Patent Publication Number: US-2022218553-A1

Title: Fitness devices

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is an international application which claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/855,086, filed May 31, 2019 and entitled “Fitness Devices,” which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The present application relates to fitness devices. Various types of fitness devices are designed for use by fitness practitioners or users to perform a variety of different types of exercises. Such fitness devices may be used in different environments, including but not limited to gyms, residential homes, hotels, recreational facilities, airports, malls, sports training facilities, orthopedic and rehabilitation facilities, physiotherapeutic and chiropractic facilities, etc. There is a need for improved fitness devices configured to provide assisted stretching and other types of exercises. 
     SUMMARY 
     Embodiments of the invention provide fitness devices for performing assisted stretching and other types of exercises. 
     In some embodiments, a fitness device comprises a base assembly, a table or other rigid support platform coupled to the base assembly, and a foot restraint coupled to the base assembly. The foot restraint is configured, responsive to a change in a relative position of the foot restraint with respect to the table, to apply a resistive force to at least one of one or more feet and one or more ankles of a user positioned in the fitness device. 
     The fitness device may further comprise one or more rotation actuators comprised within at least one of the base assembly and the table, and a controller configured to adjust a rotation of the table relative to the foot restraint utilizing the one or more rotation actuators. The fitness device may also comprise an elevation assembly coupled between the base assembly and the table, wherein at least one of the one or more rotation actuators is comprised at least partially within the elevation assembly. 
     The fitness device may further comprise one or more height actuators comprised within at least one of the base assembly, the table, and the foot restraint, and a controller configured to adjust a height of the table relative to the foot restraint utilizing the one or more height actuators. The fitness device may also comprise an elevation assembly coupled between the base assembly and the table, wherein at least one of the one or more height actuators is comprised at least partially within the elevation assembly. 
     The fitness device may further comprise one or more height actuators comprised within at least one of the base assembly and the foot restraint, one or more rotation actuators comprised within at least one of the base assembly and the table, and a controller configured to adjust at least one of (i) a height of the table utilizing the one or more height actuators and (ii) a rotation of the table utilizing the one or more rotation actuators. The fitness device may also comprise an elevation assembly coupled between the base assembly and the table, wherein at least one of the one or more rotation actuators and the one or more height actuators is comprised at least partially within the elevation assembly. 
     The fitness device may further comprise one or more sensors, the controller being configured to adjust said at least one of the height of the table and the rotation of the table based at least in part on readings obtained from the one or more sensors. 
     The one or more sensors comprise at least one force sensor configured to obtain one or more measurements of the resistive force applied by the foot restraint, and wherein adjusting said at least one of the height of the table and the rotation of the table is based at least in part on the one or more measurements of the resistive force applied by the foot restraint. The controller may be configured to adjust said at least one of the height of the table and the rotation of the table based at least in part on the one or more measurements of the resistive force applied by the foot restraint to maintain the resistive force applied by the foot restraint within a specified range. 
     The controller may be configured to adjust said at least one of the height of the table and the rotation of the table based at least in part on the one or more measurements of the resistive force applied by the foot restraint to maintain the resistive force applied by the foot restraint within the specified range during a sequence of motion of the user positioned in the fitness device. The sequence of motion of the user positioned in the fitness device may comprise raising a height of the table to provide a linear stretch on the user, and rotating the table after the linear stretch to apply additional stretch to a targeted area of a torso of the user. The sequence of motion of the user positioned in the fitness device may further comprise at least one of reversing a rotation of the table and lowering the height of the table. The additional stretch may comprise at least one of flexion, extension and lateral flexion of the torso of the user. 
     The fitness device may further comprise a cushion assembly coupled to the table, and the sequence of motion of the user positioned in the fitness device may further comprise displacing at least a portion of the cushion assembly based at least in part on a rotation of the table to provide further stretch of the targeted area of the torso of the user. 
     The one or more sensors may further comprise at least one height sensor configured to obtain one or more measurements of a displacement height of the table. The controller may be further configured to generate one or more height compensation values based at least in part on a comparison of the one or more measurements of the resistive force applied by the foot restraint and a maximum allowable resistive force, and to adjust said at least one of the height of the table and the rotation of the table based at least in part on the one or more measurements of the displacement height of the table and the generated one or more height compensation values. 
     The one or more sensors may comprise at least one rotation sensor configured to obtain one or more measurements of rotational displacement of the table. The controller may be further configured to generate a measured rotation angle of the table based at least in part on the one or more measurements of the rotational displacement of the table. The controller may be further configured to generate a reference rotation angle based at least in part on a maximum rotation angle of the table, a number of exercise repetitions of an exercise being performed by the user, and input controls, to determine a difference between the reference rotation angle and the measured rotation angle, and to adjust said at least one of the height of the table and the rotation of the table based at least in part on the determined difference between the reference rotation angle and the measured rotation angle. 
     The input controls may comprise a first input control and at least a second input control. The reference rotation angle may comprise a value larger than the measured rotation angle responsive to user activation of the first input control and the second input control. The reference rotation angle may comprise the measured rotation angle responsive to user activation of one of the first input control and the second input control. The reference rotation angle may comprise a value smaller than the measured rotation angle responsive to user deactivation of the first input control and the second input control. 
     The fitness device may further comprise a cushion assembly coupled to the table, at least a given portion of the cushion assembly being configured to tilt relative to the table, and one or more tilt actuators comprised within at least one of the table and the cushion assembly. The controller may be further configured to adjust a tilt of the given portion of the cushion assembly based at least in part on the obtained sensor readings. The given portion of the cushion assembly may comprise at least one of a pelvic cushion and a lumbar cushion of the cushion assembly. 
     The one or more sensors may comprise at least one tilt sensor configured to obtain one or more measurements of linear displacement of the given portion of the cushion assembly. The controller may be further configured to generate a measurement of a tilt angle of the given portion of the cushion assembly based at least in part on the one or more measurements of linear displacement of the given portion of the cushion assembly. The controller may be further configured to generate a reference rotation angle based at least in part on a maximum rotation angle of the table, a number of exercise repetitions of an exercise being performed by the user, and input controls, and to adjust the tilt of the given portion of the cushion assembly based at least in part on the reference rotation angle and the measured tilt angle. 
     The table may be configured for lateral rotation about a craniocaudal axis of the user positioned in the fitness device. 
     At least a portion of the foot restraint may be removably coupled to the base assembly. 
     The foot restraint may comprise a user attachment portion coupled to a base assembly mounting portion. 
     The user attachment portion may comprise at least one of one or more sets of adjustable parallel bars, one or more adjustable cuffs, one or more adjustable boots, one or more adjustable straps, one or more adjustable elastic bands, and one or more adjustable springs. 
     The base assembly mounting portion may be coupled to one or more fixed points on a platform of the base assembly. 
     The base assembly mounting portion may comprise a rounded plate rotatably affixed to a platform of the base assembly. The base assembly mounting portion may further comprise a ball joint coupling the user attachment portion to the rounded plate, the ball joint being configured for at least one of rotation and linear travel of the user attachment portion relative to the platform of the base assembly. 
     The base assembly mounting portion may comprise one or more sliding tracks affixed to a platform of the base assembly. The base assembly mounting portion may further comprise at least one of one or more straps and one or more elastic bands coupling the user attachment portion to the one or more sliding tracks, the one or more sliding tracks being configured for linear travel of the user attachment portion relative to the platform of the base assembly. 
     In some embodiments, a method of operating a fitness device comprises detecting, by a controller of the fitness device, a change in a relative position of a foot restraint with respect to a table of the fitness device, the foot restraint being coupled to a base assembly of the fitness device. The method also comprises, responsive to detecting the change in the relative position of the foot restraint with respect to the table, adjusting, using the controller of the fitness device, at least one of (i) a height of the table and (ii) a rotation of the table to apply a resistive force with the foot restraint to at least one of one or more feet and one or more ankles of a user positioned in the fitness device. 
     Adjusting said at least one of the height of the table and the rotation of the table may be based at least in part on readings obtained from one or more sensors of the fitness device. The one or more sensors may comprise at least one force sensor configured to obtain one or more measurements of the resistive force applied by the foot restraint, and adjusting said at least one of the height of the table and the rotation of the table may be based at least in part on the one or more measurements of the resistive force applied by the foot restraint. 
     In some embodiments, a computer program product comprises a non-transitory processor-readable storage medium having stored therein program code of one or more software programs. The program code when executed by a controller of a fitness device causes the controller to perform the step of detecting a change in a relative position of a foot restraint with respect to a table of the fitness device, the foot restraint being coupled to a base assembly of the fitness device. The program code when executed by the controller of the fitness device further causes the controller to perform the step of, responsive to detecting the change in the relative position of the foot restraint with respect to the table, adjusting at least one of (i) a height of the table and (ii) a rotation of the table to apply a resistive force with the foot restraint to at least one of one or more feet and one or more ankles of a user positioned in the fitness device. 
     Adjusting said at least one of the height of the table and the rotation of the table may be based at least in part on readings obtained from one or more sensors of the fitness device. The one or more sensors may comprise at least one force sensor configured to obtain one or more measurements of the resistive force applied by the foot restraint, and adjusting said at least one of the height of the table and the rotation of the table may be based at least in part on the one or more measurements of the resistive force applied by the foot restraint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1F  depict a fitness device, according to an embodiment of the invention. 
         FIG. 2  depicts planes and axes relative to a user, according to an embodiment of the invention. 
         FIGS. 3A-3D  depict aspects of a cushion assembly of a fitness device, according to an embodiment of the invention. 
         FIGS. 4A-4G  depict aspects of operation of an overhead bar of a fitness device, according to an embodiment of the invention. 
         FIGS. 5A and 5B  depict aspects of a foot restraint on a base assembly of a fitness device, according to an embodiment of the invention. 
         FIGS. 6A-6D  depict various foot restraints for use with a base assembly of a fitness device, according to an embodiment of the invention. 
         FIG. 7  depicts coupling of a foot restraint to a resistive force, according to an embodiment of the invention. 
         FIGS. 8A-8C  depict operation of a foot restraint of a fitness device, according to an embodiment of the invention. 
         FIGS. 9A and 9B  depict operation of a foot restraint of a fitness device, according to an embodiment of the invention. 
         FIGS. 10A-10E  depict operation of a foot restraint of a fitness device, according to an embodiment of the invention. 
         FIGS. 11A and 11B  depict operation of a foot restraint of a fitness device, according to an embodiment of the invention. 
         FIGS. 12A-12F  depict operation of a fitness device, according to an embodiment of the invention. 
         FIGS. 13A-13D  depict operation of a fitness device, according to an embodiment of the invention. 
         FIGS. 14A-14C  depict a foot restraint coupled to a fitness device, according to an embodiment of the invention. 
         FIGS. 15A-15C  depict a foot restraint extending from a cushion assembly of a fitness device, according to an embodiment of the invention. 
         FIGS. 16A-16H  depict a foot restraint coupled to a fitness device, according to an embodiment of the invention. 
         FIGS. 17A-17C  depict a user platform for a fitness device, according to an embodiment of the invention. 
         FIGS. 18A-18D  depict a step ramp and modular cushions for a fitness device, according to an embodiment of the invention. 
         FIGS. 19A and 19B  depict an extendable foot restraint configured for coupling with a fitness device, according to an embodiment of the invention. 
         FIGS. 20A and 20B  depict a foot restraint track system for a fitness device, according to an embodiment of the invention. 
         FIGS. 21A-21C  depict a foot restraint track system for a fitness device, according to an embodiment of the invention. 
         FIGS. 22A-22C  depict a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIG. 23  depicts operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIG. 24  depicts operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIG. 25  depicts operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIG. 26  depicts operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIG. 27  depicts operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIGS. 28A-28C  depict operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIGS. 29A-29J  depict operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIGS. 30A-30H  depict operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIGS. 31A-31H  depict operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIG. 32  depicts a ball joint in a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIG. 33  depicts a ball joint in a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIGS. 34A-34C  depict a ball joint in a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIGS. 35A and 35B  depict a movable platform for a fitness device, according to an embodiment of the invention. 
         FIGS. 36A and 36B  depict a movable platform for a fitness device, according to an embodiment of the invention. 
         FIGS. 37A-37D  depict operation of a foot restraint for a fitness device, according to an embodiment of the invention. 
         FIGS. 38A and 38B  depict operation of an elevation assembly for a fitness device, according to an embodiment of the invention. 
         FIG. 39  depicts modules for controlling the elevation and rotation of a table of a fitness device, according to an embodiment of the invention. 
         FIGS. 40A-40L  depict operation of a fitness device, according to an embodiment of the invention. 
         FIGS. 41A-41J  depict operation of a foot restraint of a fitness device, according to an embodiment of the invention. 
         FIGS. 42A-42H  depict operation of a fitness device, according to an embodiment of the invention. 
         FIG. 43  shows an example of an information processing system that may be utilized to implement at least a portion of a fitness device, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments of the invention will be described herein in the context of illustrative fitness devices, along with illustrative apparatus, systems and methods for utilizing such fitness devices. However, it is to be understood that embodiments of the invention are not limited to the illustrative methods, apparatus, systems and devices but instead are more broadly applicable to other suitable methods, apparatus, systems and devices. 
     In some embodiments, a fitness device or unit is provided for performing assisted stretching exercises, including assisted back stretching. The fitness device is designed for use by fitness practitioners, also referred to as users, for back stretching and other exercises. The fitness devices described herein are configured for use in a gym environment, a physical training facility, etc. A fitness device, in some embodiments, is configured as a mobile unit to facilitate use in a training facility environment and other use cases. 
     It is anticipated that users will be trained to operate the fitness devices described herein, such as through one-on-one interaction with a certified trainer, through self-instruction via instruction cards affixed to the fitness devices, via training pamphlets, videos, etc. 
     The fitness devices described herein may be utilized to impart various exercise actions on a user, including the application of an angular displacement about the lumbar region, for the purpose of lumbar flexion and extension. To use the fitness device, the user situates their body facing toward the fitness device (e.g., prone), facing away from the fitness device (e.g., supine) or facing sideways (e.g., lateral) to the fitness device, and then locates their feet in a footrest or foot support of the fitness device. In some embodiments, the footrest includes foot restraints with resistive motion capability, to enhance stretching of one or more of the user&#39;s back, trunk, legs, thighs, upper and lower extremities, etc. It should be noted, however, that the fitness device may be used without the footrest as desired, even in cases where the footrest is installed or attached to the fitness device. 
     In the various orientations (e.g., prone, supine, lateral), the user&#39;s arms may be positioned to rest on an arm support of the fitness device. The user&#39;s arms and other portions thereof may also or alternatively be supported with the assistance of a chest harness or other strapping from the underarms to some attachment point on a rotating table of the fitness device. This may include, in some embodiments, the user of special hand-wrist supports with integral hooks for attachment to an overhead bar or other portion of the fitness device. 
     The arm supports in some embodiments include hand grips with controls for enabling powered rotation of the entire assembly, providing full body stretching with the user. Such full body stretching may include positions of body flexion and extension of the human torso, including allowing the lower body mass and restrained feet of the user to undergo muscular stretching, aiding range of motion of all of the body&#39;s joints, including the spine or back of the user. In addition to the arm supports or rests, an overhead bar may be provided on the fitness device allowing the user to support their weight. The arm supports or rests and overhead bar, either individual or in combination, may also or alternatively provide the ability for the user to perform active isotonic exercise and stretching. The use of an overhead bar, however, is optional and not required. 
     Throughout the description, the following terms are used to describe planes and axes.  FIG. 2  shows the various planes and axes described below. Descriptions relative to the ground are described with the user standing. Descriptions relative to the user&#39;s body remain regardless of the user&#39;s orientation relative to the ground. 
     The anteroposterior axis refers to the human body axis (z-axis) which runs horizontally fore and aft through the human body, approximately through the vertical mid-point, parallel to the ground and perpendicular to the coronal plane. The anteroposterior axis is also referred to as the dorsoventral axis. 
     The coronal plane refers to the vertical plane which divides the human body between its forward (ventral) and rear (dorsal) portions. This plane contains the lateral (x) axis and craniocaudal (y) axis, perpendicular to the anteroposterior (z) axis. 
     The craniocaudal axis refers to the human body axis (y-axis) which runs vertically through the human body, perpendicular to the transverse plane. 
     The lateral axis refers to the human body axis (x-axis) which runs laterally (e.g., left/right) through the human body, roughly through the vertical mid-point, parallel to the ground and perpendicular to the sagittal plane. 
     The median plane refers to the sagittal plane located midway in the human body. The median plane contains the craniocaudal (y) axis and the anteroposterior (z) axis, perpendicular to the lateral (x) axis. The median plane is also referred to as the mid-sagittal plane. 
     The sagittal plane refers to any vertical plane which divides the human body into lateral (e.g., left and right) segments. 
     The transverse plane refers to the horizontal plane which approximately divides the human body between its upper and lower portions. The transverse plane contains the lateral (x) axis and anteroposterior (z) axis, perpendicular to the craniocaudal (y) axis. The transverse plane is also parallel to the ground with the person in a vertical position (e.g., standing upright). 
     The x-axis refers to the left-right axis through the human body. See the discussion above regarding the lateral axis. 
     The y-axis refers to the longitudinal (e.g., up/down) axis through the human body. See the discussion above regarding the craniocaudal axis. 
     The z-axis refers to the fore-aft axis through the human body. See the discussion above regarding the anteroposterior axis. 
     In the description herein, unless otherwise noted, motions will be referenced to a Cartesian coordinate system fixed to the body of the user of the fitness device, using the x-, y- and z-axis nomenclature. Further, measurement units unless otherwise noted are specified using the International System of Units (SI). Equivalent values are also specified (e.g., in parentheses) using the United States Customary System (USCS) as reference. 
     As described above, a fitness device in some embodiments is configured for use in the prone, supine and lateral positions. In some embodiments, a fitness device may include an additional pivot point that is located approximately mid-way between a lumbar support and a pelvic support, just superior to a main table pivot point and its attachment to an elevation assembly, base assembly or table of the fitness device. The additional pivot point advantageously enables partial rotation into a fixed pre-selected angle (e.g., of 0-45 degrees), preceding flexion, extension and lateral flexion stretching. The additional pivot point also enables active isotonic exercise and motion around the variable adjusted resistive pivot point along the craniocaudal (y) axis as a standalone exercise independent of rotation of the table. The table is also referred to herein as a rigid support platform of the fitness device. The additional pivot point may be solenoid released, mechanically released manually, etc. 
     For user safety and comfort, the fitness device is configured with one or more mechanisms for halting operation of the fitness device in the event of malfunction or user discomfort. Such mechanisms may include one or more emergency stop buttons, activation of which will cut supply power to the fitness device. Such mechanisms may also or alternatively include one or more user interface features and controls (e.g., on the hand grips, on the overhead bar, etc.) allowing the user to pause or stop operation of the fitness device. 
     In some embodiments, a fitness device is configured to meet one or more of the following user requirements: 
     The user is able to approach the fitness device and orient their body relative to the fitness device, in preparation for executing one or more exercise sequences, where the orientation of the user may be supine (facing away from the fitness device), prone (facing toward the fitness device), or lateral (sideways), and, if desired, in all the above positions in rotation; 
     The user is able to adjust the fitness device such that the overall height, position of the hand grips, position of the lumbar and thoracic cushions, and position of the overhead bar are located properly to fit their body size; 
     The user is able to increase and decrease the backrest angle, lumbar angle or the degree of extension of the lumbar backrest in the anteroposterior (z) axis plane, and supplemental resistive force of the fitness device to realize a desired degree of lumbar flexion, extension and lateral flexion and rotation during stretching or other exercise; 
     The user is able to secure their feet, as desired, to allow application of resistive force to enhance exercise as will be described in further detail below; 
     The user is provided with a mechanism for prescribing desired exercise parameters, including mode of operation, backrest angle, flexion and/or extension rate, resistive force, number of repetitions, etc.; 
     The user is provided with a feedback mechanism for providing feedback regarding progress status of one or more exercises and for evaluating utility of the one or more exercises; 
     The user is provided with a mechanism for starting and stopping exercise regimens; 
     The user is provided with instructional material, for initial and refresher training relating to the safe operation of the fitness device; 
     The user is able to interrupt all power to the fitness device in the event of malfunction of the fitness device or discomfort of the user; 
     The user is provided with assurance of physical safety during operation of the fitness device; and 
     The user is able to operate the fitness device in various operating environments, including but not limited to gyms, training facilities, etc. 
     In some embodiments, a fitness device is configured to meet one or more of the following functional requirements: 
     The fitness device provides one or more mechanisms for applying flexion, extension, lateral flexion and rotation of the user human torso, upon user control, via powered angular displacement (fore/aft) of the user torso with respect to the legs (about the x-axis); 
     The fitness device provides one or more mechanisms for applying supplemental flexion/extension of the user human torso, upon user control, via powered angular displacement (fore/aft) of the user pelvis with respect to the torso (pelvic tilt, about the x-axis), coordinated with the rotation motion; 
     The fitness device provides one or more mechanisms for applying supplemental resistive force at the user feet, upon user control; 
     The fitness device provides one or more mechanisms for a user to orient their physical position relative to the fitness device such that the user may be prone (facing the fitness device), supine (facing away from the fitness device), or lateral (facing sideways relative to the fitness device), and laterally flexed in varying degrees of rotation along the craniocaudal (y) axis; 
     The fitness device provides one or more mechanisms for users to locate their feet, in any of the defined orientations, such that supplemental resistive force can be applied if desired by the user; 
     The fitness device provides one or more mechanisms for the user to locate their hands in front of their body (e.g., via hand grips), when they are in the prone or supine position; 
     The fitness device provides one or more mechanisms for the user to locate their hands above their body (e.g., via an overhead bar), when they are in the prone, supine, or lateral position; 
     The fitness device provides one or more mechanisms for the user to halt motion of the fitness device during execution of one or more exercise sequences; 
     The fitness device provides one or more mechanisms for adjustment of the overall device height, to accommodate variations in user leg length; 
     The fitness device provides one or more mechanisms for up/down adjustment of the overhead bar, parallel to the coronal plane, in the direction of the y-axis; 
     The fitness device provides one or more mechanisms for in/out adjustment of the overhead bar, parallel to the lateral plane, in the direction of the z-axis; 
     The fitness device provides one or more mechanisms for up/down adjustment of the arm supports; 
     The fitness device provides one or more mechanisms for lateral adjustment of the arm supports (about the y-axis), to accommodate users of varying girth; 
     The fitness device provides one or more mechanisms for restraining the feet of the user, with allowance for motion both upward (perpendicular to the ground plane) and outward along the user dorsoventral axis (z-axis); 
     The fitness device provides for two or more modes of operation, including a manual mode of operation and repetition mode of operation, selectable via a user interface of the fitness device, where the manual mode of operation provides the user with controls to start and stop one or more exercise motions on command and to control an amount of applied resistive force, and the repetition mode of operation provides the user with controls to start and stop one or more sequences of repetitive exercise motions and to control an amount of applied resistive force; 
     The fitness device, on user command of an emergency stop, de-energizes all sources of user exercise motions, including application of resistive force applied to the feet, and may return the user to an upright position and allow the user to physically remove themselves from tension; and 
     The fitness device provides one or more mechanisms for, upon user command, returning all motions to a starting position and releasing any applied forces. 
     In some embodiments, the fitness device is configured to provide one or more of the following performance requirements: 
     The fitness device is configured to apply rotation of the human torso, in various degrees of rotation over a continuous range from 0 degrees (deg) (upright) to 60 deg (fully extended); 
     The fitness device is configured to apply prone, supine and lateral flexion of the human torso, at an angular rate of approximately 0 to 30 degrees per second (deg/sec); 
     The fitness device is configured to apply supplemental flexion/extension (pelvic tilt) and extension along the z-axis, of the user human torso, over a continuous range from 0 deg (aligned with torso) to 30 deg (forward); 
     The fitness device is configured to apply supplemental flexion/extension (pelvic tilt) of the user human torso, at an angular rate not exceeding 0 to 10 deg/sec; 
     The fitness device is configured to provide pelvic tilt coordinated with rotation, at user command; 
     The fitness device is configured to apply supplemental resistive force at the user feet, over a range from 0 to 890 Newtons (N) (200 pound-force (lbf)); 
     The fitness device is configured to enable overall height adjustment to accommodate variations in user leg length over a range from 65 centimeters (cm) (26 inches (in)) to 110 cm (43 in) measured at the inseam; 
     The fitness device is configured for up/down adjustment of the overhead bar; 
     The fitness device is configured for in/out adjustment of the overhead bar; 
     The fitness device is configured for up/down adjustment of the arm support with an adjustment application force not exceeding 90N (20 lbf), or for manual up/down adjustment of the arm support possibly using a counterweight or spring shock; 
     The fitness device is configured for lateral adjustment of the arm support through a range of ±30 deg (where 0 deg reference is perpendicular to the user coronal plane); 
     The fitness device is configured to provide free outward motion of the feet along the z-axis; and 
     The fitness device is configured to provide rotational motion of the foot restraint, over from 0 to 360 deg of rotation, about the y-axis. 
     In some embodiments, the fitness device is also configured to provide one or more interface requirements, including user interface requirements, power interface requirements and physical interface requirements. The user interface includes all mechanisms with which the user can interface with the fitness device, including command and control interfaces and user safety considerations. The power interface includes all mechanisms with which the fitness device can transfer energy to/from the environment, including constraints on power consumption. The physical interface includes all mechanisms with which the fitness device can transfer mechanical and heat energy to/from the environment, including constraints on size and mass. 
     With regard to user interface requirements, it is assumed in some embodiments that the user is trained in operation of the fitness device. The primary interface between the user and the fitness device in some embodiments is the physical interaction between the user body and the various contact points on the fitness device. These contact points include, but are not limited to, the footrest or other foot support or foot restraint, the lumbar panel, the upper body panel, the arm supports, the hand grips, and the overhead bar. In addition to the user interface, the fitness device in some embodiments provides a control interface for the user, including controls on the hand grips which function as mechanisms for operating the fitness device. 
     User interface requirements related to physical contact may include one or more of: accommodating users with body mass not exceeding 180 kilograms (kg) (400 pounds (lb)); accommodating users with height not exceeding 214 cm (84 in); accommodating users with height not less than 145 cm (57 in); accommodating users with leg length, measured at inseam, not exceeding 110 cm (43 in); accommodating users with leg length, measured at inseam, not less than 65 cm (26 in); and accommodating users with torso width not exceeding 60 cm (24 in). 
     User interface requirements related to system control may include one or more of: 
     The fitness device is configured to provide the user with a user control interface, allowing the user to specify parameters for conducting the exercise motions, where the user interface includes a control panel and/or control buttons (e.g., on the hand grips and/or on the overhead bar); 
     The fitness device is configured to provide the user with one or more mechanisms for specifying the mode of operation (e.g., manual, repetitive, etc.) at the user control interface; 
     The fitness device is configured to provide the user with one or more mechanisms for specifying the extent of torso flexion/extension at the user control interface (e.g., using one or more pre-set levels); 
     The fitness device is configured to provide the user with one or more mechanisms for specifying the extent of supplemental prone, supine and lateral flexion at the user control interface (e.g., using one or more pre-set levels); 
     The fitness device is configured to provide the user with one or more mechanisms for specifying the number of repetitions to be executed in a repetitive mode of operation at the user control interface; 
     The fitness device is configured to provide the user with one or more mechanisms for starting one or more exercise motions, at any user position while the user is positioned in the fitness device for exercise, in any position in which the fitness device is used (prone, supine, lateral); 
     The fitness device is configured to provide the user with one or more mechanisms for stopping the exercise motion, at any user position while the user is positioned in the fitness device for exercise, in any position in which the fitness device is used (prone, supine, lateral); and 
     The fitness device is configured to provide the user with one or more mechanisms for invoking an emergency stop control while the user is positioned in the fitness device for exercise, in any position in which the fitness device is used (prone, supine, lateral). 
     User safety requirements may include one or more of: the fitness device not exposing the user to surfaces that cause laceration; the fitness device not exposing the user to material that is categorized as hazardous by the Globally Harmonized System (GHS); and the fitness device not exposing the user to device-generated electrical or radiation hazards. 
     Power interface requirements may include one or more of: the fitness device is configured for operation, fulfilling all functional requirements, using residential-class electrical power as the sole source of power, with electrical power consumption not to exceed 110 volts (V) alternating current (AC)/10 amperes (A) or 220V AC/5 A (single phase). 
     In some embodiments, the fitness device meets one or more of the following size and weight requirements: an overall width, while in a configuration suitable for transport, not exceeding 90 cm (35 in); an overall height, while in a configuration suitable for intended use, not exceeding 240 cm (95 in); a maximum mass of 90 kg (200 lbm); an interface with the physical environment via the floor, supported at four corners of a base portion with non-slip feet; and the capability for adjusting the height of the floor interface, over a range of ±25 millimeters (mm) (±1 in), to allow compensation for leveling and uneven floor surfaces. 
     In some embodiments, the fitness device is configured to operate as described herein while in an indoor office-class environment with a temperature in the range of degrees Celsius (° C.) (50-95 degrees Fahrenheit (° F.)) and relative humidity within the range of 10-90%, non-condensing. 
     In some embodiments, the fitness device is configured to meet one or more transportability requirements including one or more of: providing one or more mechanisms for attaching or deploying wheels, thereby allowing local transportation across smooth, flat, hard indoor surfaces; meeting all operating requirements as described herein when situated in an operating environment such that it is level in all directions; providing one or more mechanisms for stowing or collapsing any protruding components such that a transportable configuration is achieved, to allow compliance with the requirement for maximum transportable width; and meeting all operating requirements after shipping in an environment with temperatures within the range of −10° C. to 40° C. (14-104° F.), and relative humidity within the range of 10-90%, non-condensing. 
     It is to be appreciated that the various “requirements” described above and elsewhere herein are presented by way of example only, and that in some embodiments a fitness device may conform to some, all or none of these requirements. It should be further appreciated that all material types, dimensions, ranges, etc. described above and elsewhere herein are presented by way of example only and that various other suitable materials, dimensions, ranges, etc. may be used as desired for a particular implementation. 
     In some embodiments, the fitness device is configured with an expected life greater than 10 years, with availability and reliability requirements including one or more of: minimum fitness device availability of 99% (e.g., less than 10 hours (hrs) of down-time per 1000 hrs of scheduled operation); required preventative maintenance will not exceed 5 hrs per 1000 hrs of operation; mean time between failure (MTBF) greater than 1000 hrs; and mean time to repair (MTTR) less than 5 hrs, with the provision that required parts and trained repair personnel are available at the time of failure. 
     In some embodiments, fitness devices enable various core muscle stretching activities. The fitness devices described herein are designed to increase user wellness, flexibility and mobility, range of motion, and to improve posture and overall athletic performance. As will be described in further detail below, fitness devices in some embodiments provide power resistance stretching. The disclosed fitness devices are also multi-positional, and provide for self-activated stretch and other exercise of users thereof. Thus, the fitness devices described herein provide an alternative to less effective and time-consuming core stretch regimens. It should be appreciated, however, that the fitness devices described herein may be used as a supplement to other core stretch regimens rather than as a replacement to such other core stretch regimens. The fitness devices described herein are designed to be user-friendly, providing appeal to a wide variety of users (e.g., from beginner exercise enthusiasts to professional athletes). 
     Advantageously, users of the fitness devices described herein can safely perform a variety of stretch and other exercise programs utilizing three-dimensional (3D) positioning capability. Fitness devices may therefore have custom positioning tailored towards users&#39; individual needs. In some embodiments, fitness devices are equipped with power and manual controls as well as adjustable table height, foot supports or restraints, arm supports, etc. Users can expect increased flexibility, enhanced performance, and improved posture, whether approaching or utilizing the fitness devices in the supine, prone or lateral positioning. In some embodiments, fitness devices are designed to be controlled entirely by the users thereof without requiring supervision. Instructions for use of the fitness devices may be displayed on the fitness device, on a mobile computing device of a user that is coupled or otherwise paired with or connected to the fitness device, etc. 
     Core muscle stretching may be instrumental for physical success, and is enabled using the fitness devices described herein in illustrative embodiments. Fitness devices are advantageously 3D multi-positional (e.g., supine, prone, lateral), providing self-activated power resistance stretching, enabling increased flexibility, enhanced performance and improved posture. Fitness devices described herein also provide assessment capability, and enable both active and passive user participation (e.g., in isotonic, isometric and isokinetic exercise). The fitness devices described herein may be used for a variety of purposes, including prevention, wellness, and rehabilitation. Further, controls of the fitness devices described herein are user-friendly, motivating and time efficient. 
     In some embodiments, fitness devices are used for targeted stretching and exercising of specific muscle groups to increase flexibility, mobility and strength of a user thereof. Performance of the user is also enhanced, and posture is improved through stretching. The user can decide to use the fitness device in any desired position (e.g., supine, prone, lateral). The decision is dependent on which specific muscles and joints that the user is targeting. In some embodiments, a quick reference exercise chart is affixed to the device at a side panel thereof, to guide the user to which position is best suited to meet a user&#39;s core stretching objective. The quick reference exercise chart may also be output on a display of the fitness device, or a device coupled or otherwise paired or connected thereto (e.g., a smartphone or other mobile computing device of the user). An exercise routine may involve the user utilizing the fitness device in multiple positions. Each position may affect the core muscles of the user differently. The supine position (e.g., facing away from the fitness device) provides an extension position. The prone position (e.g., facing towards the fitness device) provides a flexion position. The lateral position (e.g., facing sideways, both left and right relative to the fitness device) provides a lateral position. 
     Prior to commencing a stretch or exercise routine, the fitness device may be set up and positioned by the user. Fitness device set up and positioning, in some embodiments, includes adjusting for height of the user. The user, for example, may select a height setting on a control panel of the fitness device, which automatically raises or lowers the rotating frame of the fitness device in order to align the center of a contoured lumbar support thereof to a center of a lower back and pelvis junction of the user. The user may then select, via the control panel, the degree or intensity of the stretching force to be applied. In some embodiments, the stretching force options are graded, ranging from (1) mild to (2) moderate to (3) intense. It should be appreciated, however, that there may be fewer or more than three stretching force options. The control panel, for example, may have a dial or other continuous control range for adjusting the stretching force to more than three stretching force options. 
     The intensity of the stretch or resistance may be managed by sensors located in an ankle or foot restraint system or component of the fitness device, allowing for consistent measure of resistance during use of the fitness device. One or more sensors may also or alternatively be located on or otherwise be part of a base assembly, elevation assembly, or other component or components of a fitness device. Measurements from such sensors, in addition to managing the intensity of the stretch or resistance provided by the foot restraint system or component, may also or alternatively be used in controlling various other motion or movement of components of a fitness device. In other embodiments, however, adjustment or control of motion or movement of components of a fitness device (e.g., lift and rotation of a table, tilt of portions of a cushion assembly, etc.) may be independent of any feedback from sensors such that the sensors may be omitted. 
     When included, sensors may provide measurements or feedback of various aspects of the fitness device, including but not limited to height of a table of the fitness device, rotation of the table of the fitness device, tilt or elevation of portions of a cushion assembly, etc. In some embodiments, resistive force applied by a foot restraint provides the necessary sensor feedback to precisely determine the degree of rotation and lift of the table. It should also be noted that the fitness device may include an optional elevation assembly that enables a change in height of the table. The elevation assembly, however, may offer only an attachment point for the rotating table and not a change in height of the table (e.g., the elevation assembly remains at a fixed height). Height adjustment displacement feedback enables the table to variably rotate on its axis, such as within a rotational arch of 0 to 60 degrees, and also limits excessive elevation of the user&#39;s foot restraint system from its attachment to the base assembly. 
     Optimal user positioning may be achieved by the user placing their feet and/or ankles into a foot restraint system or component of the fitness device. Very tall and very short users, in some cases, may need to adjust a height of arm supports of the fitness device to achieve maximum benefit. The foot and ankle restraint system or component combined with the arm supports ensure proper stretching force or resistance. 
     Fitness devices, in some embodiments, include control buttons or other control interface features conveniently located at handles or hand grips that are operated by the user to initiate rotation and elevation of the upper body support platform of a fitness device to allow for full body stretching. Dynamic motion of the fitness device may be entirely power driven, enabling effective passive stretching of the muscles. A fitness device may also or alternatively be configured for manual driven motion for active stretching of the muscles. A contoured lumbar support section of the fitness device may be configured to at least one of rotate outwardly relative to a thoracic section of the fitness device and extend outwardly as an upper body support platform of the fitness device rotates away from a home position. Both the lumbar support section and the thoracic section may be embodied as cushions of a cushion assembly mounted to a table of the fitness device. The user may fine-tune the stretching experience and reduce the maximum force by limiting the extent of travel of the rotating platform (e.g., a table of the fitness device). This may be accomplished by releasing motion control buttons of the fitness device. 
     Fitness devices described herein may be programmed to perform various exercise and stretch routines. A given exercise or stretch routine may be associated with parameters for: an exercise cycle; a number of sets; a number of repetitions; and timing. The exercise cycle defines a complete rotation of the fitness device from a vertical home position to the limit of full rotation, and then back to the initial starting position. The user can decide if they want to exercise utilizing one or multiple positions (e.g., prone, supine, lateral) in one or more sets. In some embodiments, exercise cycle parameters are separately set for different positions of use of the fitness device (e.g., there may be a first exercise cycle for the prone position and second exercise cycle for the lateral position, with the first exercise cycle and the second exercise cycle having different ranges or limits of rotation). The number of repetitions in a typical regime may be to exercise between 5 and 10 repetitions in each position. It should be appreciated, however, that the user may select fewer than 5 or greater than 10 repetitions as desired. Timing parameters control the length or duration of each exercise cycle, which is expected to last between 10 and 20 seconds but may be shorter or longer as desired. The user may customize the time length of any given exercise cycle by delaying or prolonging that exercise cycle using hand-control buttons or other control interfaces of the fitness device. 
     In some embodiments, the fitness device includes an overhead bar facilitating isometric and isotonic stretching. The inclusion of the overhead bar provides the ability to implement upper body superficial and deep core muscle stretching, as well as upper extremity arm, scapular and forearm muscular and joint recruitment during the stretching process if desired. 
     Any discomfort of the user may be immediately mitigated by the user using the hand-control buttons or other control interfaces of the fitness device to stop or reverse the motion of the rotating platform of the fitness device. As an example, discomfort to resistive ankle or foot restraints, or the perception of stretching, may be mitigated using such controls. The fitness device may also be configured with various emergency stop switches, buttons or other control interfaces conveniently located on or near handle bars and hand grips accessible by the user in the prone, supine and lateral positions. 
       FIGS. 1A-1F  depict a fitness device  100  for use by fitness enthusiasts or other users for exercise, including back exercise and stretching. The fitness device  100  advantageously assists the user by enabling active stretching exercises, which are performed before, during or after one or more other physical exercises. It should be appreciated, however, that the fitness device  100  may also be used independent of other physical exercises instead of being used before, during or after one or more other physical exercises. The active stretching, in some cases, improves the effectiveness of such other physical exercises. In some embodiments, the primary exercise action imparted on the user is the application of an angular displacement about the lumbar region, for the purpose of lumbar flexion and extension exercise. 
       FIGS. 1A and 1B  depict the fitness device  100  in starting and rotated positions, respectively. The fitness device  100  includes a base assembly  102  (including an optional foot restraint described in further detail below), an elevation assembly  104 , a table  106 , a restraint and overhead bar  108  and a cushion assembly  110 . The table  106  is configured to rotate about the table rotation axis  105 . The restraint and overhead bar  108  is configured to rotate about the restraint and overhead bar rotation axis  107 . The restraint and overhead bar  108  also includes underarm supports  112 . 
     The height of the table  106  is configured to increase or decrease as stretch is applied via rotation of the table  106  about the table rotation axis  105 . For example, in some embodiments the elevation assembly  104  is actuated to raise or lower the table  106  as it rotates to provide a desired amount of stretch of a user positioned in the fitness device  100  as will be described in further detail below. It should be noted that stretch may be provided by lifting a user positioned in the fitness device  100  (e.g., via elevation assembly  104 ) instead of rotating the user by rotating the table  106  about the table rotation axis  105 . As described above, stretch may also be provided through combinations of lifting the table  106  (e.g., via elevation assembly  104 ) and rotating the table  106  (e.g., via rotation about the table rotation axis  105 ). 
       FIG. 1A  shows the fitness device  100  in a starting position, where the table  106  is in a vertical orientation. The starting height of the table  106  is adjusted via elevation assembly  104 . The elevation assembly  104  enables manual or powered lift of the table  106 . In some embodiments the elevation assembly  104  is configured for manual lift where the user lays back on the table  106  and adjusts the height to provide traction force. In other modes of operation, the fitness device  100  provides vertical movement only without rotation of the table  106 , free-floating rotation of the table  106 , vertical plus corkscrew motion of the table  106  (e.g., possibly in conjunction with foot restraints as described in further detail below), etc. 
     It should be appreciated that there are various alternatives to the single-column elevation assembly shown in  FIG. 1A , including dual-column elevation assemblies, with various telescoping mechanisms for enabling lift of the table  106 . It should further be appreciated that the location of the table rotation axis  105  shown in  FIG. 1  is presented by way of example only. In other embodiments, the table rotation axis  105  may be placed higher or lower to achieve different desired amounts and locations of stretch of a user positioned on the fitness device  100 . The fitness device  100  may also be configured with multiple table rotation axes, so as to provide further customization of amounts and locations of stretch of a user positioned on the fitness device. 
     To use the fitness device  100 , a user situates their body relative to the fitness device  100  by facing toward the fitness device  100  (e.g., prone), facing away from the fitness device  100  (e.g., supine) or laterally facing the fitness device  100 . These different positions of the user relative to the fitness device  100  will be described in further detail below in conjunction with  FIGS. 3A-3D . 
     To restrain the user on the table  106 , the user&#39;s underarms are positioned to rest on the underarm support  112  coupled to the restraint and overhead bar  108 . The user then holds onto hand grips on different portions of the restraint and overhead bar  108  that are available for the particular position of the user relative to the fitness device  100  (e.g., prone, supine, lateral). Different configurations of hand grips on the restraint and overhead bar  108  will be described in further detail below with respect to  FIGS. 4A-4G . It is also noted that use of the restraint and overhead bar  108  is optional, and that a fitness device in some embodiments may not utilize an overhead restraint. In other embodiments, a fitness device may be configured with other types of restraints, such as restraint bars that rotate laterally from sides of the table  106 , rather than or in addition to using the restraint and overhead bar  108  that rotates about the restraint and overhead bar rotation axis  107  positioned proximate an upper portion of the fitness device  100  (e.g., near to the head of the user when positioned on the fitness device  100 ). 
     Once the user is securely positioned on the fitness device  100 , the user can utilize controls (e.g., located on the base assembly  102 , elevation assembly  104 , table  106 , restraint and overhead bar  108  including hand grips thereof, etc.) to rotate the table  106  from the starting position shown in  FIG. 1A  to the rotated position shown in  FIG. 1B . Thus, the fitness device  100  is configured to provide exercise via dynamic lifting with simultaneous or coordinated rotation of the user, possibly in conjunction with optional restraints and resistance applied at the lower extremities of the user (e.g., the feet and ankles of the user) as will be described in further detail below. 
     Controls located on hand grips of the restraint and overhead bar  108  (as well as controls positioned on the table  106  or one or more other sections of the fitness device  100  providing user interface features) allow powered rotation of the table  106 , including flexion and extension and lateral flexion positioning of the human torso of the user. The lower body mass and optional foot restraints may be used to provide additional resistance. Gravity acting on the user provides additional benefits for the stretch exercises. 
     For additional stretch, the user of the fitness device  100  in some embodiments utilizes optional foot restraints which are on or coupled to the base assembly  102 . The foot restraint provides mechanisms for attaching and securing the user&#39;s feet. Use of the foot restraint also provides resistance to the forces and motions imparted on the user by the elevation and rotational motions applied by the table  106 . The foot restraint, in some embodiments, is repositionable (e.g., via rotation, translation along a track, etc.) to allow prone, supine and lateral use. The height of the table  106  in some embodiments is settable or programmable (either powered or non-powered) to compensate for user height and body proportions. It is assumed that the foot restraints described herein are configured for removable attachment or mounting to a fitness device. In some embodiments, however, a foot restraint may be formed integrally with a fitness device such that the foot restraint is not removable. 
     As noted above, the fitness device  100  includes a base assembly  102 , an elevation assembly  104 , a table  106  and a restraint and overhead bar  108 . The base assembly  102  in some embodiments includes a platform, a foot restraint, a computerized user interface, system controls, a leg force monitor, etc. The elevation assembly  104  includes one or more elevation posts (e.g., telescoping posts) to raise or lower the height of the table  106 . The table  106  also provides hand grips and a cushion assembly  110  including different cushions for the head, thoracic and lumbar sections of the body of the user. In some embodiments, the cushion assembly  110  further includes a pelvic cushion, separate from the lumbar cushion, which is rotationally secured to the lumbar cushion supporting the pelvis and thighs of the user. The pelvic and lumbar cushions may be connected for coordinated longitudinal movement and rotational movement. The feet of the user of the fitness device  100  turn with the pelvis of the user (e.g., the feet of the user follow rotational movement of the pelvis of the user). The sizing of the pelvis cushion further facilitates access to the user by an assistant or trainer. The restraint and overhead bar  108  includes underarm supports  112  as well as various hand grips. 
     The restraint and overhead bar  108  is configured to open (e.g., via rotation about restraint and overheard bar rotation axis  107 ) in order to facilitate entry of the user into the fitness device  100 , and for providing a secure restraint for the user while in the fitness device  100 . One or more actuators affixed to the base assembly  102  and/or elevation assembly  104  are configured to raise and lower the table  106 . One or more actuators affixed to the elevation assembly  104  and/or the table  106  are configured to allow the table  106  to pivot about the table rotation axis  105 . One or more actuators within the table  106  are configured to allow the different sections of the cushion assembly  110  to move relative to one another and the table  106 . In some embodiments, such various actuators comprise respective linear actuators, such as linear actuators powered by electric motors. It should be appreciated, however, that various other types of actuators may be used in place or in addition to such electric motor-powered linear actuators. 
       FIGS. 1C, 1D, 1E and 1F  illustrate a user  101  positioned in the fitness device  100  in the supine position. More particularly,  FIG. 1C  shows a front view of the user  101  in the supine position in the fitness device  100 ,  FIG. 1D  shows a side view of the user  101  in the supine position in the fitness device  100 , and  FIGS. 1E and 1F  show perspective views of the user  101  in the supine position in the fitness device  100 .  FIGS. 1C-1F  show examples where the user  101  while positioned in the fitness device  100  utilizes an optional foot restraint that is included in or affixed to the base assembly  102 . The particular type of foot restraint shown in  FIGS. 1C-1F  is described in further detail below with respect to the examples of  FIGS. 5A and 5B, 12A-12F, and 29A-34C . 
       FIG. 2  illustrates the various planes axes that are referred to throughout the description, including the left-right lateral (x) axis, the longitudinal craniocaudal (y) axis, the fore-aft anteroposterior (z) axis, the transverse plane, the coronal plane, the mid-sagittal plane, and the para-sagittal plane. 
       FIGS. 3A-3D  illustrate aspects of the cushion assembly  110 .  FIG. 3A  shows an embodiment where the cushion assembly  110  includes a combined thoracic and head cushion  302  and a lumbar cushion  304 . In some embodiments, the lumbar cushion  304  is configured to rotate about a lumbar cushion rotation axis  303 . As illustrated in  FIGS. 1A-1F , the combined thoracic and head cushion  302  may be embodied as two separate cushions (e.g., a head cushion and a thoracic cushion). It should be appreciated, however, that any number of cushions may be used as desired to provide a requisite level of comfort for users of the fitness device  100 . Any number of said cushions may be adjustable, either manually or powered via one or more actuators, and may be configured to provide additional exercise benefit in addition to providing improved comfort.  FIGS. 3B, 3C and 3D  illustrate a user  301  positioned relative to the cushion assembly  110  in the supine, prone and lateral positions, respectively. 
       FIGS. 4A-4G  illustrate aspects and operation of the restraint and overhead bar  108  of the fitness device  100 .  FIGS. 4A and 4B  show a set of two prone hand grips  402 , two supine hand grips  404 , and various overhead bar hand grips  406 . The hand grips  402 ,  404  and  406  are positioned for the user to grip while in the fitness device  100  in various positions. For example, the prone hand grips  402  are located for use by the user while in the fitness device  100  in the prone position, the supine hand grips  404  are located for use by the user while in the fitness device  100  in the supine position, and the overhead bar hand grips  406  are located for use by the user in the prone, supine, or lateral position.  FIG. 4B  more particularly shows various non-limiting example locations  406 A,  406 B,  406 C,  406 D,  406 E,  406 F and  406 G for the hand grips on the overhead bar. Some or all of the hand grips  402 ,  404  and  406  include user interface controls (e.g., buttons, switches, pressure sensors, triggers, etc.) for controlling operation of the fitness device  100 . While the hand grips  402 ,  404  and  406  are located or positioned on the fitness device  100  for easy access in the prone, supine and lateral positions, respectively, it should be appreciated that controls on the hand grips  404 ,  404  and  406  are not necessarily limited solely for use while the user is in the prone, supine and lateral positions, respectively. Further, while  FIGS. 4A-4G  illustrate controls that are part of the various hand grips  402 ,  404  and  406  of the restraint and overhead bar  108 , it should be appreciated that the controls, as well as hand grips, may instead by integrated with or affixed to portions of the table  106  and/or the cushion assembly  110  (e.g., such as in embodiments where the restraint and overhead bar  108  is omitted). 
     In some embodiments, the operation of the fitness device  100  is controlled by a user gripping each of the prone hand grips  402  (or each of the supine hand grips  404 , or two of the overhead bar hand grips, or any combination of two of the hand grips  402 ,  404  and  406 ) with the user&#39;s left and right hands. When the user actuates controls on each of the prone hand grips  402 , the table  106  will rotate. When the user actuates controls on just one of the prone hand grips  402 , the table  106  stops rotation. When the user does not actuate the controls of either of the prone hand grips  402 , the table  106  reverts from a rotated position (e.g., as shown in  FIG. 1B ) to a starting position (e.g., as shown in  FIG. 1A ). It should be appreciated that this control scheme is just one example, and that operation of the fitness device  100  may be controlled via different logic using controls on one or more of the hand grips  402 ,  404  and  406 . For example, a user in some embodiments controls the operation of the fitness device  100  (e.g., at least rotation of the table  106  about the table rotation axis  105 ) using a single hand via controls on one of the hand grips  402 ,  404  and  406 . The controls on the hand grips  402 ,  404  and  406  in some embodiments are user-programmable, such that a user is enabled to define a desired control scheme for initiating and stopping rotation via a desired sequence of application of controls on the hand grips  402 ,  404  and  406 . In some embodiments, the controls are “clip-on” or removably affixable to desired ones of the hand grips  402 ,  404  and  406  (or to one or more other portions of the fitness device  100 ) by the user for easy access in a particular position. The “clip-on” controls may be held by a trainer or instructor to assist in the exercise. 
     Controls on the hand grips  402 ,  404  and  406  are not limited to use solely for controlling the rotation of the table  106 . Controls on the hand grips  402 ,  404  and  406  (and controls elsewhere on the fitness device  100 ) are used to set any combination of the following parameters via a user interface: settable table movements such as translate up, translate down, rotate forward, rotate back, etc.; settable foot restraint resistive exercise force and limits; settable rate of stretch; settable lumbar enhancement level; settable number of repetitions; settable number of sets; automatic return; feedback settings; etc. Automatic return control allows the user to return to the starting position (e.g., as shown in  FIG. 1A ) once the selected exercise cycle is completed or intentionally canceled by the user. Lumbar enhancement level control allows the user to set a relationship between the table tilt, foot restraint force, and lumbar tilt (e.g., where the lumbar cushion  304  tilts around the lumbar cushion rotation axis  303  to increase the effectiveness of exercise). Lumbar enhancement may also be controlled by the user activating additional controls located on or near one or more of the hand grips  402 ,  404  and  406 . 
     In some embodiments, the fitness device  100  is programmed with a set of default parameters. The default parameters allow the user: to select limits prior to starting exercise; to have complete control over table movement; and to control exercise using on-board controls. The fitness device  100  is configured to be programmed with one or more presets, such as beginner, intermediate and expert. User-defined profiles for different preset stretching and exercise routines in some embodiments are loaded into the fitness device  100  through a mobile device of the user that is connected to the fitness device  100 . In some embodiments, additional incremental control is provided for increased effectiveness. 
     Feedback settings may take on various forms. In some embodiments, the fitness device  100  is configured to allow the user to set an audible tone to indicate when the user has reached a programmed level of stretch, time at a particular stretch level, etc. The fitness device  100  may also be configured to allow the user to set an audible tone with a beep rate of varying frequency to indicate when the user has reached a programmed level of stretch, time at a particular stretch level, etc. The fitness device  100  is not limited to providing auditory feedback. In other embodiments feedback is provided in the form of haptic feedback or vibration of controls on the hand grips  402 ,  404  and  406 , or on cushions of the cushion assembly  110 , etc. In some embodiments, the fitness device  110  also or alternatively includes a display screen or indicator lights for providing this and other feedback. 
     The fitness device  100  includes a user interface unit, also referred to as a UI, providing the user with the ability to control the parameters of operation of the fitness device  100 . In some embodiments, it is expected that settings are set on the UI prior to exercise. In other embodiments, however, the user adjusts settings later during the exercise cycle using the UI. The UI may be located at various positions on the fitness device  100 , including but not limited to: on the base assembly  102  in an orientation easily accessible to the user prior to getting onto the fitness device  100 ; at eye level on the back or side of the table  106  in an orientation easily accessible to the user prior to getting onto the fitness device  100 ; in an auxiliary unit co-located with the fitness device  100  or remotely located relative to the fitness device  100 ; in a re-locatable unit such that the user can see a display to track system status, such as exercise session progress, and to modify settings while on the fitness device  100  in the midst of exercise; and in an application provided on a mobile device such as a smartphone, tablet, smartwatch, etc. of the user. 
     Controls for the UI in some embodiments include one or more of: a graphical user interface (GUI) on a touchscreen; a plurality of buttons and/or switches; a plurality of buttons and/or switches with a display for indicating current selections; and on-board controls accessed at or near one or more of the hand grips  402 ,  404  and  406 , etc. In some embodiments, the on-board controls at or near one or more of the hand grips  402 ,  404  and  406  include one or more of: control buttons configured for activation by thumbs of the user; trigger-like controls activated by one or more of the fingers of the user; a control activated by squeezing the hand of the user; controls activated by twisting the hand grip (e.g., similar to a motorcycle throttle); a joystick; a sensor that detects whether a hand is holding the hand grip; and one or more secondary buttons for providing independent control of various portions of the fitness device  100 , such as a position of one or more portions of the cushion assembly  110  (e.g., a position of the combined thoracic and head cushion  302 , a position of the lumbar cushion  304 , etc.). 
     In some embodiments, the UI is configured to store local profiles of different users, so that a user is enabled to save and load customized stretch and other exercise routines while using the fitness device  100 . The local profiles may also include information allowing the fitness device  100  to automatically adjust for the height and size of different users. 
     For control of movements, some embodiments utilize the following control scheme. 
     The control scheme is described for the supine position of the user, but it should be appreciated that the same movement and controls may be used for the prone and lateral positions. The fitness device  100  is configured in some embodiments: to rotate the table  106  backwards (and apply optional foot restraint tension) when controls are activated by both the left and right hand of the user; to hold position of the table  106  (and optional foot restraint tension) constant when either the left hand or the right hand releases the control while the other hand continues to active the control; and to rotate the table  106  forwards (and release optional foot restraint tension) when the user releases the controls from both hands. In another embodiment, one hand is used to control up and down movement of the table  106  while the other hand controls the forward and backward rotation of the table  106 . In another embodiment, one rocker switch controls up and down movement of the table  106  while another rocker switch controls forward and backward rotation of the table  106  (where the rocker switches are located for access by a single hand or one by each hand of the user). In other embodiments, any of the above control schemes are utilized with separate lumbar enhancement control located on either or both of the hand grips  402 ,  404  and  406  being held by the user. In still other embodiments, any of the above control schemes are adjusted such that all controls are accessible and activatable using only one hand. 
       FIG. 4C  illustrates rotation of the restraint and overhead bar  108  about the restraint and overhead bar axis  107 . The restraint and overhead bar  108  is configured to be raised as shown in  FIG. 4C  to facilitate user entry onto the fitness device  100 , and lowered after the user is suitably positioned on the fitness device  100  to safely secure the user. Gripping the restraint and overhead bar  108  (e.g., overhead bar hand grips  406 ) provides additional isometric exercise benefits. In other embodiments, the restraint and overhead bar  108  or portions thereof swing out to either side to facilitate user entry onto the fitness device  100 . The underarm supports  112  in some embodiments are configured to translate along the x-axis to provide better fit for the user. The restraint and overhead bar  108  is positioned to provide a mechanism for securing the user onto the fitness device  100 .  FIG. 4D  shows a user  401  positioned in the fitness device  100  after rotation of the restraint and overhead bar  108  about the restraint and overhead bar axis  107  as described above. 
       FIGS. 4E and 4F  illustrate tilt or rotation of the table  106  and the lumbar cushion  304 . The table  106  tilts or rotates about the table rotation axis  105 , while the lumbar cushion  304  rotates outward  405  and inward  403  about the lumbar cushion rotation axis  303 . The lumbar cushion  304  is rotatable inward and outward in relation to the thoracic and head cushion  302 , helping to create a pelvic tilt. The tilt of the lumbar cushion  304  in some embodiments is programmed to be proportional to the tilt of the table  106 . The tilt of the lumbar cushion  304  (provided by rotation about the lumbar cushion rotation axis  303 ) relative to the tilt of the thoracic and head cushion  302  (provided by rotation of the table  106  about table rotation axis  105 ) can be selected as desired to provide more or less aggressive exercise. In other embodiments, the lumbar cushion  304  tilt can be independent of the thoracic and head cushion  302  tilt. The lumbar cushion  304  tilt control may also be set based on any combination of the user&#39;s body type, height and weight. The lumbar cushion  304 , in some embodiments, is further configured to translate along the z-axis. The lumbar cushion  304  can also have a combined rotation and translation movement as described above. In some embodiments, the lumbar cushion  304  has an internal Tillable bladder or cavity to provide enhanced stretch (e.g., by filling or emptying the bladder or cavity). The outer surfaces of the cushions of the cushion assembly  110  may be convex, flat or otherwise contoured as desired for user comfort and positioning. 
       FIGS. 5A and 5B  illustrate aspects of the base assembly  102 . As shown in  FIG. 5A , the base assembly  102  includes a platform  502 , a foot restraint  504 , a user interface  506 , and an interface  508  to the elevation assembly  104 . The platform  502  provides a stable base for the fitness device  100 , and includes rubber feet on the underside at the four corners. The foot restraint  504  is mounted in the platform  502  as shown. The foot restraint  504  in some embodiments is mounted in the platform  502  using a ball joint or a universal joint providing a pivot point at the base of the feet of the user. The platform  502  includes various sensors at different locations for measuring the forces. Such force measurements from sensors in the platform  502  or elsewhere on the fitness device  100  (or in other fitness devices described herein) may be used for controlling aspects of lift, rotation and other motion and movement of some or all portions or components of the fitness device  100 . It should be appreciated, however, that the use of sensors for measuring the forces is not a requirement. In other embodiments, lift, rotation, and other motion and movement of some or all portions of a fitness device may be controlled by limit switches, stroke length of actuators, etc., instead of or in place of software controls or coupled motions based on measurements from sensors. 
     The pivot point at the base of the feet of the user in some embodiments is counterbalanced with a pivot point at a pelvic support of cushion assembly  110  as described above, where the pivot point of the pelvic support is underneath the pelvic cushion, or below and separate from the pelvic cushion altogether (e.g., on the table  106  or another portion of the fitness device  100 ). The user interface or UI  506  provides controls for setting exercise parameters and other parameters of the fitness device  100  (e.g., by the user  501  prior to the user  501  being secured onto the fitness device  100 ). 
     In the embodiment of  FIGS. 5A and 5B , the foot restraint  504  includes sets of cushioned parallel bars or bolsters with the user  501  inserting their feet and ankles between the sets of cushioned parallel bars or bolsters. The foot restraint  504  as shown is mounted to the platform  502  via a circular section that is configured to rotate. Rotation of the foot restraint  504  enables comfortable use in different positions (e.g., prone, supine, lateral) as well as enhanced stretch. The foot restraint  504  includes or is coupled to a force monitor that measures the resistance provided by the foot restraint  504  as the table  106  is elevated and rotated. The force monitor is programmed with logic for adjusting the elevation of the table  106  as the table  106  rotates so as to provide a constant force or resistance on the lower extremities of the user  501 . The force monitor in some embodiments is also or alternatively programmed to adjust the force or resistance on the lower extremities of the user  501  as the table  106  elevates and rotates for comfort of the user  501 . In some embodiments, it is preferred that the foot restraint  504  provides limited up/down travel so that the feet of the user  501  are not lifted off the ground (or do so minimally). Some embodiments therefore provide the effects of an inversion table without having to lift the user  501  off the ground or tilting the user  501  upside down. 
     The feet of the user  501  rest between the bolsters of the foot restraint  504  that comfortably grip the feet. The bolsters of the foot restraint  504  may be cylindrical as shown, or may be another shape that is both comfortable and secure (e.g., square or rectangular, elliptical, etc.). In other embodiments described in further detail below, a foot restraint may use straps, clips, boots, etc. instead of bolsters for securing the feet of the user. The foot restraint  504  keeps the soles of the feet in contact with or close to the platform  502  of the base assembly  102 , with limited travel in the y-axis direction. In some embodiments, however, it is desired to have at least some travel in the y-axis direction for comfort of the user  501 . The foot restraint  504  allows free movement along the z-axis, as well as rotation about the x-axis (e.g., “into” the page). As shown in  FIG. 5A , the foot restraint  504  is on a circular platform that couples to the platform  502  of the base assembly  102 , with the circular platform rotating about the x-axis (e.g., via a ball joint). The ball joint enabling x-axis rotation can also travel within a slot to enable translation along the z-axis. 
     In some embodiments, the foot restraint  504  is removably coupled to the base assembly  102  of the fitness device  100 . Thus, the foot restraint  504  can be replaced with a wobble board for enabling the user to perform various balance exercises. Thus, the fitness device  100  provides a modular fitness system enabling various types of stretching and other exercise. 
     In some embodiments, controls of the fitness device  100  are configured to position the elevation and rotation of the table  106  in a manner that maintains a predetermined force (or force range) on the feet of the user  501  without elevating the feet of the user  501 . The predetermined force may be constant, or determined according to some defined function (e.g., where the predetermined force or force range is proportional to an amount of rotation, lift, tilt or other stretch experienced by the user) as described in further detail below. As the table  106  of the fitness device  100  rotates backward, the tendency will be to lift the feet of the user  501 . The controls of the fitness device  100  will compensate for this tendency, in some embodiments, by lowering the height of the table  106  and/or varying the resistance or force provided by the foot restraint  504 , thereby applying a stretch to the body without lifting the feet into the air. The foot restraint  504  includes a force sensing system that feeds into the controls of the fitness device  100  to appropriately position the elevation and tilt of the table  106  to achieve a desired stretch. It should be appreciated that the force sensing system need not be physically housed in the foot restraint  504 . In some embodiments, the force sensing system is coupled to or compromised within one or more of the base assembly  102 , the elevation assembly  104 , the table  106 , the restraint and overhead bar  108 , etc. 
       FIGS. 6A-6D  illustrate various alternative implementations of a foot restraint for use with the base assembly  102  of the fitness device  100  or other fitness devices described herein.  FIG. 6A  shows a foot restraint  604  that, similar to the foot restraint  504 , holds the feet of the user  601  between bolsters. The foot restraint  604 , however, includes a strap or bungee that couples the bolsters to a base allowing some elevation and rotation of the feet of the user  601 .  FIG. 6B  shows a foot restraint  614  that includes cuffs for affixing to the ankle of the user  601 , with the cuffs being attached to a base via a strap or bungee that allows some elevation and rotation of the feet of the user  601 .  FIG. 6C  shows a foot restraint  624  that, similar to foot restraint  614 , includes cuffs for affixing to the ankle of the user  601 . The cuffs of the foot restraint  624 , however, are coupled to the base via straps on the sides thereof instead of on the front as in the foot restraint  614 .  FIG. 6D  shows a foot restraint  634  that includes a band with an opening that the user  601  slips their feet into, with ends of the band being affixed to the base. The foot restraint embodiments shown in  FIGS. 6A-6D  allow the feet of the user  601  to raise off the base, with the force applied by an extending element (e.g., straps coupling the bolsters in  FIG. 6A  and the cuffs in  FIGS. 6B and 6C , the band in  FIG. 6D ). The extending element is configured to maintain a predetermined force, where the predetermined force may be constant or in accordance with a defined function as described in further detail below. As the feet of the user  601  are lifted due to rotation and/or elevation of the table  106 , the force is maintained while allowing generally upward movement of the foot restraints  604 ,  614 ,  624  and  634 . 
       FIG. 7  illustrates a force application system  702  coupled to a foot restraint  704 , where the foot restraint  704  represents any one of foot restraints  504 ,  604 ,  614 ,  624  and  634  described above, as well as other foot restraints described below. The foot restraint  704  is coupled to the force application system  702  via a cable or other mechanical mechanisms. An extending element of the foot restraint  704  is constrained by the force application system  702 , which may take various forms. The force application system  702  is visualized in  FIG. 7  as a pulley system with stacked weights, though this is not a requirement. The force application system  702  in some embodiments provides a direct connection to a spool on a motor that applies a settable constant or proportional force, provides a connection to a motor that applies a settable constant or proportional force through a pulley system, provides a connection to an elastic member (or a group of elastic members) that applies a selectable force that is constant or proportional to the amount of cable that is let out as a result of movement of the table  106 , provides a mechanical or electrical clutch that can be set as a constant resistant force, or as a force that is a selected function related to the amount of the extension of the foot restraint, etc. Various other mechanisms are possible, including magnetic resistance. In some modes of operation, the fitness device  100  provides resistance to a force applied by the user (e.g., for isokinetic exercise through a desired range of motion of the user). 
       FIGS. 8A-8C  illustrate operation of the foot restraint  614  on a fitness device  800  by user  801 . The fitness device  800 , similar to fitness device  100 , includes a base assembly  802 , elevation assembly  804 , table  806  and cushion assembly  810 . Whereas the fitness device  100  includes a single-piece restraint and overhead bar  108 , the fitness device  800  includes a two-piece restraint and overhead bar including overhead grip bar  808 - 1  and underarm support bar  808 - 2 . It should be appreciated that the fitness device  800  may include just one of the overhead grip bar  808 - 1  and the underarm support bar  808 - 2 . For example, in some embodiments the overhead grip bar  808 - 1  is not used, or is removably attached to the fitness device  800  as an optional component. The underarm support bar  808 - 2  may also be optional, and may be removably attached to the fitness device  800 . As illustrated in  FIGS. 8A and 8B , the placement of hand grips on the two-piece restraint and overhead bar is different than that of the one-piece restraint and overhead bar  108  of the fitness device  100 . The fitness device  800  also includes a force application system  702  that is coupled to the foot restraint  614  to provide the selectable force or resistance of the foot restraint  614  as the table  806  lifts and/or rotates. The foot restraint  614  of the fitness device  800 , as illustrated in  FIG. 8B , provides front and back symmetric foot restraint along a slot or track of the base assembly  802 . 
     As shown in  FIG. 8C , the elevation assembly  804  of the fitness device  800  has a lower housing that encloses lift and tilt actuators  811 - 1  and  811 - 2 , respectively, of the fitness device  800 . More particularly, the elevation assembly  804  includes the lift actuator  811 - 1 , which may be an electric motor-powered linear actuator, proximate a “front” of the fitness device  800  (e.g., proximate the foot restraint  614  side) which is anchored to the base assembly  802  and a bottom rotation axis  813  of the table  806  below underarm supports  808 - 2 . The lift actuator  811 - 1  provides lift for raising the elevation assembly  804 . The elevation assembly  804  also includes rotation actuator  811 - 2 , which may also be an electric motor-powered linear actuator, proximate a “rear” of the fitness device  800  near the force application system  702  side which is anchored within the elevation assembly  804  and couples to an upper rear portion of the table  806  about a rotation axis  815  coupling the bar protruding from the top of the rear of elevation assembly  804  to two bars that are coupled to upper rear portion of the table  806 . The rotation actuator  811 - 2  provides rotation of the table  806 . The lift actuator  811 - 1  and the tilt actuator  811 - 2  may move together so as to provide a desired lift and tilt movement of the table  806 . 
       FIGS. 9A and 9B  illustrate operation of the foot restraint  624  on a fitness device  900  by user  901 . The fitness device  900 , similar to fitness device  100 , includes a base assembly  902 , elevation assembly  904 , table  906  and cushion assembly  910 . Similar to the fitness device  800 , the fitness device  900  includes a two-piece restraint and overhead bar including overhead grip bar  908 - 1  and underarm support bar  908 - 2 . It should be appreciated that the fitness device  900  may include just one of the overhead grip bar  908 - 1  and the underarm support bar  908 - 2 . For example, in some embodiments the overhead grip bar  908 - 1  is not used, or is removably attached to the fitness device  900  as an optional component. The underarm support bar  908 - 2  may also be optional, and may be removably attached to the fitness device  900 . As illustrated in  FIGS. 9A and 9B , the placement of hand grips and underarm supports on the two-piece restraint and overhead bar is different than that of the two-piece restraint and overhead bar of the fitness device  800 . The fitness device  900  also includes a force application system  702  that is coupled to the foot restraint  624  to provide the selectable force or resistance of the foot restraint  624  as the table  906  lifts and/or rotates. The foot restraint  624 , as shown in  FIGS. 9A and 9B , includes an ankle cuff with a strap coupling the ankle cuff to a mushroom-shaped post on the base assembly  902 . The force application system  702  is visualized in this embodiment as a pulley weight tensioning selection mechanism, though this is not a requirement. 
     In the fitness device  900 , the elevation assembly  904  and table  906  have a slotted link assembly to eliminate the rotation rod of fitness devices  100  and  800 . The rod in fitness device  900  is constrained to stay vertical. In order to remain vertical, the anchor point will translate relative to the anchor point as the table  906  rotates. Advantageously, such a configuration enables the elevation assembly  904  to be slimmer than the elevation assembly  804 , because the actuator angles out as the table  806  rotates backwards in fitness device  800 . 
       FIGS. 10A-10E  illustrate operation of the foot restraint  634  on a fitness device  1000 . The fitness device  1000 , similar to fitness device  100 , includes a base assembly  1002 , elevation assembly  1004 , table  1006  and cushion assembly  1010 . Similar to the fitness device  800 , the fitness device  1000  includes a two-piece restraint and overhead bar including overhead grip bar  1008 - 1  and underarm support bar  1008 - 2 . It should be appreciated that the fitness device  1000  may include just one of the overhead grip bar  1008 - 1  and the underarm support bar  1008 - 2 . For example, in some embodiments the overhead grip bar  1008 - 1  is not used, or is removably attached to the fitness device  1000  as an optional component. The underarm support bar  1008 - 2  may also be optional, and may be removably attached to the fitness device  1000 . As illustrated in  FIGS. 10A and 10B , the placement of hand grips and underarm supports on the two-piece restraint and overhead bar is different than that of the two-piece restraint and overhead bars of the fitness devices  800  and  900 . The fitness device  1000  also includes a force application system  702  that is coupled to the foot restraint  634  to provide the selectable force or resistance of the foot restraint  634  as the table  1006  lifts and/or rotates. In the fitness device  1000 , the cushion assembly  1010  includes a Cartesian pad solution where the pads of the cushion assembly  1010  are configured to telescope on two axes (e.g., on the craniocaudal (y) axis and the left-right lateral (x) axis) and slide on tracks. The foot restraint  634 , as illustrated in  FIGS. 10A and 10B , is provided on a platform that slides along the base assembly  1002  with a bungie-style strap that secures the feet of a user to the sliding foot platform. 
     The elevation assembly  1004  of the fitness device  1000  also separates higher, and the elevation assembly  1004  and table  1006  provide a different rotational linkage solution. The linkage solution of the elevation assembly  1004  may use any of the configurations shown in  FIGS. 10C-10E . In the  FIG. 10C  configuration, there is a single linear actuator  1013 , positioned vertically within the elevation assembly  1004  and proximate a middle of the elevation assembly  1004 , and two guided columns  1015 - 1  and  1015 - 2  also positioned vertically within the elevation assembly  1004  on either side of the single linear actuator  1013 . In the  FIG. 10D  configuration, two actuators  1023 - 1  and  1023 - 2  are utilized. The actuators  1023 - 1  and  1023 - 2  are disposed on lateral sides and positioned vertically within the elevation assembly  1004 . The two actuators  1023 - 1  and  1023 - 2  in the second configuration are guided to stay vertical. In the  FIG. 10E  configuration, two actuators  1033 - 1  and  1033 - 2  are also utilized, disposed on lateral sides and positioned vertically within the elevation assembly  1004  similar to the  FIG. 10D  configuration. In the  FIG. 10E  configuration, however, a guided center column  1035  between the two actuators  1033 - 1  and  1033 - 2  is utilized. 
       FIGS. 11A and 11B  illustrate operation of a foot restraint  1144  on a fitness device  1100 . The fitness device  1100 , similar to fitness device  100 , includes a base assembly  1102 , elevation assembly  1104 , table  1106  and cushion assembly  1110 . The fitness device  1100  includes an underarm support bar  1108  but not an overhead support or grip bar. The placement of hand grips and underarm supports on the underarm support bar  1108  also differs from that of the fitness devices  100 ,  800 ,  900  and  1000  as illustrated in  FIGS. 11A and 11B . The underarm support bar  1108  provides dual-use underarm support pads with flip-out elbow rests for the user in the prone position. The hoop-style grips of the underarm support bar  1108  are configured to slide upward and rotate (e.g., along arc  1109 ) for supine and prone use. The foot restraint  1144  has an ankle and heel cuff that is coupled to the base assembly  1102  via a strap as illustrated. The foot restraint  1144  is also configured to travel or provide translation motion along the slot in the base assembly  1102  as illustrated in  FIG. 11B . The force application system  702  is coupled to the foot restraint  1144 . 
     The elevation assembly  1104  and table  1106  provide a multi-link variable geometry in a main trunk that mimics the human spine. The elevation assembly  1104  also separates higher than that of the fitness devices  100 ,  800 ,  900  and  1000 . The elevation assembly  1104  may achieve vertical lift in a manner similar to that described above with respect to elevation assembly  1004 . For rotation, the elevation assembly  1104  includes multipole rotary actuators to provide a curved, contoured bending back as illustrated. In some embodiments, multiple linear actuators with respective hinge points may be utilized in place of one or more of (or all of) the rotary actuators. 
     It should be appreciated that features such as the locations of hand grips, the force application system  702 , the type of restraint and/or overhead grip bars, underarm supports, cushion assemblies, table and elevation assembly linkages, foot restraints, etc. that are described with respect to one of the fitness devices  100 ,  800 ,  900 ,  1000  and  1100  may be combined in various ways. For example, the restraint and overhead bar  108  of the fitness device  100  may be replaced with any of the bars  808 ,  908 ,  1008  and  1108 . Similarly, the type of foot restraint used in fitness device  100  may vary (e.g., the foot restraint  504  may be replaced with any of the foot restraints  604 ,  614 ,  624 ,  634  and  1144 ). This is also true for fitness devices  800 ,  900 ,  1000  and  1100 . More generally, it should be appreciated that a particular feature described in conjunction with one of the fitness devices  100 ,  800 ,  900 ,  1000  and  1100  (as well as other fitness devices described below) may be used in combination with features of any other ones of the fitness devices  100 ,  800 ,  900 ,  1000  and  1100  (as well as other fitness devices described below) unless specifically noted otherwise. 
       FIGS. 12A-12F  depict operation of a fitness device  1200 , which similar to fitness device  100  includes a base assembly  1202 , elevation assembly  1204 , table  1206  and cushion assembly  1210 . The base assembly  1202  includes the foot restraint  504 . The fitness device  1200 , unlike the fitness device  100 , does not include a restraint and overhead bar  108 . Instead, the fitness device  1200  includes hand grips  1208  as illustrated.  FIG. 12A  depicts the fitness device  1200  in the starting or upright position, while  FIG. 12B  depicts the fitness device  1200  in the tilted or rotated position.  FIG. 12C  highlights aspects of the base assembly  1202  and elevation assembly  1204 . As shown in the close-up view  1203 , there is a split line between the base assembly  1202  and elevation assembly  1204 . As shown in the close-up view  1205 , the base assembly  1202  includes the foot restraint  504  that is mounted on a circular rotatable foot pivot  1250  coupled to the base assembly  1202 .  FIGS. 12D, 12E and 12F  illustrate a user  1201  operating the fitness device  1200  in the prone position. More particularly,  FIG. 12D  illustrate the user  1201  upright, while  FIGS. 12E and 12F  illustrate the user  1201  in various stretch positions via rotation of the table  1206 . 
       FIGS. 13A-13D  illustrate operation of a fitness device  1300 . The fitness device  1300  includes a base assembly  1302 , an elevation assembly  1304 , a table  1306 , a two-piece restraint and overhead bar assembly including overhead bar  1308 - 1  and underarm bars  1308 - 2 , and a cushion assembly  1310 . The height of the table  1306  is adjustable to accommodate user height and proportions via the elevation assembly  1304 . The table  1306  is configured to rotate backwards via an actuator (e.g., comprised within the elevation assembly  1304 , the table  1306  or combinations thereof) to lift the user  1301  and provide a stretch due to gravity acting on the body of the user  1301 . Although not shown in  FIGS. 13A-13D , various foot restraints may be coupled to the base assembly  1302  for use in increasing the effective stretch of the user. Examples of foot restraints configured for coupling to the base assembly  1302  include the foot restraints  504 ,  604 ,  614 ,  624 ,  634  and  1144  described above, as well as the various foot restraints described in further detail below. 
     The overhead bar  1308 - 1  and underarm support bars  1308 - 2  are adjustable for accommodating different-sized users. The overhead bar  1308 - 1  and/or the underarm support bars  1308 - 2  are also configured to swing outwards or rotate to facilitate entry of a user  1301  onto the fitness device  1300 , or for securing the user  1301  onto the fitness device  1300 . 
     The cushion assembly  1310  includes a bottom lumbar cushion and a set of head and thoracic cushions, where the different cushions adjust or slide relative to one another to accommodate user height and proportions in addition to or instead of using the elevation assembly  1304 . The lumbar cushion of the cushion assembly  1310  also rotates or translates to enhance stretch. 
       FIG. 13B  illustrates the user  1301  on the fitness device  1300  in the supine position, while  FIG. 13C  illustrates the user  1301  on the fitness device  1300  in the prone position, both with partial rotation of the table  1306 .  FIG. 13D  shows another perspective view of the fitness device  1300 , with the underarm support bars  1308 - 2  in different positions and with the elevation assembly  1304  in a lower position than that shown in  FIG. 13A . 
     The fitness device  1300  provides multifunctional exercise and conditioning, as controlled by the user  1301 . The fitness device  1300  includes the elevation assembly  1304  and table  1306  that are rotationally connected to one another via a pivot point attachment. The lower portion of the fitness device  1300  includes the base assembly  1302  and the elevation assembly  1304 . In this embodiment, the base assembly  1302  provides a single column rectangular support base sub-frame with four floor feet extensions to prevent tilting. It should be appreciated, however, that the base assembly of a fitness device may include a circular column support rather than a rectangular column support, a multiple column support, etc. The base assembly  1302  does not rotate with the user  1301 . The elevation assembly  1304  is coupled to the column support of the base assembly  1302 , and is configured to support and provide height selective adjustment as well as pivot and activation mechanisms for rotating the top portion of the fitness device  1300  (e.g., the table  1306 , overhead bar  1308 - 1 , underarm support bars  1308 - 2  and cushion assembly  1310 ) in a range (e.g., from 0 to 90 degrees, from 0 to 60 degrees, etc.). The table  1306  of the fitness device  1300  provides a metal support sub-frame, and the cushion assembly  1310  includes two individual user support cushions (e.g., a thoracic and head cushion, as well as a lumbar cushion). The top portion of the fitness device  1300  further includes underarm support bars  1308 - 2  with hand grips in both the front and rear (e.g., for use by the user  1301  in the supine and prone positions, respectively). The overhead bar  1308 - 1  also provides various hand grips (e.g., for use by the user  1301  in the lateral position, and optionally for use in the supine and/or prone positions). The table  1306 , as noted above, is rotationally attached to the elevation assembly  1304  allowing rotation of the user  1301  from the vertical to the horizontal. 
     The table  1306  of the fitness device  1300  has, at its approximate upper third portion, a bend (e.g., of approximately 30 deg) in relation to the lower two thirds portions to provide backwards and forwards spine bending of the user  1301 . The underarm support bars  1308 - 2  provide underarm tubular cushioned supports, which may be any desired shape for the comfort of the user. As noted above, the underarm support bars  1308 - 2  further include hand grips formed integrally therewith located in both the front and rear of the fitness device  1300 . It should be appreciated that in some embodiments one or more hand grips are attached to or formed integrally with the table  1306  (e.g., such as on a back portion thereof for use by the user  1301  in the prone position). The overhead bar  1308 - 1  also includes various hand grips as illustrated. The hand grips of the fitness device  1300  are configured with controls (e.g., buttons, switches, etc.) to effect rotation of the table  1306  and optionally to provide lumbar extension and tilting. Such controls are configured for use by the user  1301  to adjust the tilt of the table  1306 , to adjust force applied via optional foot restraints, to provide emergency stop switches for disabling motion of the fitness device  1300 , etc. The underarm support bars  1308 - 2  are configured to rotate in and out on separate pivots for facilitating entry and exit of the user  1301  from the fitness device  1300 . The hand grips on the underarm support bars  1308 - 2  in some embodiments are adjustable in and out to accommodate arm length size. The support pads of the underarm support bars  1308 - 2  in some embodiments are adjustable to provide additional securing of the user  1301  to the fitness device  1300 . 
     As noted above, the bottom portion of the fitness device  1300  includes the base assembly  1302  providing a single column rectangular support sub-frame. The support sub-frame of the base assembly  1302  in some embodiments includes two self-contained air cylinders for providing the ability to adjust the top portion of the fitness device  1300  (e.g., via elevation assembly  1304 ) up or down without power or compressor functions. In other embodiments, however, the base assembly  1302  and elevation assembly  1304  are powered. The base assembly  1302  and elevation assembly  1304  in some embodiments comprise two pneumatic cylinders operated by hand-lever to provide an electric screw drive mechanism for permitting powered raising and lowering of the top portion of the fitness device  1300 . This facilitates both height accommodation for the user  1301  and also allows for powered stretch functionality to move in the y-axis vertical direction as distinct and separate from power stretch (e.g., use of elastic bungees) from rotation of the table  1306 . It should be appreciated that this functionality may also be used for isometric exercise by the user  1301 , such as by requiring the user to hold or maintain a position or tilt of the table  1306  while a predetermined resistance (e.g., constant or variable) is provided through the powered mechanism of the base assembly  1302  and elevation assembly  1304 . 
     The cushion assembly  1310  includes a fixed upper torso head and thoracic support cushion, which may in some cases be configured for rotation forward. The cushion assembly  1310  also includes the lumbar back support (e.g., which may be convex shaped) providing firm ergonomic support. The lumbar back support is also configured to extend outwardly (e.g., tilting) through powered mechanisms causing a change in the radius support favoring spinal extension and flexion of the lower back and pelvis of the user  1301 , depending on the positioning of the user  1301  (e.g., prone or supine). In some embodiments, the lumbar back support is manually adjustable up and down to accommodate different user height by release of a locking slide mechanism. 
     The overhead bar  1308 - 1  extends outward to accommodate various positions of the user  1301 , including prone, supine and lateral positioning. The overhead bar  1308 - 1  is manually adjustable up and down to accommodate different user height. The overhead bar  1308 - 1  is configured with controls for effecting rotation of the table  1306  and/or the lumbar back support of the cushion assembly  1310 . The overhead bar  1308 - 1  also includes one or more emergency stop buttons and other types of user interface controls described herein. 
     As noted above, the fitness device  1300  is optionally coupled to one or more foot restraints, such as by coupling a foot restraint to the base assembly  1302  of the fitness device  1300 . The foot restraints in some embodiments provide auxiliary mechanisms for strapping the ankles and/or feet of the user  1301  to provide increased traction effects that supplement gravity. The user  1301  utilizes their arms to self-pull against additional resistance provided by the foot restraint. The user  1301  also utilizes the pull created by active rotation and lift of the table  1306  to provide such increased traction effects. The fitness device  1300  during rotation in a backwards direction is configured to provide full and direct traction effects on muscles of the entire lower extremity of the user  1301 , including the hamstrings, gluteal muscles, psoas muscles, etc., as well as the entire lower back musculature and the upper torso and arms of the user  1301 . 
     Foot restraints in some embodiments utilize bungee strapping that originates at its proximal location from the sides or underneath an attachment point to one or multiple base sub-plates configured for attachment to the base assembly  1302  of the fitness device  1300 . In some embodiments, the user  1301  places their feet in boots or cuffs with straps attached to one or more base sub-plates. In some embodiments, the user  1301  is secured to a foot restraint via straps or cuffs around the ankles of the user  1301  where the proximal end of a bungee cord attaches the ankle straps or cuffs to a sub-pedestal base, eliminating the need for base sub-plates. 
     Foot restraints in some embodiments utilize a bungee mechanism for attachment to the base assembly  1302  (e.g., via one or more base sub-plates, to a sub-pedestal base, or other type of base assembly mounting portion, etc.), with the bungee mechanism providing elastic recoil stretch with length and flexibility capabilities allowing full rotation of the table  1306  (e.g., to 60 degrees, to 90 degrees, etc.) as well as lift of the table  1306  relative to the base assembly  1302  (e.g., lift to 6 in, lift to 9 in, etc.). The bungee cords or straps of a foot restraint are interchangeable and configured for easy removal to enable the user  1301  to select amongst a variety of cords or straps with different (e.g., lighter and heavier) elastic strength to provide a wide range of customized resistance to accommodate users with different physical conditioning. 
     In some embodiments, the foot restraint includes separate right and left foot resistance cords or straps for attachment to one or more base sub-plates or sub-pedestal bases, allowing the user  1301  to select different resistance for the left foot and the right foot. The foot restraint, as noted above, may utilize ankle strapping for fastening to ankles of the user  1301  (e.g., a proximal strapping position) in various different configurations including but not limited to: one base sub-plate with fixed boots; two individual base sub-plates with separate straps; just boots or ankle straps attached directly to proximal bungees; one plate with one bungee; etc. Each end of a proximal bungee of the foot restraint is attached to the base assembly  1302  of the fitness device  1300  in various configurations, including configurations enabling sliding and/or rotation of the foot restraint. Sliding and rotation mechanisms of distal attachment of bungees (e.g., closest to the user  1301  via sub-plate and restraint straps) allow natural movement of the user  1301  during 0 to 60 degrees of full rotation of the table  1306  to accommodate changes in the position of the user  1301  (e.g., during lateral positioning of the user  1301  relative to the fitness device  1300 ). 
     The pedestal base of the foot restraint accepts a distal attachment point (e.g., in a center thereof, on left and right sides thereof, etc.), and provides forward and back translation movement so that as the table  1306  rotates in a backward direction towards 90 degrees, the bungees, cords or straps move forward and backward as necessary for comfort of the user  1301 . The pedestal base attachment points in some embodiments are on a secured roller system or track that permits gliding movement. The pedestal base of the foot restraint may have various different design configurations providing attachment to sub-plates, directly to ankle straps, cords or bungees, etc. In some embodiments, the sub-base distal strap, cord or bungee attachment point of the foot restraint allows free rotation to accommodate a user  1301  (e.g., wearing boots, cuffs, straps, etc. attached to a sub-plate or directly to the pedestal base) enabling some side-to-side or lateral positioning of the feet of the user  1301  in addition to allowing face forward or prone positioning and face outward or supine positioning. The foot restraint includes safety mechanisms for safely applying additional traction to the user  1301 , such as through a belt tensioning system, through dial control against a resistance sliding mechanism, etc. 
       FIGS. 14A-14C  illustrate a foot restraint  1402  coupled to the fitness device  1300 . As shown in  FIG. 14A , the foot restraint  1402  includes a pedestal base platform, individual foot holsters  1404 , and linkage  1406  to the vertical travel of the elevation portion  1304  of the fitness device  1300  allowing the foot restraint  1402  to move up and down with the elevation portion  1304  as desired.  FIG. 14B  shows a profile top view of the foot restraint  1402 , and  FIG. 14C  shows a perspective view of the foot restraint  1402  illustrating adjustment of the individual foot holsters  1404  (e.g., via hook and loop straps). 
       FIGS. 15A-15C  illustrate a foot restraint  1502  coupled to the cushion assembly  1310  of the fitness device  1300 . The foot restraint  1502  in this embodiment includes sets of cushioned bolsters for the user to slip their feet between and rest on the pedestal base, embodied as a laser cut steel plate  1510  and a lower stabilizing feature  1512  assembled as illustrated in  FIG. 15C . The plate  1510  and lower stabilizing feature  1512  are rotatable to accommodate a user in prone, supine and lateral positions. The foot restraint  1502 , as illustrated in  FIGS. 15A and 15C , extends from the cushion assembly to accommodate different user height. The foot restraint  1502  may also or alternatively be configured for at least one of linear and rotational (e.g., angular) displacement of members  1506  and  1507  to facilitate stretch or other exercise of a user. Such linear and rotational displacement may be enabled by one or more actuators comprised within members  1506  and  1507 .  FIG. 15B  shows that the head and thoracic and lumbar cushions of the cushion assembly  1310  rotate about pivot point  1508 , which may pinch the user as the cushion assembly  1310  is lengthened to accommodate different-sized users. Thus, as illustrated in  FIG. 15A , the cushion assembly  1310  includes a removable filler roller pad  1504  that is configured to compress and eliminate the possible pinch point shown in  FIG. 15B . 
       FIGS. 16A-16H  illustrate a foot restraint  1602  coupled to the fitness device  1300 . The foot restraint  1602 , similar to the foot restraint  1402 , is configured for removable coupling to the base assembly  1302  of the fitness device  1300 , and includes a pedestal base. The foot restraint  1602  includes a strap, cord or bungee foot band  1604  that connects to the sides of the pedestal base to secure the feet of the user  1301  to the foot restraint  1602 . As shown in  FIG. 16B , the lateral sides  1606  of the pedestal base of the foot restraint  1602  also provide an area for the user  1301  to step on prior to securing their feet to the foot restraint  1602  using the foot band  1604 . As shown in  FIG. 16C , the pedestal base of the foot restraint  1602  includes a ramp so the foot  1601  of the user  1301  can easily walk onto the pedestal base. As illustrated in  FIGS. 16D and 16E , the foot restraint  1602  permits front and back movement relative to the pedestal base.  FIGS. 16F and 16G  illustrate foot pedestals  1608  that further aid the user  1301  in getting into the fitness device  1300 .  FIG. 16H  shows a base profile  1610 . 
       FIGS. 17A-17C  illustrate a fitness device  1700  with a user platform  1704  facilitating entry of feet of a user  1701  onto the fitness device  1700 . The fitness device  1700 , as shown in  FIG. 17A , includes an access panel at a rear thereof to facilitate servicing of the fitness device  1700 , including the columnar mechanism of base and elevation assemblies thereof.  FIG. 17A  also shows a close-up view of a top of the columnar mechanism showing an opening  1706  for adjusting the lift mechanism of the fitness device  1700 , a textured material region  1708  between the opening  1706  and a main housing  1710  of the columnar mechanism, and a ventilation panel  1712  on the main housing  1710 . The lift mechanism of the fitness device  1700  is represented as lift assembly  1711 . As shown in  FIG. 17A , a thoracic cushion assembly  1703  pivots on the lift assembly  1711 . Additionally, a lumbar cushion assembly  1705  pivots on the lift assembly  1711 . The thoracic cushion assembly  1703  and lumbar cushion assembly  1705 , in some embodiments, pivots or rotates separately or independent of one another. In other embodiments, the thoracic cushion assembly  1703  and lumbar cushion assembly  1705  rotate at least partially in coordination with one another.  FIG. 17A  also illustrates forearm supports  1709 , on which a user can rest their forearms during use of the fitness device  1700 . The forearm supports  1709  may also be used to allow the user to lift themselves as part of a stretch or other exercise, possibly while gripping handles or hand grips  1707 . 
     As illustrated in  FIG. 17B , the user platform  1704  provides a drop-out platform  1714  to facilitate user entry onto the fitness device  1700 . The user platform  1704  itself may also be raised (as shown in  FIG. 17B  relative to  FIG. 17A ) during rotation of a table of the fitness device  1700  as described elsewhere herein. For example, although not shown in  FIGS. 17A-17C , the user platform  1704  may have a foot restraint removably coupled thereto as described elsewhere herein. Movement of the user platform  1704  in such embodiment will adjust a relative position of the foot restraint and the thoracic cushion assembly  1703  and lumbar cushion assembly  1705  facilitating stretch or other exercise. The user platform  1704  may also be raised and lowered to accommodate differing user height. Further, the user platform  1704  in some embodiments includes a mechanism for rotating a plate  1722  on which the user  1701  stands as shown in  FIG. 17C . In embodiments including a foot restraint, rotation of the plate  1722  may further facilitate stretch or other exercise in addition to or in place or raising or lowering the user platform  1704 .  FIG. 17B , as noted above, illustrates the user platform  1704  partially raised relative to the static base  1716  of the base assembly. The base assembly is at least partially hollow  1718  in some embodiments for adding weight as desired. A bottom of the static base  1716  also includes rubber feet  1720  (e.g., for use in a gym floor environment). 
       FIGS. 18A-18D  illustrate a fitness device  1800 . The fitness device  1800  includes rubber feet  1802  on the bottom of corners of the base assembly thereof (e.g., for static installation where the fitness device  1800  is not expected to move often). The rubber feet  1802 , however, are removable in place of interchangeable casters  1804  for use in environments where the fitness device  1800  is expected to be repositioned (or for transport of the fitness device  1800 ). The base assembly of the fitness device  1800  includes a region  1806  where a removable step ramp  1814  is configured to fit in. The removable step ramp  1814  includes a platform  1816  that is raised or lowered to facilitate user entry onto the fitness device  1800 . As shown in  FIG. 18B , the removable step ramp  1814  is modular, permitting interchanging of the platform  1816  with different sized and textured step platforms such as platforms  1818  and  1820 . The fitness device  1800  further includes modular support pads or cushions  1808  configured for attachment to a cushion assembly or table of the fitness device  1800  with magnets, cleats, etc.  FIG. 18C , for example, illustrates removal of a cushion  1822  from the cushion assembly.  FIG. 18D  illustrates a male-female cleat feature  1824  for removing the cushion  1822  and other cushions and pads from the cushion assembly of the fitness device  1800 . The fitness device  1800  also includes continuous tubing  1810  that provides an overhead bar and grips for the user in different positions.  FIG. 18A  shows a close-up view of a region of the tubing  1810  that is over-molded or otherwise formed to provide hand grips  1812  for a user of the fitness device  1800 . 
       FIGS. 19A and 19B  illustrate a fitness device  1900  configured for coupling with an extendable foot restraint  1904 .  FIG. 19A  shows a user  1901  on the fitness device in the prone position while the table thereof is rotated. As shown, the feet  1903  of the user hang freely, which may be uncomfortable for the user.  FIG. 19B  shows an extendable foot restraint  1904  that is coupled to a base of the table and extends outward from a lumbar cushion of a cushion assembly of the fitness device  1900  on which the user  1901  may rest their feet  1903  during rotation of the table of the fitness device  1900 . Although shown in  FIG. 19B  as extending straight out from the bottom of the lumbar cushion, in some embodiments the extendable foot restraint  1904  rotates about a pivot point on the table of the fitness device  1900 , as illustrated by arrow  1905 . 
       FIGS. 20A and 20B  illustrate a fitness device  2000 . The fitness device  2000  includes a track system  2002  on which a foot restraint  2004  is mounted and able to slide back and forth. The track system  2002 , as well as other types of sliding tracks and track systems described herein, in addition to allowing motion during stretching or other exercise, may also provide a convenient method of storage of the foot restraint  2004  when not in use.  FIG. 20A  depicts a user  2001  on the fitness device  2000  resting on a lumbar support cushion  2008  and with their feet attached to the foot restraint  2004  via a bungie strap  2006 .  FIG. 20B  shows a side cross-sectional view of the foot restraint  2004  on the track system, including an axis  2010  and a portion  2012  of the base assembly providing the track system  2002 . Also shown in  FIG. 20B  is the bungie strap  2006 . 
       FIGS. 21A-21C  illustrate another foot restraint  2104  on a track system of a fitness device  2100 . The feet of a user  2101  are secured to the foot restraint  2104  via a bungie band  2106 .  FIG. 21B  shows a side cross-sectional view of the foot restraint  2104 , including a board or platform  2108  on which the feet of the user  2101  rest.  FIG. 21C  shows a perspective view of the foot restraint  2104  on the track system of the fitness device  2100 . 
       FIGS. 22A-22C  illustrate a fitness device  2200  with a foot restraint  2202  providing a pair of ankle cuffs on which the feet of a user are secured. Sides of the ankle cuffs of the foot restraint  2202  are secured to a base assembly of the fitness device  2200  via straps, cords or bands that stretch, allowing some travel and flexibility in three dimensions.  FIGS. 22B and 22C  show perspective views of the foot restraint  2202 . More particularly,  FIG. 22B  illustrates an embodiment where the foot restraint  2202  has two straps, one at each side of the ankle cuffs.  FIG. 22C  illustrates an embodiment where a single strap is coupled in the middle of the two ankle cuffs. 
       FIG. 23  illustrates a fitness device  2300  on which a user  2301  is positioned. A table of the fitness device  2300  is tilted backwards, stretching the user  2301  as shown. The feet of the user  2301  are secured with foot restraint  2302 , which enhances the stretch of the user  2301  as the table of the fitness device  2300  is rotated backwards. In the  FIG. 23  embodiment, the foot restraint  2302  includes ankle cuffs affixed to a base assembly of the fitness device  2300  via multiple straps on the front and sides of the ankle cuffs. The fitness device  2300  includes hand grips  2311  facing downward (e.g., towards a base assembly of the fitness device  2300 ). The fitness device  2300  also includes a table which slides along a curved track  2313  that elevates and arches the user  2301  as illustrated. 
       FIG. 24  illustrates a fitness device  2400  on which a user  2401  is positioned. The fitness device  2400  includes a base assembly  2402 , elevation assembly  2404  and a table  2406 . The table  2406  of the fitness device  2400  is tilted backwards, stretching the user  2401  as shown. The fitness device  2400  also includes a two-piece restraint and overhead bar including overhead grip bar  2408 - 1  and underarm support bar  2408 - 2 . It should be appreciated that the fitness device  2400  may include just one of the overhead grip bar  2408 - 1  and the underarm support bar  2408 - 2 . For example, in some embodiments the overhead grip bar  2408 - 1  is not used, or is removably attached to the fitness device  2400  as an optional component. The underarm support bar  2408 - 2  may also be optional, and may be removably attached to the fitness device  2400 . 
     The feet of the user  2401  are secured with foot restraint  2414 , which enhances the stretch of the user  2401  as the table  2406  of the fitness device  2400  is rotated backwards. In the  FIG. 24  embodiment, the foot restraint  2414  includes boot straps secured around the ankle, heel and foot of the user  2401  that are coupled to the base assembly  2402  of the fitness device  2400  via straps  2415 . The straps  2415  are configured for translation movement along a track system  2417  in the base assembly  2402  as shown. In some embodiments, the straps  2415  are elastic members. In other embodiments, the straps  2415  are rigid elements. In other embodiments, the track  2417  is configured to give a determined amount of resistance as the connection to the straps  2415 . 
     The fitness device  2400  includes underarm supports  2408 - 2  with hand grips  2411 , where the underarm supports  2408 - 2  are configured to adjust for user height along a track  2413  within the table  2406  as illustrated. The overhead bar  2408 - 1  of the fitness device  2400  is also positioned along the track  2413 , such that the overhead bar can be adjusted to suit a size of the user  2401  and desired stretch or other exercise type. The overhead bar  2408 - 1  of the fitness device  2400  may also rotate to accommodate size of the user  2401  and desired stretch or other exercise type. 
       FIG. 25  illustrates a fitness device  2500  on which a user  2501  is positioned. The fitness device  2500  includes a base assembly  2502 , elevation assembly  2504  and a table  2506 . The table  2506  of the fitness device  2500  is tilted backwards, stretching the user  2501  as shown. The fitness device  2500  also includes a two-piece restraint and overhead bar including overhead grip bar  2508 - 1  and belt support  2508 - 2 . It should be appreciated that the fitness device  2500  may include just one of the overhead grip bar  2508 - 1  and the belt support  2508 - 2 . For example, in some embodiments the overhead grip bar  2508 - 1  is not used, or is removably attached to the fitness device  2500  as an optional component. The belt support  2508 - 2  may also be optional, and may be removably attached to the fitness device  2500 . 
     The feet of the user  2501  are secured with foot restraint  2514 , which enhances the stretch of the user  2501  as the table  2506  of the fitness device  2500  is rotated backwards. In the  FIG. 25  embodiment, the foot restraint  2514  includes ankle cuffs that are coupled to a base assembly of the fitness device  2500  via straps  2515  at the sides thereof. The straps  2515  are configured for translation movement along a track system  2517  in the base assembly  2502  as shown. The track system  2517  also accommodates translational motion during stretch or other exercise, such as lateral stretching when the use 2501 is positioned laterally with respect to the fitness device  2500 . The compliance of the straps  2515  may be adjusted (e.g., from very stiff to very compliant) through modification of the type or number of straps  2515  used in parallel or in series. For example, additional straps  2515  may be added in parallel to increase stiffness, and straps  2515  may be removed to increase compliance. Alternatively or additionally, straps  2515  may be connected and removed in series with one another to control stiffness and compliance. In other embodiments, straps  2515  are not used in parallel but instead a single strap  2515  is used. The single strap  2515  may be swapped out as desired (e.g., to use a more compliant or a stiffer single strap). The straps  2515  may be allowed to slide freely within the track system  2517  of the base assembly  2502  during stretch or other exercise of the user  2501 . Alternatively, the straps  2515  may be fixed at a particular point (or within some defined range of the track system  2517 ) for a particular stretch or other exercise of the user  2501 . One or more of the straps  2515  (as well as other straps described herein) may be implemented as elastic bands, bungees, sets of springs, etc. 
     Similar to the fitness device  2400 , the overhead bar support  2508 - 1  and the belt support  2508 - 2  of the fitness device  2500  are mounted in a track  2513  of the table  2506 , permitting adjustment for user size and type of stretch or other exercise. In the fitness device  2500 , the underarm supports are embodied as the belt support  2508 - 2  that holds the user  2502  in place. The overhead bar  2508 - 1  may include two distinct (left and right) portions that are mirror images of one another. The two portions of the overhead bar  2508 - 1  may, but are not required to be, connected to one another in the center. 
       FIG. 26  illustrates a fitness device  2600  on which a user  2601  is positioned. The fitness device  2600  includes a base assembly  2602 , elevation assembly  2604  and a table  2606 . The table  2606  of the fitness device  2600  is tilted backwards, stretching the user  2601  as shown. The fitness device  2600  is shown including only an underarm support  2608 , which is configured to slide along track  2613  within the table  2606  to adjust for user size and comfort. Although not shown, the fitness device  2600  may also be equipped with an optional overhead bar support as described elsewhere herein. The feet of the user  2601  are secured with foot restraint  2614 , which enhances the stretch of the user  2601  as the table  2606  of the fitness device  2600  is rotated backwards. In the  FIG. 26  embodiment, the foot restraint  2614  includes a bungie strap that goes over tops of the feet of the user  2601  such that bottoms of the feet of the feet rest on a pedestal base  2615  that is raised and lowered to adjust its angle relative to the floor. The user  2601  positions hands on hand grips  2611  as shown. 
       FIG. 27  illustrates a fitness device  2700  on which a user  2701  is positioned. The fitness device  2700  includes a base assembly  2702 , elevation assembly  2704  and a table  2706 . The table  2706  of the fitness device  2700  is tilted backwards, stretching the user  2701  as shown. The fitness device  2700  is shown including only an underarm support  2708 , which is configured to slide along track  2713  within the table  2706  to adjust for user size and comfort. Although not shown, the fitness device  2700  may also be equipped with an optional overhead bar support as described elsewhere herein. A link mechanism  2719  of the elevation assembly  2704  provides rotation of the table  2706 . The link mechanism  2719  is coupled to actuators in the elevation assembly  2705  to control tilt of the table  2706 . The user  2701  positions hands on hand grips  2711  as shown. 
     The feet of the user  2701  are secured with foot restraint  2714 , which enhances the stretch of the user  2701  as the table  2706  of the fitness device  2700  is rotated backwards. In the  FIG. 27  embodiment, the foot restraint  2714  includes ankle cuffs that are secured to the base assembly  2702  of the fitness device  2700  via bungie straps  2715 . The straps  2715  are configured for translation movement along a track system  2717  in the base assembly  2702 . The compliance of the straps  2715  may be adjusted (e.g., from very stiff to very compliant) through modification of the type or number of straps  2715  used in parallel. For example, additional straps  2715  may be added in parallel to increase stiffness, and straps  2715  may be removed to increase compliance. In other embodiments, straps  2715  are not used in parallel but instead a single strap  2715  is used. The single strap  2715  may be swapped out as desired (e.g., to use a more compliant or a stiffer single strap). The straps  2715  may be allowed to slide freely within the track system  2717  of the base assembly  2702  during stretch or other exercise of the user  2701 . Alternatively, the straps  2715  may be fixed at a particular point (or within some defined range of the track system  2717 ) for a particular stretch or other exercise of the user  2701 . 
       FIGS. 28A-28C  illustrate a fitness device  2800  on which a user  2801  is positioned. The fitness device  2800  includes a base assembly  2802 , elevation assembly  2804  and a table  2806 . The table  2806  of the fitness device  2800  is tilted backwards, stretching the user  2801  as shown. The fitness device  2800  is shown including only an underarm support  2808 , which is configured to slide along track  2813  within the table  2806  to adjust for user size and comfort. Although not shown, the fitness device  2800  may also be equipped with an optional overhead bar support as described elsewhere herein. A tilt actuator  2819  of the elevation assembly  2804  provides control of a tilt or rotation of the table  2806 . The user  2801  positions hands on hand grips  2811  as shown for support. 
     The feet of the user  2801  are secured with foot restraint  2814 , which enhances the stretch of the user  2801  as the table  2806  of the fitness device  2800  is rotated backwards. In the  FIG. 28  embodiment, the foot restraint  2814  includes boots that are secured to the base assembly  2802  of the fitness device  2800  via bungie straps  2815 . The straps  2815  are configured for translation movement along a track system  2817  in the base assembly  2802 . The compliance of the straps  2815  may be adjusted (e.g., from very stiff to very compliant) through modification of the type or number of straps  2815  used in parallel. For example, additional straps  2815  may be added in parallel to increase stiffness, and straps  2815  may be removed to increase compliance. In other embodiments, straps  2815  are not used in parallel but instead a single strap  2815  is used. The single strap  2815  may be swapped out as desired (e.g., to use a more compliant or a stiffer single strap). The straps  2815  may be allowed to slide freely within the track system  2817  of the base assembly  2802  during stretch or other exercise of the user  2801 . Alternatively, the straps  2815  may be fixed at a particular point (or within some defined range of the track system  2817 ) for a particular stretch or other exercise of the user  2801 .  FIGS. 28B and 28C  show side and perspective views, respectively, of a boot of the foot restraint  2814 . 
       FIGS. 29A-29J  illustrate operation of a foot restraint  2904  for use in a fitness device, such as fitness device  100  described above. The foot restraint  2904 , similar to foot restraint  504 , includes a set of cushion parallel bars or bolsters for a user to insert their feet between for securing the user to a base assembly of a fitness device via a circular platform  2902  that is configured to rotate. In some embodiments, the platform  2902  is configured to act as a wobble board, where the wobble board may be passive or provide feedback to a controller that assesses the balance of the user. 
       FIGS. 29A-29J  further illustrate a round ball joint  2906  enabling rotation of the foot restraint  2904 . The ball joint  2906  provides positioning flexibility for the foot restraint  2904 .  FIG. 29A  shows a perspective view of the foot restraint  2904 , while  FIGS. 29B and 29C  show cross-sectional views of the foot restraint  2904  illustrating aspects of the ball joint  2906 .  FIG. 29D  depicts linear travel of the bolsters of the foot restraint  2904 .  FIG. 29E  shows a top-down view of the foot restraint  2904 , and  FIG. 29F  shows a bottom-up view of the foot restraint  2904 .  FIG. 29G  shows a side view of the foot restraint  2904 , and  FIG. 29H  shows a cross-sectional view of the foot restraint  2904  taken along the line A-A shown in  FIG. 29G .  FIG. 29I  shows another side view of the foot restraint  2904 , and  FIG. 29J  shows a cross-sectional view of the foot restraint  2904  taken along the line B-B shown in  FIG. 29I . 
       FIGS. 30A-30H  illustrate operation of a foot restraint  3004  for use in a fitness device, such as fitness device  100  described above. The foot restraint  3004  is similar to the foot restraint  2904 , although the ball joint  3006  of the foot restraint  3004  is deeper than the ball joint  2906  of the foot restraint  2904 , thus allowing increased linear travel of the bolsters of the foot restraint  3004  relative to the linear travel of the bolsters of the foot restraint  2904 . The foot restraint  3004  includes a circular platform  3002  that is configured to rotate. In some embodiments, the platform  3002  is configured to act as a wobble board, where the wobble board may be passive or provide feedback to a controller that assesses the balance of the user. Although the platform  3002  is shown with a round shape in  FIGS. 30A-30H , it should be appreciated that other shapes may be used for the platform  3002  in other embodiments. 
       FIGS. 30A-30H  further illustrate the deeper ball joint  3006  enabling rotation of the foot restraint  3004 .  FIG. 30A  shows a perspective view of the foot restraint  3004 , while  FIG. 30B  shows a cross-sectional view of the foot restraint  3004  illustrating aspects of the ball joint  3006 .  FIG. 30C  shows a top-down view of the foot restraint  3004 , and  FIG. 30D  shows a bottom-up view of the foot restraint  3004 .  FIG. 30E  shows a side view of the foot restraint  3004 , and  FIG. 30F  shows a cross-sectional view of the foot restraint  3004  taken along the line A-A shown in  FIG. 30E .  FIG. 30G  shows another side view of the foot restraint  3004 , and  FIG. 30H  shows a cross-sectional view of the foot restraint  3004  taken along the line B-B shown in  FIG. 30G . 
       FIGS. 31A-31H  illustrate operation of a foot restraint  3104  for use in a fitness device, such as fitness device  100  described above. The foot restraint  3104  is similar to the foot restraint  2904 , although the platform  3102  of the foot restraint  3104  is oval rather than circular and includes an oblong slotted ball joint  3106  thus allowing increased linear travel of the bolsters of the foot restraint  3104  relative to the linear travel of the bolsters of the foot restraint  2904 . The foot restraint  3104  includes the oval platform  3102  that is configured to rotate. In some embodiments, the platform  3102  is configured to act as a wobble board, where the wobble board may be passive or provide feedback to a controller that assesses the balance of the user. 
       FIGS. 31A-31H  further illustrate the oblong slotted ball joint  3106  enabling rotation of the foot restraint  3104 .  FIG. 31A  shows a perspective view of the foot restraint  3104 , while  FIG. 31B  shows a cross-sectional view of the foot restraint  3104  illustrating aspects of the ball joint  3106 .  FIG. 31C  shows a top-down view of the foot restraint  3104 , and  FIG. 31D  shows a bottom-up view of the foot restraint  3104 .  FIG. 31E  shows a side view of the foot restraint  3104 , and  FIG. 31F  shows a cross-sectional view of the foot restraint  3104  taken along the line A-A shown in  FIG. 31E .  FIG. 31G  shows another side view of the foot restraint  3104 , and  FIG. 31H  shows a cross-sectional view of the foot restraint  3104  taken along the line B-B shown in  FIG. 31G . 
     Ball joints may be connected to a foot restraint in various ways.  FIG. 32  shows a ball joint  3206  configured for attachment to a foot restraint via a fixed shaft.  FIG. 33  shows a ball joint  3306  configured for attachment to a foot restraint with translation along a shaft. Through translation along the shaft, the foot restraint is provided with resistance from an elastic element.  FIGS. 34A-34C  show a ball joint  3406  configured for attachment to a foot restraint via a slot with a cone shape at rounded ends, along the foot restraint to stay parallel to a platform of a base assembly of a fitness device during rotation.  FIG. 34A  shows a side view of the ball joint  3406 , and  FIG. 34B  shows a cross-sectional side view of the ball joint  3406 .  FIG. 34C  shows a bottom-up view of the ball joint  3406 . 
       FIGS. 35A and 35B  illustrate a movable platform  3504  that is part of a base assembly  3502  of a fitness device. The movable platform  3504  is configured to translate up and down, to pivot up and down, and to combination pivot and translate. The movable platform  3504 , for example, may translate up and down to adjust for differing user height. The movable platform  3504  (and other platforms and foot restraints described herein) may be configured to be raised and lowered to provide stretching of the user with or without rotation of a table of a fitness device. Further, the movable platform  3504  (and other platforms and foot restraints described herein) may be configured to retract to provide stretching of the user with or without rotation of a table of a fitness device. The movable platform  3504 , in some embodiments, is configured for use with a foot restraint as described herein.  FIG. 35A  depicts the movable platform  3504  raised up, while  FIG. 35B  depicts the movable platform  3504  in a lowered position.  FIGS. 35A and 35B  further depict table pivot point options for an upper bar  3506  of the base assembly  3502 . The upper bar  3506  is configured in some embodiments to pivot only. In other embodiments, the upper bar  3506  is configured to pivot plus provide adjustment for differing user height. 
       FIGS. 36A and 36B  illustrate a resilient platform  3604  that is part of a base assembly  3602  of a fitness device.  FIG. 36A  shows the resilient platform  3604  spring loaded in a low position.  FIG. 36B  shows the resilient platform  3604  in a raised position, where the resilient platform  3604  lifts off the supports as the user is lifted, shown in the close-up view  3601 . The resilient platform  3604  in  FIGS. 36A and 36B  is shown as including a foot restraint  3614 , though this is not a requirement. 
       FIGS. 37A-37D  illustrate a fitness device  3700  configured with a recessed pivoting foot restraint  3714 . The fitness device  3700 , as shown, includes a base assembly  3702 , an elevation assembly  3704 , a table  3706  and a cushion assembly  3710 . The recessed pivoting foot restraint  3714  is shown retracted in  FIG. 37A , and is shown extended in  FIG. 37B . The foot restraint  3714  has a connecting link that pivots and provides resistance.  FIG. 37C  shows the foot restraint  3714  pivoting  3715  about a pivot axis  3716 .  FIG. 37D  shows translation  3717  of the foot restraint  3714  along the connecting link. It should be noted that the foot restraint in other embodiments described herein may be configured to be retracted into a recess (e.g., of a base assembly of a fitness device, of a platform configured for attachment to a base assembly of a fitness device, etc.). 
       FIGS. 38A and 38B  illustrate operation of a fitness device  3800 . The fitness device  3800  includes a base assembly  3802 , an elevation assembly  3804 , a table  3806 , an overhead bar and underarm restraint  3808 , and a cushion assembly  3810 . The fitness device  3800  also includes a foot restraint  3814  coupled to the base assembly  3802 . As shown in  FIG. 38A , the elevation assembly  3804  of the fitness device  3800  enables lateral flexion produced by tilting the table  3806  about the z-axis. The fitness device  3800 , as well as other fitness devices described herein, may include a pivot point for rotation about the craniocaudal (y) axis for manual exercise as well as enhancing the effects of rotational stretching, stretching in flexion (facing forwards), extension (facing backwards), and lateral flexion (facing sideways) in combination with rotation of the human back and torso.  FIG. 38B  shows the angle  3801  produced by raising and lowering elevation posts of the elevation assembly  3804  to different heights to provide the lateral flexion. 
       FIG. 39  depicts a set of modules, including a height control module  3902 , a rotation control module  3904 , a tilt control module  3906 , a height compensation module  3908 , a rotation motion resolution module  3910 , a rotation motion generation module  3912 , a tilt motion resolution module  3914  and a tilt motion generation module  3916 , for controlling the elevation and rotation of the table  106  of fitness device  100 . The modules  3902  through  3916  utilize a set of operating or UI parameters, including: N reps  denoting the number of exercise repetitions; θ rmax  denoting a maximum rotation angle; H ref  denoting a reference height, which may be adjust to differing user heights; and F max  denoting a maximum allowable applied force. The modules  3902  through  3916  also utilize various actuators and sensors, including: M t  denoting a tilt angle actuator; x t  denoting a tilt sensor for measuring tilt displacement; M r  denoting a rotation angle actuator; x t  denoting a rotation sensor for measuring rotation displacement; M h  denoting a height actuator; x h  denoting a height sensor for measuring height displacement; and F meas  denoting a measured force, such as on a load cell or the foot restraint of the fitness device  100 . The modules  3902  through  3916  further utilize a set of control state variables, including: θ t  denoting a measured tilt angle; θ ts  denoting a generated reference tilt angle; θ r  denoting a measured rotation angle; θ rg  denoting a generated reference rotation angle; and H comp  denoting a height compensation value for limiting an applied force on a user of the fitness device  100 . 
     In some embodiments, the height control module  3902 , rotation control module  3904  and tilt control module  3906  are implemented as proportional-integral-derivative (PID) control modules that operate according to the equation: 
     
       
         
           
             
               
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     where u(t) is the control output, e(t) is the difference between reference and measured control input state (“error”), and K p , K t , and K d  are control coefficients (proportional, integral, and derivative, respectively). 
     The height compensation module  3908  is configured to reduce the reference height, H ref  to limit the applied force on the user by the foot restraint. The height compensation module  3908  takes as input the maximum allowable applied force F max  and the measured force F meas , and provides an output height H comp  according to the equation H comp =f hc (F meas ,F max ), where f hc  denotes a height compensation function. The output height H comp  and the reference height H ref  are provided to a summer, the output of which is supplied to the height control module  3902  along with the displacement height measured by the height sensor x h . The height control module  3902  in turn activates the height actuator M h  to adjust the height of the table  106  of the fitness device  100  (e.g., using the base assembly  102  and/or elevation assembly  104 ). 
     The rotation motion resolution module  3910  and tilt motion resolution module  3914  are each configured to convert a measured rotational or linear displacement to a measured angle. The rotation motion resolution module  3910  takes as input the measured rotation displacement from the rotation sensor x r , and outputs the measured rotation angle θ r  according to the equation θ r (t)=f rm (x r (t)) where f rm  denotes a function for conversion of the measured rotation displacement and t denotes time. It should be noted that the measured rotation angle θ r  may be independent of any feedback from displacement height sensors or feedback from sensors measuring resistance from the foot restraint or base assembly sensors. The tilt motion resolution module  3914  takes as input the measured tilt displacement from the tilt sensor x t , and outputs the measured tilt angle θ t  according to the equation θ t (t)=f tm (x t (t)) where f tm  denotes a function for conversion of the measured tilt displacement. 
     The rotation motion generation module  3912  and tilt motion generation module  3916  create the exercise motion profile of the table  106  of fitness device  100 . The rotation motion generation module  3912  takes as input the parameters N reps  denoting the number of exercise repetitions and θ rmax  denoting the maximum rotation angle, and outputs the generated reference rotation angle θ rg  according to the equation θ rg  (t)=f rg  (θ rmax , N rep , S 1 , S r ) where f rg  denotes a function for generating the reference rotation angle, and S t  and S r  denote logic states (e.g., on/off) for left and right user switch controls, respectively. The tilt motion generation module  3916  takes as input the generated reference rotation angle θ rg  and generates the reference tilt angle θ tg  according to the equation θ tg (t)=f tg (θ rg (t)) where f tg  denotes a function for generating the reference tilt angle. The reference rotation angle may be based at least in part on feedback from sensors of a selected maximum ankle resistive force, or may allow rotation to the maximum limits of table rotation and limits of foot restraint motion. 
     The outputs of the rotation motion resolution module  3910  and rotation motion generation module  3912  are provided to the rotation control module  3904  to activate the rotation angle actuator M r . The outputs of the tilt motion resolution module  3914  and tilt motion generation module  3916  are provided to the tilt control module  3906  to activate the tilt angle actuator M t . 
       FIGS. 40A-40L  illustrate operation of a fitness device  4000 . The fitness device  4000  includes a base assembly  4002 , an elevation assembly  4004 , a table  4006 , a two-piece restraint and overhead bar assembly including overhead bar  4008 - 1  and underarm bars  4008 - 2 , and a cushion assembly  4010 .  FIG. 40A  shows a lumbar or pelvic cushion  4017  of the cushion assembly  4010 , where the pelvic cushion  4017  may be coupled to one or more actuators that allow the pelvic cushion  4017  to extend outwards in direction  4019 . The base assembly  4002  is also shown including an optional foot restraint  4014 . Although shown in  FIGS. 40A-40L  as utilizing a configuration similar to that described above with respect to foot restraint  504 , it should be appreciated that the foot restraint  4014  may utilize any other type of foot restraint configuration described above or elsewhere herein. 
     In the fitness device  4000 , the pivot point or table rotation axis  4005  is positioned in front of the cushions of the cushion assembly  4010 , which offers the advantage of a smaller change in height of the user for a similar rotation, versus embodiments where the pivot point is behind the cushions of a cushion assembly. This is compared with, for example, the fitness device  100  of  FIGS. 1A-1F , where the table rotation axis  105  is positioned behind the cushions of the cushion assembly  110 . Although  FIGS. 40A-40L  illustrate an example where a two-column approach is used for elevation means (e.g., similar to other figures such as  FIGS. 1A-1F ), a single-column approach may alternatively be used. 
       FIG. 40A  shows a side cross-sectional view of the fitness device  4000 , illustrating internal actuators of the base assembly  4002  configured for adjusting a height of the table  4006 . Rotation or tilt of the table  4006  is enabled via actuators of the elevation assembly  4004 . The actuators couple the elevation assembly  4004  to the back of the table  4006 . Such actuators may comprise electric motor-powered linear actuators, pneumatic actuators, hydraulic actuators, etc.  FIG. 40B  shows a front view of the fitness device  4000 .  FIG. 40C  shows a side view of the fitness device  4000  with the table  4006  in an upright or starting position, while  FIG. 40D  shows a side view of the fitness device  4000  with the table  4006  in a reclined position. 
       FIGS. 40E and 40F  show perspective views of the fitness device  4000  in the upright position with the underarm bars  4008 - 2  in open and closed positions, respectively. The underarm bars  4008 - 2 , as shown, are configured to swing outward to accommodate a user entering and exiting the fitness device  4000 , or for comfort of the user while using the fitness device  4000 .  FIGS. 40G and 40H  show perspective views of the fitness device  4000  in a reclined position with the underarm bars  4008 - 2  in open and closed positions, respectively.  FIGS. 401 and 40J  show top-down views of the fitness device  4000  with the underarm bars  4008 - 2  in open and closed positions, respectively.  FIG. 401  also illustrates lateral rotation  4007 , which may include lateral rotation of the table  4006  or portions of the cushion assembly together with other components such as underarm bars  4008 - 2 . 
       FIG. 40K  shows a front view of the fitness device  4000 , where the base assembly  4002  provides a lateral pivot point  4009  for lateral rotation of the table  4006 .  FIG. 40L  shows a front cross-sectional view of the fitness device  4000 , illustrating internal actuator  4011  and actuator  4015  (e.g., each of which may be an electric motor-powered linear actuator, a pneumatic actuator, a hydraulic actuator, etc.). The actuator  4015  is configured to provide rotation  4007  about the lateral pivot point  4009 . Internal actuator  4011  raises the elevation assembly  4004 . The lateral pivot point  4009 , in some embodiments, comprises a torsional spring, a flywheel and clutch, or another mechanism that is configured to provide variable resistance to different types of rotation (e.g., about the y-axis) during stretch or other exercise. It should be noted that the lateral pivot point  4009  illustrated in  FIGS. 40K and 40L  is optional, and that in other embodiments the fitness device  4000  does not provide or utilize the lateral pivot point  4009 . 
       FIGS. 41A-41J  illustrate operation of a foot restraint  4124  of a fitness device  4100 . The fitness device  4100 , similar to fitness device  4000 , includes a base assembly  4102 , an elevation assembly  4104 , a table (not labeled for clarity), a two-piece restraint and overhead bar assembly including overhead bar  4108 - 1  and underarm bars  4108 - 2 , and a cushion assembly  4110 . Also similar to the fitness device  4000 , the fitness device  4100  includes a pivot point or table rotation axis  4105  that is positioned in front of the cushions of the cushion assembly  4110 . The base assembly  4102  includes the foot restraint  4124 , which has a different configuration relative to the foot restraint  4014  of fitness device  4000 . 
       FIG. 41A  shows a perspective view of the fitness device  4100 , and  FIG. 41B  shows a close-up view of the foot restraint  4124 .  FIG. 41C  shows a close-up cross-sectional view of the foot restraint  4124 . The foot restraint  4124  includes a set of parallel bars with bolsters  4126 , a base plate  4128 , and a peg interconnection  4130 . The base plate  4128  and peg interconnection  4130 , in some embodiments, may be a single piece. In other embodiments, the base plate  4128  and peg interconnection  4130  are distinct pieces. The peg interconnection  4130 , as detailed in the cross-sectional view of  FIG. 41C , has a wire  4134  that provides tension or resistive force. The wire  4134  runs through a guide  4132  below the base plate  4128 . The wire  4134  may be connected to a force application system (e.g., force application system  702 ), or could by a compliant member and may be adjusted from very stiff to very compliant by changing out the type of wire used, adding springs along the length of the wire, adding springs at the attachment point of the wire to the structure, or adding or subtracting the number of wires used in series or in parallel. 
       FIG. 41D  shows a close up view of the foot restraint  4124  where the base plate  4128  is elevated relative to a platform of the base assembly  4102 . The base plate  4128  is an example of what is more generally referred to herein as a base assembly mounting portion. The base plate  4128 , and other base assembly mounting portions, may be removable and configured for easy reattachment to the base assembly  4102  as required or desired by the user. The base plate  4128  elevates as the user is lifted during stretch or exercise of a user of the fitness device  4100 . The wire  4134  provides a controllable amount of tension or resistive force to such lifting or rotation of the base plate  4128 . The controllable amount of tension or resistive force may be implemented in a manner similar to that described above with respect to  FIG. 39 .  FIG. 41E  shows a close-up cross-sectional view of the foot restraint  4124  during the elevation described above with respect to  FIG. 41D . 
       FIGS. 41F-41I  illustrate linear travel of the parallel bars and bolsters  4126  of the foot restraint  4124 .  FIG. 41F  shows a top-down view of the foot restraint  4124  while the parallel bars and bolsters  4126  are extended outward from the sliding track  4136 , and  FIG. 41G  shows a side view of the foot restraint  4124  during such linear extension outward from the sliding track  4136 .  FIG. 41H  shows a top-down view of the foot restraint  4124  where the parallel bars and bolsters  4126  are not extended outward from the sliding track  4136 , and  FIG. 41I  shows a side view of the foot restraint  4124  without the linear extension outward from the sliding track  4136 . The outward extension of parallel bars and bolsters  4126  may be spring loaded, moved by a linear actuator, moved by a lever or other means, in order to open up to allow the user to insert the user&#39;s ankles and then retract to capture the ankles. 
       FIG. 41J  shows a top-down view of the foot restraint  4124  with different shaped bolsters  4127  relative to the parallel bars and bolsters  4126  shown in  FIGS. 41A-41I . It is to be appreciated that the particular size and shape of the bolsters in foot restraints may be varied as desired for comfort of the user. In some embodiments, for example, the bolsters are made modular such that different users of a fitness device can adjust the type and size of bolsters utilized. A user may also remove the bolsters altogether, such that the parallel bars are bare or exposed. The different shaped bolsters  4127  have a taper that would allow the user to more easily slide the ankles into the foot restraint  4124 . This would be particularly helpful when the outward extension of parallel bars and bolsters  4127  is spring loaded. 
       FIGS. 42A-42H  illustrate operation of a fitness device  4200 . The fitness device  4200  includes a base assembly  4202 , an elevation assembly  4204 , a table  4206 , a two-piece restraint and overhead bar assembly including overhead bar  4208 - 1  and underarm bars  4208 - 2 , and a cushion assembly  4210 . The fitness device  4200  includes a pivot point or table rotation axis  4205  that is positioned behind the cushions of the cushion assembly  4210 , although this is not a requirement. In other embodiments, the pivot point or table rotation axis may be in front of (or in line with) the cushions of the cushion assembly as described above in conjunction with, for example,  FIGS. 40A-40L . The base assembly  4202  includes optional foot restraint  4214 . Although shown in  FIGS. 42A-42H  as utilizing a configuration similar to that described above with respect to foot restraint  504 , it should be appreciated that the foot restraint  4214  may utilize any other type of foot restraint configuration described above or elsewhere herein. 
       FIG. 42A  shows a side view of the fitness device  4200 .  FIG. 42A  shows the fitness device  4200  in what is referred to herein as a starting, ready or default position that the fitness device  4200  returns to after a user has exited. 
       FIG. 42B  also shows a side view of the fitness device  4200 , but  FIG. 42B  omits element labels for components of the fitness device  4200  so as to illustrate adjustability of the fitness device as shown with reference numerals  4211 ,  4213  and  4215 . Element  4211  illustrates height adjustment provided by the base assembly  4202  and elevation assembly  4204 , so as to accommodate user height. Element  4213  illustrates height adjustment of the underarm bars  4208 - 2 , and element  4215  illustrates height adjustment of the overhead bar  4208 - 1 . The overhead bar  4208 - 1  and underarm bars  4208 - 2  are advantageously configured for independent adjustment for accommodating different sized users as well as user preference and comfort. The fitness device  4200  is thus configured for adjustment to fit and accommodate different users. Users, for example, may first lock or otherwise position their feet in the foot restraint  4214 , then close the underarm support bars  4208 - 2  (e.g., which may swing outward and close as described above). Users may then grasp hand grips on the underarm support bars  4208 - 2  providing controls for actuating the various height adjustments  4211 ,  4213  and  4215 . Hand grips on the underarm support bars  4208 - 2  may also or alternatively be used for initiation and manual controlled operation of any or all rotational movement and stretching of the table  4206 . Users can also utilize such controls to initiate stretch or other exercise (e.g., by pressing or activating controls as described elsewhere herein). 
       FIG. 42C  shows a side view of the fitness device  4200  with a user  4201  positioned therein. As illustrated, an approximate center of a lumbar or pelvic cushion  4219  of the cushion assembly  4210  is aligned with a belly button  4217  of the user  4201  via height adjustment using the base assembly  4202  and the elevation assembly  4204 . The underarm support bars  4208 - 2  may also be height-adjusted as desired by the user  4201 .  FIG. 42D  shows the user  4201  positioned in the fitness device  4200  in a reclined position.  FIG. 42D  labels with element  4221  an approximate centerline of a body of the user  4201 . 
       FIGS. 42E-42H  illustrate a supine exercise and stretch sequence. For clarity of illustration, the user  4201  is not shown in the views of  FIGS. 42E-42H , but the approximate centerline  4221  of the body of the user  4201  is shown. More particularly,  FIG. 42E  shows a view similar to that of  FIG. 42D , but with the user  4201  not shown only the approximate centerline  4221  thereof.  FIG. 42F  illustrates core stretch of the user  4201 , where the feet of the user  4201  lift slightly off a platform of the base assembly  4202  while remaining in the foot restraint  4214 . This lift is enabled via actuators in the base assembly  4202  and/or elevation assembly  4204 , with the amount of lift shown as element  4223 .  FIG. 42F  also illustrates angular reference lines  4225  and  4227 . The angular reference line  4225  in  FIG. 42F  shows an approximate 15-degree gap between a thoracic cushion and a pelvic or lumbar cushion of the cushion assembly  4210 . The thoracic section of the cushion assembly  4210  is at a zero-degree position as shown with angular reference line  4227 . 
       FIG. 42G  illustrates rotation of the table  4206  backwards, while the lumbar and pelvis section or cushion of the cushion assembly  4210  rotates outwardly or extends directly outwardly relative to the thoracic section of the cushion assembly  4210  in direction  4231 . The 15-degree gap (e.g., of angular reference line  4225 ) between the thoracic cushion and the lumbar or pelvic cushion starts to decrease proportionally to the thoracic section angular reference line  4227 , at the rate of approximately 1 degree to every 3 degrees that the thoracic section moves. Simultaneously, or otherwise in conjunction with such rotation of the table  4206  backwards, the upper section of the fitness device  4200  (e.g., the table  4206 ) lowers  4229  to keep the feet of the user  4201  on or very close to a platform of the base assembly  4202 . The legs and feet of the user  4201  lift off the platform of the base assembly  4202 , and move outward with the thighs and hips of the user  4201  in an alternate configuration. A fluid motion of the upper body, lower body, thighs legs, and feet of the user  4201  are thus enabled following a gentle, graceful arc. It should be appreciated that any proportional rate or direction of movement between thoracic section angular reference line  4227  and the thoracic section of the cushion assembly  4210  in direction  4231  or the opposite direction can be programmed into the fitness device  4200 . Additionally, the downward movement  4229  can be preprogrammed to a predetermined rate as desired. 
       FIG. 42H  illustrates further rotation of the table  4206  backwards relative to  FIG. 42G . The rotation described above with respect to  FIG. 42G  continues to the position shown in  FIG. 42H , with the angular reference line  4225  at 0 degrees and the angular reference line  4227  at 45 degrees. The position of  FIG. 42H  may correspond to a full supine stretch of the user  4201  enabled by the fitness device  4200 . The user  4201  can dwell at the full stretch position for some desired time period, until the user  4201  reverses the rotation action by activating user interface controls of the fitness device  4200  (e.g., pressing a down button or other control on hand grips of the underarm support bars  4208 - 2 ). The fitness device  4200  will then revert to the starting position illustrated in  FIG. 42E . 
     It should be appreciated that the supine stretch and exercise sequence shown in  FIGS. 42E-42H  may be repeated by the user  4201  as desired. It should also be appreciated that the user  4201  is not required to go to the full stretch position shown in  FIG. 42H  in each or in any repetition of the supine stretch and exercise sequence. Instead, the user  4201  may control the range of motion of the fitness device  4200  as desired, including where different repetitions provide different amounts of rotation. 
     It should be further appreciated that  FIGS. 42E-42H  illustrate just one example stretch and exercise that is enabled using the fitness device  4200  in the supine position. When the user is in a prone or lateral position, other types of stretch are enabled via lift and rotation of the table  4206 . When in such other positions, the user  4201  may utilize different sets of controls of the fitness device  4200 . For example, when the user  4201  is in the prone position, controls provided on hand grips on a back or side of the cushion assembly  4210  or table  4206  may be used to activate the stretch or other exercise. When the user  4201  is in the lateral position, the user  4201  may adjust the foot restraint  4214  (e.g., via rotation of a base plate of the foot restraint  4214  in the platform of the base assembly  4202 ) and does not close the underarm support bars  4208 - 2 . In the lateral position, the user  4201  may utilize controls on the overhead bar  4208 - 1  for activating the stretch or other exercise. 
       FIGS. 42A-42H , as detailed above, illustrate core muscle stretching exercises performed on fitness device  4200 . The fitness device  4200 , as well as other fitness devices described herein, however, are not limited solely for use with core stretching. Various other types of stretching and exercise motions are enabled using the fitness devices described herein. 
     In various embodiments, aspects of a fitness device may be implemented using one or more information processing systems. For example, controls and the user interface of the fitness device, as well as the various modules described above with respect to  FIG. 39 , may be implemented at least in part using one or more information processing systems. In addition, controllers and control mechanisms for actuators may also be implemented at least in part using one or more information processing systems.  FIG. 43  shows an example of an information processing system  4300  that may be utilized to implement the controls, user interface,  FIG. 39  modules, controllers and control mechanisms, and other aspects of the fitness devices described herein. The information processing system  4300  in  FIG. 43  includes a plurality of processing devices  4302 - 1 ,  4302 - 2 ,  4302 - 3 , . . .  4302 -K (collectively, processing devices  4302 ), which communicate with one another over a network  4304 . 
     The controls or user interface of a fitness device described herein may be configured using one or more of the processing devices  4302  to implement its associated functionality. For example, algorithms for controlling and coordinating the elevation and tilt or rotation of the table of a fitness device may be implemented using one or more of the processing devices  4302 , such as processing device  4302 - 1 , which comprises a processor  4310  and a memory  4312 . The processing device  4302 - 1  may be suitably coupled to other hardware of a fitness device (e.g., actuators) that support various functionality of the fitness device. The processor  4310  executes software program code stored in the memory  4312  in order to control the performance of processing operations and other functionality. Such functionality includes, but is not limited to, controlling the lift and rotation of a table of the fitness device, controlling the rotation of a lumbar support, raising and rotating a foot restraint, varying a resistance of a foot restraint, controlling movement of overhead bars and underarm support bars, implementing controls and the user interface of a fitness device, etc. The processing device  4302 - 1  also comprises a network interface  4314  that supports communication over one or more networks such as network  4304 . 
     The processor  4310  may comprise, for example, a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor (DSP), or other similar processing device component, as well as other types and arrangements of processing circuitry, in any combination. 
     The memory  4312  stores software program code for execution by the processor  4310  in implementing portions of the functionality of the processing device  4302 - 1 . A given such memory that stores such program code for execution by a corresponding processor is an example of what is more generally referred to herein as a processor-readable storage medium having program code embodied therein, and may comprise, for example, electronic memory such as static random-access memory (SRAM), dynamic random-access memory (DRAM) or other types of random-access memory (RAM), read-only memory (ROM), magnetic memory, optical memory, or other types of storage devices in any combination. 
     Articles of manufacture comprising such processor-readable storage media are considered embodiments of the invention. The term “article of manufacture” as used herein should be understood to exclude transitory, propagating signals. 
     Other types of computer program products comprising processor-readable storage media can be implemented in other embodiments. 
     In addition, embodiments of the invention may be implemented in the form of integrated circuits comprising processing circuitry configured to implement processing operations associated with the embodiments described herein. 
     Although not shown in  FIG. 43 , other ones of the processing devices  4302 - 2  through  4302 -K are assumed to be similarly configured with respective processors, memories and network interfaces. 
     One or more of the processing devices  4302  in a given embodiment can include, for example, laptop, tablet or desktop personal computers, mobile telephones, or other types of computers or communication devices, in any combination. 
     Communications between the various elements of an information processing system  4300  comprising processing devices  4302  associated with respective components or assemblies of a fitness device may take place over one or more networks, represented in  FIG. 43  as network  4304 . Such networks can illustratively include, for example, a global computer network such as the Internet, a wide area network (WAN), a local area network (LAN), a satellite network, a telephone or cable network, a cellular network, a wireless network implemented using a wireless protocol such as WiFi or WiMAX, or various portions or combinations of these and other types of communication networks. 
     An information processing system as disclosed herein may be implemented using one or more processing platforms, or portions thereof. 
     For example, one illustrative embodiment of a processing platform that may be used to implement at least a portion of an information processing system comprises cloud infrastructure including virtual machines implemented using a hypervisor that runs on physical infrastructure. Such virtual machines may comprise respective processing devices that communicate with one another over one or more networks. 
     The cloud infrastructure in such an embodiment may further comprise one or more sets of applications running on respective ones of the virtual machines under the control of the hypervisor. It is also possible to use multiple hypervisors each providing a set of virtual machines using at least one underlying physical machine. Different sets of virtual machines provided by one or more hypervisors may be utilized in configuring multiple instances of various components of the information processing system. 
     Another illustrative embodiment of a processing platform that may be used to implement at least a portion of an information processing system as disclosed herein comprises a plurality of processing devices which communicate with one another over at least one network as in the  FIG. 43  information processing system. 
     Again, these particular processing platforms are presented by way of example only, and an information processing system may include additional or alternative processing platforms, as well as numerous distinct processing platforms in any combination, with each such platform comprising one or more computers, servers, storage devices or other processing devices. 
     For example, other processing platforms used to implement embodiments of the invention can comprise different types of virtualization infrastructure in place of, or in addition to, virtualization infrastructure comprising virtual machines. Thus, it is possible in some embodiments that system components can run at least in part in cloud infrastructure or other types of virtualization infrastructure. 
     It should therefore be understood that in other embodiments different arrangements of additional or alternative elements may be used. At least a subset of these elements may be collectively implemented on a common processing platform, or each such element may be implemented on a separate processing platform. 
     Also, numerous other arrangements of computers, servers, storage devices or other components are possible in an information processing system. Such components can communicate with other elements of the information processing system over any type of network or other communication media. 
     As indicated previously, components or functionality of the system as disclosed herein can be implemented at least in part in the form of one or more software programs stored in memory and executed by a processor of a processing device. 
     Accordingly, a given component of an information processing system implementing functionality as described herein is illustratively configured utilizing a corresponding processing device comprising a processor coupled to a memory. The processor executes program code stored in the memory in order to control the performance of processing operations and other functionality. The processing device also comprises a network interface that supports communication over one or more networks. 
     The particular configurations of information processing systems described herein are exemplary only, and a given such system in other embodiments may include other elements in addition to or in place of those specifically shown, including one or more elements of a type commonly found in a conventional implementation of such a system. 
     For example, in some embodiments, an information processing system may be configured to utilize the disclosed techniques to provide additional or alternative functionality in other contexts. The disclosed techniques can be similarly adapted for use in a wide variety of other types of information processing systems. 
     It is also to be appreciated that the particular process steps used in the embodiments described above are exemplary only, and other embodiments can utilize different types and arrangements of processing operations. For example, certain process steps described as being performed serially in the illustrative embodiments can in other embodiments be performed at least in part in parallel with one another. 
     It should again be emphasized that the embodiments of the invention as described herein are intended to be illustrative only. Other embodiments of the invention can be implemented utilizing a wide variety of different types and arrangements of components of a fitness device, including combinations of features described in conjunction with different ones of the figures. Also, the particular types and configurations of base assemblies, elevation assemblies, tables, overhead bars, underarm support bars, hand grips, user interfaces, controls, cushion assemblies, foot restraints, etc. can be varied in other embodiments. Furthermore, the way in which a particular fitness device is utilized can be varied, such as between providing powered stretching and isometric exercises. In addition, the particular assumptions made herein in the context of describing certain embodiments need not apply in other embodiments. These and numerous other alternative embodiments will be readily apparent to those skilled in the art.