Abstract:
Machines, apparatuses, systems and methods for providing adjustable tension to a cable system using a pivotally mounted leverage mechanism that employs an adjustably positionable weight. Embodiments are used in exercise and other muscle strengthening devices, and may include an electronic control system for monitoring, recording a user&#39;s progress, and for altering or releasing tension to the cable system based on feedback from the user. Embodiments include a user interface for inputting information for particular exercises or workouts, as well as outputting/downloading information following exercises or workouts.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to cable tensioning systems, and more particularly to unique and compact adjustable cable tensioning systems, apparatus, machines and related methods for use in such applications as weight training, exercising, muscle toning, muscle development, and the like. 
     2. Description of Related Art 
     Weight training is a common form of exercise to increase strength and build muscle. A typical weight lifting apparatus includes a bar that is capable of receiving weights on both ends. The user places the desired weights on the bar, and then lifts the bar so that the weights act as resistance to the muscles of the user. A certain number of repetitions of the lift are performed in order to complete a particular exercise. Typically, the most beneficial parts of the exercise are the last few repetitions where the user may become fatigued, but where maximum muscle strength is developed. Because of the fatigue factor, the user may become exhausted and unable to complete the exercise with the selected weights. This results in at least two problems. First, in order to complete the set of repetitions, if fatigue sets in, the user may be required to stop the exercise, change the weight resistance (which may include both removing and replacing weights), and then resume. This may interrupt critical timing in the exercise. Second, the fatigue experienced by the user is dangerous in that the weights may be dropped or mishandled, resulting in injury to the user. A second person or spotter is typically used to assist the weight lifter to catch the weight in case fatigue causes a problem. However, a second person is not always available which may expose the weight lifter to unnecessary risk of injury. 
     In order to avoid having to add and remove physical weights to change the resistance, numerous weightlifting systems have been developed as alternatives to bar and weight systems that employ cable and pulley systems to transfer weight loads, such as those described in U.S. Pat. No. 5,407,403 and U.S. Patent Application Publication No. 2005/0233871. In order to avoid the need for a second person to act as a spotter, cable and pulley systems have also been developed for use as spotter systems, such as those described in U.S. Pat. Nos. 5,048,826, 5,310,394, 5,314,394, and 6,558,299. Unfortunately, none of these inventions provides a simple, compact weight resistance system that has the combined capabilities of (a) providing variable adjustability in the amount of tension (weight) placed on the cable, including automatic tension adjustment (reduction or release) near the end of a set of repetitions when the user is becoming fatigued; and (b) providing an automatic spotting/safety function without the need for a second person. 
     Electronic monitoring and feedback systems for weightlifting have also been developed, as described in U.S. Pat. Nos. 5,785,632 and 5,993,356. 
     It is therefore desirable to provide the combined capabilities of variable and automatic tension adjustability, including reduction and potential release (spotting) in a compact tension resistance system that may be adapted for use in numerous different weight lifting methods and apparatus. It is further desirable that such systems provide real time feedback to the user during exercise, and record the results of the user&#39;s exercise for future use. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide apparatuses, machines, systems and methods for providing adjustable tension to cable, rope, wire, cord, chain, belt, strap or other similar devices (sometimes referred to herein for convenience using the general term “cable”) using a pivotally mounted leverage mechanism that is associated with one or more adjustably positionable weights. In embodiments of the invention, one or more cables are attached to the leverage mechanism which provides tension to the cable(s). Tension to the cable(s) may be increased or decreased by changing the position of the weight(s) associated with the leverage mechanism. Embodiments of the invention may be used in exercise and other muscle strengthening devices, and may include an electronic control system for monitoring and recording a user&#39;s progress, and altering or releasing tension to the cable system based on feedback from the user. Embodiments of the invention may also include a user interface for inputting information for particular exercises or workouts, as well as outputting/downloading information following exercises or workouts. 
     In some embodiments, the leverage mechanism includes an elongated threaded screw member that is rotated using a drive motor attached at one end of the screw member. A carriage may be provided in these embodiments that is movably engaged with the screw member so that rotation of the screw member by the drive motor causes the carriage to move along the length of the screw member. In these embodiments, rotation of the screw member in one direction will cause the carriage to move in one direction along the lever member, and rotation in the opposite direction will cause the carriage to move in the opposite direction along the lever member. In some embodiments, the screw member itself may be pivotally (and rotatably) mounted in order to act as a lever. 
     A cable is attached directly or indirectly at or near one end of the lever mechanism or screw member. Tension on the cable is increased or decreased depending on the position of the weight (which may be on a carriage) on the lever member. 
     In alternative embodiments, the carriage may be movably provided on one or more elongated rails, tracks or other supports. In these embodiments, the rail, track or support is pivotally mounted in order to act as a lever, and a cable is attached directly or indirectly near one end of the rail, track or support. It is to be appreciated that the movable weight or the carriage supporting the weight may be directly or indirectly attached to any suitable motion imparting device, such as a pneumatic or hydraulic piston assembly, a rod and motor assembly, a threaded screw member as described above, a chain and sprocket system, a motor and belt system, or the like. Movement of the piston, motor, chain, belt etc. causes the weight or carriage to move along the rail, track or other support lever. Tension on the cable is increased or decreased depending on the position of the weight or the carriage on the lever. 
     It is to be appreciated that the carriage may be provided in any suitable form so long as it is movable along the lever mechanism according to the movement of the motion imparting device. In some of these embodiments, additional weight is provided on or attached to the carriage. 
     In the preferred embodiments, one end of a cable is attached directly or indirectly near an end of the leverage mechanism, and the other end of the cable is attached to and threaded around a rotatably mounted disc, pulley or sprocket for communication of tension to such disc, pulley or sprocket. In these embodiments, the central axis of such disc, pulley or sprocket is attached to a rod. A separate cam is also attached to this rod such that the disc and cam share a common axis in the rod. One end of a second cable is attached to and wrapped around the outside edge of the cam, and the opposite end of the second cable is attached directly or indirectly to a weight lifting bar or the like for communication of tension to such bar. It is to be appreciated that the outside edges of the disc and cam may have a U-shaped cross section in embodiments using a cord-like structure for the two cables in order to receive and guide the cables. Other embodiments may use sprockets and chains or belts, which may be connected, on one end to cables leading to the lever mechanism and on the other end to the lifting bar. 
     In some embodiments, tension is imparted to the disc by the first cable, then transmitted to the cam through the rod, and then transmitted directly or indirectly to the lifting bar through the second cable. The amount of tension may be varied depending on the position of the carriage, and/or the associated weight thereon, relative to the point at which the first cable is attached to the leverage mechanism. The tension may also affected by the location of the pivot. As the lifting bar is moved, it pulls on the second cable thereby causing the cam to rotate. This rotation is resisted by the tension imparted to the cam from the leverage mechanism through the first cable, and rod and/or disc. When the tension provided by the second cable is greater than the tension provided by the first cable, both the cam and disc rotate, causing the leverage mechanism to move through an arc about its pivotal mount. The outside edge of the cam is preferably shaped so as to provide even tension to the second cable to compensate for variations as the leverage mechanism moves through this arc. This shape of the cam helps maintain consistent cable tension throughout the upward and downward strokes of the lifting bar. 
     It is to be appreciated that the amount of tension imparted increases as the carriage and/or weight are moved closer to the end of the leverage mechanism where the first cable is attached (for example, at a point that is away from the pivot); similarly, the amount of tension is decreased as the carriage and/or weight are moved away from the end of the leverage mechanism where the first cable is attached (for example, at a point that is toward the pivot). It is to be appreciated that the leverage mechanisms of the present invention may be provided in different lengths, and that the weight(s) associated with the carriage may be provided in different amounts depending on the space availability and the tension requirements of the user. For example, and without limitation, a relatively short leverage mechanism may be provided with a heavy weight such that slight movement of the weight and/or carriage results in a significant change in tension; but, if a longer leverage mechanism is provided with the same weight the same amount of movement by the weight and/or carriage would provide a lesser change in tension. In some examples, a longer leverage mechanism could allow for a greater maximum tension than a shorter one. 
     In the preferred embodiments, the position of the weight and/or carriage is calibrated in order to allow calculation of the amount of tension provided by the leverage mechanism. An electronic interface and processing system may be provided in these embodiments so that a user may electronically select and/or adjust the tension (“weight”) placed on the cables by changing the position of the weight on the lever mechanism. This replaces the need to add or remove actual physical weights as in a traditional weight-lifting setup. The electronic system may monitor the user&#39;s resistance to tension on the cable during use in order to detect potential fatigue in the user. In these embodiments, if the user&#39;s resistance drops, the electronic system may automatically adjust (lessen) the tension on the cable by causing the weight and/or carriage to move, in order to reduce the tension on the cable and allow the user to stop, alter or continue exercise at a different level. The electronic interface may also provide signals to the user during use, such as digital readouts, alarms, audible commands or the like. In some embodiments, the electronic system may also record data from a user&#39;s exercise workouts for compilation and later review by the user to measure muscle strength gain, for evaluation, for comparison to previous workouts, for developing future workouts, etc. In some embodiments, data recorded through the electronic system may be transmitted or downloaded to another computerized device, including portable and/or hand-held computing devices, either simultaneously with the performance of a workout, or afterwards. 
     In embodiments of the invention, the electronic system detects when the lifting speed of the cables decreases or stalls, and automatically/incrementally reduces the tension on the cables so that the speed stays the same. This has the effect of being an “automatic spotter” allowing the lifter to complete a lift with lesser weight. In emergency situations (e.g., a prolonged stall, or a sudden loss in resistance by the user—which may be measured in fractions of a second) the tension on the cables may be completely released or interrupted in order to avoid injury to the user. In some embodiments, a separate spotter cable may be provided with a latch or other movement arresting mechanism that may be engaged to prevent the lifting bar from falling on the user. 
     Several embodiments of the present invention may be implemented in various exercise machines. For example, and without limitation, embodiments of the invention may be implemented in weight lifting systems, bench press systems, squat systems, knee lift systems, hand or arm pull systems, leg presses, calf raisers, and others. Embodiments of the present invention may be used at gymnasiums, in the medical field for strengthening, development and/or rehabilitation of infirm or injured persons, and in weight or strength training camps. 
     It is therefore an object of the present invention to provide variable and automatic cable tension adjustability, including tension reduction and potential tension release, in a compact tension resistance system that may be adapted for use in numerous different exercise or strengthening methods and apparatus. 
     It is also an object of the present invention to provide cable-based systems, apparatus, machines and methods for exercise and improving muscle strength in which the tension (weight) on the cable(s) may be adjusted by a user without manually attaching or removing physical weights. 
     It is also an object of the present invention to provide cable-based systems, apparatus, machines and methods for exercise and improving muscle strength in which the user&#39;s activity is monitored, and the tension (weight) on the cable(s) is automatically adjusted according to the monitored activity. 
     It is also an object of the present invention to provide cable-based exercise or strength improvement systems and methods for providing real time feedback to a user during exercise, and real time cable tension adjustment during exercise. 
     It is also an object of the present invention to provide cable-based exercise or strength improvement systems and methods capable of acting as an automatic spotter to monitor and automatically reduce or eliminate tension (weight) on the cable system if user fatigue is detected. 
     It is also an object of the present invention to provide cable-based exercise or strength improvement systems and methods capable of recording and storing the results of a user&#39;s exercise, and making those results available for download onto a hand held or other electronic device. 
     Additional objects of the invention will be apparent from the detailed description and the claims herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional side view of an embodiment of the invention showing a lifting bar near the middle of a stroke, resting on supports. 
         FIG. 1A  is a sectional side view of an alternative embodiment of the invention showing a piston assembly. 
         FIG. 2  is a sectional side sectional view of an embodiment of the invention showing a lifting bar near the top of a stroke. 
         FIG. 3  is a perspective view of an embodiment of the invention showing a lifting bar near the top of a stroke. 
         FIG. 4  is a perspective view of an embodiment of the invention showing a lifting bar near the bottom of a stroke. 
         FIG. 5  is a perspective view of an embodiment of the invention showing a lifting bar near the top of a stroke. 
         FIG. 6  is a perspective view of an embodiment of the invention showing a lifting bar near the middle of a stroke. 
         FIG. 7  is a perspective view of an embodiment of the invention showing a lifting bar near the bottom of a stroke. 
         FIG. 8  is a perspective view of an embodiment of a leverage mechanism of the present invention. 
         FIG. 9  is a partially exploded view of the leverage mechanism of  FIG. 8 . 
         FIG. 10  is a perspective view of an embodiment of a cam and disc assembly of the present invention. 
         FIG. 11  is a front view of the assembly of  FIG. 10 . 
         FIG. 12  is a top view of the assembly of  FIG. 10 . 
         FIG. 13  is a side view of the assembly of  FIG. 10 . 
         FIG. 14  is a perspective view of an alternative embodiment of the present invention. 
         FIG. 15  is a schematic view of an alternative embodiment of the invention. 
         FIG. 16  is a partially cut-away sectional side view of an embodiment of the invention incorporating an emergency tension interruption apparatus. 
         FIG. 17  is a side view of a part of the emergency tension interruption apparatus of  FIG. 16 . 
         FIG. 18  is an end view of a part of the emergency tension interruption apparatus of  FIG. 16 . 
         FIG. 19  is a top view of a part of the emergency tension interruption apparatus of  FIG. 16 . 
         FIG. 20  is a side view of a part of the emergency tension interruption apparatus of  FIG. 16 . 
         FIG. 21  is a side view of a part of the emergency tension interruption apparatus of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, and referring particularly to the exemplary embodiments of  FIGS. 3-9 , it is seen that these embodiments include a leverage system for installation inside a cabinet or frame  19  comprising an elongated member  20  having a track  21  (see  FIG. 9 ) for supporting a movable carriage  25  using wheels, guides or other supports  26 . At least one weight  24  is provided with, on or made a part of carriage  25 . Member  20  is pivotally mounted at  23  so that it may operate as a lever. It is to be appreciated that in other embodiments (such as the embodiment illustrated in  FIG. 15 ), that weight  24  may be movably provided directly on lever member  20 . 
     In the embodiments illustrated in  FIGS. 3-9 , a threaded screw  29  is provided in parallel with lever member  20 . A drive motor  30  is provided, preferably at one end of screw  29 , to impart rotation to it. A threaded bore (see  FIG. 9 ) is provided in carriage  25  for receiving screw  29 , so that as screw  29  is turned by motor  30 , carriage  25  moves along the length of screw  29 . It is to be appreciated that turning screw  29  in one direction will cause carriage  25  to move towards, motor  30 , and turning screw  29  in the opposite direction will cause carriage  25  to move away from motor  30 . It is to be appreciated that in other embodiments, weight  24  may be movably provided directly on lever member  20  and that screw  29  may be threaded through a bore in weight  24  itself. However, it is to be appreciated that other means of moving weight  24  on lever member  20  are contemplated in accordance with some embodiments of the present invention. For example, and without limitation, motor  30  and screw  29  can be replaced with a piston  36  engaged with the carriage  25  as shown in  FIG. 1A . 
     One end of a first cable  35  is attached near one end of lever member  20 , at a distance from pivot  23 . The opposite end of cable  35  is wrapped around an outside edge of a rotatable circular disc  37  and may be anchored thereto. Disc  37  is attached to a rod  38  that is rotatably mounted a distance from the end of lever member  20 . A cam  39  is also attached to rod  38  and/or disc  37 . It is to be appreciated that disc  37  may have a round circumference, but that cam  39  may not. Rotation of disc  37  causes cable  35  to impart a pulling force at the end of lever member  20  where cable  35  is attached, which causes this proximal end of lever member  20  to move in an arcuate direction about pivot  23 . The closer that weight  24  (with or without carriage  25 ) is to this proximal end of lever member  20  and/or the point of attachment of first cable  35 , the more pulling force is required through cable  35  to move lever member  20  in the arcuate direction  52 . 
     One end of a second cable  42  is wrapped around an outside edge of cam  39  and may be anchored thereto. The opposite end of this cable is attached directly or indirectly to a lifting bar  49 . Cable  42  is preferably split, or otherwise functionally divided, and threaded through one or more pulleys  43 , terminating at opposite ends of lifting bar  49 . In some embodiments, cable  42  may be attached to a separate pulley  45  that is engaged with a third cable  51 , the ends of which are attached near the ends of bar  49  (See, e.g.,  FIG. 14 ). It is to be appreciated that as bar  49  is lifted as shown in  FIGS. 3-4 , a pulling force is transmitted through cable  42  to cam  39 . This force is transmitted directly, or through rod  38 , to disc  37 , and then through cable  35  to the proximal end of lever member  20 . Resistance to this force is provided by the weight  24 , which may be provided on carriage  25 . The amount of resistance may be changed by changing the position of weight  24  and/or carriage  25  on lever member  20 . The movement of weight  24  on carriage  25  in the embodiments of  FIGS. 2-9  is accomplished by the operation of motor  30 , encoder  31  and screw  29 . The outside edge of cam  39  may be shaped so as to keep the tension on cable  42  and lifting bar  49  consistent, in order to compensate for the upward/downward stroke of the bar  49  and the corresponding arcuate movement  52  of lever  20 . It is to be appreciated that the shape of such a cam is related, among other things, to the length of the distance between pivot  23  and the proximal end of lever  20 . 
     Detail of an exemplary cam and disc assembly are shown in  FIGS. 10-13 . In this embodiment, one end of cable  35  is attached to the proximal end of lever  20 , and the opposite end is wrapped over an outside edge of disc  37 , and attached thereto. The position of weight  24  on lever  20  determines the amount of tension provided through cable  35  to disc  37 . Disc  37  is attached to central rod  38 . Cam  39  is also attached to central rod  38 . However, in some embodiments, disc  37  and cam  39  may be engaged together, for example, and without limitation, by rivets, screws, and/or bolts. In other embodiments, disc  37  and cam  39  can both be integrated on a unitary material, for example, and without limitation, by injection molding or casting. These alternative embodiments eliminate the need for rod  38 . Referring back to the exemplary embodiments of  FIGS. 10-21 , it is seen that one end of another cable  42  is engaged over the outside edge of cam  39  and attached thereto, leading directly or indirectly to lifting rod  49 . It is to be appreciated in order to rotate disc  37  rod  38  and/or cam  39 , an opposing force equal to or greater than that from cable  35  is necessary. This opposing force is transmitted from lifting rod  49  through cable  42  to cam  39 , and in the illustrated embodiment, through rod  38  to disc  35 . 
     In the exemplary embodiment shown in  FIGS. 3 and 4 , the position of carriage  25  and weight  24  has been moved toward the end of lever  20  for a maximum load (for example, and without limitation, 190 lbs.).  FIG. 3  shows the position of an exemplary leverage system of the present invention near the top of a lifting stroke, and  FIG. 4  shows the change in position near the bottom of a lifting stroke. In the exemplary embodiment shown in  FIGS. 5-7 , the position of carriage  25  and weight  24  has been moved toward the middle of lever  20  for a normal load (for example, and without limitation, 140 lbs.).  FIG. 5  shows the position of an exemplary leverage system of the present invention near the top of a lifting stroke,  FIG. 6  shows the change in position near the middle of a lifting stroke, and  FIG. 7  shows the change in position near the bottom of a lifting stroke. 
     Referring to the illustrated exemplary embodiment of  FIG. 15 , it is seen that some embodiments of the invention may include an electronic system  53  having either manual inputs such as buttons, dials, switches, or the like (including without limitation one or more keypads), and/or electronic inputs and outputs such as a magnetic or optical reader, USB or other port, etc. provided on or with a user interface  54 . A display is also provided in preferred embodiments of the user interface  54 . The user may input his/her identity and other information regarding the desired workout using any of these inputs (keypad, manual ID number input, magnetic ID card, upload from a portable electronic device, etc.). Embodiments of the system  53  maintain information about each user and workouts performed by that user, from inputs on interface  53  or other data sources, discussed more fully below, for later review and/or download. A user&#39;s workout parameters may include such things as, without limitation, the weight(s) (tension) to be applied during a particular workout; number of repetitions for the workout; desired time interval(s) between repetitions and/or a time to complete the entire workout; any scheduled changes to be made to the tension during the workout (e.g. increasing, decreasing and/or alternating tension for different repetitions in the workout); ranges of acceptable deviations from any of tension, repetitions, time interval(s), etc.; and/or whether or not to record feedback from the workout. It is to be appreciated that different combinations of these selections may be made by the user to more particularly tailor a given workout or exercise regimen. 
     Some embodiments of the invention include a port or networking link  56  that allows data stored in the electronic system of the present invention to be accessed and/or downloaded, directly or indirectly, from or onto another device, such as a PDA, iPod, local storage, removable storage, network storage, network computer, or the like. This makes the data available for the user to incorporate into other databases, programs or devices for archival, study, entertainment, competition or other purposes. For example, and without limitation, a person going through rehabilitation following an accident or injury is able to keep track of exercises performed on machines of the present invention, and make comparisons to determine whether improvements are taking place over a period of time. 
     The programmable electronic system  53  is provided to control, among other things, motor  30  and the position of carriage  25  and/or weight  24  on lever mechanism  20  via screw  29 . An encoder  31  is provided with motor  30 , which is preferably a servo motor. Encoder  31  is calibrated in conjunction with motor  30 , shaft  29 , and weight  24  so that system  53  knows the precise position of weight  24  on lever  20  which can be used to determine the amount of weight (tension) provided on cable  35 . The precision of the amount of weight provided depends on the type of encoder used, but in an exemplary embodiment, encoder  31  may count as many as 10,000 pulses for each rotation of shaft  29 , although other less-precise encoders may be used and still provide satisfactory precision. 
     Referring to the exemplary alternative embodiment of  FIG. 15 , it is seen that a servo motor  30  and associated encoder  31  are provided in a roughly parallel orientation with lever  20 . One end of motor  30  and a corresponding end of lever  20  are each provided with a rotatable wheel or sprocket around which a belt, chain, cable or other motion transmitter is provided to transfer rotational movement from the wheel or sprocket  60  on motor  30  to the wheel or sprocket  61  on lever  20 . Wheel  61  is, in turn, associated with movable weight  24  such that rotation in one direction causes weight  24  to move in one direction along lever  20 , and rotation in the opposite direction causes weight  24  to move in the opposite direction along lever  20 . 
     Using the interface  54  and/or link  56 , a user may select a desired amount of tension (for example, and without limitation, 140 lbs.), and in response, the system  53  operates motor  30  to move weight/carriage  24 / 25  to an appropriate location on lever  20  to provide the requested resistance to the cables leading to lifting bar  49 . System  53  may or may not use an additional controller or other driver  55  to operate motor  30 . The user interface  54  preferably includes controls that are easy to read and use, that are positioned close to the user, so that, if desired, adjustments in tension may be easily and quickly accomplished before, after or even during a set of repetitions. 
     Another encoder  32  is provided with rod  38 , as shown in  FIG. 14 . During use, the programmable electronic system  53  monitors information received from encoder  32  which indicates the time and distance expended by the user during lifting repetitions. When this information is combined with the weight position information from encoder  31 , system  53  can indicate the amount of force, energy, or other exercise parameters expended by the user. The system is preferably programmed to move the weight/carriage  24 / 25  in order to reduce the tension on the cables, if a decrease in the force provided by the user is detected through encoder  32 . This reduction in tension is accomplished in real time, and may help the user to maintain consistency in the amount of time the user takes to complete a repetition by, for example, lowering tension level. For safety purposes, if a drastic reduction, loss, or unexpected reversal in force from the user is detected through encoder  32 —indicating significant user fatigue—the programming in system  53  may cause motor  30  to rapidly move weight  24  away from the proximal end of lever  20 , so as to release or reduce tension to the cables leading to the lifting rod  49 , thereby acting as a spotter, to avoid injury to the user. 
     In some embodiments, a ratchet system such as that shown in  FIGS. 16-21  may be provided with disc  37 , rod  38  and/or cam  39 . In these embodiments, if an emergency situation is detected, the ratchet system may be engaged to prevent disc  37 , rod  38  and/or cam  39  from rotating backwards, thereby acting as a spotter and preventing any tension from being imparted to bar  49 . Referring to the exemplary spotter system embodiment of  FIGS. 16-21 , it is seen that cam  39  is provided with a plurality of slotted openings  66 . A safety latch housing  68  is provided supporting a spring-loaded latch  70 . Latch  70  is designed to fit into one of the openings  66  of cam  39 . A pin  72  attached to an electronically activatable coil  69  that is engaged with latch  70  to hold it off from insertion into one of openings  66  during normal use. However, should an emergency situation be detected, coil  69  may be activated in order to pull pin  72  from latch  70 , causing springs  71  to urge latch  70  forward for engagement into the nearest opening  66 , thereby preventing rotation of cam  39 , and preventing tension from being transmitted to bar  49  through cable  42 . It is to be appreciated other embodiments of spotter devices may be used including without limitation, devices to arrest movement of the cables, devices to disconnect or detach (release) one or more cables, etc. For example, and without limitation, instead of being provided in conjunction with the cam  39 , the ratchet system (including the latch and openings described above) can be used in conjunction with the disc  37 , rod  38 , or some other device rotatable around rod  38 . In other examples, the safety system can include a separate device engaged with the rod  38 , such as a mechanical or electromechanical brake. 
     In some embodiments, one or more additional hold-off or safety cables (not shown) may be attached to the lifting bar  49 , and to a safety mechanism similar to that shown in  FIG. 16 . Should the system detect fatigue in the user, this safety mechanism may be engaged so that the safety cable(s) arrest downward movement of the lifting bar to prevent it from falling or landing on the user. 
     In most embodiments, upon each start-up, motor  30  preferably moves the weight  24  back to a given home or start position such as  57 , and may also perform diagnostics or other internal tests to ensure calibration of the system and encoders. It is expected that the system calibration may be certified by a local city or state weight and measurement department to confirm delivered tension (weight) to bar  49 . 
     Additional programming may be provided in the electronic system to allow the user to designate different amounts of tension/resistance for different repetitions of a set. For example, and without limitation, the user may program the first five repetitions of a set to be at 140 lbs., and the next five to be at 120 lbs. Accordingly, for this example, during use, system  53  will cause weight  24  to be moved after the first five repetitions to a different position on lever  20  in order to change the tension on cables from 140 lbs. to 120 lbs. In other examples, and without limitation, a user may set a total number of repetitions at a given tension or tension reduction per repetition; or the user may establish a second set of repetitions with a lower or higher tension such as: 10 repetitions at 120 pounds tension; or 15 repetitions at 120 pounds tension, then back off or add ½ to 20 pounds per repetition; or a first set of repetitions at one tension, followed by a second set of repetitions at a lower or higher tension. It is to be appreciated that in other examples, and without limitation, the user may program alternating, increasing, decreasing or other variations in tension (weight) for different strokes or repetitions during one or more workouts. In other examples, a predefined weight lifting program can be stored in the system, provided through interface  54  or link  56 . 
     It is to be appreciated that other variations may be employed by the system, including without limitation, weight (tension), stroke and/or time, in order to compensate for real-time variations encountered by a user during a given workout. 
     For example, and without limitation, a user may select a total number of repetitions and a weight (tension) start point. The system  53  may then reduce or hold a selected amount of weight for every stroke until the repetition count is completed. In this example, the user may enter 150 pounds for the start weight and 10 repetitions. The user also sets the weight to be reduced per stroke from a range of ½ pound steps to 20 pounds per stroke. During such a workout, the tension is changed, for example, by ½ pound each repetition. At the end of the 10 repetitions, the tension is removed, leaving the weight of the bar  49  only. 
     With respect to stroke, it is to be appreciated that encoder  32  on shaft  38  may be used to keep track of the total stroke distance. As an example, and without limitation, when a first-time or new user enters his/her identification into the system (e.g. swipes a card), the system may require the user to go through a set of repetitions (e.g. 5 of them) at a low tension to learn the users stroke distance and save it in association with the user&#39;s ID. This information is gleaned from encoder  32  as the user causes shaft  38  to rotate during each repetition. In some examples, the system may also require the user to hold bar  49  (perhaps at ¾ stroke) as the tension is increased, while at the same time monitoring any movement on shaft  38  to determine the approximate strength abilities of the user. The stroke and/or strength information may then be used later during this user&#39;s workouts; for example, during a later workout, as encoder  32  monitors the stroke distances for the user, the system may reduce tension (by moving weight  24  on lever  20 ) if it detects that the user is not reaching his/her pre-determined stroke distance during a set of repetitions. This reduction in tension may enable the user to continue reaching the full stroke distance albeit at a lower tension (weight). The weight reduction information may also be recorded so that the user may review it after the workout to see when and by how much the weight was reduced in order for the user to complete a given workout while maintaining the same stroke distance. This feature may be enabled or disabled at the discretion of the user. 
     With respect to time, it is to be appreciated that encoder  32  on shaft  38  may be used to keep track of the time it takes for a user to complete each stroke. As an example, and without limitation, an initial time benchmark may be established for a user to complete one stroke and/or an average time may be calculated for a user based on strokes completed during one or more actual workouts. Then, during a later workout, as encoder  32  monitors the stroke time for the user, the system may reduce tension (by moving weight  24  on lever  20 ) if it detects that the user is taking more time than the benchmark/average stroke time during a set of repetitions. This reduction in tension may enable the user to continue reaching the full stroke within the average/benchmark time albeit at a lower tension (weight). The weight reduction information may also be recorded so that the user may review it after the workout to see when and by how much the weight was reduced in order for the user to complete a given workout while maintaining the same stroke time. This feature may be enabled or disabled at the discretion of the user. 
     It is to be appreciated that embodiments of the invention may be set to reduce or eliminate the tension to bar  49  if the user holds the bar in a fixed position for a minimal time interval (timeout) following the start of movement in a repetition—indicating fatigue (inability to move the bar further). The timeout may be any appropriate pre-set time interval, but should be short enough to avoid injury yet long enough not to interrupt an otherwise normal workout. In other variations, a total time for a series of repetitions may be established by the user and if that time is exceeded, then tension to bar  49  may be released. Recording of any or all of this information may be enabled or disabled at the discretion of the user. 
     It is to be understood that variations, modifications and combinations of the elements of the various embodiments of the present invention may be made without departing from the scope thereof. It is also to be understood that the present invention is not to be limited by the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the foregoing specification.