Abstract:
A treadmill comprising a frame for supporting the treadmill on a supporting surface, a deck, secured to the frame to be supported thereby, the deck having a front, a rear, a right and left side, and a tread surface extending from proximate the front to proximate the rear for supporting the weight of a user thereabove. A first roller, may be connected proximate the front of the deck to rotate with respect to the deck, a second roller, may be connected proximate the rear of the deck to rotate with respect to the deck. A belt may be connected to pass continuously over the tread surface and around the first and second rollers, to provide a fully exposed top surface, for unobstructed walking thereon by a user. A motor may be configured to drive the belt, the motor being positioned laterally between the right and left sides of the deck, and below the deck at a location longitudinally between the first and second rollers.

Description:
RELATED APPLICATIONS 
     This application is a continuation of a United States Provisional Patent Application, Serial No. 60/181, 315, filed on Feb. 9, 2000 and directed to a Lightweight, Clear-Path, Equilibrated Treadmill. 
    
    
     BACKGROUND 
     1. The Field of the Invention 
     This invention relates to exercise equipment and, more particularly, to novel systems and methods for configuring, driving and adjusting treadmills. 
     2. The Background 
     In an effort to generally improve one&#39;s health, many people regularly exercise. Some may be motivated by a desire to lose excess weight, while others may be motivated to exercise so that they feel invigorated and have the energy they need to better perform daily activities. Still, others may exercise to combat the effects of a physical ailments such as heart disease or diabetes. 
     Many methods of exercising exist. Fitness centers have been developed to provide a location where paying members may use a variety of exercise equipment and participate in aerobic classes. These fitness centers, however, are typically expensive and involve travel time. As appreciated by those who exercise, it is possible to walk, run, cycle, or the like outdoors. However, outdoor activities are often limited by the weather. In many locations, winter conditions make outdoor exercise unpleasant. Furthermore, outdoor exercise can prove to be a safety hazard for persons exercising alone. 
     Indoor treadmills have proven to be an effective and popular choice of exercise equipment. An indoor treadmill allows a user to exercise in the privacy of his/her home or apartment. Therefore, a user is no longer limited by the weather or the time of day. The treadmill can provide exercise across a variable range of difficulty. A user may adjust the incline of the treadmill to simply walk on a horizontal plane or run at a demanding pace on an incline. These advantages have made treadmills very popular. 
     Treadmills are not, however, without their limitations. Treadmills typically occupy a relatively large amount of space, when compared to other pieces of personal exercise equipment. It is not typically desirable, aesthetically or volumetrically, to leave a treadmill in the public areas of a house or apartment. Due to space limitations, the open public areas of a house or apartment are typically the only spaces large enough to accommodate typical treadmills. 
     Treadmills currently available are heavy, bulky, hard to store, difficult to hide, difficult to transport, and must be professionally delivered adding significant cost and greatly restricting usage. The need exists for a compact, lightweight, stable, easily shipped, easily deployable, easily storable, high quality, home treadmill. Such a treadmill would provide all the benefits of traditional treadmills, while eliminating many of the disadvantages and drawbacks of traditional treadmills. 
     BRIEF SUMMARY AND OBJECTS OF THE INVENTION 
     In view of the foregoing, it is a primary object of the present invention to provide a treadmill that has a small footprint, is readily deployable, is readily and easily storable, and operates smoothly. 
     It is an object of the invention to provide a treadmill designed specifically to allow the efficient use of the power source. 
     It is an object of the invention to provide a home exercise treadmill that uses up to date composite materials to eliminate labor, weight, and cost. 
     Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, an apparatus and method are disclosed, in suitable detail to enable one of ordinary skill in the art to make and use the invention. 
     In certain embodiments an apparatus and method in accordance with the present invention may include a treadmill constructed of composite materials. Constructing the treadmill of composite materials may eliminate over 80% of the metal and weldments of the traditional treadmill. A composite deck may be pivotably connected to a frame. The rigidity of the deck may be designed to meet the treadmill&#39;s strength requirements. Additionally, all nuts may be cast into the composite deck, making the frame, rollers, and motor easily attachable to these mounting points. 
     The deck may be configured to have a smooth, flat tread surface with rollers attached to the front and rear extremes. Moreover, the deck may be further configured with aesthetic skirting to hide the under workings of the treadmill. The deck may be formed in a contiguously molded unit by reaction injection molding (RIM) or rotational molding (Rotomold) processes. The use of composite materials may result in a dramatic reduction in labor, manufacturing machinery, product weight, and production and shipping costs. 
     In certain embodiments, a third roller may be incorporated on the bottom of the deck. A belt may be configured to encircle the deck from front to back, encompassing the front roller, the rear roller, and the third roller. The third roller may be configured to provide sufficient space inside the area encircled by the belt for a motor to fit. By configuring the motor to fit inside the area encircled by the belt, the treadmill may be produced with a compact design as well as allow for the belt to be driven by the rear roller. In another embodiment, the motor is configured to secure to the deck at a location outside the area encircled by the belt while still allowing for a rear drive. 
     The rear drive requires approximately one third less horsepower and torque than a comparable front drive unit. The reduction is caused by the motor pulling the belt from a location much closer to the point at which the load is applied. With the motor secured to the treadmill at a location substantially below the deck, the treadmill may be configured to be hood-less, exposing the entire top belt surface. Current treadmills often use hoods to cover the motor and other drive mechanisms that extend beyond the deck surface. The hood-less design provides for an overall treadmill length approximately eight inches shorter than current treadmills, while providing the same amount of exposed usable belt. 
     Proximate the third bottom roller may be a fulcrum. From the fulcrum forward, the front of the deck may be raised, thus, tilting the tread surface to an incline. The fulcrum may be further configured to allow the front of the deck to be positioned lower than the rear of the deck, thus tilting the tread surface to a decline. The center pivot incline system requires approximately one third less travel to produce the same incline found on typical designs that pivot from the rear. The positioning of this lower pivot creates a balanced or equilibrated deck. A lift mechanism may be mounted between the frame and the front end of the deck. The lift mechanism regulates the incline and firmness of the deck. In certain embodiments, the lift mechanism may be a pair of hydraulic cylinders fed by a small hydraulic pump. The center pivot and resulting balanced deck greatly reduce the load that must be resolved by the lift mechanism, thus, simplifying the necessary mechanical design and associated costs. 
     In certain embodiments, an air bearing may float the belt over the tread surface by forcing air through numerous ports that run the length of the tread surface. The air ports may be concentrated in the center of the tread surface rather than at the outer edges. The central concentration of air ports allows the center of the belt to float and the edges to seal, producing maximum lift on the belt and resulting in the belt riding over a cushion of air. The cushion of air cleans the belt and deck surfaces, which in turn minimizes belt and deck wear. The air may also cool the belt, thus, minimizing belt stretch. 
     In the space created by the third roller, a plenum may be attached to the bottom of the deck. The plenum may be configured to enclose the area directly below the air ports in the tread surface. A small fan may be installed in the plenum wall to pull air into the enclosed cavity. The resulting pressure forces air through the ports in the tread surface and lifts the belt. To balance the air pressure under the belt, the plenum may be tapered toward the front of the deck. 
     An upright may be configured to extend upward from the frame under the treadmill and may support a console and stabilizers. The upright and stabilizers may be configured to be adjustable. The upright may be positioned at a variety of angles from substantially upright to substantially down. In the down position, the upright lays flat approximately parallel to the deck. The upright may also be configured to be removable for transport and storage. The adjustability of the upright also makes the treadmill easy to ship, store, move, and hide. The upright may be configured to have a locking system. The locking system typically maintains the upright in a selected position. 
     A light may be configured to emit a beam onto the surface of the belt. A shutter moving across the beam may be configured to produce on/off fluctuations. The light may be synchronized to the motor speed and may be used as a pacing mechanism by the user. 
     The treadmill may be further configured to have a small proximity sensor mounted to the upright. The proximity sensor may emit a beam, which, when interrupted, activates the motor. The sensor may be configured such that a user in close proximity to the sensor and between two and four feet above the deck interrupts the beam. Accordingly, when the beam is not interrupted, the drive is deactivated. If a user leaves the tread surface, the sensor will stop the belt, thus providing a safety mechanism. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
     FIG. 1 is a perspective, exploded view of the treadmill; 
     FIG. 2 is a top perspective view of the treadmill with portions of the belt and side skirting removed in order to expose the deck surface, as well as the inner workings of the treadmill; 
     FIG. 3 is a bottom perspective view of the treadmill with the belt and side skirting removed in order to expose the structure of the deck and plenum; 
     FIG. 4 is close-up, perspective view of the treadmill fulcrum area illustrating a simple support of the third roller, the third roller axle forming the fulcrum and axis of rotation; 
     FIG. 5 is a close-up, perspective view of the treadmill fulcrum area illustrating one embodiment wherein the deck skirting provides the structure to support the third roller and the fulcrum; 
     FIG. 6 is close-up, side view of one embodiment of a drive mechanism; 
     FIG. 7 is close-up, side view of a plurality of locations where the motor may be configured to secure to the deck; 
     FIG. 8 is a free body diagram of the treadmill with all relevant forces represented as vectors; 
     FIG. 9 is a side view of the treadmill with the deck positioned at a decline; 
     FIG. 10 is a side view of the treadmill with the lift mechanism embodied as a hydraulic cylinder and with the deck at an incline; 
     FIG. 11 is a side view of the treadmill with the lift mechanism embodied as a two force member and with the deck at an incline; 
     FIG. 12 is a side view of the treadmill with the lift mechanism embodied as a scissor hinge and with the deck in a horizontal position; and 
     FIG. 13 is a perspective view of a presently preferred embodiment of the entire treadmill. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented in FIGS. 1 through 13, is not intended to limit the scope of the invention. The scope of the invention is as broad as claimed herein. The illustrations are merely representative of certain, presently preferred embodiments of the invention. Those presently preferred embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. 
     Those of ordinary skill in the art will, of course, appreciate that various modifications to the details of the Figures may easily be made without departing from the essential characteristics of the invention. Thus, the following description of the Figures is intended only by way of example, and simply illustrates certain presently preferred embodiments consistent with the invention as claimed. 
     Referring to FIG. 1, the treadmill  10  of the present invention may be supported and stabilized by a frame  12 . A deck  14  may be pivotably secured to the frame  12 . The deck  14  is configured to have a front and a rear end defining a longitudinal direction  11   a  and a right side and left side defining a lateral direction  11   b.  The longitudinal direction  11   a  and the lateral direction  11   b  are substantially orthogonal to one another. 
     A tread surface  16  extends from proximate a front roller  18  to proximate a rear roller  20 . The tread surface  16  is configured to support the weight of a user thereabove. The front and rear rollers  18 ,  20  are capable of rotation with respect to the deck. A third roller  22  may be connected to the deck  14  below the tread surface  16  at a location spaced longitudinally  11  a between the front and rear rollers  18 ,  20 . A continuous belt  24  encircles the deck  14  being substantially supported by the front roller  18 , the rear roller  20  and the third roller  22 . A motor  26  is configured to drive the belt  24 . The motor  26  may be positioned longitudinally between the front and rear rollers  18 ,  20 . An air bearing mechanism  28  distributes pressurized air between the tread surface  16  and the belt  24  for supporting the belt  24  on a layer of the pressurized air. 
     Referring to FIGS. 2 and 3, the deck  14  is pivotably connected to the frame  12  at a fulcrum  30 . The fulcrum  30  defines an axis of rotation  32  of the deck  14  with respect to the frame  12 . The axis of rotation  32  may be defined by an axle  33  of the third roller  22 . In another embodiment (not shown) the axis of rotation  32  may be located below the third roller  22 . The axis of rotation  32  need not be directly below the third roller  22 , but may be located proximate the third roller  22  toward a front end  34  of the treadmill  10  or proximate the third roller  22  toward a rear end  36  of the treadmill  10 . 
     The third roller  22  and fulcrum  30  may be positioned at any convenient longitudinal  11   a  location between the front end  34  and the rear end  36  of the treadmill  10 . The position of the fulcrum  30  may be determined by achieving a desirable balance between the weight of the front and rear portions  34 ,  36  of the deck  14 . Furthermore, the spacing between the fulcrum  30  and the tread surface  16  may be varied to accommodate maximum desired angle of incline or decline for the deck  14 . That is, by increasing the distance between the fulcrum  30  and the tread surface  16 , the deck  14  may be inclined or declined to a steeper angle. 
     The belt  24  has a top belt surface  38 , which longitudinally covers the tread surface  16  and a bottom belt surface  40  passing below the deck  14  to form a continuous loop. The belt  24  may be constructed of any material that provides the necessary strength, durability, resistance to stretch, and frictional characteristics. 
     The front, rear, and third rollers  18 ,  20 ,  22 , may be configured to support and tension the belt  24 . The front and rear rollers  18 ,  20  may also be configured to ensure proper tracking of the belt  24 . Tracking may be accomplished by providing a shoulder or other stop mechanism (not shown) on the rollers  18  and  20  to prevent migration of the belt  24  past a particular location on the rollers  18 ,  20 . Another embodiment may include a roller  18 ,  20  having a diameter that decreases toward a lateral  11   b  center  41  of the deck  14 . Such a decreasing diameter promotes migration of the belt  24  to the desired center location  41 . 
     The front and rear rollers  18 ,  20  may be constructed of plastic, a variety of polymers, rubber, metal, a variety of metal alloys, a variety of composites, or any material that provides the necessary wear resistance and sufficient static coefficient of fiction with respect to the belt  24  to prevent unwanted slip between the belt  24  and rollers  18 ,  20 . The static coefficient of fiction with respect to the belt  24  may be a characteristic of the roller  18 ,  20  material itself or the result of an applied finish. Additionally, the rollers  18 ,  20  may be modified to provide a rough surface (not shown) to promote gripping of the belt  24 . 
     In another embodiment, the front and rear rollers  18 ,  20  may be configured to act as momentum fly wheels. Such a configuration may be accomplished by increasing the rotational inertia of the rollers  18 ,  20  to resist sudden changes in belt  24  speed. Such a configuration tends to relieve the pulsating loads of each user foot step that is typically overcome by the motor  26 . 
     The deck  14  may be constructed of a variety of woods, plastics, polymers, reinforced polymers, composites, metals, metal alloys, or any material that exhibits the necessary rigidity, strength, and wear resistance. The deck  14  may be formed of a tread surface  16  supported by rails (not shown) attached thereto. The tread surface  16  may have a skirting  42  attached thereto. The skirting  42  may provide additional rigidity and also improve the aesthetic appeal of the treadmill  10  by extending downward (not shown) to cover and hide the underside of the deck  14 . 
     In another embodiment, the tread surface  16  may be formed or molded to provide the necessary rigidity and strength, thus eliminating the need for the addition of strengthening rails. Such rigidity may be provided by a rib structure  43  molded to support the tread surface  16 . The ribs  43  may be configured to run longitudinally  11   a,  laterally  11   b,  or any combination of longitudinal  11   a  and lateral  11   b  directions. Furthermore, the ribs  43  may be configured to run angularly with respect to each other and/or with respect to the aesthetic skirting  42  of the deck  14 . 
     The spacing between laterally  11   b  and longitudinally  11   a  extending ribs  43  may be selected to provide the necessary strength to support a user exercising on the tread surface  16 . The thickness and height of the ribs  43  may also be varied to control and the rigidity and strength of the tread surface  16 . 
     In certain embodiments, the ribs  43  form a mesh, which may be attached to the underside of the tread surface  16  to provide the strength that is necessary to support the user. Such a construction would allow the tread surface  16  and ribs structure  43  to be constructed of different materials selected to provided optimum performance for their given purposes. The ribs  43  may be configured for optimum strength, while the tread surface  16  material may be selected to have a low friction with respect to the belt  24 . 
     In one presently preferred embodiment, the deck  14  is a contiguously molded unit formed of any suitable material. The material may also be selected from the group consisting of a homogeneous polymeric composition, a structurally reinforced polymeric composition, and a substantially homogeneous polymeric composition containing structurally reinforcing fibers distributed substantially evenly therethrough. The contiguously molded deck  14  may be configured to contain the tread surface  16 , the skirting  42 , and the ribbing  43  to produce a sufficiently strong and rigid single piece deck  14 . 
     The deck  14  may be further configured to have air ports  44 . The air ports  44  may be distributed in a manner promoting the efficient insertion of air between the tread surface  16  and the top belt surface  38 . The ports  44  may be sized to deliver larger amounts of air to selected locations than other selected locations to improve the lift produced on the top belt surface  38 . In one embodiment, the air ports  44  are concentrated along the lateral  11   b  center  41  of the tread surface  16  and sized to provide the largest air insertion at the lateral  11   b  center  41  of the deck with decreasing delivery of air at the lateral  11   b  extremes  45 . 
     Air may be introduced to the air ports  44  by any suitable air transport. In one presently preferred embodiment, the air is delivered to the ports  44  by a plenum  46 . The plenum  46  secures to the underside of the tread surface  16 , directly below the air ports  44 . The plenum  46  may be molded of a polymer or formed of sheet metal or any other suitable material. The plenum  46  encloses the underside of the air ports  44  and forms a sealed cavity with the only exit being the air ports  44 . Air may be introduced into the plenum  46  by a fan  47  located in the plenum  46  wall. The fan  47  forces air into the plenum  46 . The pressurized plenum  46  delivers air at uniform pressure to the air ports  44  for subsequent insertion under the top belt surface  38 . The top belt surface  38  is lifted off the tread surface  16 , resulting in reduced frictional forces therebetween. 
     Referring to FIG. 4, the third roller  22  spaces the bottom belt surface  40  away from the deck  14 . In actuality, the third roller  22  need not be a roller or rotatable at all. Any mechanical extension (not shown) that holds the bottom belt surface  40  away from the deck  14  and allows the bottom belt surface  40  to easily slide with respect thereto, is sufficient. All devices and mechanical extensions that maintain spacing between the bottom belt surface  40  and the deck  14  will be hereafter referred to as a third roller  22 . The third roller  22  provides the space under the tread surface  16  that is necessary to accommodate the motor  26 , if desired, and plenum  46 . 
     In an alternate embodiment, the third roller  22  may be omitted. As discussed hereinabove, the third roller  22  provides spacing between the bottom belt surface  40  and the deck  14 . If no need exists for spacing, the third roller  22  may be omitted. Such a situation might be occasioned by a reduction in the size of the plenum  46  or by the securing of the motor  26  at a location outside the area encircled by the belt  24 . 
     The third roller  22  may be supported away from the deck  14  by any suitable support structure  48 . The support structure  48  may extend from the deck  14  and be secured to the third roller axle  33 . The support  48  may be constructed of any material having the required characteristics, such as strength and rigidity. Additionally, FIG. 4 illustrates an embodiment of the third roller axle  33  providing the fulcrum  30  between the frame  12  and the deck  14 , as discussed hereinabove. 
     Referring to FIG. 5, the support for the third roller  22  may be provided by the skirting  42 . FIG. 5 illustrates an embodiment wherein the skirting  42  extends downward to provide a location to secure the third roller axle  33 . Furthermore, the skirting  42  may be configured to provide the structure required to support the deck  14  on the fulcrum  30 . As discussed hereinbove, the fulcrum  30  may be positioned proximate, or below as illustrated, the third roller  22 . 
     The embodiment of FIG. 5, does not include aesthetic skirting  42  with support structure on the inner surface (toward bottom belt surface  40 ). Ribs  43 , similar to those discussed hereinabove, may be added to the inner surface of the aesthetic skirting  42  to increase the rigidity, strength, and durability. In this way, the aesthetic skirting  42  may be strengthened and stiffened sufficient to support the weight of a user exercising on the treadmill  10 . 
     Referring to FIG. 6, the motor  26  may be configured to drive the belt  24 . In one presently preferred embodiment, the motor  26  is configured to rotate the rear roller  20 , which provides a more efficient drive mechanism than treadmills having a front drive system. The motor  26  may be secured to the deck  14  on the rear side  36  of the fulcrum  30 . In such a configuration, the weight of the motor  26 , one of the heaviest components on the treadmill  10 , will tend to counteract the weight of the front end  34  of the treadmill  10 . The motor  26  may be configured to impart motion to the rear roller  20  by any suitable drive mechanism. Such drive mechanisms may include with limitation gears, chain belts, v-belts, shaft drive, or the like. 
     One presently preferred embodiment, transfers rotation from a pulley  50  secured to a motor shaft  51  to a pulley  52  rigidly secured to the rear roller  20  by a timing belt  54 . The pulleys  50 ,  52  may be sized to provide optimum speed and power in rotating the belt  24 . If desired, the motor shaft  51  may be further configured to rotate a fly wheel (not shown). The fly wheel may be configured to have a large rotational inertia, which would resist sudden changes in belt  24  speed. Such a configuration may relieve the pulsating loads of each user foot step that is typically overcome by a motor  26 . 
     FIG. 7 illustrates other possible locations of the motor  26  in relation to the deck  14 . The motor  26  may be secured at a location  56  substantially above the fulcrum  30 . The motor  26  may also be configured to be secured at a location  57  substantially below or slightly behind the rear roller  20 . The motor  26  may further be configured to be secured to the deck  14  at a plurality of locations between location  56  and location  57 . In order to accommodate the several possible motor locations, the motor  26  may be configured for securement to the deck  14  from a location inside or outside the area encircled by the belt  24 . 
     FIG. 8 is a free body diagram of the deck  14  rotatable about the fulcrum  30 . The weight of the rear portion  58  comprises the weight of the rear end  36  of the deck  14  including the motor  26  enclosed inside the enclosure. The weight of the front portion  60  comprises the weight of the front end  34  of the deck  14 . A foot of a user (not shown) applies a force  62  to the rear portion  36  of the deck  14 . The other foot of the user (not shown) applies a force  64  to the front portion  34  of the deck  14 . A lift mechanism (not shown) may impart a positive or negative force  66  on the front portion  34  of the deck  14 . 
     The present invention provides a method for incline adjustment that minimizes the force  66  that must be applied by a lift mechanism (not shown) to change the incline of the deck  14  with respect to the frame  12 . The fulcrum  30  located substantially between the front  34  and rear  36  ends of the deck  14  allows the user to apply at least a portion of the user&#39;s weight  62  behind the fulcrum  30 , thus, aiding in lifting the front portion  34 . In fact, by adjusting the weight applied on the front  64  and rear  62  portions of the deck  14 , the user may be able to lift the front portion  34  without the aid of the lifting mechanism  66 . By greatly reducing the lifting force  66  required to lift the front portion  34  of the deck  14 , the lifting mechanism itself may be greatly simplified in design and capacity as compared to traditional treadmills, thus reducing weight and cost. 
     Referring to FIG. 9, the deck  14  is shown at a decline. In one presently preferred embodiment, the fulcrum  30  may be configured to allow the front end  34  of the deck  14  to be positioned below the rear end  36  of the deck  14 , thus, producing an angle of descent  67 . The angle of descent  67  allows the user to simulate walking, jogging, or running downhill. Downhill exercise uses a different muscle group of the user than does uphill exercise. In order to obtain a well rounded workout, it is advantageous to have a treadmill that is able to provide a declining, level, and inclined tread surface  16 . 
     As discussed hereinabove, the distance between the fulcrum  30  and the tread surface  16  may be increased to provide for an increased angle of decline  67 . The greater the distance between the fulcrum  30  and tread surface  16 , the more the front portion  34  of the deck  14  may lower with respect to the rear portion  36  of the deck  14 . 
     Referring to FIG. 10, the deck  14  is shown at an incline with respect to the frame  12 . The incline may be provided and held by a lift cylinder  68  or by a pair of lift cylinders  68 . The lift cylinder  68  may be any hydraulic system. The working fluid may be any suitable fluid such as air or an oil. In one embodiment, the lift cylinder  68  may be driven by a small hydraulic pump (not shown) that provides a lifting force  66 . The amount of force  66  that must be generated by the lift cylinder  68  can be controlled by the user as discussed hereinabove. Furthermore, the incline produced by the lift cylinder  68  may be remotely controlled by a user while exercising on the treadmill  10 . 
     In another embodiment, the lift cylinder  68  provides no force. The user controls the incline and the lift cylinder  68  functions as a damper to provide smooth adjustment from one incline to another. The lift cylinder  68  may further be configured to contain a valve, such as a check valve (not shown), which restricts flow in and out of the lift cylinder  68 , thus providing a lock for maintaining the deck  14  at a desired incline. The valve may be actuated by a user while operating the treadmill  10 . The modulus of the entrapped hydraulic fluid can provide a spring to cushion the foot impacts of the user on the deck  14 . The selection of the hydraulic fluid determines the spring constant of the spring. 
     FIG. 11 illustrates another alternative embodiment for an incline adjuster  70 . The incline adjuster  70  may be configured to have a two force member  72  mounted between a pivot  74  secured to the deck  14  and a frame pivot  76 . In this embodiment, the pivot  76  is configured to slide along a length of the of the frame  12  in a longitudinal direction  11   a.  The lift mechanism  70  slides along the frame  12  in response to the weighting applied by a user, as discussed hereinabove. When the desired incline has been achieved, the user may remotely activate a lock  78 , which secures the pivot  76  to the desired location along the frame  12 . When a new incline is desired by a user, the lock  78  may be released and locked again at the new incline. 
     FIG. 12 illustrates an embodiment of a scissor lift mechanism  80 . One end of an upper scissor leg  81  is pivotably connected to one end of a lower scissor leg  82  at a scissor pivot  83 . The opposite end of scissor leg  81  is pivotably connected to the deck pivot  74  and the opposite end of lower scissor leg  82  is pivotably connected to the frame pivot  76 . A drive screw  84  attaches to the scissor lift  80  at the scissor pivot  83 . The opposite end of the drive screw  84  is attached to a drive  86 . The drive  86  is pivotably connected to the frame  12  and is configured to rotate the drive screw  84 . The rotation of the drive screw  84  pulls the scissor pivot  83  toward the drive  86 , thus elevating the deck front  34 . The scissor lift  80  may be configured to lock the deck  14  at a desired incline. 
     In another embodiment of the present invention, a reverse scissor lift (not shown) may be employed to modify the incline of the deck  14 . In a reverse scissor mechanism, the scissor pivot  83  may be located on the drive  86  side of the pivots  74 ,  76 . Rotation of the drive screw  84  would then increase the distance between the drive  86  and the scissor pivot  83  thus extending the pivot legs  81 ,  82  and modifying the incline of the deck  14 . 
     Additionally, the scissor lift mechanism  80  may be configured for manual adjustment. In this embodiment, the scissor lift mechanism  80  may be rotated 180 degrees so that the drive  86  extends toward the front  34  of the treadmill  10 . In such a configuration, the drive  86  may comprise a hand crank (not shown) accessible from the front  34  of the treadmill  10 . 
     The present invention may be embodied with other lift mechanisms and incline adjusters without departing from its structures, methods, or other essential characteristics as broadly described herein. The embodiments described hereinabove are to be considered in all respects only as illustrative, and not restrictive. 
     FIG. 13 illustrates an embodiment of the entire treadmill  10 . A user registration  87  extends upward so as to be positioned in front of a user (not shown) operating the treadmill  10 . The user registration  87  may be secured at its lower extreme to the deck  14  or the frame  12 . The user registration provides a visual reference with which the user can gauge his/her position on the treadmill  10 . The user registration  87  further provides a location for information and controls needed for efficient operation of the treadmill  10 . 
     In one embodiment, the user registration  87  comprises an upright  88  extending upward from the frame  12 . If desired, the upright  88  may be configured as a single pole extending upward on only one side of the treadmill  10 . The upright  88  may additionally be configured to support a console  90 . 
     In one embodiment the console  90  is a collection of electronic readouts and controls. The readouts and controls can provide the user with any information or control that might be convenient. Readouts might include the speed of the belt  24 , distance traveled, calories burned and degree of incline of the deck  14 . Controls might include speed adjustment of the belt  24 , incline adjustment, incline lock activation, and the like. The upright  88  may be further configured to support one or more stabilizers  92 . The stabilizers  92  provide structures for a user to grab to steady himself/herself. The stabilizers  92  may be formed to any geometry that might add to the safety or convenience of the user. 
     The user registration  87  may be further configured to be adjustable. The upright  88  may be positioned in a variety of positions from completely upright (as shown), to completely down, laying flat proximate the deck  14 . The upright  88  may also be configured to be removable for transport and storage. The adjustability of the upright  88  and stabilizers  92  make the treadmill easy to ship, store, move, and hide. The different positions of the upright  88  and stabilizers  92  may be configured to have a locking system (not shown), thus holding the user registration  87  in a selected position. 
     The user registration  87  may be further configured to have a pacing mechanism (not shown) to aid a user in maintaining a desired pace. One embodiment of the pacing mechanism may comprise a light configured to emit a beam onto the surface of the belt  24 . A shutter moving across the beam may be provided to produce alternating on/off illumination of a location on the belt  24 . The light may be synchronized to the speed of the motor  26  and may be used as a pacing mechanism by the user. 
     The user registration  87  may be further configured to have a safety mechanism (not shown) configured to stop the belt  24  from rotating if the user leaves the tread surface  16 . In one embodiment the safety mechanism is a tether connecting a user to the treadmill  10 . If the user leaves the tread surface  16 , the tether pulls a switch that stops the belt  24 . In another embodiment, the safety mechanism is configured to be a proximity sensor mounted to the upright  88 . The proximity sensor may emit a beam which, when interrupted, activates the motor  26 . A user in close proximity to the sensor and between two and four feet above the tread surface  16  interrupts the beam. When the beam is not interrupted, the belt  24  is stopped. Thus, when a user leaves the tread surface  16 , the sensor will not be interrupted and the belt  24  will stop. 
     From the above discussion, it will be appreciated that the present invention provides a treadmill having a center pivot. The center pivot provides an equilibrated deck. The motor may be configured to drive the belt from the rear, resulting in an efficient power usage. The efficient power usage may allow a relatively small motor to be used without lowering performance. Furthermore, the motor may be mounted below the tread surface, thus allowing the entire tread surface to be exposed and usable. The efficient use of all the tread surface allows the deck to be significantly shorter than current treadmills. The upright is configured to be removed or to be rotated a flat position proximate the deck. The treadmill may be constructed of composite materials producing a strong design that weighs much less than traditional treadmills. The relatively short deck, the foldable upright, and low weight of the present invention result in a treadmill that is compact, lightweight, stable, easily shipped, easily deployable, and easily stored. 
     The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.