Abstract:
A sacral support assembly for use with a seat is provided. The seat includes a seat frame. An adjustable sacral support assembly is connected to the seat frame. The sacral support assembly includes a sacral support member adapted to support the sacrum of a seated user even when an obstruction is located between the user and the sacral support assembly. A method is also provided for delivering primary support to a user&#39;s sacrum and sacral-pelvic anatomy and secondary support to the remaining regions of the spine and/or adjacent anatomy to reduce fatigue, increase comfort, structural balance, stability, and posture control for a user, and a system for adjusting and controlling the load distribution from the sacral anatomy to the spine and other anatomical structures adjacent to a user&#39;s sacrum, for example, the pelvis, lumbar, thoracic and cervical regions.

Description:
FIELD OF THE INVENTION 
   The present disclosure relates generally to a seat having an adjustable support system for controlling the posture and/or balance of a seated person. 
   BACKGROUND 
   Many people in modem society spend extended amounts of time seated at work, school, home, and/or while traveling. Millions of people sit during lengthy commutes to and from work. Once at work, they sit continuously in an office chair for numerous hours. Additionally, many occupations require spending much of the day seated in an automobile. For example police officers, truck drivers, and taxi cab drivers, have jobs that require spending much of the day seated in an automobile. Similarly, airplane pilots spend much of the day seated in airplane seats. 
   For the most part, seats have several elements in common. They have a bottom portion, or seat pan, which receives the bulk of a user&#39;s weight, and a seatback, against which a user reclines. As relates to the seatback, a wide variety of mechanisms have been developed that purportedly provide back support for a user. Nevertheless millions of people continue to suffer from chronic and severe back pain caused by sitting for extended amounts of time. This is because conventional seatbacks have yet to provide back support that proactively resolve the medical causes of back pain, rather than the symptoms of back pain. 
   By way of background, the spine has four regions: cervical (neck), thoracic (upper back), lumbar (lower back), and sacral (tail bone). The sacrum is a large triangular fusion of five vertebrae that forms the base of the spine. The sacrum is located between the pelvic bones, which include the left and right ilium. The ilia each have a posterior border portion known as the posterior superior iliac spine (“PSIS”). The lumbar region includes the five vertebrae located above the sacrum, the thoracic region includes the twelve vertebrae located above the lumbar region, and the cervical region includes the seven vertebrae located above the thoracic region. Each region of the spine transitions into the adjacent region(s). For example, there is a thoracic-lumbar transition extending between thoracic vertebra 12(T12) and lumbar vertebra 1(L1). 
   As viewed from the side, the spine of a person with good posture forms a rearward curve known as the thoracic or kyphotic curve, and two forward projecting curves known as the lumbar or lordotic curve and the cervical curve. When taken together, these three curves form an S-shaped portion of the spine. This S-shape provides a great deal of strength, stability, flexibility, and endurance because the body primarily relies on the skeletal structures (i.e., the vertebrae) to support the weight of a persons body, rather than primarily relying on the musculature for support. 
   Relating to a user&#39;s posture, conventional seats have a number of shortcomings. First, conventional seats cause a user&#39;s spine to collapse from an S-shape into a C-shape. This collapse occurs because of improper back support. Stated differently, conventional seats lack strategically located support. Without strategically located support, the sacrum tilts rearward, and causes the spine to assume a C-shape. When the spine is in a C-shape, the user primarily relies on the musculature for support rather than skeletal structures. Sitting with the spine in a C-shape and over-relying on the musculature for support can lead to a number of immediate problems, for example, increased fatigue, increased pressure on the lumbar discs, or the creation of muscle stresses, strains, and spasms. Moreover, various long-term problems can also occur. These problems include pain in the lower back muscles, discomfort between the shoulder blades, tightening of neck muscles and muscle soreness and headaches. 
   A second problem is that conventional seats lack a contoured surface match between the surface of the seat and the surface of a user&#39;s anatomy. For example, conventional seats lack a proper nesting or receiving portion for the PSIS. In particular, the seat back pressures the PSIS. This can lead to poor posture, which often results in varying degrees of discomfort and back or spine problems. Forth, conventional seats provide poor distribution of the load forces experienced by the user. 
   Somewhat recently, it has been recognized that a spinal support device for applying a directed and concentrated force on the sacrum to properly position the pelvis and spine of a user could be constructed. In U.S. Pat. No. 6,125,851 (“the &#39;851 patent”), a spinal support device is disclosed that helps support the sacrum of a user to induce the spine to take the preferable shape found in a normal standing posture. 
   While the &#39;851 patent in part addresses the void created by seats around the sacral region, there still exists an urgent need to implement proper sacral support integrated within seatbacks, such as those used in residential seating, office seating, and/or vehicular seating. In particular, there exists a need to provide proper sacral support in a system that is integral to a seatback and adjusts according to the preferences of a variety of users that differ from each other in proportion and size. In addition, there exists a need to provide improved load distribution across the surrounding pelvic area, especially around the PSIS. 
   A full support system is also urgently needed, including proper primary sacral support combined with secondary or complementary support for other regions of the spine. Moreover, proper sacral support is urgently needed by persons that have obstructions between their backs and the seatbacks. For example, police officers often wear a belt with a handcuff wallet. The handcuff wallet forms a bulge or obstruction that makes sitting with good posture particularly difficult. Similarly, military personnel wear various body armors, and construction workers often wear bulky tool belts that can cause the spine to shift out of proper alignment when the worker is in a seated position. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to an improved seat. According to a first aspect of the present invention, the improved seat delivers adjustable, specific, stabilizing support, and contoured fit to a user&#39;s sacrum and sacral-pelvic anatomy, while allowing the user to wear a waist pack, a belt having a handcuff wallet, body armor, a tool belt, or other obstruction. The improved seat effects changes in a user&#39;s sacral anatomy that result in user efficiency, strength, and muscle control. The improved seat actively targets and controls specific portions of the sacrum, thereby increasing the comfort, endurance, and stability of a user. This is accomplished in an adjustable, convenient manner for users who differ from each other in proportion and size. Furthermore, the improved seat provides anatomically contoured fit by offering a surface match between the contours of a user&#39;s anatomy and the seatback. 
   According to a second aspect of the present invention, a sacral support assembly for use with a seat is provided. The sacral support assembly provides a support mechanism that primarily supports the sacrum and sacral-pelvic anatomy, while providing secondary or complementary support for one or more of the remaining regions of the spine. 
   As used herein the term “connected to” is intended to be interpreted broadly and to include direct and indirect connections. 
   As used herein the term “vehicle” is intended to be interpreted as broadly including transportation-related applications in general, for example, automobiles, airplanes, boats, trains, wheelchairs, etc. 
   These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings where: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front perspective view of an adjustable support system including a retracted sacral support and a retracted thoracic-lumbar support; 
       FIG. 2  is a side view of an adjustable support system including a sacral support and a thoracic-lumbar support; 
       FIG. 3  is a front perspective view of an adjustable support system including a sacral support in an extended position and a thoracic-lumbar support in an extended position; 
       FIG. 4  is a side view of an adjustable support system including a sacral support in an extended position and a thoracic-lumbar support in an extended position; 
       FIG. 5  is a front perspective view of an adjustable support system including a sacral support in an extended position and a thoracic-lumbar support in a partially extended position; 
       FIG. 6  is a side view of an adjustable support system including a sacral support in an extended position and a thoracic-lumbar support in a partially extended position; 
       FIG. 7  is an exploded view of a sacral support; 
       FIG. 8  is an exploded view of a complementary support; 
       FIG. 9  is a front perspective view of a sacral support in an extended position; 
       FIG. 10  is a front perspective view of a sacral support in a retracted position; 
       FIG. 11  is a side view of a sacral support in a retracted position; 
       FIG. 12  is a front perspective view of a sacral support in a retracted and tilted position; 
       FIG. 13  is a front perspective view of a seat having a sacral support and a thoracic-lumbar support; 
       FIG. 14  is a front perspective view of a seat having a sacral support, a thoracic-lumbar support, and a load distribution material; 
       FIG. 15  is a front perspective view of a seat having a sacral support, a thoracic-lumbar support, and a load distribution material; 
       FIG. 16  is a front perspective view of a seat having a sacral support, a thoracic-lumbar support, and a load distribution material; 
       FIG. 17  is a front perspective view of a seat having a sacral support, a thoracic-lumbar support, and a load distribution material; 
       FIG. 18  is a rear sectional view of a load distribution material for use with a sacral support system; 
       FIG. 19  is a rear sectional view of a load distribution material for use with a sacral support system; 
       FIG. 20  is a rear sectional view of a load distribution material for use with a sacral support system; 
       FIG. 21  is a rear sectional view of a load distribution material for use with a sacral support system; 
       FIG. 22  is a side sectional view of an adjustable support system including a sacral support in a retracted position and a complementary support in a retracted position; 
       FIG. 23  is a front perspective view of an adjustable support system including a sacral support in a retracted position and a complementary support in a retracted position; 
       FIG. 24  is a side sectional view of an adjustable support system including a sacral support in an extended position and a complementary support in an extended position; 
       FIG. 25  is a front perspective view of an adjustable support system including a sacral support in an extended position and a complementary support in an extended position; and 
       FIG. 26  is an exploded view of an adjustable support system including a sacral support and a complementary support. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The invention is described with reference to the drawings in which like elements are referred to by like numerals. The relationship and functioning of the various elements of this invention are better understood by the following detailed description. However, the embodiments of this invention as described below are by way of example only, and the invention is not limited to the embodiments illustrated in the drawings. It should also be understood that the drawings are not to scale and in certain instances details have been omitted, which are not necessary for an understanding of the present invention, such as conventional details of fabrication and assembly. Moreover, it should be noted that the invention described herein includes methodologies that have a wide variety of applications, including, for example, office, residential, and commercial seating applications. 
   Referring to the drawings,  FIG. 1  illustrates an embodiment of the present invention, and particularly, an adjustable support system having a sacral support system and a complementary support system. The adjustable support system can control the position of the user&#39;s sacral-pelvic region, thoracic-lumbar area, mid and upper thoracic area, or a wide variety of other parts of a user&#39;s back. Such support ultimately can be used to control the user&#39;s overall seated posture. 
   In general, the sacral support system includes a sacral support member that is configured to tilt vertically along a plane formed by the seatback. This allows a user wearing a utility belt, a waist pack, a handcuff wallet, body armor, or other obstructive element (even as small as a belt loop), to contact the sacral support without creating an uncomfortable pressure zone around the user&#39;s sacral area. The tilt feature thus allows the seatback to comfortably accommodate or nest an obstructive element without sacrificing comfort or sacral support. The sacral support system also includes a delivery mechanism that a user can use to adjust the amount of sacral support delivered by the sacral support system. 
   The sacral support system can be used either alone or in cooperation with complementary support system. In general, the complementary support system includes a support member and a delivery mechanism that is controlled by the user. The complementary support can be positioned within the seatback at a wide variety of positions that correspond with different areas of a user&#39;s back. For example, the complementary support system can be located within the seatback at a position corresponding with the thoracic-lumbar transition or the upper thoracic region of a user. The sacral support system and the complementary support system are each discussed in detail as follows. 
   Referring to  FIG. 1 , sacral support system  5  includes a sacral support member  14 , which is located within the seatback at a position that corresponds with the sacrum and sacral-pelvic anatomy of a user. The sacral support member is engineered to support the sacrum and sacral-pelvic anatomy of a user. The sacral support member preferably is formed of a substantially rigid material, such as steel, plastics, or carbon fiber, but materials providing a similar level of support can also be used. Sacral support member  14  is generally flat, pear-shaped, and oriented with a larger width at a top portion and a smaller width at a bottom portion. This shape and orientation coincides with the shape and orientation of the sacrum of a user. More specifically, an upper portion of sacral support member  14  has a horizontal width of approximately 3.25 inches. A lower portion of sacral support member  14  has a horizontal width of approximately 2.6 inches. Preferably, the vertical length of sacral support member  14  is approximately 5.25 inches. 
   The top width of sacral support member  14  can vary from 3 times the width of the sacrum of a user at the level of the sacral base of the user to approximately equal to the width of the sacrum of a user at the level of the sacral base of the user. The width of sacral support member  14  decreases progressively from a top portion to a bottom portion of sacral support member  14 . The width of the bottom portion is approximately greater than or equal to the width of the sacrum of a user at a level corresponding with the bottom portion. However, as discussed below, the dimensions of the sacral support member  14  may vary depending on a variety of factors. 
   Since sacral support member  14  is preferably rigid and mainly supports the sacrum, it is preferable to provide a load distribution material between sacral support member  14  and the sacrum of a user, as illustrated in  FIGS. 14-17 . For example, as illustrated in  FIG. 15 , load distribution material  98  provides a surface that adjusts to the contours of the sacrum and sacral-pelvic area of a user. Alternatively, as illustrated in  FIG. 18 , load distribution material  98  provides a contoured, nesting area for the PSIS&#39;s of the ilias. Other preferred arrangements and designs of the load distribution material are illustrated in  FIGS. 14-17  and  18 - 21 . For example,  FIG. 19  illustrates an embodiment in which the load distribution material  102  is partially butterfly-shaped.  FIG. 20  illustrates and embodiment in which two load distribution materials,  104  and  106 , are provided.  FIG. 21  illustrates a load distribution material  109  designed to generally cover the anatomical surfaces of the sacral-pelvic area, while also avoiding the PSIS&#39;s of the ilias. 
   In use, when sacral support member  14  is in an engaged position, the load distribution material improves load distribution across soft tissues of the sacral area of the user and avoids localized pressure on the PSIS&#39;s of the ilias. Preferably, conventional support materials may be used to provide load distribution, such as compressed foams, plastics or strips of lightweight metals, for example aluminum. The size and shape of the load distribution material may be altered to accommodate the user&#39;s specific anatomical contours and provide improved support and fit. The size and shape of the load distribution can also be altered depending on the particular seat trim package. For example, bucket type seats configured for racing applications can be outfitted with relatively rigid load distribution materials, so as to provide greater support and load distribution. 
   In addition, cushioning is preferably provided between the user, the front portion of the seatback and load distribution material. The cushioning may be formed of conventional cushioning materials such as foam. Accordingly, in a preferred embodiment, a front portion of the seatback is followed by a cushioning, which is followed by a load distribution material, which is followed by sacral support member  14 . Alternatively, a load distribution material can be provided between the front portion of the seatback and the cushioning. 
   It should be understood that the amount of load distribution material, cushioning, and the dimensions of the sacral support member are related, and can be altered while still achieving the desirable levels of sacral support and contoured fit. For example, to some extent, a sacral support member having smaller dimensions than discussed above may be used if a relatively large load distribution material or cushion is provided between the sacral support member and the user. Conversely, a larger sacral support member than suggested above may be used if relatively less cushioning and load distribution material is provided between the sacral support member and the user. Also, the sacral support member, the load distribution material and cushion may be formed of a unitary structure while still achieving the preferred results of sacral support and contoured fit. Similarly, the load distribution material can be attached directly to the sacral support member. 
   When the sacral support is in an engaged position, sacral support member  14  extends approximately between 1.5 inches and 3 inches forward with respect to a plane created by the seatback. It has been discovered that delivering sacral support member  14  a distance greater than about 3 inches forward of the plane created by the seatback is unnecessary. One embodiment of sacral support system shown in  FIGS. 1-6  and  9 - 12  is designed to deliver sacral support member  14  up to 1.25 inches forward of the plane created by the seatback. Notwithstanding this, alternative embodiments of the present invention may deliver sacral support member  14  a maximum distance up to or greater than 3 inches forward of the plane created by a user&#39;s back, or a maximum distance less than 3 inches forward of the plane created by a user&#39;s back, as described in detail below. 
   The overall distance of travel of sacral support member  14  toward the user depends on a variety of factors. For example, the overall distance of travel of sacral support member  14  may change depending on the location where the sacral support system is mounted within a seat frame, the size of the seat frame, the type of material used to cover the seat, and the thickness of any cushioning and load distribution material that may be located between the seat cover and sacral support member. 
   In addition to sacral support member  14 , sacral support system  5  includes a delivery mechanism having pitch poles  34 , cam profile channel  38 , parallel bar  40 , compression spring  44  and actuator cable  28 , as illustrated in  FIG. 7 . When used as a stand-alone unit, i.e., without a complementary support system, the sacral support system is attached to the seatback frame. As will become apparent to one of ordinary skill in the art, the cam profile channel  38  can be secured to the seatback frame, for example, by welding. Alternatively, when used in combination with a complementary support system, the sacral support system can be secured to base plate  16 , as shown in  FIG. 1 . In turn, base plate  16  is secured to the seat frame. 
   The delivery mechanism for adjusting the position of sacral support member  14  is illustrated in  FIGS. 9-10 . In particular, pin  55  is inserted through holes in pitch poles  34  and support base  36  so as to pivotally connect pitch poles  34  to support base  36 . This connection allows the support base to tilt relative to the pitch poles. A wide variety of alternative mechanisms for attaching the pitch poles to the support base will become readily apparent to one of ordinary skill, for example, a ball and socket connection. 
   As shown in  FIG. 9 , pin  54  is inserted through holes in pitch poles  34  and is used to slidably connect pitch poles  34  to cam profile channel  38 . The ends of pin  54  form cams that slide along the upper cam profiles  62  in cam profile channel  38 . In addition, pegs  56  are inserted into peg holes in pitch poles  34  and parallel bar  40 . Each peg  56  provides a cam surface that slides along lower cam profile  64  in cam profile channel  38 . Since the parallel bar is connected to both pitch poles, the pitch poles travel in tandem along the path created by cam profiles  62  and  64 . As illustrated in  FIGS. 9-10 , the geometry of cam profiles  62  and  64  define the path along which the sacral support member ultimately travels. Accordingly, the geometry of cam profiles  62  and  64  can be altered to change the path along which the sacral support member travels. For example, cam profiles  62  and  64  can be configured so that the sacral support member initially travels in a first direction and subsequently in a second direction. 
   As illustrated in  FIGS. 9 and 10 , in operation, a user determines the amount of desired sacral support and then operates the sacral support system to alter the position of the sacral support member. In a disengaged position sacral support member  14  provides minimal or no support to a user&#39;s sacrum or sacral area. As desired, a user may adjust the position sacral support member  14  toward the user&#39;s sacrum to provide increased support. In particular, when the sacral support system is used as a stand-alone support system (i.e., without a complementary support system), a standard take-up motor  99  can be used to control the position of the sacral support member relative to a user. 
   As take-up motor retracts actuator cable  28 , the end of actuator cable  28  that is adjacent to spring  44  causes spring  44  to compress against parallel bar  40 . As the energy stored in spring  44  increases, spring  44  eventually forces parallel bar  40  to move pitch poles  34 . Consequently, sacral support member  14  travels toward the user&#39;s sacral area as desired by the user. Conversely, the take-up motor can be operated to let out actuator cable  28 , thereby returning the sacral support member to a retracted position. Spring  44  and pressure from the seatback and cushioning material assist in returning the sacral support member to a fully retracted position. 
   When the sacral support system is in a fully or partly extended position, spring  44  forms a spring suspension. In particular, as a user reclines against the engaged sacral support member, the user&#39;s sacrum creates a rearward force on sacral support member. This force is distributed to pitch poles  34 , causing pitch poles  34  to rotate counter-clockwise. As pitch poles  34  rotate, sacral support member  14  tilts backward at an angle that substantially coincides with the tilt of a user&#39;s sacrum. As a result, sacral support member  14  automatically adjusts to the natural tilt of a user&#39;s sacrum, while simultaneously providing an adjustable supporting force. In addition, spring  44  continually urges the sacral support member towards a user, thereby providing continuous support, even as the user shifts between wide varieties of seated positions. The adjustable supporting force can be tailored by changing the size or stiffness of the compression spring, as required by various seating environments. 
   As stated above, sacral support system  5  can be used in cooperation with complementary support system  7 . Complementary support system  7  can be located at a wide variety of positions within the seatback so as to correspond with various targeted areas of the spine or adjacent anatomical structures of a user. For example, complementary support  7  can be located within the seatback at a position that allows a user to control fit, comfort and posture. In one such example, complementary support  7  can be located within the seatback at a level corresponding with a user&#39;s spine at the area between about thoracic vertebra 12 and lumbar vertebra 1. Alternatively, complementary support  7  can be located within the seatback at a position corresponding with the scapulae or paravertebral muscles of a user. Likewise, complementary support  7  can be located within the seatback so as to provide improved fit, comfort, and posture control by improving the contoured surface contacts between the user&#39;s anatomy and the seating surface. 
   As illustrated in  FIG. 8 , complementary support  7  includes a support member  18 , pitch poles  46 , parallel bars  50 , and a pull cable assembly  32 . Support member  18  can be formed of a rigid material, as described above relative to the sacral support member. Support member  18  is shaped to correspond with a targeted region of the back. For example, as shown in  FIGS. 1-6  and  8 , support member  18  is rectangular, so as to provide support to the thoracic-lumbar transition of a user&#39;s spine.  FIGS. 13-17  illustrate the location of support member  18  relative to the seatback and seat frame  4 . In particular,  FIGS. 13-17  illustrate support member  18  positioned within the seatback at a location that corresponds with the thoracic-lumbar transition of a user&#39;s spine. 
   The support member of the complementary support system can also be provided with a load distribution material as described above relative to sacral support member  14 .  FIGS. 15-17  provide various shapes in which a load distribution material  98  can be provided within a seatback. Additionally, a cushioning material as described above is also provided between the user and the support member  18 . 
   Referring to  FIG. 6 , support member  18  is pivotally connected by pegs  60  to pitch poles  46 . Pitch poles  46 , are slidably positioned within the walls of cam profile channel  48 , which is secured to base plate  16 . In general, the pitch poles are configured so that an end of the pitch poles travels away from the cam profile channel and toward a user&#39;s back. To achieve this, pins  58  are inserted into holes in pitch poles  46  and positioned within cam profiles  70  and  72 . In addition, parallel bars  50  connect pitch poles  46 . Parallel bars  50  are rotatably secured to pitch poles  46  by pins  60 . Parallel bars  50  force the pitch poles to move simultaneously relative to cam profile channel  48 . Because pins  58  track cam profiles  70  and  72 , the free ends of the pitch poles travel in a relatively linear path away from the cam profile channel. As a result, support member  18  is urged towards the targeted portion of the user&#39;s back. 
   Referring to  FIG. 8 , a drive system is used to deliver the complementary support member. The illustrative drive system includes a complementary support actuator  32 , a cable guide  74 , a cross-bar  76  connected to parallel bars  50 , a compression spring  52 , and a spring cap  53 . Complementary support actuator  32  is disposed axially through spring  52  and the center hole provided in cross-bar  76 . Spring cap  53  secures complementary support actuator to spring  52 . As such, when complementary support actuator  32  is pulled through cable guide  74 , pressure builds between spring  52  and cross-bar  76 . When the force stored in spring  52  exceeds the outside pressure applied by the seatback, parallel bars  50  begin to move toward cable guide  74 . As a result, support member  18  moves toward the user&#39;s back. 
   Referring to  FIGS. 1-6 , sacral support system  5  and complementary support system  7  are used in combination to provide both sacral support and thoracic-lumbar support. The adjustable support system can deliver support in a variety of configurations, which can be controlled by the user. For example,  FIGS. 1 and 2  illustrate a first embodiment of the present invention in which the sacral support member  14  and the complementary support member  18  are both retracted.  FIGS. 3 and 4  illustrate sacral support member  14  and complementary support member  18  fully extended.  FIGS. 5 and 6  illustrate sacral support member  14  fully extended and complementary support member  18  partly extended. 
   As illustrated in  FIGS. 1-6 , the adjustable support system can be configured so that a single control unit synchronously controls the position of both the sacral support system and the complementary support system. As shown in  FIG. 3 , actuator cables  24 ,  28 , and  32  are connected to lever  26 . When the main actuator cable  24  is retracted, lever  26  travels downward relative to the seatback. As a result, actuators  28  and  32  are retracted, thus effecting delivery of sacral support member  14  and support member  18 . The ratio of sacral support to complementary support is adjustable. This ratio can be adjusted by changing the position where the actuator cables are attached to lever  26 . As such, the adjustable support system can be configured so that the sacral support travels farther toward a user than the complementary support, thereby providing a greater level of specific support and comfort. 
   In addition, the adjustable support system of  FIGS. 1-6  includes a suspension. In use, pressure applied to the sacral support by a user&#39;s sacrum is counterbalanced by pressure applied to the complementary support by a user&#39;s thoracic-lumbar area. Moreover, springs  44  and  52  provide additional comfort by at least partly absorbing rearward forces created, for example, when a user changes positions in the seat, drives over uneven terrain, or encounters turbulence, depending on the application in which the adjustable support system is used. The stiffness of the spring suspension can be changed by using either stiffer or less stiff springs  44  and  52 , or by eliminating springs  44  and  52  altogether. 
   Adjustable support system  10  can be controlled by a conventional electric take-up motor or manually. A conventional rotary cam drive can facilitate manual operation. Other suitable drive systems include worm drives, and chain drives. Indeed, many alternate drive systems that can effect movement of an actuator cable or lever can be used to control the adjustable support system  10 . Moreover, it should be noted that the sacral support system can be configured to function synchronously or independently of complementary support system. 
   Referring to  FIGS. 22-26 , a second embodiment of an adjustable support system  10  is shown, including sacral support system  5  and complementary support system  7 . Adjustable support system  10  is configured to deliver sacral support member  14  and complementary support  18  a distance of 3 inches or more toward a user. Sacral support member  14  is configured as described above with respect to the previous embodiment. Complementary support member  18  is formed from a rigid, rectangular block, as illustrated in  FIG. 22 . 
   As illustrated in  FIG. 26 , similar delivery mechanisms are used to deliver the sacral support member and the complementary member. Sacral support system  5  includes lift arms  129 , cantilever arms  131 , and sacral support actuator cable  133 . As illustrated in  FIG. 24 , lift pin  141  is disposed through cam profiles  137  and lift arms  129 . Cantilever pin  143  is disposed through cantilever arms  131  and lift arms  129  so as to pivotally connect cantilever arms  131  to lift arms  129 . Support pin  145  secures an end of cantilever arms  131  to base plate  116 . Actuator cable  134  is secured to lift pin  141 . 
   Actuator cable  133  can be operated by a take-up motor or manually, as described above with respect to the previous embodiments. In particular, retraction of actuator cable  133  causes lift pin  141  to slide along cam profiles  137 . As lift pin  141  slides along cam profiles  137 , lift arms  129  pivot about cantilever arms  131  and cantilever pin  143 . Sacral support member  14 , which is pivotally attached to lift arm  129  (to provide a tilt as described above), travels towards a user&#39;s sacral area, thereby providing increased sacral support as shown in  FIGS. 24-25 . To decrease the amount of sacral support, a user operates the take-up motor (or manual drive) let out actuator cable  133 . As actuator cable  133  is returned to a disengaged position, the rearward force provided by the seatback and the user&#39;s sacrum moves sacral support member  14 , lift arms  129 , and cantilever arms  131  into a disengaged position, as shown in  FIGS. 22-23 . Optionally, a spring return system can be included to assist in returning the sacral support member to a disengaged position. To add a spring return system, a pin  167  is inserted into holes  163 , and a spring is used to connected pin  167  and lift pin  141 , as shown in  FIG. 25 . 
   Similarly, complementary support system  7  includes lift arms  127 , cantilever arms  125 , and complementary support actuator cable  134 . As illustrated in  FIG. 24 , lift pin  151  is disposed through cam profiles  139  and lift arms  127 . Cantilever pin  153  is disposed through cantilever arms  125  and lift arms  127  so as to pivotally connect cantilever arms  125  to lift arms  127 . Support pin  155  secures an end of cantilever arms  125  to base plate  116 . Actuator cable  134  is secured to lift pin  141 . 
   Actuator cable  134  can be operated by a take-up motor or manually, as described above with respect to the previous embodiments. In particular, retraction of actuator cable  134  causes lift pin  151  to slide along cam profiles  139 . As lift pin  151  slides along cam profiles  139 , lift arms  127  pivot about cantilever arms  125  and cantilever pin  153 . Complementary support member  18 , which is pivotally attached to lift arm  127 , travels towards a user&#39;s thoracic-lumbar area, thereby providing increased support as shown in  FIGS. 24-25 . To decrease the amount of complementary support, a user operates a take-up motor (or manual drive) let out actuator cable  134 . As actuator cable  134  is returned to a disengaged position, the rearward force provided by the seatback and the user&#39;s thoracic-lumbar area moves complementary support  18 , lift arms  127 , and cantilever arms  125  into a disengaged position, as shown in  FIGS. 22-23 . Optionally, a spring return system can be included to assist in returning the complementary support member to a disengaged position. To add a spring return system, a pin  169  is inserted into holes  161 , and a spring is used to connected pin  169  and lift pin  151 , as shown in  FIG. 25 . 
   Referring to  FIG. 22 , when sacral support system  5  and complementary support system  7  are in a fully retracted position, sacral support member  14  and complementary support  18  are generally flush with support base  116 . As a result, the user experiences little or no sacral or complementary support from the sacral support member and the complementary support member. As in the previous embodiments, the sacral support system can be provided as a stand-alone support system or in combination with the complementary support system. When the adjustable support system is provided with a sacral support system and a complementary system, the adjustable support system can be operated by a single motor  99 . For example, referring to  FIG. 26 , actuator cable  24  controls actuator cables  133  and  134 , and in turn, sacral support system  5  and complementary support system  7 . Additionally, since actuator cables  133  and  134  are interconnected by lever  26 , the adjustable support system  10  of  FIGS. 22-26  is controlled as described above with respect to  FIGS. 1-6 . That is, the ratio of sacral support to complementary support is adjustable by changing the position where the actuator cables are attached to lever  26 . Thus, the adjustable support system illustrated in  FIGS. 22-26  can be configured so that the sacral support travels farther toward a user than the complementary support, thereby providing a greater level of specific support to a user&#39;s sacral-pelvic area. In addition, since the adjustable support system and the sacral support system are both secured to lever  26 , rearward pressure applied to the sacral support by a user&#39;s sacrum or an obstructive element is counterbalanced by rearward pressure applied to the complementary support by a user&#39;s thoracic-lumbar area. 
   The embodiments described above and shown herein are illustrative and not restrictive. The scope of the invention is indicated by the claims rather than by the foregoing description and attached drawings of individual embodiments. The invention may be embodied in other specific forms without departing from the spirit of the invention. For example, other support systems may be used with the present invention. In addition, the shape and construction of the load distribution material and associated structures could be varied while still achieving the preferred functionality. For example, a unitary structure may be used instead of a separate cushion, load distribution material, and sacral support member. Additional cushions and load distribution materials may be included between the sacral support member and the user in accordance with the principles discussed above. In another alternative, the cushioning and/or load distribution materials may have cut-out portions adapted to, for example, receive the sacral support member or the PSIS&#39;s of the ilias. In yet another alternative, the load distribution material may partially support or cover the PSIS&#39;s of the ilias. In still another embodiment, a load distribution material and/or cushioning could be omitted entirely. In another embodiment, a pair of supports corresponding to the PSIS&#39;s of the ilias can be selectively adjusted in a rearward direction, thereby creating a central sacral support area. Accordingly, these and other changes that come within the scope of the claims are intended to be embraced herein.