015]     What is clearly needed is a modularly enhanced ski-excising device that provides further distinct advantages for the expanding field of users. Such an improved device could provide further adjustability of power band tension, and additional pivoting action for suspended footpad assemblies to provide a more realistic simulation of skiing movements and dynamics in varying skiing terrain. What is also clearly needed is an improved method and apparatus enabling the user to quickly interchange footpad assemblies of a wheeled carriage assembly having additional attachments for rehabilitation and selective body strengthening, which simulates the range of motion and balance required in many sports other than downhill skiing, accurately reproducing lateral movements required in most sports, thereby optimizing rehabilitation and helping to prevent injury to the user. Such an improved apparatus incorporates additional safety features, which further protect the user from injury during operation of the exercise apparatus.  
       SUMMARY OF THE INVENTION  
       [0016]     In a preferred embodiment of the present invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the track, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one articulated footpad mounted to the wheeled carriage, and a set of three power bands. The apparatus is characterized in that the power bands are arranged concentrically, with an outer, an inner, and a middle band, joined at one point each to the wheeled carriage and at at least two points each to the underlying frame structure, and in that the attachment of the middle power band to the underlying frame structure is through a pair of adjustment mechanisms having two rollers each, the adjustment mechanisms attached to the underlying frame structure on each side of center.  
         [0017]     In a preferred embodiment, in each adjustment mechanism, the middle power band passes under one of the rollers and around the other. Also in a preferred embodiment the roller which the middle band passes around can be fixed at any one of at least three positions in the adjustment mechanism, each position at a different distance from the center of the apparatus, to adjust tension on the middle band.  
         [0018]     In another aspect of the invention, in a mechanism for mounting a roller between two vertical walls spaced apart by a first distance, the roller for restraining and guiding a power band for a ski exercising apparatus having a wheeled carriage rolling on partially arcuate rails, the power band affixed to the carriage and passing around a roller in the mechanism, an improved roller axle is provided, comprising a first element including an axle portion of a first diameter and a length equal to the first distance, having a concentric threaded hole on a first end, an engagement portion concentric with the axle portion, of a length equal to a thickness of one of the walls, and larger in diameter than the axle portion to match a diameter of a hole in the one of the walls, and a head portion concentric with the axle portion and larger in diameter than the hole, for inserting through the hole and extending the axle portion between the two walls, and a second element including a head portion equivalent to the head portion of the first element and an engagement portion equivalent to the engagement portion of the first element, and also including a male threaded portion extending from the engagement portion for mating with the concentric threaded hole of the first element, the second element for inserting through a hole in the other of the two walls, equivalent to the hole ion the first of the two walls, and for engaging with the first element to form an axis for a roller to be mounted between the walls, and also for stabilizing and strengthening the mechanism.  
         [0019]     In yet another aspect of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the track, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one articulated footpad mounted to the wheeled carriage, and at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track. This apparatus is characterized in that the rails have a central arcuate portion of a width of twelve inches or less, joined to straight portions on each side of the arcuate portion, the straight portions extending at equal angles downward and outward from the central arcuate portion to the underlying frame structure. In a preferred embodiment the apparatus is characterized in that the overall height of the track above the underlying frame structure is a least ten inches.  
         [0020]     In still another aspect a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, and a slide plate mounting to the wheeled carriage for providing attachment of elements interfacing to a human user. This apparatus is characterized in that the slide plate comprises spaced apart rounded parallel rails extending in the direction of movement of the wheeled carriage, the rails for engaging rounded grooves of one or more separate elements to be mounted to the slide plate.  
         [0021]     In another preferred embodiment the apparatus is characterized in that the slide plate further comprises a plurality of holes arranged in linear matrix in the direction of the extension of the rails, the holes for selective positional mounting of the separate elements to be mounted. In another one or more spring-loaded pin extensions extend from the slide plate to act as safety retainers for the separate elements joined to the slide plate by engaging with the rounded rails.  
         [0022]     In still another preferred embodiment a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, a substantially linear slide plate having spaced apart rounded rails extending in the direction of movement of the wheeled carriage, the slide plate mounting to the wheeled carriage, and at least one attachment plate having rounded grooves spaced-apart compatibly with the rounded rails, the attachment plate mounted to the linear slide plate by engaging the rounded grooves of the attachment plate with the rounded rails of the slide plate.  
         [0023]     In this apparatus there may two attachment plates in a preferred embodiment. Further, attachment plates may comprise a normally extended spring pin, which, by being retracted, allows the attachment plate to be translated along the rails of the slide plate, and by being allowed to extend, engages a hole in the slide plate to position the attachment plate on the slide plate.  
         [0024]     In yet another embodiment a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, a substantially linear slide plate having spaced apart rounded rails extending in the direction of movement of the wheeled carriage, the slide plate mounting to the wheeled carriage, at least one attachment plate having rounded grooves spaced-apart compatibly with the rounded rails, the attachment plate mounted to the linear slide plate by engaging the rounded grooves of the attachment plate with the rounded rails of the slide plate, and a foot pad attached to the attachment plate for engaging a user&#39;s foot to operate the apparatus. Also in a preferred embodiment there are two attachment plates engaging the slide plate and two foot pads, one attached to each attachment plate. In some embodiments the foot pad comprises a planar portion for engaging a user&#39;s foot at a first height, and a pivot axis at a second height above the first height, such that the plane of the planar portion may rotate as the carriage descends from side to side.  
         [0025]     In still another aspect of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, and a handgrip apparatus joined to the wheeled carriage, enabling a user to grasp the handgrip apparatus and operate the exercising apparatus. Also in a preferred embodiment the handgrip apparatus provides two handgrips, one for each of a user&#39;s hands, spaced apart in the direction of translation of the wheeled carriage on the track. In some embodiments the handgrip apparatus provides four handgrips in two sets of two, one set provided at a height higher than the other set. In still other embodiments apparatus of further comprising a substantially linear slide plate having spaced apart rounded rails extending in the direction of movement of the wheeled carriage, the slide plate mounting to the wheeled carriage, and at least one attachment plate having rounded grooves spaced-apart compatibly with the rounded rails, the attachment plate mounted to the linear slide plate by engaging the rounded grooves of the attachment plate with the rounded rails of the slide plate, the handgrip apparatus attached to the attachment plate.  
         [0026]     In yet another aspect of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, and at least one substantially planar interface for a user&#39;s feet joined to the wheeled carriage by a linear translation mechanism allowing limited free motion of the interface in a direction at substantially a right angle to direction of travel of the wheeled carriage on the track. Also in a preferred embodiment the exercising apparatus comprises two planar interfaces for a user&#39;s feet, each joined to the wheeled carriage by a linear translation mechanism allowing limited free motion for each interface in a parallel direction at substantially a right angle to direction of travel of the wheeled carriage on the track. In other embodiments the linear translation mechanism comprises a foot-pad carriage mounted on rollers riding in linear slots in the translation mechanism. In still other embodiments the exercising apparatus comprises a substantially linear slide plate having spaced apart rounded rails extending in the direction of movement of the wheeled carriage, the slide plate mounting to the wheeled carriage, and at least one attachment plate having rounded grooves spaced-apart compatibly with the rounded rails, the attachment plate mounted to the linear slide plate by engaging the rounded grooves of the attachment plate with the rounded rails of the slide plate, the translation mechanism attaching to the attachment plate.  
         [0027]     In still another aspect of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, and at least one substantially planar interface for a user&#39;s feet joined to the wheeled carriage by an arcuate translation mechanism allowing limited arcuate motion of the interface about a pivotal axis located at a height greater than the height of the footpad and extending in the direction of motion of the wheeled carriage. Also in a preferred embodiment the exercising apparatus comprises two planar interfaces for a user&#39;s feet, each joined to the wheeled carriage by an arcuate translation mechanism allowing limited arcuate motion of the interface about a pivotal axis located at a height greater than the height of the footpad and extending in the direction of motion of the wheeled carriage. In other embodiments the arcuate translation mechanism comprises a foot-pad carriage mounted on rollers riding in arcuate slots in the translation mechanism. Also in other embodiments there may be a substantially linear slide plate having spaced apart rounded rails extending in the direction of movement of the wheeled carriage, the slide plate mounting to the wheeled carriage, and at least one attachment plate having rounded grooves spaced-apart compatibly with the rounded rails, the attachment plate mounted to the linear slide plate by engaging the rounded grooves of the attachment plate with the rounded rails of the slide plate, the arcuate translation mechanism attaching to the attachment plate.  
         [0028]     In still another embodiment of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, and at least one substantially planar interface for a user&#39;s feet joined to the wheeled carriage by a linear translation mechanism allowing limited free motion of the interface in a direction at substantially a right angle to direction of travel of the wheeled carriage on the track, and by a curvilinear translation mechanism allowing limited arcuate motion of the interface about a pivotal axis above the height of the footpad and extending in the direction of motion of the wheeled carriage. Also in a preferred embodiment thee exercising apparatus comprises two planar interfaces for a user&#39;s feet, each joined to the wheeled carriage through both of the linear and arcuate translation mechanisms. In other embodiments the linear and arcuate translation mechanisms may comprise carriages mounted on rollers riding in separate linear and arcuate slots in the translation mechanism. In still other the exercising apparatus may further comprise a substantially linear slide plate having spaced apart rounded rails extending in the direction of movement of the wheeled carriage, the slide plate mounting to the wheeled carriage, and at least one attachment plate having rounded grooves spaced-apart compatibly with the rounded rails, the attachment plate mounted to the linear slide plate by engaging the rounded grooves of the attachment plate with the rounded rails of the slide plate, the arcuate translation mechanism attaching to the attachment plate.  
         [0029]     In still another preferred embodiment of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, and a system for monitoring travel of the wheeled carriage in operation.  
         [0030]     In some preferred embodiments the system for monitoring comprises an endless tether attached to the carriage and passing over rollers mounted to the underlying frame structure at points spaced to either side from center. In other preferred embodiments the system for monitoring further comprises a sensing roller turned by the tether as the carriage translates, the sensing roller enabled to provide a signal proportional to the direction and extent of rotation of the sensing roller. The sensing may be accomplished by interruption of an optical sensor. Further, the rollers mounted to the underlying frame structure may be integrated with rollers provided for anchoring and guiding the at least one power band.  
         [0031]     In yet a further embodiment of the invention there is an electronic system including a display for compiling and displaying movement statistics related to the exercising apparatus. In this system input and output elements of the electronic system, including the display, are located at a position observable by and accessible to a user of the apparatus.  
         [0032]     In still another preferred embodiment of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, a support frame mounted to the underlying frame structure, providing a support bar in a convenient position for a user to grasp by hands for support during use of the exercising apparatus, and an elastic tether system including an anchor point to the exercising apparatus and an attachment interface for a user&#39;s body, the tether system for imposing variable tension on the user&#39;s body while operating the exercising apparatus.  
         [0033]     In preferred embodiments the elastic tether system includes at least one pulley through which the tether passes between the user and the anchor point. Also in some preferred embodiments the anchor point is to the support frame to one side of the user, and the pulley is mounted to the support frame to the other side of the user. The attachment interface to the user&#39;s body may comprise a band for mounting to one of a user&#39;s upper leg, knee, or lower leg.  
         [0034]     In yet another preferred embodiment of the invention a ski exercising apparatus is provided, comprising a set of at least two parallel, partially arcuate rails joined to an underlying frame structure at opposite ends, the rails providing a track rising from each end, a wheeled carriage riding on the rails, such that the carriage, in side-to-side movement rises to a maximum height at the center of the track, and descends from the center to each side, at least one power band attached to the carriage and engaging mechanisms mounted to the underlying frame structure at opposite sides of center of the track, at least one substantially planar interface for a user&#39;s feet joined to the wheeled carriage, and a set of two flag mechanisms joined to the underlying frame structure at opposite ends of the structure, each flag mechanism having a mechanical interface activated by contact with the wheeled carriage in operation, such that the user may see the flag of either of the flag mechanisms move each time contact is made with the wheeled carriage. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0035]      FIG. 1A  is an elevation view of a frame structure of a ski-exercising device according to an embodiment of the present invention.  
         [0036]      FIG. 1B  is a cross section taken along line  1 B- 1 B of  FIG. 1A .  
         [0037]      FIG. 2  is a plan view of the frame structure of  FIG. 1  with added components illustrated according to an embodiment of the present invention.  
         [0038]      FIG. 3  is a perspective view of a center portion of the structure of  FIG. 1  with covering components removed.  
         [0039]      FIG. 4  is a perspective view of a wheeled carriage-assembly shown without an upper carriage according to an embodiment of the present invention.  
         [0040]      FIG. 5  is a perspective view of an upper carriage-assembly supporting a suspended footpad mounted according to an embodiment of the present invention.  
         [0041]      FIG. 6  is an elevation view of a wheeled carriage-assembly and mounted foot platforms according to an embodiment of the present invention.  
         [0042]      FIG. 7A  is perspective broken-view of a portion of a rail, transverse end member, and end-cap according to an embodiment of the present invention.  
         [0043]      FIG. 7B  is an elevation view of an end-side of the end cap of  FIG. 7A .  
         [0044]      FIG. 7C  is an elevation view of a bottom-side of the end cap of  FIG. 7B .  
         [0045]      FIG. 8  is a perspective view illustrating various components of a quick-release roller assembly according to an embodiment of the present invention.  
         [0046]      FIG. 9A  is a plan view of an elongated footpad and carriage-assembly according to an embodiment of the present invention.  
         [0047]      FIG. 9B  is an elevation view of the footpad and carriage assembly  FIG. 9A .  
         [0048]      FIG. 10  is an elevation view of the frame structure of  FIG. 1  illustrating roller-band tensioning hardware according to an embodiment of the present invention.  
         [0049]      FIG. 11A  is a broken view of a potion of toothed rails and a toothed gear of  FIG. 10  according to an embodiment of the present invention.  
         [0050]      FIG. 11B  is an elevation view of the handle assembly of  FIG. 10 .  
         [0051]      FIG. 11C  is an elevation view of the rail-guide bracket of  FIG. 10 .  
         [0052]      FIG. 11D  is a right-side view of the bracket of  FIG. 11C .  
         [0053]      FIG. 11E  is a broken view of a portion of the bottom toothed-rail, roller, and bracketed roller-mount of  FIG. 10 .  
         [0054]      FIG. 11F  is a broken view of the bottom toothed-rail, roller, and bracketed roller-mount of  FIG. 10  as seen from an overhead vantage.  
         [0055]      FIG. 12  is a perspective view of an adjustable double footpad module according to an embodiment of the preset invention.  
         [0056]      FIG. 13A  is a plan view and  FIG. 13B  is a side view of a slotted base-plate according to an embodiment of the present invention.  
         [0057]      FIG. 13C  is an end-view of the slotted cam-rod of  FIG. 12 .  
         [0058]      FIG. 14  is a cross-sectional view of a main wheel, a keeper wheel, and a semi-arcuate rail according to an alternate embodiment of the present invention.  
         [0059]      FIG. 15  is a cross section of an integral captive rail and wheel arrangement in an embodiment of the present invention.  
         [0060]      FIG. 16  is an elevation view of a ski-exercising device illustrating an optional third power band according to another embodiment of the present invention.  
         [0061]      FIG. 17  is an elevation view of a ski-exercise device illustrating adjustable tensioning structures for an optional third power band according to an embodiment of the present invention.  
         [0062]      FIG. 18A  is an elevation view of an adjustable tensioning structure of  FIG. 17 , and a roller axle.  
         [0063]      FIG. 18B  is an elevation end view of the adjustable tensioning structure and roller axle of  FIG. 18A  and a roller axle nut.  
         [0064]      FIG. 19  is an elevation view of a frame structure of the ski-exercising device of  FIG. 17 .  
         [0065]      FIG. 20A  is a top view of an adjustable mounting plate according to an embodiment of the present invention.  
         [0066]      FIG. 20B  is a section view of the mounting plate of  FIG. 20A  taken along section line  20 B- 20 B.  
         [0067]      FIG. 21A  is a top view of a sliding attachment plate according to an embodiment of the present invention.  
         [0068]      FIG. 21B  is a section view of the sliding attachment plate of  FIG. 21A  taken along section line  21 B- 21 B.  
         [0069]      FIG. 22  is a top view of the mounting plate of  FIG. 20A  and a pair of sliding attachment plates of  FIG. 21A  according to an embodiment of the present invention.  
         [0070]      FIG. 23  is an elevation view of a suspended footpad assembly and the sliding attachment plate of  FIG. 21A .  
         [0071]      FIG. 24  is an elevation view of the footpad assembly and attachment plate of  FIG. 23  and the mounting plate of  FIG. 20A  attached to a carriage assembly according to an embodiment of the present invention.  
         [0072]      FIG. 25A  is a top view of the mounting plate and attachment plates of  FIG. 22 , a pair of suspended footpad assemblies of  FIG. 24  and a carriage assembly according to an embodiment of the present invention.  
         [0073]      FIG. 25B  is an elevation view of the mounting plate, attachment plates, suspended footpad assemblies and carriage assembly of  FIG. 25A .  
         [0074]      FIG. 26A  is an elevation view of an upper body conditioner (UBC) elevated grip according to an embodiment of the present invention.  
         [0075]      FIG. 26B  is a top view of the UBC elevated grip of  FIG. 26A .  
         [0076]      FIG. 27A  is a top view of a UBC lower grip according to an embodiment of the present invention.  
         [0077]      FIG. 27B  is a side elevation view of the lower grip shown in  FIG. 27A .  
         [0078]      FIG. 28A  is a top view of the mounting plate, attachment plates and carriage of  FIG. 25A , and a pair of UBC elevated grips and a pair of UBC lower grips affixed to the attachment plates according to an embodiment of the present invention.  
         [0079]      FIG. 28B  is an elevation side view of the mounting plate, attachment plates, carriage, UBC elevated grips and UBC lower grips of  FIG. 28A .  
         [0080]      FIG. 29A  is a top view of a footpad pivot base according to an embodiment of the present invention.  
         [0081]      FIG. 29B  is an elevation side view of the footpad pivot base of  FIG. 29A .  
         [0082]      FIG. 29C  is an elevation end view of the footpad pivot base of  FIG. 29A .  
         [0083]      FIG. 30A  is an elevation end view of a footpad pivot support structure according to an embodiment of the present invention.  
         [0084]      FIG. 30B  is an elevation side view of the footpad pivot support structure of  FIG. 30A .  
         [0085]      FIG. 30C  is a top view of the footpad pivot support structure of  FIG. 30A .  
         [0086]      FIG. 31A  is a top view of a pivot roller base assembly according to an embodiment of the present invention.  
         [0087]      FIG. 31B  is an elevation end view of the pivot roller base assembly of  FIG. 31A .  
         [0088]      FIG. 31C  is an elevation side view of the pivot roller base assembly of  FIG. 31A .  
         [0089]      FIG. 32A  is an elevation view of the footpad pivot base of  FIG. 29B , footpad pivot support structure of  FIG. 30B  and the pivot roller base assembly of  FIG. 31B  according to an embodiment of the present invention.  
         [0090]      FIG. 32B  is an elevation end view of the footpad pivot base, footpad pivot support structure, and pivot roller base assembly of  FIG. 32A .  
         [0091]      FIG. 33A  is an elevation view of a roller axle assembly according to an embodiment of the present invention.  
         [0092]      FIG. 33B  is an elevation end view of the roller axle assembly of  FIG. 33A .  
         [0093]      FIG. 34  is an elevation side view of a cable-securing axle according to an embodiment of the present invention.  
         [0094]      FIG. 35  is an elevation side view of an optical sensor assembly according to an embodiment of the present invention.  
         [0095]      FIG. 36  is an elevation view of the frame structure of  FIG. 17 , the carriage assembly, mounting plate, attachment plate, and suspended footpad assemblies of  FIG. 25A , and sensor system according to an embodiment of the present invention.  
         [0096]      FIG. 37  is a top view of the carriage assembly, mounting plate, attachment plate, suspended footpad assemblies, and sensor system of  FIG. 37 .  
         [0097]      FIG. 38  is a perspective view of an adjustable flag assembly according to an embodiment of the present invention.  
         [0098]      FIG. 39  is an elevation view of the carriage assembly, mounting plate, attachment plate, suspended footpad assemblies, and sensor system of  FIG. 38  incorporating a pair of flag assemblies of  FIG. 36  according to an embodiment of the present invention.  
         [0099]      FIG. 40  is an elevation view of the carriage assembly, mounting plate, attachment plate, suspended footpad assemblies, sensor system and flag assemblies of  FIG. 39 , incorporating a progressive resistance cord system according to an embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0100]     It is the object of the present invention to provide a ski exercising apparatus similar to that apparatus covered in cross-related documents above that is modularly enhanced such that, among other improvements, changing applications on the apparatus may be performed with minimal effort. It is also an object of the present invention that the above apparatus be generally and innovatively improved to accomplish a goal of maintaining a light weight while increasing strength and durability of the apparatus. A further object of the present invention is to provide such an apparatus as described above having a lower profile, improved safety features, and having fewer assembly parts with which to contend. It is also an object of the present invention to more accurately simulate the motions and dynamics of skiing in terrain, which varies in steepness, bumpiness and other aspects of the terrain, as well as skiing in such terrain at varying speeds and aggressiveness. Yet another object of the present invention is to provide a ski apparatus having a monitoring system integrated therein which provides the user with information pertaining to the workout in order to enable the user to best utilize the apparatus and maximize effectiveness of the workout or training. Such information may include elapsed time from start to finish of the workout, goal determination and accomplishment, energy or calories expended by the user, speed of turns, side travel distance of the wheeled carriage, and so on. It is still further an object of the present invention to provide such a ski exercising apparatus which, when used with special attachments and other new and novel apparatus, becomes a versatile rehabilitation and training tool that simulates the range of motion and balance required in many sports other than downhill skiing. Such an apparatus is enabled for selectively stretching, strengthening or rehabilitating specific areas of the body, core stabilization, balance training and many other aspects of selected training and exercise. Such an apparatus and system accurately reproduces the lateral movements required in most sports, thereby optimizing rehabilitation and helping to prevent injury to the user. Such a ski-exercising apparatus is described in enabling detail below.  
         [0101]      FIG. 1  is an elevation view of a frame structure  11  of a ski-exercising apparatus  9  according to an embodiment of the present invention. Apparatus  9  is provided having a generally similar frame-architecture to previously described exercisers disclosed in related U.S. patents issued to the inventor except for novel improvements that are described below. For the purpose of clarification, only a frame structure  11  of apparatus  9  is described in this embodiment. Additional components not seen here are described later in this specification.  
         [0102]     In a preferred embodiment of the present invention, frame structure  11  comprises a pair of semi-arcuate rails  22  that are held parallel to each other and are affixed at either end of each rail to a pair of transverse end-members  27 . As this is an elevation view, only one of the pair of rails is seen. The spacing and parallelism is seen in plan view  FIG. 2 . This arrangement of rails  22  affixed to members  27  forms the basic frame-structure  11  of apparatus  9 . One notable difference between semi-arcuate rails  22  and the fully arcuate rails disclosed in related patents such as rails  15  of U.S. Pat. No. 5,147,257, is as the respective descriptors imply. That is, as in  FIG. 1A , rails  22  are arced only in their center portions  23  and illustrated by a dimensional notation E. The dimension lines associated with portion  23  mark the locations where the arced portion of each rail  22  ends at positions sharing an equal distance from a theoretical vertical center of rails  22 .  
         [0103]     The total distance E in a preferred embodiment is approximately 26 inches, defined as that portion of each rail  22  that is arced. The stated arc of arcuate portion  23  has a radius of approximately 76 inches although a somewhat higher or lower radius may be used in other embodiments. Non-arcuate portions of rails  22  are witnessed by element numbers  19  and  21  on the left and right side of apparatus  9  as seen in this view. The lengths (taken horizontally) for rail portions  19  and  21  are approximately 15 inches respectively. Rail portions  19  and  21  are substantially straight from their junctures with arcuate portion  23 . The dimensions cited above are intended to be approximate only. When including an approximate 2.36-inch (6 cm) diameter for each transverse member  27 , the approximate overall length of frame structure  11  is about  61  inches. Semi-arcuate rails  22  may be manufactured from heavy-gauge steel tubing as described in U.S. Pat. No. 5,147,257. In one embodiment, rails  22  may be made of extruded steel or aluminum bars rather than steel tubing, and rails may be solid or hollow in different embodiments. Such rails may often also be formed in a forming die to manufacture tracks.  
         [0104]     Solid aluminum bars may in some circumstances offer more strength than steel tubing in terms of flexing or bending while retaining a lightweight characteristic. Moreover, such bars may be extruded to comply with varied shapes as may be desired, and may also be produced in hollow configurations. In this particular embodiment, rails  22  are solid and round in cross-section (rods). The semi-arcuate design and solid structure of rails  22  adds considerable strength and durability causing less flex when rails are in use. It is not specifically required that rails  22  be of round cross-section in order to practice the present invention. The inventor intends merely that keeping a round cross-section consistent with previously used steel tubing is consistent with conventional wheels used on wheeled-carriage assemblies such as carriage  11  described in U.S. Pat. No. 5,147,257.  
         [0105]     In another embodiment, rails  22  may be extruded and then die-formed to a shape that may conform to an alternate wheel design. Such an embodiment is described later in this specification. The size of rails  22  is approximately 2.5 cm. (1-inch) in diameter as is consistent with previous related embodiments. However, this should not be construed as a limitation in diameter but only a preference in balancing durability with lightweight characteristics. Other diameters for rails  22  are plausible. Transverse members used in an embodiment where rails are aluminum will also be made of aluminum tubing to facilitate welding. However, where rails are steel tubing or rods, transverse members will typically be manufactured from steel tubing. A durable polymer coating is applied to all visible parts and surfaces of apparatus  9  in order to provide a resistance to corrosion and for appearance purposes.  
         [0106]     The straight portions of rails  22  to each side of arcuate portion  23  provide a carriage movement in operation that more nearly simulates an actual skiing experience, as has been testified to by users of the apparatus.  
         [0107]     In a preferred embodiment of the present invention, rails  22  are welded to transverse members  27  to form a one-piece truss-frame insuring long life and durability along with ease of assembly of associated elements. However, many fastening methods are known and practiced in the art and could also be used to affix rails  22  to transverse members  27 . The frame structure  11  of apparatus  9  also comprises belt guides  24  located in a substantially centered and parallel position in-between rails  22  and welded, at opposite ends, to transverse members  27  and to a support frame member  31  supporting the rails in the centered arcuate portion. Belt guides  24  allow a power band such as element  23  of  FIG. 5A  of &#39;257 to be separated from the floor or carpet during operation, thus contributing to longer life and sparing wear and discoloration of the floor or carpet. A belt guide of the type disclosed herein has not been previously taught. A pair of raised ribs  26  running the length of belt guides  24  on each side of member  31  are provided and adapted to allow a power band to avoid contact with the bottom of belt guide  24  further reducing wear and noise.  
         [0108]     Support member  31  is provided for the purpose of lending additional support to the frame structure  11  of apparatus  9 , and for housing mechanisms associated with operation of the exerciser. A structure of the same name is illustrated in  FIG. 5A  (element  55 ) of &#39;257 and member  31  is analogous to that member, but improved in function. For example, support member  31  as illustrated herein, is longer in length than the aforementioned member  55  thereby supporting more area of rails  22 . Support member  31  may be provided as one piece or as a plurality of components welded together such that one single piece is formed. Support member  31  is made wider than previously disclosed support members such that it may be welded in some embodiments to the outside edges of rails  22  instead of having rail-inserted tabs as described with member  55  of  FIG. 5A  in &#39;257. Welding support member  31  to the outside edges of rails  22  increases the strength and durability of frame structure  11 , and allows further improvements described more fully below.  
         [0109]     Support member  31  is further welded to belt guides  24  as previously described, effectively adding these components to frame structure  11  so as to form a single contiguous and integral frame, thereby lending strength, durability, and eliminating assembly requirements. Also welded to support member  31  is a tension-adjustment structure  25 . Structure  25  in this embodiment is a u-shaped structure welded to the bottom of member  31  such that two vertical planes are presented, one on each side of the power band path, with holes for positioning rollers for adjustment of power band tension. The length of structure  25  is such that it extends beyond each side of member  31 , as shown, and guides  24  weld to structure  25 . In this manner structure  25  becomes a part of the overall welded structure  11  adding durable strength to the structure as a whole. Additionally, two roller brackets  34  are illustrated, housing rollers  35  in this embodiment, and these are also welded to transverse members  27  and to belt guide  24 , and are part of frame structure  11  of apparatus  9 . Much assembly is avoided and much durability and strength is added by providing a multi-component but single piece welded frame architecture for apparatus  9  as will readily be appreciated by one with skill in the art.  
         [0110]     A protective resilient, non-skid pad  29  is provided and mounted in a position beneath support member  31 ., Pad  29  may be affixed to support member  31  by gluing, fastening such as by recessed screws, or other known methods. The purpose of pad  29  is to protect floor coverings from contact with support member  31  so as to avoid scratching and the like, as well as to keep apparatus  9  from skidding when in use. This pad also provides service in reducing vibration and noise. Four resilient end-caps  17  are provided to cover the ends of transverse members  27 . End-caps  17  provide non-skid contacts between apparatus  9  and a floor or other support surface.  
         [0111]     Another component illustrated in this embodiment is an optional support frame  14  for a novice user to hold on to for stabilization while using apparatus  9 . Support frame  14 , termed an Assistant Coach by the inventor, comprises a tubing structure  16 , a cross member  13 , and padded gripping areas  15 . Tubing structure  16  may be a one-piece tube bent to form structure  16 , or a combination of straight and curved pieces, which are provided and assembled to form structure  16 . Steel or another form of durable tubing of an approximate 1-inch diameter may be used. Other sizes are also useful.  
         [0112]     Gripping areas  15  (one on each side) may be formed of a durable synthetic material such as a dense polyurethane foam, vinyl, or other materials known for providing a gripping surface to tube handles and the like that are common in the field of exercise equipment. In one embodiment, gripping areas  15  may be removed such as by conventional methods known in the art. In another embodiment, gripping areas  15  are permanent such as sprayed on or glued. Cross member  13  may be manufactured from a durable plastic or other material such as sheet steel or aluminum. Cross member  13  may in some embodiments be welded to tube structure  16 . In other embodiments, other known fastening techniques such as nut and bolt, or metal screws may be used. There are many possibilities.  
         [0113]     Support frame  14  is welded or fastened to two transverse members similar to members  27  but not seen here because of the direction of view (see  FIG. 2  element  49 ). Such members act as an optional extension to transverse members  27  at the rear of apparatus  9 . By removing resilient end-caps  17  from the rear or front of apparatus  9 , support structure  14  may be connected to the transverse members  27  of frame structure  11 . In some embodiments an additional interface and support element is added between elements  11  and  27 .  
         [0114]      FIG. 2  is a plan view of the frame structure  11  of apparatus  9  of FIG. I with added components illustrated according to an embodiment of the present invention. As previously described, support frame  14  is an optional extension to frame structure  11  of apparatus  9 . A user wishing to install support frame  14  simply removes two end caps  17  from the rear of frame structure  11  and connects the support frame. The point of connection for the two structures is illustrated as line  51  at either end of device  9 .  
         [0115]     Transverse members  49  each have a fitting end  52  that is of a smaller diameter over a suitable length than the inside diameter of transverse members  27 . The diameter is small enough so that transverse members  49  may be easily fit into transverse members  27  such that when fully inserted lines  51  are formed representing the joining of each structure. Circular shims (not shown) that are once split through along a longitudinal edge of each shim are used to obtain a snug fit between transverse members  27  and  49 . Such shimming methods are well known in the art. Setscrews (not shown) or other known types of fasteners may be used to secure the installation.  
         [0116]     As seen in this overhead view, power band guides  24  extend from each end of the structure (members  27 ) toward the center and are welded at opposite ends to structure  25 , which in turn welds to member  31  ( FIG. 1A ). Roller brackets  34  are welded to transverse members  27  and to belt guide  24  as previously described above. Two rollers  47  and  45  are illustrated as mounted to tensioning structure  25 . Rollers  47  and  48  are provided and adapted to support a central power band  46 . Likewise, a power band  43  is supported by rollers  35  and  37 . An additional roller (not shown) is provided for further support of power band  46  and is centered in-line and in-between rollers  47  and  45  at a raised position such that a triangular configuration of the three rollers is formed. Power bands  43  and  46  are manufactured of a proprietary rubber compound or similar material as described in U.S. Pat. No. 5,147,257. Aforementioned rollers such as rollers  35  and  37  are manufactured of polypropylene or similar material in a preferred embodiment.  
         [0117]     Tension-adjustment structure  25  acts as a rigid mounting location for rollers  47  and  45 . A plurality of openings provided in collinear arrangement through opposite-facing sides of structure  25  are used to mount rollers  47  and  45  via a quick-release pin-and-shaft mounting technique that is described in detail later in this specification. By removing and re-mounting rollers in different positions on structure  25 , tension adjustments to power band  46  may be affected.  
         [0118]     A wheeled lower carriage assembly indicated as element  33  in  FIG. 2 , but best seen in  FIG. 4 , rides on rails  22 . This carriage is described in further detail below with reference to  FIG. 4 . Foot platforms  39  and  41  are mounted to an upper platform unit  89 , which in turn mounts to the lower wheeled carriage assembly by fasteners  53 . The arrangement of an upper platform for footpads mounting as a unit to a lower wheeled carriage allows different footpad arrangements to be quickly and easily traded on a standard wheeled carriage.  
         [0119]     Center fastener  54  is not used when installing and removing upper foot platforms, because it is a mounting fastener for a power-band roller beneath carriage  33 . A clearance hole is provided in the upper platform for this fastener.  
         [0120]     Foot platforms  39  and  41 , in the arrangement shown, provide a parallel skiing simulation that is one option for mode of operation with apparatus  9 . By swapping upper platforms with different foot interface arrangements the overall apparatus can be quickly adapted to other applications, as will be clearer with following description.  
         [0121]     In the embodiment shown, foot platforms  39  and  41  each have a footpad surface thereon. Footpad surface  38  is affixed to platform  39 , and footpad surface  42  is affixed to platform  41 . Footpad surfaces  38  and  42  are preferably made of a non-skid durable rubber material. Surfaces  38  and  42  may be installed using an adhesive, or other known methods such as screw fasteners or the like. Similarly, other materials may be used instead of rubber as long as a non-skid effect is maintained.  
         [0122]     Rollers  35 ,  37 ,  47 ,  45 , and the previously described roller (not shown) that completes a triangular configuration with rollers  47  and  45  are now significantly larger in diameter than rollers previously disclosed in related applications. Whereas previously disclosed rollers were described as having about a 1-inch (2.5 cm) diameter, the rollers of the present invention have substantially a 2-inch (5 cm) diameter and are crowned. That is, the rollers are somewhat curved on the outer surface that meets the power band, so there is a marginally larger diameter at the center plane of the roller than at the roller edges. This improvement in design ensures that the power bands always remain centered on the rollers, which obviates contact with roller brackets and the like, reducing frictional wear to the power bands, and leads to smoother and quieter operation of apparatus  9 .  
         [0123]      FIG. 3  is a perspective view of the center portion of frame structure  11  of  FIG. 1  with covering components removed to show the elements beneath. As previously described, support member  31  is welded to rails  22 . In this example, a plurality of individual welds  55  is placed symmetrically along the length of support member  31 . There are three welds  55  shown in this example, however, there may be more or fewer such welds without departing from the spirit and scope of the present invention. In one embodiment, a continuous weld may run the entire length of support member  31 . Also in this example, welds  55  are illustrated as being placed from the outside edges (rear-edge welds not visible) of support member  31  to the outside of rails  22 . There are many possibilities regarding number of and location of welds  55 .  
         [0124]     Tensioning structures  25 , as described with reference to  FIGS. 1 and 2 , are welded to belt guides  24  and to support member  31 . Brackets  25  are shown with rollers  47  and  45  mounted thereon. A suitable thickness for the material used to manufacture support member  31  and belt guide  24  is about 3 mm. or ⅛ of an inch. In one embodiment of the present invention, aircraft quality aluminum may replace sheet steel for such components where possible. Using high quality aluminum instead of materials such as steel cited in related applications helps to strengthen frame structure  11  as well as to reduce weight.  
         [0125]     Yet another marked improvement over the prior art is in the method of clamping the ends of power bands. In related documents it is described that the central resilient element has it&#39;s ends clamped at one location while a second resilient element has its ends clamped at locations on either side of the central clamp. Therefore three clamping locations exist for securing the free ends of power bands. In this example, only one clamping location  57  is required. Clamp  57  secures both the ends of power band  43  and those of power band  46  of  FIG. 2 . This method reduces work-steps required to install power bands. A single clamping location also ads considerable safety in that only one clamp must be checked for integrity therefore lessening the possibility of error in set-up. In this particular example, clamp  57  is a bar clamp utilizing two standard hex-head nuts and bolts to effect tightening.  
         [0126]      FIG. 3  also illustrates the positioning of rollers  45  and  47  in structures  25 . The position of the rollers in this embodiment can be changed into any other of the holes in the sides of structures  25  to adjust the tension on the inner power band.  
         [0127]      FIG. 4  is a perspective view of wheeled carriage-assembly  33  shown without an upper foot-platform  89  according to an embodiment of the present invention. As disclosed in related applications such as U.S. Pat. No. 5,147,257, for example, there are four main weight-bearing wheels that are mounted to the carriage body and adapted to make contact on the upper surfaces of rails  22  such that the carriage assembly may ride side-to-side on the rails as urged by a user. The wheels are approximately 2 cm wide and are machined using an ultra high molecular weight (UHMW) long-chain polymer material as described in U.S. Pat. No. 5,147,257. A standard button-head shoulder-bolt (not shown) forms the shaft of each wheel. Ball bearings, washers, a lock washer, and a castle nut complete the assembly components for mounting wheels to the carriage body as described in U.S. Pat. No. 5,147,257.  
         [0128]     As in &#39;257, there are four main wheels that ride on upper surfaces of rails  22 . Two are visible in this embodiment and are represented by element numbers  67  and  68 . The remaining two main wheels are located toward the rear portion of carriage assembly  33  and are therefore hidden from view by carriage body  70 , and are not represented in  FIG. 4  to avoid unnecessary detail. These main wheels are mounted rotationally to carriage body  70 .  
         [0129]     Wheels  67  and  68  in a preferred embodiment are mounted at an approximate  12  degree angle from vertical with the angle toward the space in-between rails  22  such that they make contact with a more inwardly surface of each rail. The rolling surface of each wheel is concave such that the radius across the width of each wheel substantially matches the cross-sectional radius of rails  22 . Wheels  67  and  68  as well as two main wheels that are not visible here are mounted through provided openings strategically located on carriage body  70 .  
         [0130]     In this embodiment, an additional set of four keeper wheels is provided of which two wheels  71  and  69  are visible in this view. Two other keeper wheels are located toward the rear of carriage assembly  33  and are hidden in this view by carriage body  70 . Components forming the shaft and mounting hardware for keeper- wheels  71  and  69  are the same as those already described for wheels  67  and  68 .  
         [0131]     Keeper wheel  71  and  69  are strategically located beneath rails  22  at angled positions that are inverted from the angled positions of main wheels  67  and  68 , and directly below weight-bearing wheels. Two angled mounting brackets  75  and  73  are provided and adapted to secure keeper wheels  71  and  69  by being also mounted to upper wheels  67  and  68 . Wheels at the rear of carriage assembly  33  (not shown) are similarly secured as brackets  75  and  73  run the entire length of carriage assembly  33 .  
         [0132]     In this embodiment brackets  73  and  75  are secured to the upper wheels and the lower wheels, so the lower keeper wheels are positioned by the upper wheels, which are mounted to the carriage body. In other embodiments brackets  73  and  75  may extend further upward and be fastened to the underside of the carriage, such as by rivets or welding. The brackets may, for example, be fastened by any convention joining means. Angled mounting-brackets  75  and  73  assume an inclusive angle of approximately 140 degrees such that each wing is substantially parallel to desired wheel positions when mounted. Ideally, carriage assembly  33  will remain resident on rails  22  when changing applications. This will allow for interchangeability of pre-assembled modules that are complete with selected foot platforms mounted. Upper platforms such as platform  89  of  FIG. 2  may vary in physical appearance depending on the application; however, identical fastening locations allow interchangeability with carriage assemblies such as carriage assembly  33 .  
         [0133]     There are yet additional improvements made to assembly  33  over the prior art. One such improvement is the provision of two clamping locations  63   a  and  65   a  located on the under-surface of carriage body  70  for the outer power band. A clamp bar  63  is illustrated as one of two such clamp bars that are used to secure resilient element  43 . A second clamp bar for clamping location  65   a  is not shown, but may be assumed to be present. Previous embodiments disclosed in related documents describe only one clamping location located directly beneath the center of the carriage assembly. An advantage of having power band  43  clamped in two locations is that noise caused by a resilient element flapping against the underside of the carriage body is eliminated, and the carriage is stabilized even further.  
         [0134]     Roller  59  is a third roller previously described to form a triangular configuration of rollers to support power band  46  of  FIG. 2 . Like all rollers described in this specification, roller  59  is crowned for the purpose of guiding resilient member  46  such that it remains centered on the rollers.  
         [0135]     In this embodiment, roller  59  assumes a position much nearer in proximity to the underside of carriage body  70  than in the cross-referenced patents. This is due in part to the larger diameter (2 inch) attributed to rollers of the present invention as opposed to previously disclosed I inch diameter rollers in related documents. In addition, roller  59  is simply mounted in a position that is nearer the underside of carriage body  70  by means of a roller bracket  61 . This is done to reduce wear caused by resilient members rubbing and slapping against each other, and also, to reduce associated noise. The clearance is carefully designed as well so that, as the roller carriage moves to each side and back on the rails, the slack portion of the outer power band is carried to the side in the direction of carriage motion, which also reduces noise and sudden engagement.  
         [0136]     It will be apparent to one with skill in the art that there are other possible wheel arrangements that may be used with carriage assembly  33  than the one illustrated herein without departing from the spirit and scope of the present invention. For example, the tilt angle of main and keeper wheels may be more or less than 20 degrees as mentioned in this embodiment. There may also be more or fewer main and or keeper wheels than is illustrated here.  
         [0137]     In one embodiment, independent wheel pairs comprising one main wheel and an associated keeper wheel may be bracketed independently such that there are four independently movable wheel sets.  
         [0138]      FIG. 5  is a perspective view of an upper platform assembly  90  supporting a suspended footpad  79  mounted to a carriage assembly  33  (wheels and brackets not shown) according to an embodiment of the present invention.  
         [0139]     In this example, a single suspended footpad  79  is provided and adapted to be pivotally suspended over upper platform assembly  90 , termed a cradle in related U.S. Pat. No. 5,020,793, by means of two pivot points  85  and  87 . Each pivot point  85  and  87 , in a preferred embodiment, comprises a journal bearing, a spacer bushing, and a threaded stud with suitable lock washers and a nut fastener. There are equivalent ways known in the art to accomplish such a pivot. A suitable rubber cover is provided and adapted to fit over pivot points  85  and  87  to protect components from corrosion and general exposure. Pivot points  85  and  87  are arraigned in collinear fashion on opposite facing support wings represented by element number  81 . The pivots are fixedly mounted in vertical structures  83 , which are a part of the platform that mounts to carriage  33 . As described in U.S. Pat. No. 5,020,793, footpad  79  may swing freely about pivot points  85  and  87  as illustrated by double arcs that represent direction of swing.  
         [0140]     The general application illustrated in this example is as stated in the aforementioned related document whereas a user places only one foot in footpad  79  after it is installed on apparatus  9  of  FIG. 1 . By traversing back and forth over rails  22  of  FIG. 1 , he or she experiences a benefit of simulated edging. As the length of traversing approaches maximum length of rails  22 , footpad  79  pivots maximally about pivot ends  85  and  87 .  
         [0141]     Also noted herein is a no-skid surface  93  provided in the same fashion as previously disclosed in  FIG. 2  (elements  38  and  42 ). The fasteners for mounting the upper platform to carriage  33  are not seen in this view, but are the same as previously described for upper platforms in this disclosure.  
         [0142]     According to a preferred embodiment of the present invention, footpad  79  with upper platform assembly  90  may be removed as one unit from and installed as one unit onto any wheeled carriage- assembly having suitable mounting locations. In this way, a carriage assembly such as assembly  33  of  FIG. 2  may be kept resident on apparatus  9  of  FIG. 2  with the loosening, removing, and re-tightening of only two hex-head nuts being required to change applications. This method reflects the modular nature of accessories such as footpad  79  mounted to upper platforms according to a preferred embodiment. Loosening and tightening bolts may be performed with the aid of a convenient T-handle socket tool (not shown) adapted to fit hex-head nuts  53 . In a preferred embodiment, all hex-head nuts subject to requirements of being removed and replaced due to the change of applications are the same size fitting the T-handle socket tool.  
         [0143]     Carriage assembly  33  is shown in this example to illustrate orientation of footpad  79 . Carriage assembly  33  may be of a different overall length than assembly  33  of  FIG. 2 . For example, a single footpad such as footpad  79  does not require a longer carriage assembly whereas a dual footpad installation would require a longer carriage assembly. In a preferred embodiment, carriage assembly  33  of  FIG. 2  has a maximum length such that all modular accessories are supported. That is not to say, however, that a modular accessory cannot have it&#39;s own carriage of a different overall length.  
         [0144]     Carriage assembly  33  of  FIG. 2  would preferably remain resident on rails  22  of apparatus  9  ( FIG. 2 ), especially if keeper wheels are used as previously described. However, in an alternate embodiment where keeper wheels are not used, the carriage assembly illustrated in this example may have main wheels installed and may be thought of as one module comprising assembly  33 , upper platform  90 , and footpad  79 . In this embodiment, a roller such as roller  59  of  FIG. 4  may be shared between different applications. A quick release of roller  59  and removal of bar clamps such as clamp  63   a  of  FIG. 4  will also allow removal and replacement of different modules. However, removing bar clamps entails much more effort on the part of a user. The added effort may be offset by the fact that different applications may require different tensioning adjustment with respect to a resilient member such as member  46  of  FIG. 2 .  
         [0145]     In addition to providing a single footpad in modular fashion as illustrated herein, in a further embodiment an upper platform is provided having two such single suspended footpads may be mounted in spaced-apart fashion. In yet another embodiment an upper platform assembly is provided wherein the spacing between suspended footpads is adjustable, and the adjustment apparatus is described further below with reference to  FIG. 12 . Also, because of added keeper wheels such as wheels  69  and  71  of  FIG. 4 , retaining a wheeled carriage on rails  22 , footpad(s)  79  may be significantly extended in length without the risk of tipping carriage  33  off of rails when in use.  
         [0146]      FIG. 6  is an elevation view of wheeled carriage-assembly  33 , upper platform  89 , and mounted foot platforms  39  and  41  of  FIG. 2  according to an embodiment of the present invention. Part of the upper carriage walls are broken out in this figure for the purpose of enabling a view of inner components, and the bottom plate of upper platform  89  is therefore shown partially in cross-section.  
         [0147]     As with previously disclosed embodiments described in related documents, footpads  39  and  41  are pivotally mounted to pivot supports  103  and  105  respectively. Supports  103  and  105  are part of the upper-platform assembly not removed in this example. There are four pivot supports such as supports  103  and  105  with the remaining two identical supports positioned directly behind and to the backside of assembly  33  and therefore not seen in this view. Pivot pins  102  and  111  form a pivotal connection between depended ears  109  and  110  and an identical set of depended ears (not shown) located at the backside of footpads  39  and  41  respectively. A section-view of this relationship is detailed and described in &#39;257  FIG. 6 . Footpads  39  and  41  are die-cast in one embodiment to include the described depended ears.  
         [0148]     A link-rod  115  is provided and attached to pivot points  104  and  113 . The above-described configuration including components is duplicated at the backside of the assembly.  
         [0149]     The connected link-rod assembly enables footpads  39  and  41  to pivot in unison during operation of apparatus  9  of  FIG. 2 . Resilient blocks  97  and  95  are provided as shock absorbers and are made of rubber or other suitable resilient materials.  
         [0150]     Link-rod  115  is of a length such that when attached to pivot points  104  and  113  with footpads  39  and  41  brought to their center-most position about pivot rods  102  and  111 , that each footpad is canted, in some embodiments, somewhat toward the center (canted positions not specifically shown). However, in other embodiments it is desired that footpads  39  and  41  may be adjusted to assume a more level profile to facilitate use by more experienced users.  
         [0151]     There are two ways to accomplish this task. In one embodiment, a second set of link-rods (not shown) is provided of a shorter overall length than the set represented by link-rod  115 . By replacing link-rods  115  with the shorter rods, footpads  39  and  41  may be canted to a more level position. This, of course assumes that footpads  39  and  41  as used, in this embodiment, with link-rod  115  are canted in as described above. This method requires that four link-rods be provided with the modular footpad-assembly, two for the canted-in configuration, and two for the more level configuration.  
         [0152]     In another embodiment link rods are provided that are themselves adjustable, so the effective length of the rods, and therefore the degree of cant of the footpads may be adjusted within certain limits.  
         [0153]      FIG. 7A  is perspective broken-view of a portion of a rail  22 , transverse end-member  27 , and end-cap  17  according to an embodiment of the present invention. In a preferred embodiment, rails  22  are welded to a location (W) above the longitudinal centerline of transverse end-members  27 . The higher location allows keeper wheels such as wheels  71  and  69  of  FIG. 4  from coming in contact with the floor at maximally traversed locations on rails  22 . End-cap  17  now has a corrugated bottom for shock absorption as well as additional no-skid protection.  
         [0154]      FIG. 7B  is an elevation view of an end-side of end cap  17  of  FIG. 7A . End-cap  17  is molded of rubber-like material as described in previous embodiments. In order to improve over previous designs, a series of alternating raised portions  119  and grooves  117  are provided to form a corrugation feature extending across the bottom surface of cap  17 . As described above, this adds a no-skid enhancement and a shock absorption enhancement.  
         [0155]      FIG. 7C  is a plan view of a bottom-side of end cap  17  of  FIG. 7B . In addition to a corrugation formed by hills  119  and valleys  117 , a pattern containing a plurality of through openings is provided generally through the bottom surface of end cap  17  and extending into the inner space reserved for housing the circular end of transverse member  27  of  FIG. 7A . These openings are also illustrated in  FIG. 7B  as vertical dotted lines but are not described or witnessed. Openings  121  provide additional shock absorption capability. There are nine such openings in this example, however, it will be apparent to one with skill in the art that more or fewer openings  121  may be provided. Moreover, differing patterns may be used as well.  
         [0156]      FIG. 8  is a perspective view illustrating components of a quick-release roller-assembly according to an embodiment of the present invention. As previously described in  FIGS. 2 and 4  above, rollers supporting power bands such as roller  47  illustrated here, are crowned. Such a crowned area is labeled and illustrated by an accompanying witness arrow. A dimension C represents the diameter of roller  47  at the crowned area. It has been described above that a preferred diameter is 2-inches for rollers, which is assumed to be taken at the crowned area leaving the end diameters of each roller less than two inches in diameter. However, in some embodiments, the crowned area of a roller such as roller  47  may be larger than 2-inches.  
         [0157]     A roller shaft or pin  123  is provided and adapted to be an axle for roller  47  between elements of structure  25  of which broken portions are represented here. Pin  123  has a spring-loaded detent  125  in one end and a pull ring  124  through a hole in the other end. Through-openings in elements  25 , each having a polymer bushing  127 , are provided to receive pin  123 . By placing a roller in position between brackets  25 , pin  123  may be placed through selected collinear bracket-holes with bushings  127  and roller  47 . Pin  123  is of sufficient length such that it protrudes past the outer surfaces of structure  25  on both sides, and when in place detent  125  prevents accidental withdrawal. The quick-release pins for rollers provide a means of quickly re-positioning rollers in structure  25  for tensioning adjustment. In an alternative embodiment later described, the rollers may be adjustably spaced even more simply using a dialed adjustment mechanism.  
         [0158]      FIG. 9A  is a plan view of an elongated footpad  133  and carriage-assembly  33  according to an embodiment of the present invention. A single footpad  133  is provided and adapted as a snowboard simulator presented as an option for apparatus  9  of  FIG. 2 . Footpad  133  is pivotally mounted to an upper platform assembly  89  in much the same fashion as footpads  39  and  41  of  FIG. 6  except that footpad  133  is centrally mounted and there is no link-rod assembly required. Carriage assembly  33  is also illustrated in this example to show orientation only. A non-slip surface  135 , preferably made of rubber-like material, is provided as in other embodiments previously described. Raised edges  131  are provided around the outer edges of footpad  133  for added protection from slipping.  
         [0159]     A dimension L (length) is provided to be sufficient for allowing a user to place both feet on footpad  133  in positions similar to those used in snowboarding. A standard example would be standing sideways one foot spaced apart from the other about shoulder width. The exact dimension may vary according to application, however  25  inches should be sufficient for most users. A dimension W (width) is provided to be sufficient for covering the length of a users shoe or boot, about 15 inches.  
         [0160]     In some embodiments not shown, there may be molded or otherwise formed positions to engage a user&#39;s feet, and fastening arrangements are also possible.  
         [0161]     In another preferred embodiment of the invention the mounting of the single footpad for simulating operation of a snowboard is as shown for the footpads of  FIG. 5 , with the footpad suspended from pivots higher than the foot position.  
         [0162]     The application presented here is only possible in an embodiment wherein keeper wheels are used such as wheel  71  and  69  of  FIG. 4 . Footpad  133  and upper platform  89  is a modular accessory and may be easily mounted to carriage assembly  33  of  FIG. 2  by removing two hex-head nuts  132 , placing the unit over carriage assembly  33  of  FIG. 2  and then replacing and re-tightening the nuts. Clearance holes  134  are provided through footpad  133  to allow access for a T-handle socket-tool such as the one previously described in  FIG. 5 .  
         [0163]      FIG. 9B  is an elevation view of mounted footpad  133  of  FIG. 9A . As described in previous embodiments, footpad  133  is die-cast. However, other suitable materials and forming methods may also be used. Depended ears  137  are provided at either end on the underside of footpad  133  for the purpose of accepting a pivot rod  141  through collinear and opposite facing openings. Pivot rod  141  also extends through collinear openings provided in support wings  142  arranged in similar opposite facing fashion as depended ears  137 . When mounted, pivot rod  141  extends through all four collinear openings in depended ears  137  and support wings  142 . Pivot rod  141  also extends through both walls of the upper platform assembly  89  of  FIG. 9A  (not shown). Pivot rod  141  may be secured to the above mentioned carriage walls by castle nuts or other types of fastening nuts (not shown) as described in U.S. Pat. No. 5,147,257.  
         [0164]     In this example, there are no link-rods or other required hardware to direct rotation of footpad  141 . Rather, a resilient stop is provided and adapted to stabilize the rotation of footpad  133  while in use. Stop  139  is analogous to resilient blocks  97  and  95  of  FIG. 6  in that it acts to impede and direct rotation. However, resilient stop  139  is provided as one piece rather than two pieces in this example. Stop  139  also extends the length of carriage assembly  89  such that maximum support is afforded. When not in use, footpad  133  rests against stop  139  in a centered and level position.  
         [0165]     In one embodiment, stop  139  has two areas within its molded architecture that are hollow or perhaps filled with a less dense material than rubber. These areas are shown here by dotted polygonal shapes. The respective areas lie, one beneath the left side of footpad  133 , and one beneath the right of footpad  133 . When footpad  133  is in use such as on apparatus  9  of  FIG. 2 , the areas within stop  139  are caused to collapse under pressure of a respective side of footpad  133  during normal rotation. For example, each time a user traverses to one side of apparatus  9 , the opposite-side area is caused to collapse. Several factors dictate the amount of collapse. These factors include a user&#39;s weight, speed of traverse, and any hard motions urged on footpad  133  by the user. Preferably, resilient stop  139  is manufactured to withstand sudden shock, and be strong enough to support a considerable stress without complete collapse. Advanced users may simulate back and forth movements experienced in snowboarding.  
         [0166]      FIG. 10  is an elevation view of frame structure  11  of  FIG. 1  illustrating an optional roller/band tensioning hardware  143  according to an embodiment of the present invention. According to this embodiment of the present invention, an optional apparatus and method is provided for tensioning a central power band such as band  46  of  FIG. 2 . Instead of a quick-release method for rollers as described in  FIG. 5 , whereby rollers are removed and then re-mounted in different positions, structure  25  on each side now has an elongated slot  153  for enabling a mounted roller such as roller  45  to be loosened and slidably positioned. Each structure  25  has opposite slots  53  on either side of belt-guide  24  such that a pair of slots  153  may accept a roller assembly such as for rollers  45  and  47 .  
         [0167]     Rollers  47  and  45  are, in this embodiment, held by an upper toothed-rail  145  for roller  45 , and a lower toothed-rail  147  for roller  47 , further illustrated in following  FIG. 11A . Bracketed roller mounts (not detailed) on the roller side of each toothed rail form a rigid connection between the roller shafts of respective rollers to respective toothed rails. Toothed rail  145  is rectangular in cross-section and has a plurality of gear-teeth (not shown) arraigned along its length in the manner of a gear rack. In some embodiments a standard gear rack may be used.  
         [0168]     When positioned properly, toothed rail  145  presents its gear teeth in a downward direction or along its bottom surface. Toothed rail  147  is identical to toothed rail  145  and they are, in fact, interchangeable. An inverse positional relationship exists with toothed rails  145  (top rail) and  147  (bottom rail) such that respective gear tracks will face each other. Toothed rails  145  and  147  are held parallel and in position by a rail guide  150 , as shown in  FIG. 10  and  11 C and D. Rail guide  150  has two rail-keepers installed thereon and adapted to hold toothed rails  145  and  147  in a parallel relationship and at the required distance apart. These are a rail keeper  149  positioned left of center, and a rail keeper  151  positioned right of center. The above-mentioned components of hardware  143  are manufactured of a durable material to provide wear resistance, for example, and there are several suitable materials for such applications.  
         [0169]     A gear (pinion)  159 , as shown in  FIG. 11A  and B, is provided and adapted to mesh with opposite-facing gear tracks as presented on toothed rails  145  and  147 . In this example, the gear is positioned directly behind of and forms a part of a gear-handle assembly  155 . Hardware  143  may be conveniently mounted to the inside front surface of U-shaped support member  31  with conventional fasteners as known in the art. A cutout opening  157  is provided through the front wall of U-shaped support structure  31  to enable user access to a gear-handle assembly  155  for the purpose of adjusting tension. In some embodiments there is an access door.  
         [0170]     In operation, a user adjusts power band tension to a greater or lesser amount by turning gear-handle assembly  155  clockwise (more tension) or counterclockwise (less tension). When the desired tension is achieved, he or she then releases a spring-loaded handle, and the positions are maintained. It may be assumed, of course, that a power band such as band  46  of  FIG. 2  is in place during this operation. An incremental scale is preferably provided as a stamped or otherwise marked convention on the front face of support member  31 , or along surfaces of the guides for the adjustment assembly. This will allow a user to return to known tension amounts without experimentation.  
         [0171]     It will be apparent to one with skill in the art that a method for mounting hardware  143  to frame structure  11  may differ from the specific apparatus illustrated here without departing from the spirit and scope of the present invention. For example, U-shaped support member  31  may have a suitable slot running along its length for hardware  143  to fit into. There are other possibilities.  
         [0172]      FIG. 11A  is a broken view of a portion of toothed rails (racks)  145  and  147  and a toothed gear (pinion)  159  of  FIG. 10  according to an embodiment of the present invention. Gear  159 , as previously described in  FIG. 10 , is positioned between and meshes with toothed rails  145  and  147 .  
         [0173]      FIG. 11B  is an elevation view of the handle assembly  155  of  FIG. 10 , and its integration with gear  159  and its mounting and operation. In this embodiment gear  159  is fixedly mounted to a shaft  173  that extends through opposite frame members  167  and  175  carried by bearings  177 . A serrated wheel  165  is slidably mounted to shaft  173  outside the area of gear  159  by a spline on the shaft and the wheel. Shaft  173  has an end  161  and a compression spring which urges wheel  165  toward frame member  167 . Pins  169  fit into matching holes in frame member  167 , urged by spring  165 . A user may grasp wheel  165 , pull it toward end  161  against spring  165 , whereby pins  169  are withdrawn from the matching holes in frame member  167 , and the wheel is free to turn the gear. By turning the gear in either direction the user can then move rollers  47  and  45  either closer together or further apart, thus adjusting the tension on the power band. When the user releases the wheel, the spring causes the pins to re-engage, and the rollers are then retained in the new positions.  
         [0174]     It will be apparent to one with skill in the art that there are many other mechanisms that may be employed to create a spring-loaded engagement handle for gear  159  without departing from the spirit and scope of the present invention. Other handle functions and assembly requirements may differ from the example shown here. The inventor intends the above-described handle assembly to be only one example.  
         [0175]     The skilled artisan will understand that supporting guide  150 , as shown in  FIG. 11C  and  FIG. 11D , and other supporting elements for the rack-and-pinion mechanism described above may be accomplished in a number of different ways, and is within the skill of engineering practitioners. Detailed description of this portion of the mechanism is therefore not undertaken here.  
         [0176]      FIG. 11E  is a broken view of a portion of lower rack  147 , roller  47 , and a bracketed roller-mount  187  of  FIG. 10 . As previously described, a roller such as roller  47  is mounted to a rack such as rack  147  by means of a bracketed roller mount shown here as element  187 . Roller mount  187  is adapted to fit over the ends of a roller axle by virtue of a forked construction, similar in some respects to a mount for a paint roller, for example.  
         [0177]      FIG. 11F  is a plan view of the assembly of  FIG. 11E . As can be seen in this view, roller mount  187  is a simple forked bracket structure fastened to the end of rack  147 . Guide ends  188  are provided for guiding in slots of the rail guides  150  to constrain the translation direction in operation. In a preferred embodiment these guides are of a UHMW material for low-friction and for noise and vibration reduction.  
         [0178]      FIG. 12  is a perspective view of an adjustable double-footpad upper module  195  according to a further embodiment of the present invention. This model is termed the Double Black Diamond model by the inventor. As previously noted in  FIG. 5 , a suspended footpad assembly such as footpad  79  may be double mounted in an adjustable manner. Two suspended footpads  79  are illustrated in this embodiment mounted in a locked position on an adjustable plate assembly  189 . Footpads  79  are similar in construction to footpad  79  of  FIG. 5 ; hence they retain the same element number here.  
         [0179]     Plate assembly  189  is an intermediary base that bolts on to a wheeled carriage such as carriage  33  of  FIG. 4 . Plate  189  has two opposite facing edges that provide guide channels  193  and  194  for movable suspended footpad assemblies. Channel  193  on one side is best illustrated in  FIG. 12 . Channel  193  is adapted to house a slotted cam-rod  191 , which is adapted to lock the movable footpad assemblies in place.  
         [0180]     Cam-rod  191  has a plurality of slots  192  arranged in equally spaced and collinear fashion, and presented over the entire length of channel  193  along one side of the plate assembly. The purpose of slots  192  is to engage a plurality of equally spaced teeth provided on one edge each of two toothed base-plates (not shown here but illustrated below), one each affixed to the bottoms of footpad assemblies  79 .  
         [0181]     A spring-loaded lever  197  is provided on one end of cam-rod  191  and is adapted to cause rotation of cam-rod  191  within channel  193  enabling slots  192  to be presented inward as shown or rotated back into channel  193  as directed by a user. Spring lever  197  in this embodiment fastens to channel  193  such that a wound spring engages a fixed location in the channel while the opposite end of the spring is retained by lever  197  creating a spring tension. There are several ways known in the art for a spring lever to be mounted such that a shaft or other part is put under spring tension. The spring-loaded arrangement provides for the cam rod to be always urged into the locked position for the footpad assemblies, so these assemblies may only be moved to adjust center distance under positive direction of the user.  
         [0182]     By manually rotating spring lever  197  a user can unlock the footpad assemblies and manually move each to a new position as desired. In this way, footpads may be slidably inserted from either end of adjuster-plate  189 , as indicated by directional arrows, and adjusted to any desired spacing related to center distance. When desired positions are attained, letting go of spring lever  197  locks the footpads in place on plate assembly  189 . In one embodiment, a safety lock is provided to give added assurance that the footpad assemblies will stay in position during operation. Channel  194  on the opposite side is adapted to house non-toothed edges of the aforementioned toothed base-plates.  
         [0183]      FIG. 13A  is a plan view of a toothed base-plate  199  according to an embodiment of the present invention, and  FIG. 13B  is a side view of the base plate of  FIG. 13A . As previously described, footpads  79  of  FIG. 12  each have a toothed base-plate  199  installed on the bottom surfaces of associated footpad assemblies  79  ( FIG. 12 ). Each base-plate  199  has a row of equally spaced teeth  205  presented along one edge for the purpose of engaging slots  192  of  FIG. 12  in cam  191 . In this embodiment, base-plate  199  has two spacer bars  201  and  203  adapted to space it from the underside of the outer frame member of a footpad assembly when mounted.  
         [0184]     Bars  201  and  203  are, in this example, formed of one piece with base-plate  199 , however, in other embodiments, they may be separate mounted structures. There are four threaded holes  207  (two for each spacer bar) provided through base-plate  199  and spacer bars  201 , and  203  for mounting purposes. Machine screws or the like may be used for mounting plate  199  to the outer frame member of each footpad assembly. As seen in  FIG. 13B , bolt holes  207  are chamfered on the side making contact with carriage assembly  33  such that they lay flat and may slide without scratching or marring the surface.  
         [0185]      FIG. 13C  is an end-view of the slotted cam-rod  191  of  FIG. 12  in this embodiment. Cam-rod  191  has a slotted portion  192  as previously described, a radiused back-grind  209 , and a flat portion  207 . As slots  192  are rotated in the direction of the arrow, engaging teeth  205  on base-plate  199  of  FIG. 13A  are released at the beginning point of back-grind  209 . As flat  207  rotates so as to face teeth  205 , a small amount of space is created between the top land portions of teeth  205  and the surface of flat  207  enabling footpad assemblies such as footpads  79  to be moved to a different position or removed altogether.  
         [0186]     It will be apparent to one with skill in the art that there may be more than one general configuration of slots and teeth than is illustrated here without departing from the spirit and scope of the present invention. For example, a base-plate such as plate  199  may be slotted while a cam-rod such as rod  191  is toothed. There may be more or fewer slots and teeth presented, and so on. In an alternate embodiment, footpad assemblies may be lowered in from the top with teeth and slots remaining in a rigid configuration on both sides of a base-plate and on opposite facing structures mounted to an adjuster-plate wide enough to support this type of fitting. Clamps could be used to secure the footpad assemblies after lowering them into place.  
         [0187]     In another embodiment of the present invention an alternative adjustment mechanism for footpads may be used comprising one or more spring-loaded pop-up detents. A first footpad assembly may be mounted to the plate assembly separately, allowing for individual adjustment, or with a second footpad as an assembly. A pop-up detent can be mounted on an edge of a footpad assembly in a position so that when a user manually pulls back and then releases a spring-loaded pin within the detent assembly, the pin slides in and out of a slot or hole on the face or edge of the plate assembly, the pin and slot or hole being in-line when the desired footpad position is attained. The plate assembly can have a plurality of such slots or holes arranged in equally spaced and collinear fashion. A spring-loaded detent assembly could comprise a cylindrically shaped casing open on the end facing the hole or slot and containing a pin that slides in and out in both directions. A protrusion or attachment to the pin serves as a handle enabling a user to manually pull the pin back within the casing. Within the casing and located behind the pin a spring of roughly the same diameter of the pin provides outward tension to the pin when a user manually pulls it back using the handle. When a user manually releases the pin in the mounted detent assembly the spring tension behind the pin pushes the pin into the aligned slot or hole and locks the footpad assembly into the desired position. Once locked into the desired position by the pin assembly, the footpad assembly may be otherwise mainly secured to the plate assembly by utilizing many different methods. By again pulling back the pin a user can unlock the footpad assembly and adjust to another position as desired. This manner of spring-loaded pin arrangement within the detent assembly provides for the locking pin to be always urged into the outer or locked position. In addition to the footpad adjustment functionality of the pop-up detent assembly, in various alternative embodiments the detent assembly may have more or less of an integral role of securing the footpad assembly to the plate assembly.  
         [0188]     It will be apparent to the skilled artisan that there are alternative arrangements and mechanisms that might be used to allow the footpads to be spaced and secured with the new spacing. The mechanisms described above are but a few of the possibilities. There are many others. For example, an intermediate plate assembly could be provided wherein there are two plates with one telescoping into the other, and having a locking apparatus to fix the relative positions when the desired separation is achieved. In this embodiment one footpad would be mounted to one of the telescoping plates and the other footpad to the other.  
         [0189]      FIG. 14  is a cross-sectional view of a semi-arcuate rail  217  with a main wheel  213 , and a keeper wheel  215  in position according to an alternate embodiment of the present invention. As previously described in  FIG. 1  above, semi-arcuate rails, shown round in  FIG. 1  and other Figs. in embodiments described above, may also be extruded to provide opposite channels for wheels, and then die-formed to obtain a desired semi-arcuate shape. This embodiment is especially useful for applications having footpads or platforms of exceptionally large dimensional features (length and width) than standard assemblies. Keeper-wheels such as wheels  215  and wheels  71  and  69  of  FIG. 4  provided added restraint in order to prevent an assembly from tipping or otherwise being lifted from rails during operation.  
         [0190]     Rail  217  is shown welded in this illustration to frame member  31 , and in embodiments of the overall apparatus using such extruded rails, the rails would also be welded to end rails  27  as described previously for rails  22 . Wheels  213  and  215  are not shown as assembled to a wheeled carriage in this illustration, but would in practice be mounted to such carriages in much the same manner as already described for wheels used with round rails.  
         [0191]      FIG. 15  is a cross-section view through a rail  219  in yet another embodiment of the invention, showing a wheel assembly  221  having a shaft  223 , with the wheel engaged in rail  219 . In this embodiment rails  219  replace rails  22  or  217  shown in other embodiments, and are formed in an arc or an arc with straight-leg portions as taught elsewhere in this disclosure. Rails  219  may be extruded from suitable material, or may be formed by bending a plate and then forming the necessary arc using a die or other suitable tool. In preferred embodiments rails  219  are welded to structure  31  as shown, and also to end rails  27  (not shown).  
         [0192]     In this embodiment Wheels  221  are mounted to a wheeled carriage by shafts  223  in various positions to support the carriage in its to-and-fro movements on (in) rails  2   19 . Some wheels are mounted to contact the upper portion of rails  219  as shown in  FIG. 15 , and others are mounted to contact the lower portion of rails  219 , thus accomplishing the functions of the wheeled carriage taught with reference to  FIG. 4  having keeper wheels. It will be apparent to the skilled artisan that there are a variety of positions wheels may be mounted to accomplish the purpose.  
         [0193]      FIG. 16  is an elevation view of a ski-exercising apparatus  301  according to an embodiment of the invention illustrating an optional third power band. Apparatus  301  is provided having elements similar to those of exercisers previously described herein except for novel improvements described below. For this reason only the improvements are described. To better illustrate elements within, additional roller-mount openings similar to those of tensioning structure  25  of  FIG. 1A  are not shown but may be assumed to be present, and cut-away views are shown of the wheeled carriage and support member.  
         [0194]     Apparatus  301  provides a third power band  302  assembled between the first, or outer, power band and the second, or inner, power band. In this embodiment the free ends of third power band  302  are illustrated as fastened at clamp  306 , having one end clamped between the free ends of the outer band and the other end in between the ends of the outer and inner bands. It will be apparent that the clamping locations of power bands and positions of clamped free ends may vary. A tensioning structure  303  is provided, illustrated as a modification to a tensioning structure such as that of  FIG. 1A , having a longer length and properties to support a third power band and hardware. Tensioning structure  303  is welded in this embodiment to the bottom surface of the central frame structure similarly to embodiments previously described. Rollers  304  and  305  are rotatably mounted to the outer positions of tensioning structure  303  providing support to third power band  302 , third power band  302  extending from clamp  306  passing under the inner rollers mounted between rollers  304  and  305  and passing under and over rollers  304  and  305  back toward center, over a third roller rotatably mounted under the wheeled carriage and fastened with the outer power band to the underside of the wheeled carriage by clamps  307  and  308 .  
         [0000]     Improvements  
         [0195]      FIG. 17  is an elevation view of a ski-exercise apparatus  401  illustrating adjustable tensioning structures for an optional third power band according to an embodiment of the present invention. Apparatus  401  in this embodiment provides many of the features and elements of apparatus previously described herein except for new and novel improvements described in detail below, therefore, only the improvements are described.  
         [0196]     Apparatus  401  provides a third power band  302  assembled between the first, or outer power band, and the second, or inner power band, as described previously for apparatus  301  of  FIG. 16 . However, apparatus  401  provides a pair of improved tensioning structures for the optional third power band.  
         [0197]     Tensioning structure  405  is illustrated as a modification to a tensioning structure such as structure  303  of  FIG. 16 , and is provided as a separate structure which, in the embodiment illustrated is affixed at each end to the bottom surface of the central frame structure  404  in similar locations to embodiments described in previous embodiments, utilizing a common fastener such as a bolt and nut. In alternative embodiments, tensioning structures  405  may be welded directly to central frame structure  404 . Tensioning structure  405  is somewhat longer in length and has a lower profile than that of structure  303  of  FIG. 16 . Tensioning structure  405 , in a preferred embodiment, is manufactured of strong, lightweight aluminum material, and may be die cast, machined, or otherwise formed utilizing similar strong, lightweight material in alternative embodiments.  
         [0198]     Tensioning structure  405  differs significantly, however, from that of  FIG. 16  in that a second tension roller  409  is provided to increase smoothness of operation of the ski apparatus under extreme tensioning as the wheeled carriage travels from side to side on the parallel rails during operation. As shown in the illustration, the optional third power band  302  is assembled between the first, or outer power band, and the second, or inner power band, the ends clamped at the bottom of the central frame structure  404 , and the upper portion of the power band clamped at two locations under the wheeled carriage, similarly to apparatus  301  of  FIG. 16 .  
         [0199]     The routing of power band  302  differs, however, from that of apparatus  301  of  FIG. 16  in that it passes under the second tension roller  409 , and then over and under the main roller  407  and then back towards the center of the central frame structure where it is clamped along with the ends of the first, outer power band and second, inner power band.  
         [0200]     A plurality of through openings  411  are provided for tensioning structure  405  enabling the resistance point to be altered, thereby enabling the user to adjust the amount of tension encountered by the wheeled carriage when it travels to the outermost lateral positions. A total of three through openings  411  are provided in the embodiment illustrated, located near the upper edge of the body of structure  405  starting near the center and linearly arranged towards the outer edge of the structure. However, in alternative embodiments number and exact location of through openings  411  may differ to provide a varying range of tension adjustment positions.  
         [0201]      FIG. 18A  is an elevation view of adjustable tensioning structure  405  of  FIG. 17 , and a roller axle. The support structure of tensioning structure  405  is provided by bracket  425  which is unshaped, comprising a base  426  and a pair of walls  427  extending upward from base  426  on either side. Through openings  420  extend through base  426  for the purpose of fastening tensioning structure  405  to the bottom of the central frame structure of the ski apparatus.  
         [0202]     Structure  405  utilizes an improved roller axle  413  for rotatably securing roller  407  to the structure through one of the sets of through lo openings  411 . Through openings  412  are provided at the opposite end of bracket  425  for rotatably securing tension roller  409  utilizing a standard clevis pin fastener  421 .  
         [0203]     A plate  417  is provided for adding stability and preventing flexing of walls  427  of tensioning structure  405 . Another function is to prevent the third band from interfering with the second band. Plate  417  is rectangular in shape and substantially flat, and has a plurality of through openings located near each of the corners for accommodating screw fasteners (not shown), securing plate  417  is adapted to fasten down to the upper surface of each wall  427 , utilizing holes  419  which extend down into walls  427  for accommodating the screw fasteners, and once fastened, bridges the gap between the inner surfaces of each wall  427 .  
         [0204]     Tensioning structure  405  is adapted to mount to the bottom of the central base structure of ski apparatus previously described in the present application and in related patents and applications referenced herein, using standard fasteners inserted through openings  420 , which extend through the thickness of base  426 , and a slight modification to the existing bottom central base structure of existing ski apparatus by adding mounting holes for such fasteners, or in other embodiments, tensioning structure may be fixedly attached by welding structure  405  to the central base structure of existing ski apparatus, for example.  
         [0205]      FIG. 18B  is an elevation end view of tensioning structure  405  and roller axle  413  of  FIG. 18A  and a roller axle nut. In this view, walls  427  are shown extending up from either end of base  426  forming the U-shape of the overall structure of the bracket, and conical roller  407  is located in its mounting position between the inner surfaces of each wall  427 . Roller  407  is rotatably secured to walls  427  by inserting roller axle  413  through a first opening  411  of wall  427 , completely through passage  423  extending through the center of roller  407 , and is then secured with roller axle nut  414 . Roller axle  413  and roller axle nut  414  each have a collar, collar  416  and  423  respectively, each of which has a diameter somewhat less than that of through openings  411  of walls  427 , such that a snug fit is achieved when roller axle  413  and roller axle nut  414  are inserted into walls  427 .  
         [0206]     Roller axle  413  has an internally-threaded end portion  422  on the opposite end of roller axle  413  from collar  416 , matching and externally-threaded end portion  424  of roller axle nut  414 , for enabling roller axle nut  414  to be securely affixed to the threaded end of roller axle  413 . Roller axle  413  is of such a length that when fully inserted through the first opening  411  in wall  427 , the far edge of threaded portion  422  extends only to the edge of roller  407 , stopping just short of the inner surface of the opposing wall  427  through which roller axle nut  414  is inserted, such that roller axle  413  and roller axle nut  414  may be securely tightened together when attaching roller  407  to walls  427 , and still allow for free rotation of roller  407  around shaft portion  418  of roller axle  413 . In some embodiments a clevis pin with an R-clip is used instead.  
         [0207]     When securely tightened together through openings  411  of walls  427  and through roller  407  as described above, the roller axle assembly additionally becomes a stabilizing cross member adding strength to the overall structure at one end of structure  405 , and adds significantly to the overall structural integrity also enhanced by cross member plate  417  at the opposite end of the structure.  
         [0208]     A pair of slots  428  extend up into the bottom of each wall  427  of tensioning structure  405  at each edge of base  426  and extend along the entire length of structure  405 , and are adapted to fit snugly over the upwardly extending portions of power band guide  24  of ski apparatus  9 , for example, of  FIG. 1B  and  FIG. 2 . Power band guides  24 , as is more clearly seen in  FIG. 1B , has sides on either end that extend upward from the base of the frame structure. Slots  428  of tensioning structure  405  extend up into walls  427  to a distance somewhat greater than the height of the overly extending sides of power band guide  24 , thereby allowing the bottom surface of base  426  to securely rest upon the upper surface of the bottom of power band guide  24 , and enabling for a more secure attachment of tensioning structure  405  to the bottom central frame structure of the ski apparatus. In alternative embodiments of the present invention, slots  428  of tensioning structure  405  may also enable the user to slide structure  405  in its aligned position along band guides  24 , for example, and relocate structure  405  towards the center of the frame structure of the ski apparatus, or outward, in various predetermined attachment locations, thereby enabling still further adjustability of the location of the additional tension point provided by tensioning structure  405  in embodiments herein described.  
         [0209]      FIG. 19  is an elevation view of the frame structure of ski-exercising apparatus  401  of  FIG. 17 . Frame structure  404  is provided in this embodiment having generally similar frame architecture to frame structure of ski apparatus described in the present application and in related U.S. patents and applications referenced herein except for novel differences relating to the parallel rails described below. For clarity, only the frame structure is described in this embodiment, as additional elements, such as power bands, and wheeled carriage assembly and related hardware have been adequately described herein in the preceding specification, and are removed in the present illustration.  
         [0210]     Frame structure  404  comprises a set of semi-arcuate rails  415 , only one of which is visible as this is an elevation view, which are held parallel to each other and affixed to transverse members at either end of frame structure  404 , generally similar to previous embodiments, along which a wheeled carriage assembly, such as carriage assembly  33  of  FIG. 4 , travels during normal operation of the ski exercising apparatus, as described herein for other embodiments. Rails  415 , however, have several notable differences when compared to rail sets utilized in ski apparatus of previous embodiments described thus far.  
         [0211]     Rails  415  extend at an angle upward beginning at either end of frame structure  404 , towards the center, and are held parallel to each other and affixed at either end of each rail to a pair of transverse end-members, the center portion supported by support members  440 , similarly to that for previous ski apparatus embodiments. As this is an elevation view, only one of the pair of rails is seen. One notable difference between semi-arcuate rails  415  and those disclosed in the present and related patents is that rails  415  are arced in their center portions  447 , as illustrated by a dimensional notation F, and the arcuate portion of rails  415  is substantially shorter than that of previous embodiments. The dimension lines associated with arcuate portion  447  mark the locations where the arced portion of each rail  415  ends at positions sharing an equal distance from a theoretical vertical center of rails  415 .  
         [0212]     The total dimension F in a preferred embodiment is substantially less than the approximately 26 inches defined by dimension (E) of frame structure  11  of  FIG. 1A  of the present application, for example.  
         [0213]     Non-arcuate portions of rails  415  are witnessed by element numbers  443  and  445  on the left and right side of frame structure  404  as seen in this view. Non-arcuate rail portions  443  and  445  are substantially straight from their junctures with arcuate portion  447 . The lengths (taken horizontally) for rail portions  443  and  445  are substantially longer than the approximately 15 inches respectively, of rails portions in previous embodiments, such as non-arcuate portions  19  and  21  of frame structure  11  of  FIG. 1A , for example. It must be noted that the dimensions cited above are intended to be approximate only, and may vary somewhat in alternative embodiments. The approximate overall length of frame structure  404  is about 61 inches, similar in length to frame structure  11  of  FIG. 1A .  
         [0214]     Another notable difference between rails  415  and those of previous embodiments, such as those of frame structure  11  of  FIG. 1A , is that non-arcuate portions  443  and  445  of rails  415  each extend upward from the transverse members at the outward ends of frame structure  404 , at a steeper angle towards the center compared to previously described embodiments, and the arcuate portion, which is substantially shorter than those of previous embodiments, has a maximum height at the center which is measured substantially higher, approximately three inches in this example, than the maximum arcuate portion height of rails  19  of  FIG. 1A , for instance.  
         [0215]     The steeper angle and longer length of non-arcuate portions  443  and  445  of rails  415 , and the shorter length and increased height of arcuate portion  447  provides for a faster descent of a wheeled carriage assembly traveling from side-to-side along rails  415 , thereby enabling a stronger more abrupt stop at the end of each lateral stroke, particularly when an optional third power band, as shown for ski exercise apparatus  401  of  FIG. 17 , is utilized. The inventor has discovered that operating a ski exercise machine utilizing rails having such an increased angle and height more closely simulates the increased lateral dynamic forces actually encountered during extreme downhill skiing, and other sports requiring explosive power in lateral movements, and therefore provides exercise for a participant in such activity, having maximum benefit to the user of such an exercise machine.  
         [0216]     Such specific high-intensity training for the enhancement of explosive power is often termed plyometric training in the art, and it is to exercise apparatus improvements in this field of exercising that many of the embodiments described presently and subsequently in the specification are related. The plyometric training method utilizing exercise apparatus elements in embodiments of the present invention is to be used in conjunction with other power development methods in a complete training program to improve the relationship between maximum strength and explosive power. Emphasis in such a training method is placed on generating the highest possible force in the shortest period of time, and reducing or stopping this force at the end of the action. Plyometric training has a primary role in training as well as rehabilitation programs, and, as will be further detail below, apparatus and methods of the present invention provide improvements to the current art relating to exercise apparatus and other hardware providing such training capability.  
         [0217]     It is known in the art that plyometric training may be applied in various exercises which specifically target certain areas of the body for muscle strengthening or rehabilitation. The specific areas of the body often include those other than areas of the legs or hips, for example. In these cases it is desirable to be able to quickly and easily interchange exercise attachments utilizing a single exercise apparatus, and be able to utilize a single exercise apparatus, such as that described herein having a tensioned lateral movement primarily designed for ski exercising, for providing such varied exercises targeting different specific areas of the body.  
         [0218]      FIG. 20A  is a plan view of an adjustable slide plate according to an embodiment of the present invention. Slide plate  451  is provided for. enabling the user to quickly and easily interchange exercise attachments utilizing a ski exercise apparatus and wheeled carriage assembly of the present invention. Slide plate  451  is adapted for mounting to a wheeled carriage assembly, such as carriage assembly  33  of  FIG. 4 , and allowing exercise attachments to be adjustably mounted to plate  451 , easily repositioned at different locations along slide plate  451 , and quickly remove for interchanging with other additional exercise attachments, and further is provided with additional safety features not disclosed in previous embodiments, such as plate assembly  189  of  FIG. 12 .  
         [0219]     Slide plate  451  is preferably manufactured of strong, lightweight aluminum material, or other suitable material having similar properties providing the best combination  6 f strength, rigidity, and light weight, and has an elongated, rectangular shape having a length substantially greater than the width, the length being such that a pair of footpad assemblies may be mounted at the desired width stance in accordance with that used typically for downhill skiing, for example or for other sports and exercise motions, as will be further detail below in other embodiments of the present invention.  
         [0220]     Slide plate  451  is adapted for mounting to the upper surface of a wheeled carriage assembly, such as carriage assembly  33  of  FIG. 4 , in a location centered on the carriage assembly. A pair of through openings  457  are provided in the center of plate  451  for slide plate  451  to the upper platform of the wheeled carriage, and are spaced apart from each other at a distance equal to the spacing between the pair of mounting holes for carriage  33  of  FIG. 2 , fastened by the pair of nuts  53 .  
         [0221]     Slide plate  451  in the present embodiment described, however, improves significantly over upper mounting platform  89  of carriage  33  of  FIG. 2 , for example, in that slide plate  451  allows a pair of footpad assemblies, or other exercise attachments, to be independently and adjustably mounted to the carriage assembly such that various width stance positions can be utilized, and each independently mounted attachment assembly may be quickly repositioned along plate  451  and then re-secured in the new position.  
         [0222]     Slide plate  451  has a center through opening  458  for allowing access to the center fastener used as previously described for mounting the power band roller bracket  61  to the underside of carriage  33  of Fig. as shown for  FIG. 4 . A plurality of holes  455  extending partially down into the upper surface of plate  451 , are arranged linearly along the length and on either side of the center of plate  451 , and each hole  455  is equally spaced from an adjacent hole  455  on either the left or right side of through holes  457 . Holes  455  represent the locations for a wide choice of width stance positions for mounting a pair of footpad assemblies, as will be described further below in enabling detail.  
         [0223]     Slide plate  451 , has on each side extending along the length, a rounded edge  453 , the rounded portion extending somewhat upward from the upper flat surface of slide plate  451 . The rounded shape of edges  453  is better illustrated in  FIG. 20B . Edges  453  provide a guide rail on each longest side of plate  451 , and have the purpose of locating and guiding an attachment plate for mounting a footpad assembly, or other exercise attachment assembly, as will be shown in further embodiments presented below.  
         [0224]     Plate  451  also has a push-pin safety button  452  located near each end, provided as an additional safety feature in the embodiment presented. Safety buttons  452 , are standard spring-tensioned push-pins which, in their normal relaxed position, extend upwardly from the surface of plate  451  by the spring tension. Safety buttons  452  may be manually depressed into a cavity which extends down into the surface, such that the upper surface of the pin portion of safety pin  452  is at least flush with the surface of plate  451 . The safety function of these pins is to retain any carriage unit engaged to the slide plate from moving off the ends of the plate after assembly, unless the pin is intentionally depressed. This function is described and illustrated additionally in description below.  
         [0225]     Plate  451  has a groove channel  459  extending along the entire length of plate  451  in a center location. Channel  459  comprises a slot opening  461  which opens into an internal passage  466  (hidden view) beneath the surface of plate  451 . The internal space formed by passage  466  is substantially wider than slot opening  461 , and has the purpose of allowing a special nut fastener, fastened to a standard bolt fastener, to slide freely within passage  466  along the entire length of plate  451 , enabling adjustability in mounting positions for attaching a sliding attachment plate.  
         [0226]      FIG. 20B  is a section view of plate  451  of  FIG. 20A  taken along section line  20 B- 20 B. The inventor provides  FIG. 20B  to better illustrate several of the elements described above for  FIG. 20A , as well as additional elements not shown in  FIG. 20A . Plate  451  has a rectangular central structure  464 , which protrudes down from the bottom surface of plate  451 , and extends along the entire length of plate  451 . Structure  464  encompasses internal passage  466 , and additionally provides added strength and rigidity to the overall structure of plate  451 . Plate  451  also has a pair of L-shaped side structures  462  extending down from the bottom of plate  451  to a distance equal to that of structure  464 , and located approximately midway between edges  453  and central structure  464 , on either side of structure  464 . Structures  462  also extend the entire length of plate  451 , adding still further to the overall structural rigidity of plate  451 , and accommodate push-pin safety buttons  452 .  
         [0227]     Structures  462  each have a substantially flat and level bottom surface  454 , and central structure  464  has a bottom flat surface  456 , which is flush with bottom surfaces  454  of structures  462 . Bottom surfaces  456  and  454  form the base surface which contacts the upper surface of a wheeled carriage assembly to which plate  451  is mounted according to an embodiment of the present invention, detailed further below. Through openings  457  are shown extending completely through side structures  462  and width stance adjustment holes  455  are shown extending partially down into plate  451  from the surface. Through opening  458  is shown extending down from the bottom of passage  466 , providing an opening through flat bottom surface  456  of structure  464 .  
         [0228]     The rounded shape of guide rail edges  453  on each side of plate  451 , and the substantially flat upper surface are readily apparent in this view. Safety buttons  452  are shown in their relaxed positions, extending upwardly from the surface of plate  451 . As described above, safety buttons  452  may be manually depressed down into cavities (not shown) within structures  462  adapted for the purpose.  
         [0229]     Slot opening  461  is shown extending down into the surface of plate  451 , opening into internal passage  466 , the internal rectangular space formed by passage  466  having a width substantially greater than that of slot opening  461 .  
         [0230]      FIG. 21A  is a top view of a sliding attachment plate according to an embodiment of the present invention. Attachment plate  460  is provided in a preferred embodiment of the present invention as an interface for adjustably mounting various independent exercise attachments, such as a suspended footpad assembly as described above, to the wheeled carriage assembly of a ski exercise apparatus. Attachment plate  460  is provided to enable the user to quickly and easily attach, reposition or remove such exercise attachments to plate  451 , which attaches to a wheeled carriage assembly.  
         [0231]     Plate  460  is manufactured similarly to slide plate  451 , utilizing strong, lightweight material such as aluminum, or some other material having similar properties. Plate  460  is substantially rectangular in shape, substantially flat, and has a pair of edge channels  469 , one on each side of plate  460 , extending along the entire length of plate  460 . Edge channels  469  are rounded on the outside surface, extending somewhat down from the bottom surface of plate  460 , and are adapted to closely fit over the rounded edges  453  of slide plate  451 . Each edge channel  469  has a rounded inner surface, whose dimensions closely equal the outer dimensions of edges  453  of plate  451 .  
         [0232]     Attachment plate  460  is adapted for sliding over an end of slide plate  451 , and, guided by rounded edge channels  469  encompassing rounded edges  453  of plate  451 , is enabled to freely slide back and forth along the length of plate  451 . Plate  460  has a plurality of mounting holes  465 , arranged on either side from the center of plate  460 , which are provided for attaching such as an independent suspended footpad assembly, or some other attachment, to upper surface of plate  460  utilizing standard bolt or screw fasteners. Mounting holes  465  are spaced apart on either side of the center of plate  460 , at a distance defined by dimension (S).  
         [0233]     Plate  467  is also provided with through opening  467  located in the center, and passing completely through the thickness of plate  460 . Through opening  467  has the purpose of enabling insertion of a bolt fastener through plate  460 , for attaching plate  462  slide plate  451 , utilizing a special nut, as will be detailed further below.  
         [0234]     A pair of pull-pins  463  are provided for the embodiment shown, one pull-pin  463  located on either side of the center of plate  460 , near one end. Pull-pins  463  are standard, spring-tensioned devices which are provided for locating attachment plate  460  in the exact desired position on slide plate  451 , according to the various positions of width stance adjustment holes  455  of plate  451 . Pull-pins  463 , each have a pin portion (not shown)&#39;which extends below the bottom surface of plate  460 , adapted to fit securely into locator holes  455  of plate  451 . Spring tensioning of each pull-pin  463  urges the pin portion into the extended position, and by manually raising pull-pins  463  from above, the pin portions may be retracted up into the body of attachment plate  460 .  
         [0235]      FIG. 21B  is a section view of attachment plate  460  of  FIG. 21A  taken along section line  21 B- 21 B. In this view, the rounded out and inner surfaces of edge channels  469  are clearly visible, the inner rounded surface of each edge substantially equaling the dimensions of the outer rounded surface of edges  453  of plate  451 . Through opening  467  is shown passing completely through the thickness of plate  460 , and mounting holes  465  are shown extending through plate  460 . Mounting holes  465  in this embodiment are threaded holes for which standard bolt fasteners may be threaded for attaching such as an independent footpad assembly. In alternative embodiments however, mounting holes  465  may or may not be threaded, depending on whether or not only a threaded bolt, or bolt and nut combination is utilized for mounting the attachment to attachment plate  460 .  
         [0236]     Pull-pins  463 , located on either side of the center through opening  467 , are clearly shown in this view mounted to the upper surface of plate  460 , each pull-pin  463  having a pin portion  468  which, in the relaxed position, are urged downward by spring tensioning, extending to a distance somewhat below the bottom surface of plate  460 . Pull-pins  463  are provided with handle grasps  464  enabling the user to easily grasp the pull-pins and raise the mechanism such that the bottom of each pin portion  468  may be elevated above the bottom surface of plate  460 .  
         [0237]     A clearance channel is designed into plate  460 , located directly below each row of width stance adjustment holes  465 , providing clearance for the lower end of a bolt fastener, and possibly a nut fastener if so incorporated, when an attachment such as a footpad assembly is secured to the upper surface of plate  460 . In such a manner, plate  460 , with pull-pins  463  raised, may freely slide along the length of slide plate  451  of  FIG. 20A ,B while the footpad assembly is secured to plate  460 .  
         [0238]      FIG. 22  is a top view of slide plate  451  of  FIG. 20A  and a pair of sliding attachment plates  460 A and B of  FIG. 21A  according to an embodiment of the present invention. The manner in which attachment plates  460 A and B are adjustably mounted to slide plate  451  is illustrated in this view. For the purpose of clarity, attachment plates  460 A and B are shown not to have an exercise attachment, such as a suspended footpad assembly affixed thereto.  
         [0239]     As mentioned above, plates  460 A and B are adapted to slide over the ends of slide plate  451 , guided by rounded edges  453  of plate  451  which are encompassed by the rounded edge channels of each plate  460 . In attaching attachment plate  460 A to slide plate  451 , first the user manually raises both pull-pins  463  at the same time, allowing plate  460 A to slide over the end of plate  451 . Next, the user releases pull-pins  463  into the relaxed, extended position, and then depresses push-pin safety button  452 , such that clearance is provided for sliding attachment plate  460 A further onto plate  451  towards the center. Although pull-pins  463  of attachment plate  460 A are naturally extended due to the spring tensioning, plate  460 A still freely slides along plate  451  until the lower pin portions of pull-pins  463  encounter one set of width stance adjustment holes  455 .  
         [0240]     Attachment plate  460 B is shown in this view after sliding it over the left end of plate  451 , located in a desired stance position, in this case, the sixth position to the left of center. Once attachment plate  460 B slides over the end of plate  451  towards the center, the user may hold pull-pins  463  in the raised position while sliding plate  460 B, until pull-pins  463  align directly above the desired set of adjustment holes  455 , at which time the user releases pull-pins  463 , which urges the lower pin portion of the pull-pins down into adjustment holes  455 . Repositioning attachment plate  460  simply involves manually raising pull-pins  463 , sliding plate  462  new desired position, aligning pull-pins  463  with the new set of adjustment holes  455  at the new location, and then releasing pull-pins  463 , thereby locking plate  460  into the new position.  
         [0241]      FIG. 23  is an elevation view of a suspended footpad assembly  470  and a sliding attachment plate  460  of  FIG. 21A . Suspended footpad assembly  470  is similar to suspended footpad assemblies previously described herein, such as footpad  79  of  FIG. 12 , and in related U.S. patents and applications, comprising a footpad support structure  473 , a pivoting footpad  476  which has support wings  475  extending upward from footpad  476  on either side, suspended within support structure  473  by a pair of pivot points  474  a set of four through holes  471  (only two of which are shown in this elevation view) pass through the base of support structure  473 , and are aligned with a set of four mounting holes  465  of attachment plate  460 . Footpad assembly  470  is lowered down onto the upper surface of attachment plate  460 , holes  471  of support structure  473  aligned with holes  465  of plate  460 , and footpad assembly  470  is then affixed to plate  460  utilizing standard screw fasteners  479 .  
         [0242]     Although a suspended footpad assembly is shown in the illustration for attaching to attachment plate  460 , a variety of attachments other than a suspended footpad assembly as shown, such as are described further in detail, may be attached to attachment plate  460 , according to alternative embodiments of the present invention, thereby providing the user the ability to perform exercises on a ski apparatus such as has been described, in training for sports other than downhill skiing, and for strengthening and rehabilitation exercises as well, without departing from the scope and spirit of the present invention.  
         [0243]      FIG. 24  is an elevation view of footpad assembly  470  and attachment plate  460  of  FIG. 23  and slide plate  451  of  FIG. 20A  attached to a wheeled carriage assembly according to an embodiment of the present invention. For simplicity, not all of the elements previously described are shown in this view, only those elements pertinent to the present description.  
         [0244]     As shown in the illustration, slide plate  451  is attached to carriage assembly  484  utilizing bolt fasteners  486 , which are inserted up through openings in the upper surface of carriage assembly  484 , and are then secured by nut fasteners  487 . The manner in which slide plate  451  attaches to carriage  484  is not limiting, however, in describing embodiments of the present invention. For example, bolt fasteners  486  may be inserted down through the provided openings of slide plate  451 , and secured with a nut fastener from below the upper surface of carriage assembly  484 , or alternatively a type of fastener other than bolt fasteners  486  and nut fasteners  487  may be utilized in various embodiments. What is important, however, is that whichever type of fastener is used, the nut fastener or head of a bolt fastener must not project substantially above the upper surface of slide plate  451 , so as not to interfere with the sliding of attachment plate  460 .  
         [0245]     Suspended footpad assembly  470  is affixed to attachment plate  460  utilizing screw fasteners  479 , thereby forming a footpad/plate assembly  472 . Assembly  472  is adjustably mounted to plate  451  according to an embodiment of the present invention, with edge channels  469  of attachment plate  460  neatly encompassing the rounded outer edges  453  of plate  451 , guiding attachment plate  460  as it slides along the length of plate  451 . Once assembly  472  is positioned on slide plate  451  at the desired width stance location according to location adjustment holes  455  of plate  451 , pull-pins  463  (not shown) are released, urging the lower pin portions into the adjustment holes  455  of plate  451 , thereby locking assembly  47 2 into the desired position on plate  451 .  
         [0246]     Assembly  472  is fixedly attached to slide plate  451  utilizing bolt fastener  480 , which is inserted down through center hole  467  of attachment plate  460 , before assembly  472  is mounted to plate  451 . In practice of mounting footpad/plate assembly  472  to plate  451 , suspended footpad assembly  470  is pre-attached to attachment plate  460  utilizing screw fasteners  479 , as described above. Bolt fastener  480  is then inserted down through center opening  477  of the base of footpad support structure  473 , through center opening  467  of attachment plate  460 , and a special nut fastener  482  is then partially threaded onto the threaded portion of bolt fastener  480 . Footpad/plate assembly  472 , with bolt fastener  480  extending below the bottom surface of attachment plate  460 , then slides onto the end of slide plate  451 , as described above, such that the threaded portion of bolt fastener  480  passes along in between slot opening  461  of plate  451 , and the attached nut fastener  482  slides along the rectangular passage  466  within the center structure  464  of plate  451 . Once assembly  472  has been positioned as desired, and pull-pins  463  have released down into the proper set of adjustment holes  455  of plate  451 , locking assembly  472  into position on plate  451 , bolt fastener  480  may then be tightened from above the base of support structure  473  of suspended footpad assembly  470 , thereby securing assembly  472  to plate  451 . Nut fastener  482 , in the embodiment shown, is square in shape and substantially flat, and is prevented from rotating within passage  466  while bolt fastener  480  is tightened, due to the width dimensions of nut fastener  482  being just somewhat less than the width of passage  466 .  
         [0247]      FIG. 25A  is a top view of slide plate  451  and attachment plate  460  to of  FIG. 22 , a pair of suspended footpad assemblies of  FIG. 24  attached to a wheeled carriage assembly according to an embodiment of the present invention. In this view a pair of independent footpad/plate assemblies  472 , each comprising a suspended footpad assembly  470  attached to attachment plate  460 , are mounted to plate  451 , each assembly  472  located at the desired width stance position by aligning pull-pins  463  over the desired set of adjustment holes  455  of plate  451 . In the example shown, each assembly  472  is first slid over each end of plate  451  after manually depressing each push-pin safety button  452 , and is then slid towards a center of plate  451  and located at the third position outward from the center of slide plate  451 . Once pull-pins  463  are centered over the desired set of adjustment holes  455 , pull-pins  463  are released, thereby urging the lower pin portions down into their respective adjustment holes  455 , securing each footpad assembly in its location. Each assembly  472  is then secured to plate  451  using the bolt fastener  480  and nut fastener  482 , combination (not shown) as described above for  FIG. 24 .  
         [0248]     Slide plate  451  is shown in this view mounted to the upper surface of wheeled carriage assembly  484  as described for  FIG. 24 , utilizing bolt fasteners  486  and nut fasteners  482  (not shown). In a preferred embodiment of the present invention, width stance adjustment holes  455  of plate  451 , which correspond to the various different width stance locations, are sequentially numbered, or otherwise similarly marked, outward from the center on the upper surface of plate  451 , such that the width stance position of the pair of footpad/plate assemblies may always be centered on plate  451 , regardless of the width stance chosen. For example, in the illustration given, footpad/plate assembly  472 A his located at the third width stance position to the left from the center position of plate  451 , and assembly  472 B is located at the third position to the right of the center position of plate  451 . For proper centering and balance each assembly  472  is located at the same numbered or marked position outward from the center. For instance, for a wider width stance position, assembly  472 A may be positioned at the sixth set of adjustment holes  455  to the left of the center of plate  451 , as shown in  FIG. 22 , and assembly  472 B would then be located at the six set of adjustment holes  455  to the right of the center of plate  451 . The distance from the first footpad assembly from the center of plate  451  should always be equal to the distance between the second footpad assembly from the center of plate  451 , for proper centering and balance.  
         [0249]     If, for any reason, attachment bolt fastener  480  securing assemblies  472  to plate  451  loosens inadvertently, or the pull-pins somehow dislodge, during operation, push-pin safety buttons  452 , always protruding upward from the upper surface of plate  451  in their normally relaxed position, will stop assemblies  472  from sliding of the end of plate  451 , thereby providing an additional safety feature for the user if such an instance occurs.  
         [0250]      FIG. 25B  is an elevation view of slide plate  451 , attachment plates  460 , suspended footpad assemblies  470  and wheeled carriage assembly  484  of  FIG. 25A . Again, for simplicity, many elements previously described herein are not shown in this view, such as fasteners, elements of carriage assembly  484 , and so on. Only elements pertinent to the present description are illustrated and described here. Both footpad/plate assemblies  472 , each comprising a suspended footpad assembly  470  attach to an attachment plate  460  per shown mounted to plate  451  according to an embodiment of the present invention, each assembly  472  located at the third position outward from the center of plate  451 . Pull-pins  463  of plates  460  are shown in the relaxed extended position, the lower pin portions of each extending down into the respective adjustment holes  455  of plate  451 . Assemblies  472  may be easily and quickly repositioned inward or outward along the length of plate  451  simply by loosening bolt fastener  480  (not shown) which fixedly attaches each assembly  472  to plate  451 , raising pull-pins  463  such that the lower pin portions are elevated above adjustment holes  455  of plate  451 , and sliding assemblies  472  along plate  451  to the new positions, with pull-pins  463  and the desired set of adjustment holes  455  aligned with each other at the new positions, at which time pull-pins  463  will naturally extend down into the new adjustment holes  455  as described above.  
         [0251]     Push-pin safety buttons  452  are shown at each far end of plate  451 , in their relaxed extended positions, which prevent assemblies  472  from sliding of the ends of  451 . Safety buttons  452  may be depressed to allow assemblies  472  to slide of the end allowing the user to quickly and easily interchange various sliding attachment assemblies formed by attachment plate  460  and a suspended footpad assembly, such as assembly  470 , or other attachments for different exercises, as described previously.  
         [0252]     As described above for previous embodiments illustrated, attachment plate  460  is adapted for mounting footpad assemblies for ski exercises, as shown in previous illustrations, and may also be used for fixing other exercising attachment elements for providing a variety of different exercises possibilities to the user utilizing a ski apparatus as described herein and in related U.S. patent and applications referenced herein.  
         [0000]     Upper Body Conditioning  
         [0253]     The inventor of the present invention has discovered that the ski apparatus embodied in the present application and related patents and applications, may be effectively used for allowing advanced upper body conditioning (UBC) and core muscle and body strengthening exercises. The ski apparatus of the present invention, when used with special exercise attachments as are subsequently described, provides what is known in the art as neuromuscular training. It is for this area of exercising that the following new and novel attachments, used with the ski apparatus of the present invention as described herein, are provided. Such attachments, as will be described below in enabling detail, allow the exercise therapist or trainer to accomplish a number of exercises including shoulder strengthening and stabilization, as well as alternate core muscle conditioning, while allowing the therapist/trainer to spot control upper body movements.  
         [0254]      FIG. 26A  is an elevation view of an upper body conditioner (UBC) elevated grip according to an embodiment of the present invention. UBC elevated grip  490  is provided as one part of a dual-handle attachment system allowing such exercises and strengthening/rehabilitation as described above, which can be adjusted quickly into several different width settings for providing different exercises specific to different areas of the body.  
         [0255]     UBC grip  490  in aid for embodiment comprises a hollow, lightweight tubular metal structure formed by tubing  493 , having a grip covering  498  formed of rubberized foam material or similar material providing a comfortable but secure grip to the user. UBC grip  490  as a straight portion on the upper end defined by dimension (G), which forms an upper grip portion which allows the user to grasp the attachment directly from above. Angled portions, defined by dimensions (H), extend downward from the ends of the upper grip portion G, which provide the user with an elevated gripping portion accessed from the side. Each angled portion H then curves downward and inward towards the center, and then angles perpendicular to the straight upper grip portion G, forming mounting extensions  495 , which are clearly illustrated in  FIG. 26B .  
         [0256]     Mounting extensions  495  provide the mounting interface with which to mount UBC grip  490  to an attachment plate  460 , such as described previously. Each mounting extension  495  has a set of through openings  496 , each opening  496  passing completely through tubing  493 , for accommodating standard bolt fasteners.  
         [0257]      FIG. 26B  is a top view of UBC elevated grip  490  of  FIG. 26A . From this vantage point, mounting extensions  495  can now clearly be seen extending perpendicular to the direction of upper grip portions of dimensions (G) and (H). A pair of through openings  496  are shown extending through each mounting extension  495 . The distance between the center of each set of through openings  496 , defined by dimension (K), is equal to the distance between the center of each opposing set of mounting holes  465  of attachment plate  460 , defined by dimension (S), of  FIG. 21B , such that the mounting holes  496  of mounting extensions  495  aligned with a set of mounting holes  465  of attachment plate  460 .  
         [0258]      FIG. 27A  is a top view of a UBC lower grip according to an embodiment of the present invention. UBC lower grip  510  is formed of lightweight metal tubing  513  of similar composition and diameter of that of UBC elevated grip  490  of  FIG. 26A , B., and also comprises a grip covering  517  covering a substantial portion of the length of grip  510  in two sections. A pair of through openings  515  are provided for mounting grip  510  to an attachment plate assembly for ultimately mounting to a wheeled carriage assembly of a ski apparatus as will be further described herein. Through openings  515  extend completely through both sides of tubing  513 , and have a center-to-center distance, defined by dimension (L), equal to that of dimension (K) of elevated grip  490  of  FIG. 26B . A grip portion  519 , opposite of the mounting end, having a length substantially greater than the portion defined by dimension (K), provides a large gripping area enabling the user to fully grasp grip  510  by hand.  
         [0259]      FIG. 27B  is an elevation view of UBC lower grip  510  of  FIG. 27A . Lower grip  490  is provided as a second part of a dual-handle attachment system allowing such exercises and strengthening/rehabilitation as described above, the system being quickly and easily adjustable into several different width settings for providing different exercises specific to different areas of the body. In this view the lower grip portion  519  is shown having an angled portion extending downward from one end of the mounting portion, the angled grip portion defined by dimension (J). Lower grip portion  519  is angled such that the user is enabled for gripping from the side, at a lower level than back at which grip  510  is mounted, providing the user with varying grip positions for strengthening and rehabilitation of different parts of the body.  
         [0260]     Upper grip  490  and a lower grip  510 , when used with the ski apparatus and wheeled carriage and attachment mounting apparatus described herein, provide a new and unique dual-handle gripping system mountable to the wheeled carriage of the ski apparatus of the present invention, having the benefits of being quickly adjustable into many different width positions and quickly and easily interchangeable with, such as, ski footpad assemblies as described herein. The user is thereby enabled for achieving a number of advanced lateral-motion strengthening, stretching, stabilization and rehabilitation exercises not previously available for any lateral-motion ski apparatus of the prior art, as well as for minimizing the time and effort involved in changing the exercise function of the ski apparatus.  
         [0261]      FIG. 28A  is a top view of UBC elevated grips  490  of  FIG. 26A  and UBC lower grips  510  of  FIG. 27A , attachment plates  460 , slide plate  451  and wheeled carriage  484  of  FIG. 25A , assembled according to an embodiment of the present invention. Slide plate  451  is affixed in the center position to the upper surface of roller carriage  484  utilizing standard bolt fasteners passed through openings  457  in the center, as described previously for  FIG. 25A , B. Also described in  FIG. 25A , B, suspended footpad assemblies are attached to the slide plates  460  forming a footpad/plate assembly  472 , and the assembly then slides over the ends of plate  451  towards the center for mounting on slide plate  451  at the desired position according to width stance adjustment holes  455 .  
         [0262]     However, in the embodiment presently illustrated the suspended footpad assemblies have been replaced with two upper body conditioning (UBC) grip assemblies each comprising one elevated grip  490  and one lower grip  510 , each set of grips mounted to a sliding attachment plate  460 , thereby forming UBC attachment assemblies  491 . UBC attachment assemblies  491 , as seen from the perspective given in this view, are formed by first placing elevated grip  490  atop an attachment plate  460 , aligning the four through openings of the mounting portions of grip  490  with four mounting openings of attachment plate  460 , the length of the upper grip portion of grip  490  perpendicular to the longer length of attachment plate  460 . A set of standard bolt fasteners  514  secure the portion of grip  490  towards the grip portion, securely to the upper surface of attachment plate  460 .  
         [0263]     Before securing the other end of the mounting portion of grip  490 , a lower UBC grip  510  is placed atop each end of the mounting portion of UBC grip  490 , the length of each lower grip  510  parallel to that of upper grips  491 , and its pair of mounting through openings  515  aligned with the end pair of through openings  496  of upper grip  490 , which align with mounting holes  465  of plate  460 . A pair of standard bolt fasteners  516 , significantly longer than bolt fasteners  514 , having sufficient length to pass completely through the thickness of both lower grip  510  and upper grip  490 , are then used to secure grips  510  over grips  490  and then to plate  460 . In a preferred embodiment, as is true for suspended footpad assemblies  472  of  FIG. 25A , each attachment assembly  491  comprising an elevated grip  490 , lower grip  510  and sliding attachment plate  460  is pre-assembled, and therefore quickly and easily interchangeable on slide plate  451  with those of suspended footpad assemblies  472  of  FIG. 25A , for example, or other attachment assemblies in alternative embodiments, and may also be quickly relocated to different positions on slide plate  451  as desired.  
         [0264]      FIG. 28B  is an elevation view of slide plate  451 , attachment plates  460 , wheeled carriage  484 , UBC elevated grips  490  and UBC lower grips  510  of  FIG. 28A . The inventor provides the elevation view to clearly illustrate the multiple gripping locations provided by the UBC system described herein, and the mounting configuration when attached to attachment plate  460 . Slide plate  451  is attached to carriage assembly  484  in a similar manner to that described herein for  FIG. 24  above, and attachment plate  460  is shown as it fits over slide plate  451 , also similar to that previously described for  FIG. 4 .  
         [0265]     Lower grip  510  is shown secured atop the mounting extensions of upper grip  490  secured with standard bolt fasteners  516  which are tightened into the mounting holes of attachment plate  460 . As can be seen in this view, a void is formed by the rectangular indention into the under surface of plate  460 , allowing bolt fasteners  516  to be tightly secured UBC assembly  491  is free to slide back and four along the length of slide plate  451 .  
         [0266]     The lower angled portion of lower UBC grip  510  provides the user with a gripping position from the side which positions the grip lower than the level of the upper surface of wheeled carriage  484 , for enabling such exercises which require the body of the user to be at a low angle to the floor. UBC upper grips  490  provide several additional gripping angles including at least two gripping positions at different angles on either angled side, and a straight upper portion spanning the angled ends providing a lengthy gripping portion from directly above. The variety of such upper and lower gripping areas provided by UBC assembly  491  enable many different additional lateral stretching and stabilization exercise movements using the ski apparatus of the present invention, as will be apparent to the skilled artisan.  
         [0267]     In embodiments of the present invention described herein, or part of or related to U.S. patents and applications referenced herein, independent-action suspended footpad assemblies for mounting on a wheeled carriage of the ski apparatus have been described previously utilizing embodiments of the present invention. Referring out to  FIG. 25A , B, the independent footpad assemblies, such as assemblies  472  of  FIG. 25A  may be adjusted to different width stances on the slide plate which attaches to the wheeled carriage assembly, by means of the sliding attachment plate coupled to the suspended footpad assemblies, which forms the interchangeable footpad assembly unit. Footpad assemblies  472  slide along the length of slide plate  451  until locked into their position according to the width stance adjustment holes of the sliding plate, and are then locked into the desired location by pull-pins  463 , and a securing bolt fastener as described previously, thereby preventing forward, backward or lateral of the footpad assembly  472  on plate  451 .  
         [0268]     Referring again to  FIG. 25A , the suspended footpad assemblies  472  comprise a suspended footpad which pivots from side to side within the structure of the frame of the footpad assembly, to more closely simulate, during operation of the ski apparatus, at least the lateral motions, forces and dynamics exerted on the lower extremities of the user during actual downhill skiing. However, it is known that there are many other forces other than lateral forces, which exert on the lower extremities of the user during downhill skiing, particularly over steep and sharply variable terrain. During such conditions, the users feet are not held parallel for any significant period of time, and particularly when skiing over steep, bumpy terrain, the tips of the skis are constantly moving up and down, thereby pivoting each ski independently at the skiers ankles.  
         [0269]     A significant need thereby exists in the field of ski training apparatus for such extreme conditions, and in many other conditions as well, for the capability in a ski exercise machine to accurately reproduce such forces and movements other than lateral pivoting of the footpad assembly, as described thus far. Applicant&#39;s invention, in embodiments presented below in enabling detail, provides a new and novel interface for mounting a footpad assembly to the wheeled carriage of the ski apparatus of the present invention, providing the tensioned lateral movement and footpad pivoting action of embodiments disclosed herein, and also incorporating the ability for each footpad to slide forward and backward independently from one another, and still further incorporating independent front to back pivoting of each footpad assembly. The user of such an improved apparatus is enabled to better simulate the actual movements, forces and dynamics of the sport, to a significant degree, and further achieve a level of balance controls, due to the front to back sliding and pivoting action of each independent footpad assembly, that is not achievable in prior art ski exercise apparatus.  
         [0270]      FIG. 29A  is a top view of a footpad pivot base according to an embodiment of the present invention. Pivot base  520  is preferably manufactured of strong, lightweight metal such as aluminum or some other material of similar strength and rigidity, and provides the supporting base structure portion for a sliding/pivoting footpad attachment interface system, as well as enabling a front to back sliding action for the footpad assembly, as will be shown in the embodiments detailed below.  
         [0271]     Pivot base  520  is rectangular in shape, having outside dimensions approximately equal to that of sliding attachment plate  460  of  FIG. 21  (A, B). The Pivot base  520  comprises a support base portion  533 , which is substantially flat and has a material thickness of approximately ½-¾ in., sufficient for substantial overall strength and rigidity of the structure. A set of through openings  529  extend completely through the thickness of base portion  533  located near each of the corners of base  533 , located to correspond with the mounting holes of the upper surface of the sliding attachment plate  460  disclosed herein, enabling mounting of pivot base  520  to attachment plate  460  using standard bolt fasteners. Pivot base  520  is also provided with a center through opening  531  enabling access to the center sliding securing bolt and nut fastener for securing attachment plate  460  to slide plate  451 , as described above.  
         [0272]     Pivot base  520  comprises a pair of elongated support structures  523  protruding upward from base  533  to a height substantially greater than the thickness of base  533 , and extending parallel to the length of base  533 . Structures  523  are preferably attached permanently to the upper surface of base  533 , or in alternative embodiments may be otherwise securely affixed to the upper surface of base  533  using standard fasteners, and so on. Each support structure  523  resembles a rectangular bar having a thickness approximately equal to the thickness of base  533 , and a height approximately twice that distance.  
         [0273]     Located near the outward opposite ends of each structure  523 , a pair of elongated slots  525  are formed completely through the thickness of structures  523 , the set of elongated slots of one structure  523  aligned with those of the opposite structure  523 . Each elongated slot  525  is adapted to accommodate the wheels of a roller assembly supporting a rolling footpad pivot support structure, as will be further detailed below.  
         [0274]      FIG. 29B  is an elevation side view of footpad pivot base  520  of  FIG. 29A , which illustrates the height and shape of structure  523  and location of elongated roller slots  525 . In the example shown, a pair of elongated slots  525  are shown, each slot  525  identical in size to the other within each support structure  523 , the left ends of each slot  525  distanced from each other as defined by dimension (M). Dimension (M) is equal to the distance between the rollers of a pair of roller assemblies on one side of a rolling footpad pivot support structure, as will be shown below, such that the outer ends of each elongated slot  525  provide a stop point for the rolling footpad pivot support structure, providing the range limit for the rollers traveling within slots  525 . The inner surfaces of each slot  525  form a roller surface  527  providing a smooth surface onto which a roller may travel.  
         [0275]     In alternative embodiments, however, the size and number of elongated roller slots  525  may vary depending on the size of the roller assemblies adapted to travel within, and their distance apart from each other, as well as the distance of travel desired. In some alternative embodiments support structures  523  may be secured to base  533  utilizing such as standard bolt fasteners, for example, allowing the user to interchange existing structures with other structures which may have elongated slots of different length, size, location and so on, to accommodate different rolling pivot support structures, for example. The preferred embodiment illustrated utilizes a pair of elongated slots  525  which are located within structure  523  so as to form a large supporting bridge of material between each elongated slot within a structure  523 . The inventor has determined that two such slots are the preferable configuration for the preferred embodiment, combining sufficient roller travel distance defined by the length and location of slots  525 , with substantial structural integrity.  
         [0276]     Through openings  529  are shown (hidden view) extending completely through the thickness of base  533  for accommodating bolt fasteners for securing structure  520  to an attachment plate  460 , in one embodiment, and through opening  531  is seen extending through the thickness of base  533  at the center, allowing access from above to the sliding securing bolt and nut fastener for attachment plate  460 .  
         [0277]      FIG. 29C  is an elevation end view of footpad pivot base  520  of  FIG. 29A . From this perspective the pair of elongated support structures  523  can be seen extending up from support base  533  near each edge, with the elongated slots  525  shown extending completely through each support structure  523 , forming the inner roller surfaces  527 . The center-to-center distance between each elongated slot  525 , as defined by dimension (L) is equal to the center-to-center distance between opposite rollers on a rolling support pivot plate adapted to travel within slots  525 , as will be shown further in detail. The width of dimension (L) may vary, however, in alternative embodiments depending on the width of the rolling support plate utilized. For example, as mentioned above, support structures  523  may be removably and adjustably attached to base  533  using bolt fasteners such that the support structures may be repositioned at different widths on support base  533  and re-secured utilizing different sets of mounting holes in support base  533 .  
         [0278]      FIG. 30A  is an elevation end view of a footpad pivot support structure according to an embodiment of the present invention. Footpad pivot support structure  540  is a further key element in the new and innovative dual-action footpad assembly attachment system which enables an attached footpad assembly to slide forward and backward as well as pivot forward to backward, to a predetermined degree. Pivot support structure  540  is manufactured using similar materials and process as for support base  520 , having the best combination of light weight and overall structural rigidity.  
         [0279]     Pivot support structure  540  comprises a base portion  541  having a thickness approximately equal to that of base  533  of support structure  520 , approximately ¾ inches in the embodiment presented, and having a rectangular shape also having similar in dimensions to that of rectangular shape of support structure  520 . A center through opening  554  is provided in base  541  for allowing the user access from above to the center sliding securing fastener, such as fastener  480  describe for  FIG. 24 .  
         [0280]     A pair of vertical support members  547  forms walls extending upward from the upper surface of base  541  along each opposite edge, forming a distinct U-shaped structure, support member  547  extending to a height approximately equal to half the width of base  541  in the embodiment shown, and extending along the entire length of base  541 . Support member  547  has a thickness somewhat greater than that of base  541 , and are preferably permanently attached to base  541  by welding, or casting, or the like, or in alternative embodiments may be removably attached to base  541  using standard bolt fasteners, for example, and the width distance between support member  547  may also be adjustable by utilizing different sets of mounting openings (not shown) through base  541 , for instance, similarly to structures  523  of support structure  520 , so as to accommodate additional elements of different sizes, and so on.  
         [0281]     Each vertical support member has a large, arcuate slot  543 , curving somewhat upward at each end from the center, extending completely through the thickness of walls  547 . The inner surface  544  of each arcuate slot  543  is modified to provide a smooth roller surface, similarly to that of elongated roller slots  525  of  FIG. 29 B , except for the outer opening of arcuate slot  543  is somewhat greater than the opening to the inside of support members  547 , adapted as such for accommodating a roller assembly while minimizing lateral movement of the rolling assembly, as will be shown in greater detail in embodiments presented below. Dimension (Q), as shown in the illustration, defines the distance between the beginnings of the larger outward-facing opening of arcuate slots  543  of opposing vertical support structures  547 .  
         [0282]     A plurality of through openings  545  extend completely through the thickness of one wall  547 , shown on the left in  FIG. 30A , and a corresponding number of threaded openings  546 , having the same number and pattern of through openings  545 , extend into the opposite support member  547 . Arcuate slot  543  and openings  545  and  546  are better illustrated, however, in the following figures.  
         [0283]     Pivot support structure  540  is provided with a pair of roller support structures  549  which are similar in size and rectangular bar-shape to structures  523  of support structure  520  of  FIG. 29C , and are also, in a preferred embodiment, permanently attached by welding or formed by other permanent means on the bottom surface of base  541 , and extend along the entire length of base  541 . Roller support structures  549  extend down from the bottom surface of base  541 , and are provided with a plurality of mounting holes  555 , in this case a total of four, for the purpose of rotatably attaching four roller assemblies  552 , one pair of roller assemblies  552  attached to each roller support structure  549 , facing outward. Roller assemblies  552  comprise a roller  551  rotatably secured to support structures  549  utilizing roller axles  553  secured within mounting holes  555  of structures  549 . In the embodiment presented roller assemblies  552  heavy-duty, high-performance rollers designed to withstand substantial downward force while still rotating freely. Roller assemblies  552  are designed to at least support the weight of any exercise user adding that additional lateral forces related to the tensioned side-to-side action operation of a wheeled carriage assembly during operation of a ski apparatus as previously described.  
         [0284]     In the embodiment presented footpad pivot support structure  540  is adapted to roll freely back and forth within the set of elongated roller slots  525  of support structure  520  of  FIG. 29 , supported by roller assemblies  552 . Roller assemblies  552  are located beneath base  541  on structures  549  such that the center-to-center distance between each opposing roller  551 , defined by dimension (N) in the example presented, is equal to dimension (L) between structures  523  of support structure  520  of  FIG. 29C . In alternative embodiments however, dimensions (N) and (L) may vary somewhat, as long as they are equal in dimension to each other.  
         [0285]      FIG. 30B  is an elevation side view of footpad pivot support structure  540  of  FIG. 30A . The size and shape of arcuate slot  543  is clearly seen in this view, as are the locations of through openings  545 . As mentioned previously, although only one vertical support member  547  is visible in this elevation view, threaded openings  546  extending into the opposite (hidden) support member  547  are located and spaced identically to through openings  545 . The grooved roller surface formed by the inner walls of arcuate slot  543  is also clearly visible in this view.  
         [0286]     Two of the four roller assemblies  552  are visible in this view attached to facing side of one of structures  549 , near the forward and rearward ends of structure  549 , approximately halfway between the top and bottom of structure  549 . As mentioned previously relative to support structure  520  of  FIG. 29B , elongated slots  525  each provide a forward or rearward stopping point for roller assemblies traveling back and forth within. Dimension (M) defines the distance between the left edge of a first elongated slot  525 , and that of the second slot  525 . In the embodiment presently illustrated, the center-to-center distance between the forward and rearward roller assemblies  552 , defined by dimension (P) in the illustration, is exactly equal to that of dimension (M) of  FIG. 29B . As with the center-to-center width dimensions of opposing roller assemblies, as shown in  FIG. 30A , the center-to-center length dimension (P) of  FIG. 30B  may vary in alternative embodiments as long as it equals dimension (M) of  FIG. 29B , as it is preferable that when footpad pivot support structure  540  is rolling back and forth within elongated slots  525  of support structure  520 , the stopping points provided by the ends of elongated slots  525  should stop both rollers at exactly the same time when the rolling travel distance of support structure  540  has reached the limit.  
         [0287]      FIG. 30C  is a top view of footpad pivot support structure  540  of  FIG. 30A . In this view, the rectangular shape of base  541  is now clearly seen, and with vertical support members  547  located at each opposite edge of base  541 . All four roller assemblies  552  are seen in the hidden view, rotatably to roller support structures  549  attached near each end, structures  549  each having a thickness approximately equal to vertical support members  547 , and extending along the entire length of base  541  approximately halfway between the center and either edge of base  541 . Through opening  554  is shown extending completely through the center of base  541  for accessing the sliding attachment plate securing fastener as described above.  
         [0288]      FIG. 31A  is a top view of a pivot roller base assembly according to an embodiment of the present invention. Pivot roller base assembly  560  is provided as a further key element in the new and novel dual-action pivoting footpad attachment assembly of the present invention. Base assembly  560  is provided as essentially a rolling base adapted for attaching an exercise attachment such as suspended footpad assembly  470 , shown in  FIG. 24 . Base assembly  560  comprises a base portion  563 , which is rectangular in shape, substantially flat and manufactured of strong, lightweight aluminum or similar material similarly to other footpad pivot system elements described above. Base  563  has a width dimension, which is somewhat less than the distance between the internal walls of vertical support members  547  of pivot support structure  540  of  FIG. 30A , enabling roller base assembly  560  to freely move forward and backward between vertical support members  547 , while minimizing side play. A distance (S) defines the distance between the inner edges the rollers of each set of forward or rearward roller assemblies  565  on opposing sides of base  563 , a distance defined as dimension (R) in the illustration, is equal to dimension (Q) of  FIG. 30A  defining the distance between the beginning of the larger outward-facing openings of arcuate slots  543  of vertical support members  547 . Rollers  565  of roller base assembly  560  travel along roller surface  544 , as shown for support structure  540  of  FIG. 30B , within the larger outward-facing openings formed in arcuate slots  543 .  
         [0289]     A plurality of threaded mounting holes  566 , one located near each corner of base  563 , extend somewhat down into the surface of base  563 , and are positioned on base  563  in accordance with the location of the mounting through openings  471  of footpad support structure  473  of  FIG. 23 , such that suspended footpad assembly  470 , for example, may be mounted in a center position to the upper surface of base  563 , aligning four through openings  471  of footpad assembly  470  with the four corresponding mounting holes  566 , and securing with standard screw or bolt fasteners, as described for  FIG. 23 . As with previous elements illustrated above, a center through opening  564  is also provided extending completely through the thickness of base  563  allowing the user to access the sliding securing faster for the sliding attachment plate  460  described previously  
         [0290]     Pivot roller base  560  also comprises a set of four roller assemblies  565  rotatably mounted to the sides of base  563  near each of the forward and rearward corners, utilizing roller axles  567  and threaded openings, (not shown), extending into the sides of base  563 . Roller base  560  is provided in this embodiment as essentially a sturdy, rolling platform adapted to travel forward and backward within arcuate slots  543  of vertical support members  547  of footpad pivot support structure  540  of  FIG. 30 , while an independent footpad assembly is mounted thereupon as described above.  
         [0291]     As described for footpad pivot support structure  540  of  FIG. 30 , roller assemblies  565  are heavy-duty, high-performance roller assemblies known in the art, capable of supporting at least the weight of exercising user as well as the additional forces placed thereupon by operation of the ski apparatus machine.  
         [0292]      FIG. 31B  is an elevation end view of pivot roller base assembly  560  of  FIG. 31A , clearly showing the thickness of base portion  563  and two of the four threaded mounting holes  566  (hidden view) extending somewhat down into the upper surface of base  563 , and center through opening  564  can be seen extending completely through the thickness of base portion  563 .  
         [0293]     Two of the four roller assemblies  565  are shown in this elevation view, rotatably attached to the sides of base  563 , each roller assembly  565  positioned approximately level with base portion  563 .  
         [0294]      FIG. 31C  is an elevation side view of pivot roller base assembly  560  of  FIG. 31A . From this perspective only two of the four roller assemblies  565  are shown rotatably mounted on one side of base  563 , secured with roller axles  567 . Mounting holes  566  can be seen at their locations near the front and rear ends of base  563 , with through opening  564  extending through the thickness of base  563  at its center.  
         [0295]      FIG. 32A  is an elevation view of footpad pivot base  520  of  FIG. 29B , footpad pivot support structure  540  of  FIG. 30B , and pivot roller base assembly  560  of  FIG. 31C , assembled according to an embodiment of the present invention. Footpad pivot roller assembly  580  is provided as a new and novel dual-action pivoting mounting interface for attaching such as a suspended footpad assembly  470  to a sliding attachment plate  460 , and ultimately to a wheeled carriage of a ski exercise apparatus such as described herein.  
         [0296]     As shown in this view, and described previously, footpad pivot support structure  540  rolls back and forth freely within elongated roller slots  525  of roller base  520 , suspended by roller assemblies  552  rotatably attached to the sides of roller support structures  549  of pivot support structure  540 . The distance range of travel for pivot support structure  540  within roller base  520  is limited by the length of each elongated roller slot  525 .  
         [0297]     Although it is not shown in this view for reasons of simplicity, roller base  520 , in practice of the invention, may be preassembled to a sliding attachment plate  460  for adjustably mounting onto a slide plate  451  mounted to a wheeled carriage  484 , as described for previous figures, or alternately, may also be mounted directly to the upper surface of the wheeled carriage of the ski apparatus exercise machine. In either application, pivot support structure  540  travels freely within elongated slots  525 , providing the free range of motion forward and backward for pivot support structure  540 .  
         [0298]     Pivot base assembly  560  is shown in this view positioned between vertical support members  547 , only one of which is seen in this elevated view, supported by roller assemblies  565  rotatably attached to each side of base assembly  560 , which travel freely within arcuate slots  543  along roller surface  544  adapted for the purpose. As can be seen in this view, base assembly  560  is enabled to travel within arcuate slots  543 , a distance range defined by the outer ends of arcuate slots  543 , and in doing so, enables a tilting action forward or backward for base assembly  560 . In practice of the invention, a suspended footpad assembly, such as footpad assembly  484  of  FIG. 24  is secured to the upper surface of base assembly  560 , and therefore, when attached, tilts forward and backward in accordance with base assembly  560  within arcuate slots  543 .  
         [0299]     The purpose and function of the plurality of through openings  545  of vertical support members  547  also now becomes apparent in this view. From this perspective, through opening  545  are shown arranged linearly, at a slight angle, near each end of arcuate slot  543 . As mentioned previously for  FIG. 30B , a corresponding set of threaded openings  546  (not shown) extending into the opposing vertical support member  547  (also not shown), arranged according to the locations of through openings  545 . Through openings  545  accommodate insertion of a threaded pivot stop bolt  585 , which is of sufficient length such that when fully inserted through an opening  545  the threaded end of pivot stop bolt  585  extends to a corresponding threaded hole  546  in the opposite vertical support member  547 , such that pivot stop bolt  585  may be secured to the threaded hole  546 . An identical pivot stop bolt  585  may also be inserted and threaded as described above that the opposite end of arcuate slot  543 , such that a stop bolt  585  is secured at either end of arcuate slot  543 . The purpose of stop bolts  585  is to provide the user a means for limiting the amount of travel of base assembly  560  within arcuate slot  543 , thereby limiting the tilting action of base assembly  560 , and ultimately an attached suspended footpad assembly. The travel of base assembly  560  within arcuate slot  543  is limited by the bottom corner of base assembly  560  making contact with an inserted pivot stop bolt  585 , as shown in the example presented. The travel/tilting range of base assembly  560  within arcuate slots  543  is increased by inserting pivot stop bolts  585  through outward sets of through openings  545  and threaded holes  546  of vertical support members  547 , and is thereby decreased by inserting pivot stop bolts  585  through inward sets of openings  545  and threaded holes  546 . The number and location of through openings  545  and threaded holes  546  in vertical support members  547  may vary in alternative embodiments of the present invention, those shown in this view are only exemplary.  
         [0300]      FIG. 32B  is an elevation end view of footpad pivot base assembly  520 , footpad pivot support structure  540 , and pivot roller base assembly  560  of  FIG. 32A . In this view, roller assemblies  552  are shown rotatably attached to roller support structures  549 , and positioned within the elongated slots of structures  523  of support structure  520 . Roller assemblies  565 , rotatably attached to pivot base assembly  560 , are positioned within arcuate slots  543  of vertical support members  547  of pivot support structure  540 . One of stop bolts  585  is shown in this elevation view inserted through opening  545  of a first vertical support member  547 , and its threaded end secured into threaded hole  546  of the second vertical support member  547 .  
         [0301]     The assembly shown in  FIGS. 32A and 32B  is meant to be mounted in pairs in a preferred embodiment to a wheeled carriage in the exercise apparatus such that the direction of translation of support structure  540  and of pivot base  560  is at right angles to the direction of travel of the wheeled carriage side-to-side. This arrangement allows a foot pads engaged to elements  560 , thus to a user&#39;s two feet, to translate to a limited degree forward and backward independently and to also rock arcuately, adding these degrees of freedom to the action of the overall apparatus, simulating much more truly the actual experience of slalom skiing.  
         [0000]     Energy Monitoring  
         [0302]     As mentioned above in the background section of the present application, one object of the present invention is to provide a ski apparatus having a monitoring system integrated therein which provides the user with information pertaining to the workout in order to enable the user to best utilize the apparatus and maximize effectiveness of the workout or training. Such information may include elapsed time from start to finish of the workout, goal determination and accomplishment, energy or calories expended by the user, speed of turns, side travel distance of the wheeled carriage, and so on. It is preferable that such a monitoring system is electronic and capable of being retrofitted to all ski exercise apparatus described herein in the present application and in related U.S. patents and applications included herein by reference. Elements of such a new and novel electronic monitoring system and apparatus, termed LifeBeat (LB) by the inventor of the present application, are disclosed in the following figures in enabling detail.  
         [0303]      FIG. 33A  is an elevation side view of a LifeBeat (LB) cable-securing axle according to an embodiment of the present invention. LifeBeat (LB) axle  610  is provided in this embodiment as a roller axle mechanism which enables the connection of an optical sensor actuating cable (not shown) to the underside of a wheeled carriage assembly of a ski exercise apparatus as described herein. LB axle  610  is designed to replace an existing roller axle mounted beneath the wheeled carriage assembly of a ski exercise apparatus which is being retrofitted with monitoring sensor elements as will be described further below in enabling detail.  
         [0304]     LB axle  610  comprises an axle shaft portion  611  onto which an existing carriage roller, such as roller  59  of  FIG. 4 , is rotatably mounted. LB axle  610  also comprises an enlarged stop collar  615  adapted for preventing LB axle  610  from rotating within the carriage roller bracket beneath the wheeled carriage. LB axle  610  comprises an internal threaded portion  614  on one end for securing LB axle  610  to the roller bracket utilizing a standard threaded nut fastener, and an external threaded portion at the opposite end of axle shaft portion  611 , for securing the end of an actuating cable for the optical sensor system as will be described below.  
         [0305]      FIG. 33B  is an elevation end view of cable-securing LB axle  610  of  FIG. 33A . Stop collar  615  of LB axle  610  is clearly shown in this view having a flat portion  617  on either side for preventing LB axle  610  from rotating within the roller mounting bracket of the wheeled carriage assembly, once LB axle  610  is attached.  
         [0306]      FIG. 34  is an elevation side view of a LifeBeat (LB) carriage wheel roller axle assembly according to an embodiment of the present invention. LB roller axle  590  is adapted for retrofitting with roller axles securing existing end rollers of a ski exercise apparatus being retrofitted with the monitoring system of the invention, such as those securing rollers  35  and  37  of ski apparatus  9  of  FIG. 2 . However, LB roller axle assemblies  590  provide a carriage wheel rotatably mounted to roller axle  595  at one end, secured by lock nut  597  and washers  591  and  596 .  
         [0307]     Roller axle  595  is shown in this embodiment as an existing roller axle securing the end power band rollers, such as rollers  35  and  37  of apparatus  9  of  FIG. 2 . LB axle  610  of  FIG. 33A  is shown in this view threaded onto the threaded end of existing roller axle  595 , and a carriage wheel  593  is rotatably mounted over LB axle  610 , secured by lock nut  597 . Star washers  599  are provided for more securely attaching roller axle  595  to the end power band roller mounting brackets, as is illustrated further below.  
         [0308]      FIG. 35  is an elevation side view of an optical sensor unit according to an embodiment of the present invention. LB sensor assembly  600  comprises an optical sensor unit  601 , which senses rotational changes of an attached sensor carriage wheel  603 , secured to optical sensor unit  601  by roller axle bolt  605 . A monitor wire  607  carries the sensed signals from the optical sensor unit to a conventional electronic monitor display unit (not shown) which may be attached to the frame of the ski apparatus, or may otherwise be provided with its own stand, enabling viewing of the displayed monitoring results by the exercising user, and enabling the exercising user to enter information into the monitor display unit. Such a unit and display is common to, for example, commercially-available treadmills.  
         [0309]      FIG. 36  is an elevation view of frame structure  404  of  FIG. 17 , wheeled carriage assembly  484 , slide plate  451 , attachment plate  460 , and suspended footpad assemblies  472  of  FIG. 25A , incorporating an electronic monitoring sensor system according to an embodiment of the present invention. As previously mentioned, elements comprising the LB monitoring system herein described may be retrofitted to existing ski exercise apparatus described in and in related U.S. patents and applications. Ski apparatus  701  is one such machine, comprising a set of semi-arcuate rails  415  upon which wheeled carriage  484  travels back and forth as described herein. For simplicity, a broken view is given for wheeled carriage  484  to show hidden elements, and many other elements such as the three power bands have also been omitted from this view for enabling a detailed view of the key components of the LB monitoring system.  
         [0310]     Suspended footpad assemblies  470  are mounted to sliding attachment plates  460 , which in turn are mounted to slide plate  451 , which is mounted to the upper surface of wheeled carriage  484 , as previously described herein. Wheeled carriage  484  has a power band roller bracket extending down from the underside containing a mounted power band roller, but in the embodiment shown the existing power band roller axle has been retrofitted with LB axle  610 , as shown in  FIG. 33A .  
         [0311]     At each end of apparatus  701 , the existing roller axles rotatably mounting the outer power band rollers at each end, have been replaced with LB roller axle assemblies  590  as shown in  FIG. 34 . LB sensor assembly  600  is mounted to the lower frame structure, near the center, as shown in the illustration, and be attached monitor wire leads away from LB sensor assembly  600  to an external monitor display and input device, as described above.  
         [0312]     An actuating cable  620  is attached at one end of LB axle  610  under wheeled carriage  484 , and is then routed to a first LB roller axle assembly  590  as shown, around the carriage wheel of the first roller axle assembly  590 , and then towards the LB sensor assembly  600 . Cable  620  is then wrapped once around sensor carriage wheel  603  of LB sensor assembly  600 , and then routes on towards the second LB roller axle assembly  590  securing the opposite end roller, where it is routed up and over the carriage wheel of the second LB roller axle assembly  590 , and then back up to LB axle  610  under carriage  484 . The second end of cable  620  is then secured along with the first end to LB axle  610  utilizing standard lock nut fasteners.  
         [0313]     Spring  623  provides constant tension to LB cable  620  once it is properly routed as described around the carriage wheels of LB roller axle assemblies  590  at each end of apparatus  701 , around sensor carriage wheel  603  of LB sensor assembly  600  and attached at both ends at LB axle  610  under carriage  484 . During operation of ski apparatus  701  wheeled carriage travels laterally along rails  415 , as described previously, but sensor carriage wheel  603  of LB sensor assembly  600  is now rotated in one direction or the other in direct relation to physical movements of wheeled carriage  484  along rails  415 . LB sensor assembly  600  and its monitoring display device (not shown) are adapted to interpret the signals provided by the rotating carriage wheel of LB sensor assembly  600  and reproduce the signals on the display monitor in meaningful information readable by the user, such as elapsed time from start to finish of the workout, goal determination and accomplishment, energy or calories expended by the user, speed of turns, side travel distance of the wheeled carriage, and so on.  
         [0314]      FIG. 37  is a top view of the frame structure and sensor system of  FIG. 36 . In this view, LB cable  620  is clearly shown as it routes over carriage wheels  593  of end LB roller axles  590 , and once around sensor carriage wheel  603  of LB sensor assembly  600 , each free end of LB cable  620  attached to LB axle  610 . For simplicity, wheeled carriage  484  is not shown in this view. As shown in the illustration, roller axle carriage wheels  593 , sensor carriage wheel  603 , and a cable attach point of LB axle  610  or all aligned with each other such that LB cable  620  routes over and around them in a straight line.  
         [0315]      FIG. 38  is a perspective view of an adjustable flag assembly according to an embodiment of the present invention. Flag assembly  702  is provided by the inventor as part of the LifeBeat monitoring system described thus far, and has the purpose of giving the exercising user a clear visual and audible indication when the wheeled carriage assembly reaches a certain lateral range limit. Flag assembly  702  comprises a mounting base  715  having an upper clamp  713  secured to mounting base  715  by four bolt fasteners  709 . Clamp  713  is adapted to fit snugly over the rounded shape of transverse end-members  27  of the frame structure of the ski apparatus, a shown in  FIG. 7A , B.  
         [0316]     Flag assembly  702  is also provided with a plurality of flag locator holes  711  extending down into the upper surface of mounting base  715 , adapted for attaching a flag  705  by inserting flag stem  707  into one of locator holes  711 , providing a wide choice of flag stem mounting positions on mounting base  715 .  
         [0317]      FIG. 39  is an elevation view of the frame structure, wheeled carriage assembly, slide plate, attachment plate, suspended footpad assemblies, and sensor system of  FIG. 36  incorporating a pair of flag assemblies  702  of  FIG. 38  according to an embodiment of the present invention. The manner in which flag assemblies  702  are attached at each end of frame structure  701  in one embodiment is clearly seen in this view, utilizing clamp  713  and bolts  709 , which secure mounting base  715  to each rounded transverse member at either end of frame structure  701 . In this example flag  705  are inserted into locator holes near the outermost locator hole position. In other embodiments the method and apparatus for holding flags may be different. During operation of the ski exercise apparatus, carriage  484  travels laterally along rails  415 , and when the outermost travel distance range is achieved by the user, the end of plate  451  mounted on wheeled carriage  484  makes physical contact with flag  705 , giving the user an instant visual and audible indication that the desired outermost travel distance range has been achieved.  
         [0000]     Additional Exercise Equipment  
         [0318]     As previously mentioned, a still further object of the present invention to enable the ski exercising apparatus of the present invention to be used with additional special attachments and other new and novel apparatus, to become a versatile rehabilitation and training tool that simulates the range of motion and balance required in many sports other than downhill skiing, and for selectively stretching, strengthening or rehabilitating specific areas of the body, core stabilization, balance training and many other aspects of selected training and exercise, not possible with using only the ski apparatus as described thus far in the present application. Such a ski exercise apparatus used with such special attachments accurately reproduces the lateral movements required in most sports, thereby optimizing rehabilitation and helping to prevent injury to the user.  
         [0319]     The inventor of the present application has discovered that the ski apparatus of the present invention, in addition to providing the tensioned lateral movement and balance exercises described herein utilizing suspended footpad assemblies and dual-action pivoting independent footpad attachment mechanisms, may also be used for exercises which create progressive resistance to the knee, hip and pelvic core musculature, allowing the user and therapist/trainer the option of implementing isolated progressive resistance at different levels.  
         [0320]      FIG. 40  is an elevation view of the frame structure, wheeled carriage assembly, slide plate, attachment plate, suspended footpad assemblies, sensor system and flag assemblies of  FIG. 39 , an optional support frame and an exercising user, incorporating a progressive-resistance cord system according to an embodiment of the present invention, for providing such isolated progressive resistance exercises, as described above. Ski exercise apparatus  801  comprises the frame structure  701  previously described, including improved semi-arcuate rails  415 , and wheeled carriage assembly  484  utilizing a set of suspended footpad assemblies adjustably attached to carriage  484 , as described above.  
         [0321]     The embodiment illustrated however, comprises an optional support frame  803  for a novice user to hold on to for stabilization while using ski apparatus  801 . Support frame  803 , termed Assistant Coach by the inventor, is equivalent to support frame  14  as described for  FIG. 1A , comprising a set of arcuate rails  807 , each having a grip covering portion, and a transverse cross member  811  which provides stability to the overall frame structure.  
         [0322]     An exercising user  805  is shown operating ski exercise apparatus  801  according to embodiment of the present invention described herein thus far, except that additional resistance is incorporated into the lateral movements of the user, by using the new and unique attachment cord with pulley system, anchor straps and resistance cords designed to be used with support frame  803 .  
         [0323]     Core muscle strengthening may be accomplished utilizing the ski exercise apparatus of the present invention with the use of resistance during exercises on the machine. Resistance cords attached to the upper leg of the user, for example, provide resistance for internal and external rotation, abduction and adduction of the femur during the lateral movements. Resistance cords may also be alternatively attached to a waist strap worn by the exercising user giving resistance to the pelvis and lumbar spine through lateral movements on the exercise apparatus.  
         [0324]     In the embodiment shown, a strap  815  is attached around the upper thigh of the user, and attached to strap  815  is an attachment cord  821 . Attachment cord  821  is routed to and through pulley  817 , which is anchored to support frame  803  just below where it meets cross member  811 , utilizing anchor strap  819 . Cord  821  is routed around the wheel of pulley  817  and then down at an angle where it is attached to an adjusting strap  823 . An elastic resistance cord  825  is anchored at one end to the lower straight portion of support frame  803  opposite from pulley  817 , utilizing another anchor strap  819 , and is connected at the other end to adjusting strap  823 .  
         [0325]     As user  805  moves wheeled carriage assembly  804  laterally across rails  415 , added resistance is selectively applied to the upper thigh area of user  805 , by virtue of the resistance of cord  825 . Resistance cords  825  may be supplied with varying lengths and elasticity to allow the option of implementing isolated progressive resistance at different levels. The length of adjusting strap  823  may also be adjusted to further add to the choice of resistance options. The system comprising movable anchor straps  819  cord  821 , pulley  817  and adjusting strap  823  allow the option of implementing isolated progressive resistance from multiple heights and angles along support frame  803 . Further, a larger version of strap  815  may be used to secure cord  821  to the user&#39;s hip, waist, or chest area, depending on the selective training preference.  
         [0326]     It is noted that the example shown in  FIG. 40  is exemplary only, as the possibilities for achieving different resistance and selectively applying the resistance to specific areas of the body while exercising are plentiful. For example, the user may attach strap  815  to the opposite leg, switch locations of anchor straps  819  and pulley  817  for adding resistance to the other leg while exercising, or in other instances, cord  821 , pulley  817  and adjusting strap  823  may not be used at all, and the user may wish to anchor a resistance cord by one end to each side of a waste belt, and anchor the other ends of the resistance cords directly to frame  803  to the side, giving resistance to the pelvis and lumbar spine through the lateral movements to both sides of the ski apparatus. It will be apparent to the skilled partisan that the possibilities for applying selective resistance to specific parts of the body utilizing the elements described herein is virtually unlimited.  
         [0327]     It will also be apparent to one with skill in the art that the many improvements to existing ski-exercising equipment described as separate embodiments herein add durability, safety, much-improved operating characteristics which more closely simulate the lateral movements required in many sports, adjustability of footpad or other exercise attachments, manufacturability, and convenience over apparatus of the prior art. Moreover, future applications may now be implemented by developing new upper platform assemblies, and still be integrated easily with the improved rail and carriage apparatus, and improved adjustable attachment mechanisms as taught herein. Therefore, the present invention should be afforded the broadest scope possible. The spirit and scope of the present invention is limited only be the claims that follow.