Patent Publication Number: US-10780010-B2

Title: Reduced friction surface and method of use

Description:
FIELD AND BACKGROUND OF THE DISCLOSED TECHNOLOGY 
     The disclosed technology relates generally to reduced friction massage surfaces and devices, and, more specifically to massage surfaces formed utilizing multiple ball transfer units and method of use. 
     As known, a healthy spine is formed of bony vertebrae, which are interconnected by intervertebral joints and are held together by intervertebral ligaments. Between the vertebrae are disposed intervertebral discs formed of a fibrous tissue, which perform a damping function. The spine is retained in a normal state by a muscular framework supporting the vertebrae, joints, ligaments, and discs. 
     With age, for natural reasons as well as due to increased loads and a variety of other reasons, the muscular framework supporting the spine weakens. Consequently, the load on the intervertebral joints increases, and the mobility of the intervertebral joints and of the spine in general is impaired. Additionally, the intervertebral discs often become thinner and their damping function may deteriorate or be lost. As a result, the load on the vertebrae increases, causing the spine to compress and shorten. The damage to the spine and spinal cord and impaired movement of the spine and body, may result in various types of muscular dysfunction and/or dysfunction of the internal organs. 
     Decompression or stretching of the spine, as achieved, for example, by use of massage and massage surfaces, removes some of the load from the spine and helps improve or restore the function of the spinal cord. Consequently, stretching of the spine may also improve or restore muscular mobility and may strengthen the muscular framework supporting the spine. As such, decompression of the spine may be the start of a process of normalizing the function of the spine and restoring disturbed functions of the human body. 
     Stretching of the spine over a massage surface, requires motion of the body over the surface. As is well known in the laws of physics, a frictional force exists between a moving object and a surface on which the object is moving. As such, in order to move an object lying on a surface, one must overcome the frictional force by making an effort, or apply a force, greater than the frictional force. As the frictional force decreases, the force required to move the object also decreases. 
     Many different methods and devices have been proposed for reducing the frictional force between a moving object and a surface on which the object is moving. Some such methods and devices make use of balls to reduce the friction. 
     U.S. Pat. No. 5,096,308 to Sundseth is directed to ball units including a load-bearing ball seated in an essentially radially symmetric bearing units having ball bearings in a bearing shell. The load-bearing ball is held in the bearing unit by a securing apparatus. The bearing unit has a supporting structure that enables the bearing unit to be fixed in an opening of a carrier plate in such a way that it can support a load. Detents are provided to lock the unit in the opening against the load direction. 
     U.S. Pat. No. 3,466,697 relates to a spring-loaded ball transfer or caster unit, which includes means for releasably securing the ball unit to structures with which the ball unit is associated, and/or means serving to limit movement of the ball responsive to a load applied to the ball. Such ball transfer units are usable in a pallet or platform for moving a container or box, as on a conveyer belt. 
     However, there is a need in the art for massage surfaces which reduce the friction between the body of the person being massaged and the massage surface, to allow for easier and more effective stretching of the person&#39;s spine. 
     SUMMARY OF THE DISCLOSED TECHNOLOGY 
     The disclosed technology relates generally to massage surfaces and devices, and, more specifically to massage surfaces and devices formed utilizing multiple ball transfer units. 
     In accordance with an aspect of one embodiment of the present invention, there is provided a ball transfer unit including: 
     a housing element including:
         an elongate stem terminating, at one end thereof, in a base portion having a concave upper surface; and   a cylindrical portion extending from the base portion around the concave upper surface and forming a hollow cup;       

     a coating disposed within the hollow cup at least on the concave upper surface, the coating formed of a material having a low friction coefficient; 
     a plurality of ball bearings disposed within the hollow cup in engagement with the coating; and 
     a motion transfer ball disposed at least partially within the hollow cup in engagement with the plurality of ball bearings, 
     wherein the motion transfer ball is free to rotate in any direction relative to the hollow cup with substantially no friction. 
     In accordance with another aspect of one embodiment of the present invention, there is provided a reduced friction device for applying force to a body part of a human, the device including: 
     a base frame; and 
     a reduced friction surface mounted onto the base frame, the reduced friction surface including a plurality of ball transfer units each including a housing element housing a motion transfer ball, the plurality of ball transfers units arranged such that adjacent ones of the plurality of ball transfer units engage one another, 
     wherein each of the motion transfer balls is adapted for omnidirectional rotation relative to a corresponding the housing element and independently of other the motion transfer balls, 
     wherein the reduced friction surface is adapted to have the body part placed thereon during performing of a physical activity applying force to the body part, while reducing friction between the body part and the surface. 
     In some embodiments, each of the plurality of ball transfer unit includes: 
     the housing element, which includes:
         an elongate stem terminating, at one end thereof, in a base portion having a concave upper surface; and   a cylindrical portion extending from the base portion around the concave upper surface and forming a hollow cup;       

     a coating disposed within the hollow cup at least on the concave upper surface, the coating formed of a material having a low friction coefficient; 
     a plurality of ball bearings disposed within the hollow cup in engagement with the coating; and 
     the motion transfer ball disposed at least partially within the hollow cup in engagement with the plurality of ball bearings, 
     wherein the motion transfer ball is free to rotate in any direction relative to the hollow cup with substantially no friction. 
     In some embodiments, a diameter of the elongated stem is significantly smaller than a diameter of the base portion. 
     In some embodiments, a diameter of the motion transfer ball is commensurable with the size of the vertebral discs and intervertebral distances. In some embodiments, the diameter of the motion transfer ball is within the range of 15 mm to 40 mm. 
     In some embodiments, the coating is formed of at least one of metal, plastic, wood, glass, bone, or a combination thereof. 
     In some embodiments, a diameter of each of said ball bearings is in the range of 2 mm to 6 mm. 
     In some embodiments, a ratio between the diameter of the motion transfer ball and the diameters of the ball bearings is in the range of 5:1 to 20:1. 
     In some embodiments, each of the motion transfer ball, or the single motion transfer ball of one ball transfer unit, is formed of at least one of metal, plastic, wood, glass, bone, or a combination thereof. 
     In some embodiments, all the motion transfer balls are formed of the same material, the same material being selected from the group consisting of metal, plastic, wood, glass, bone, or a combination thereof. 
     In some embodiments, all the motion transfer balls have an equal diameter. 
     In some embodiments, the reduced friction surface includes a plurality of ball transfer unit blocks, each ball transfer unit block including a subset of the plurality of ball transfer units mounted onto a bracket, in each the ball transfer unit block, adjacent ones of the subset of ball transfer units engage one another, and the plurality of ball transfer unit blocks are arranged such that, for each first and second adjacent ball transfer unit blocks, that at least some of the ball transfer units of the first ball transfer unit block engage at least some of the ball transfer units of the second ball transfer unit block. 
     In some embodiments, the physical activity includes at least one of massage, sports exercise, medical exercise, muscle rehabilitation exercise, joint rehabilitation exercise, spinal decompression, and post-traumatic rehabilitation. 
     In some embodiments, the plurality of ball transfer units is arranged such that the body part placed on the surface engages only the motion transfer balls and does not engage the housing elements. 
     In some embodiments, the ball transfer units are arranged such that a load of the body part is substantially equally distributed among ones of the motion transfer balls disposed beneath the body part. 
     In some embodiments, the reduced friction surface includes a concave surface or a convex surface. 
     In some embodiments, the reduced friction surface is a planar surface. 
     In some embodiments, the reduced friction surface is angled at an acute angle with respect to the horizon. 
     In accordance with a further aspect of one embodiment of the present invention, there is provided a method for constructing a reduced friction device for use during physical activity applying force to a body part of a human, the method including: 
     obtaining a plurality of groups of ball transfer units as described hereinabove; 
     for each group in the plurality of groups, placing the stem of each the ball transfer unit in the group in a corresponding bore in a bracket, thereby to form a plurality of ball transfer unit blocks, wherein, in each the ball transfer unit blocks, adjacent ones of the ball transfer units engage one another; and 
     mounting the plurality of ball transfer unit blocks onto a surface frame such that for each first and second adjacent ones of the plurality of ball transfer unit blocks, at least one ball transfer unit of the first block engages at least one ball transfer unit of the second block, thereby to form a reduced friction surface. 
     In accordance with yet another aspect of one embodiment of the present invention, there is provided a method for treating a body part of a human subject, the method including: 
     constructing a reduced friction device as described hereinabove; 
     placing the body part of the human subject on the reduced friction surface; and 
     while the body part engages the reduced friction surface, performing a physical activity on the body part. 
     In some embodiments, performing a physical activity includes performing at least one of massage, sports exercise, medical exercise, muscle rehabilitation exercise, joint rehabilitation exercise, gravitational spinal decompression, and post-traumatic rehabilitation exercise. 
     In some embodiments the method further includes, prior to the placing the body part, angling the reduced friction surface relative to the horizon, and wherein the performing a physical activity includes performing the physical activity while the reduced friction surface is angled relative to the horizon. 
     In some embodiments, the force applied to the body part when the reduced friction surface is angled relative to the horizon is a gravitational force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A, 1B, 1C, 1D, and 1E  are, respectively, a perspective view illustration, a top plan view illustration, a side plan view illustration, a bottom plan view illustration, and a sectional illustration, of a ball transfer unit according to an embodiment of the disclosed technology. 
         FIGS. 2A and 2B  are, respectively, a perspective view illustration and a top plan view illustration of a bracket for housing a plurality of ball transfer units according to an embodiment of the disclosed technology. 
         FIGS. 3A, 3B, 3C, and 3D  are, respectively, a perspective view illustration, a narrow side plan view illustration, a broad side plan view illustration, and a top plan view illustration of a ball transfer unit block including the bracket of  FIGS. 2A and 2B  having housed therein ball transfer units of  FIGS. 1A to 1E . 
         FIG. 4  is a top plan view illustration of a surface formed of a plurality of ball transfer unit blocks of  FIGS. 3A to 3D  according to an embodiment of the disclosed technology. 
         FIGS. 5A, 5B, 5C, and 5D  are perspective view illustrations of the ball transfer unit block of  FIGS. 3A to 3D  mounted onto a base frame, according to four different embodiments of the present invention. 
         FIGS. 6A and 6B  are perspective view illustrations of a flat massage surface formed of a plurality of ball transfer unit blocks of  FIGS. 3A to 3D  mounted onto a linear base frame, where in  FIG. 6A  the linear surface base the ball transfer unit blocks are disposed in a dedicated track within the base frame, and in  FIG. 6B  the ball transfer unit blocks are disposed above the base frame. 
         FIGS. 7A and 7B  are perspective view illustrations of a convex massage surface formed of a plurality of ball transfer unit blocks of  FIGS. 3A to 3D  mounted onto a convex base frame,  FIG. 7B  being an enlargement of a portion of  FIG. 7A . 
         FIG. 8  is a schematic illustration of using a massage table including the flat massage surface of  FIG. 6A or 6B  to stretch the spine of a subject lying on the massage table. 
         FIGS. 9A and 9B  are schematic illustrations of using a convex massage barrel constructed according to the present invention, to stretch the hip joints of a human subject straddling the massage barrel and to stretch the spine of a subject lying on the massage barrel. 
         FIGS. 10A and 10B  are schematic illustrations of using a massage surface, constructed according to the present invention, for performing exercises and stretching the spine of a human subject against gravity, where in  FIG. 10A  the massage surface is convex, and in  FIG. 10B  the massage surface is flat. 
         FIGS. 11B and 11A  schematically represent the human spine in the compressed state and in the stretched (decompressed) state, respectively. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSED TECHNOLOGY 
     In an embodiment of the disclosed technology, a plurality of ball transfer units are used together to form a reduced friction surface. The reduced friction surface lies on a base, and is particularly useful for carrying out a physical activity on, or applying force to, a body part on the surface. For example, the body part may be massaged while on the reduced friction surface, or may be stretched so as to decompress the spine. Carrying out the physical activity on the reduced friction surface is particularly advantageous in that little friction is present thereby allowing for movement while applying less force, and the mass of the body part is distributed on the ball transfer units, and is spread out thereby, which is advantageous when stretching muscles or decompressing the spine. 
     According to an aspect of some embodiments of the teachings herein, there is provided a reduced friction device for applying force to a body part of a human, the device including a base frame, and a reduced friction surface mounted onto the base frame, the reduced friction surface including a plurality of ball transfer units each including a housing element housing a motion transfer ball, the plurality of ball transfers units arranged such that adjacent ones of the plurality of ball transfer units engage one another, wherein each of the motion transfer balls is adapted for omnidirectional rotation relative to a corresponding the housing element and independently of other the motion transfer balls, and wherein the reduced friction surface is adapted to have the body part placed thereon during performing of a physical activity applying force to the body part, while reducing friction between the body part and the surface. 
     Embodiments of the disclosed technology will become clearer in view of the following description of the drawings. 
     Reference is now made to  FIGS. 1A, 1B, 1C, 1D, and 1E , which are, respectively, a perspective view illustration, a top plan view illustration, a side plan view illustration, a bottom plan view illustration, and a sectional illustration, of a ball transfer unit according to an embodiment of the disclosed technology. 
     As seen, a ball transfer unit  10  is arranged about a longitudinal axis  12 , and, in some embodiments, is symmetrical with respect to the longitudinal axis. Ball transfer unit  10  includes a housing element  100  formed with an elongate stem  102  arranged along the longitudinal axis  12 . The stem  102  is terminated at an upper end thereof, in a base portion  104 . In some embodiments, such as the illustrated embodiments, the stem  102  is generally cylindrical. 
     The base portion  104  extends from stem  102  to a concave upper surface  106 , which, in some embodiments, may have a circular cross section. Typically, a diameter of the base portion  104  is significantly greater than a diameter of stem  102 , such that an annular shoulder  108  forms where stem  102  is connected to the lower surface of base portion  104 . This is particularly important in order to arrange, or pack, the ball transfer units very close to one another, as described in further detail hereinbelow. For example, a ratio between the diameter of stem  102  and the diameter of base portion  104  may be at most 1:2, at most 1:3, or at most 1:4. The specific ration between the diameter of stem  102  and the diameter of base portion  104  affects the overall weight of the housing element  100 . Extending upwardly from base portion  104 , about concave upper surface  106 , is a cylindrical portion  110 , having a diameter equal to, or slightly greater than the diameter of base portion  104 , such that an annular shoulder  112  forms where base portion  104  is connected to the cylindrical portion  110 . In some embodiments, such as the illustrated embodiment, the shoulder  112  may be slanted relative to the longitudinal axis  12 . Cylindrical portion  110  includes an outer wall  113 , which terminates, at an upper end thereof, in a lip  114 , which may be inwardly curved or slanted relative to the longitudinal axis  12 . Concave upper surface  106 , together with inner wall  116  of cylindrical portion  110 , form a hollow cup. 
     A coating  120  is disposed within the hollow cup on concave upper surface  106 , and, in some embodiments, on a lower portion of inner wall  116 . The coating  120  must be smooth so as to allow ball bearing engaged therewith to roll on the coating  120 . In some embodiments, the coating  120  may be formed of a material having a low friction coefficient, such as metal, plastic, wood, glass, bone, or a combination thereof. In some embodiments, the hardness of the coating should be equal to or greater than the hardness of the material from which the ball bearings are formed, to avoid deformation of the coating during use. 
     A plurality of ball bearings  130  are disposed within the hollow cup, and engage the coating  120  at concave upper surface  106 . A motion transfer ball  140  is placed within the hollow cup above ball bearings  130  and rests thereon, without engaging inner wall  116  of cylindrical portion  110 . At least a portion of the motion transfer ball  140  extends out of the housing element  100 , above lip  114 . Motion transfer ball  140  is free to rotate in any direction (omnidirectional rotation) relative to the hollow cup, with substantially no friction, due to its rolling on ball bearings  130  which engage and roll over coating  120 . 
     In some embodiments, concavity of inner wall  116  also ensures that motion transfer ball  140  cannot “pop out” of the housing element  100 . 
     In some embodiments, the motion transfer ball  140  is formed of at least one of metal, plastic, wood, glass, bone, or a combination thereof. 
     In some embodiments, a diameter of the motion transfer ball  140  is commensurable with the size of the vertebral discs and intervertebral distances. In some embodiments, the diameter of the motion transfer ball  140  is within the range of 15 mm to 40 mm. In some embodiments, a diameter of each ball bearing  130  is within the range of 2 mm to 6 mm. In some embodiments, a ratio between the diameter of each ball bearing  130  and the diameter of motion transfer ball  140  is in the range of 1:5 to 1:20. 
     Reference is now made to  FIGS. 2A and 2B , which are, respectively, a perspective view illustration and a top plan view illustration of a bracket suitable for housing a plurality of ball transfer units  10  according to an embodiment of the disclosed technology. 
     As seen in  FIGS. 2A and 2B , a bracket  200  includes a receiving portion  201  defining an outer surface  202 , the receiving portion  201  including a plurality of through-going receiving bores  204 , and at least one support  206  which supports the bracket  200  when standing on a base surface. The receiving bores  204  are typically circular, and have a circumference greater than the circumference of stem  102  ( FIGS. 1A to 1E ) and smaller than the circumference of base portion  104  of a ball transfer unit  10 . 
     In some embodiments, such as the embodiment illustrated in  FIGS. 2A and 2B , the receiving bores  204  are arranged in a single line, and the receiving surface comprises an elongate strip. In other embodiments (not shown), the receiving bores  204  may be arranged in multiple lines, a matrix, a square, a rectangle, or any other suitable arrangement. The shape of the receiving portion  201  and of surface  202  is selected to accommodate the arrangement of the receiving bores  204 . In some embodiments, the distance from one receiving bore  204  to a second, adjacent receiving bore  204 , is fixed. 
     In the embodiment illustrated in  FIG. 2A , the support  206  includes two support walls, extending from edges of the receiving portion  201  along an elongate side thereof. However, in other embodiments the support  206  may include four support walls extending from all four edges of the receiving portion, or any other configuration of support walls disposed along edges of the receiving portion. In some embodiments, the support  206  may include, in addition to support walls, a support base (not shown). In general, any suitable configuration of the support  206  is considered to be within the scope of the present invention, provided that the support  206  does not block the receiving bores  204  or interfere with the ability to accommodate stems  102  of ball transfer units  10  in the bores  204 . 
     Reference is now made to  FIGS. 3A, 3B, 3C, and 3D , which are, respectively, a perspective view illustration, a narrow side plan view illustration, a broad side plan view illustration, and a top plan view illustration of a ball transfer unit block  300  including bracket  200  of  FIGS. 2A and 2B  having housed therein a plurality of ball transfer units  10  of  FIGS. 1A to 1E . 
     As seen in the Figures, ball transfer unit block  300  includes a plurality of ball transfer units  10  disposed in bracket  200  such that stems  102  are received within receiving bores  204 . In some embodiments, annular shoulders  108  of ball transfer units  10  engage surface  202  of receiving portion  201 , as seen in  FIGS. 3A and 3B . In other embodiments, the stems  102  are supported such that annular shoulders  108  are disposed above, and are spaced from, the outer surface  202  of the receiving portion  201 . Since the motion transfer balls  140  of the ball transfer units  10  do not engage one another, each motion transfer ball  140  is capable of omnidirectional rotation relative to the housing element and independently of other motion transfer balls in the block. 
     It is a particular feature of the present invention that the receiving bores  204  are spaced such that the outer walls  113  of adjacent ball transfer units  10  engage one another, as seen clearly in  FIGS. 3C and 3D . Additionally, as seen clearly in  FIG. 3C , all the ball transfer units  10  are at a uniform height, when disposed in bracket  200 . This is particularly important for even load distribution on the ball transfer units, as explained in detail hereinbelow. 
     Each ball transfer unit  10  is fixed to bracket  200  by means of a nut, welding, glue or other means suitable for fixing housing element  100  of the ball transfer unit  10  to the bracket without restricting the movement of the ball bearings  130  or motion transfer ball  140 . 
     In some embodiments, all the motion transfer balls  140  in the block  300  are formed of the same material. In some embodiments, all the motion transfer balls  140  in the block  300  have the same diameter. 
     Reference is now made to  FIG. 4 , which is a top plan view illustration of a surface formed of a plurality of ball transfer unit blocks  300  of  FIGS. 3A to 3D  according to an embodiment of the disclosed technology. 
     As seen in  FIG. 4 , the brackets  200  of the ball transfer unit blocks  300  are arranged in parallel to one another, and are sufficiently close to one another such that outer walls  113  of adjacent ball transfer units  10  engage one another. 
     In some embodiments, the ball transfer unit blocks  300  are arranged such that empty space between ball transfer units  10  will be minimized. In one such embodiment, illustrated in  FIG. 4 , the outer wall  113   a  of a specific ball transfer unit  10   a  engages outer walls  113   b  of six neighboring ball transfer units  10   b , in a honeycomb like structure. In such embodiments, some of the ball transfer unit blocks  300  may have a greater number of ball transfer units than others. In the illustrated embodiment, ball transfer unit blocks  300   a  each include five ball transfer units, whereas ball transfer unit block  300   b  includes four ball transfer units. 
     Reference is now made to  FIGS. 5A, 5B, 5C, and 5D , which are perspective view illustrations of a ball transfer unit block  300  mounted onto a base frame, according to four different embodiments of the present invention. As seen, in each of  FIGS. 5A to 5D , a single ball transfer unit block  300  including a plurality of ball transfer units  10  is mounted onto a base frame  500  including two frame walls disposed in parallel to one another. 
     In the embodiment of  FIG. 5A , frame walls  502   a  each have a flat, or horizontal, upper edge  504   a . In the embodiment of  FIG. 5B , frame walls  502   b  each have a concave upper edge  504   b . In the embodiment of  FIG. 5C , frame walls  502   c  each have a mildly convex upper edge  504   c . In the embodiment of  FIG. 5D , frame walls  502   d  are hemispherical, and as such define a convex or hemispherical edge  504   d.    
     In all the illustrated embodiments, the ball transfer unit block  300  is placed at the center of the frame walls. However, it is appreciated that the ball transfer unit block  300  may be disposed anywhere along the edge of the frame wall, regardless of the curvature, or lack thereof, of the edge of the frame wall. 
     The ball transfer unit block  300  may be connected to the frame walls by any suitable means. In some embodiments, the frame walls included dedicated tracks, and the bracket  200  of the ball transfer unit  300  may be seated in, or snap fit into, the dedicated tracks. In other embodiments, the bracket  200  of the ball transfer unit  300  may be disposed upon the edge of the frame wall, and may be secured thereto by any suitable means, such as adhesive, soldering, nuts and bolts, nails, and the like. 
     Reference is now made to  FIGS. 6A and 6B , which are perspective view illustrations of a flat massage surface formed of a plurality of ball transfer unit blocks  300  mounted onto a linear base frame. 
     As seen in  FIGS. 6A and 6B , massage surfaces  600  thereof each include a plurality of ball transfer unit blocks  300 , arranged similarly to the arrangement shown in  FIG. 4 , mounted onto a base frame  602 . Specifically, the ball transfer unit blocks  300  are arranged such that the brackets  200  thereof are disposed in parallel to one another, and the ball transfer units  10  of adjacent blocks  300  engage each other in a honeycomb structure. 
     In the embodiment of  FIG. 6A , the base frame  602  includes a pair of frame walls  604   a  each including a planar, horizontal, upper surface  606   a . A channel  608  is disposed along each of frame walls  604   a , slightly beneath upper surface  606   a , the channel defining a resting surface upon which rest the brackets  200  of the ball transfer unit blocks  300 . 
     In the embodiment of  FIG. 6B , the base frame  602  includes a pair of frame walls  604   b  each including a planar, horizontal, upper surface  606   b . The brackets  200  of ball transfer unit blocks  300  rest directly on upper surface  606   b.    
     As discussed hereinabove, the brackets  200  may be secured to their resting surface, be it the channel  608  or the upper surface  606   b , using any suitable means, such as adhesive, soldering, nuts and bolts, nails, and the like. 
     Reference is now made to  FIGS. 7A and 7B , which are perspective view illustrations of a convex massage surface  700  formed of a plurality of ball transfer unit blocks  300  mounted onto a convex base frame,  FIG. 7B  being an enlargement of a portion of  FIG. 7A . 
     As seen, the convex massage surface  700  includes two frame walls  702 , each terminating, at an upper end thereof, in a convex surface  704 . A plurality of ball transfer unit blocks  300 , arranged similarly to the arrangement shown in  FIG. 4 , mounted onto a convex surface  704 . Specifically, the ball transfer unit blocks  300  are arranged such that the brackets  200  thereof are disposed in parallel to one another, and the ball transfer units  10  of adjacent blocks  300  engage each other in a honeycomb structure. 
     Turning now to  FIG. 8 , the Figure is a schematic illustration of a massage table  800  including a flat massage surface, similar to the massage surfaces shown in  FIGS. 6A and 6B , being used to stretch the spine of a subject lying on the massage table. 
     As seen in  FIG. 8 , the massage table  800  includes table supports  802 , which may be table legs as known in the art, and a table plate  804 . Table plate  804  includes, in a portion thereof, a flat massage surface  806 , which may be similar to massage surfaces  600  described hereinabove with reference to  FIGS. 6A and 6B . Other portions of table plate  804  do not define a massage surface, and have a flat or horizontal upper surface  808 . In some embodiments, the motion transfer balls of the massage surface  806  are disposed above upper surface  808 . In other embodiments, the motion transfer balls are flush with upper surface  808 . 
     The massage table  800  is usable to promote relaxation of muscles, and consequently, straightening and decompression of the spine. In the illustrated embodiment, a user  810  is lying on table plate  804  such that at least a torso thereof is disposed above massage surface  806 . In some embodiments, the massage surface  806  is constructed such that the user&#39;s body only engages the motion transfer balls  140 , and does not touch the housing elements  110  of the ball transfer units  10 . 
     Placement of the user&#39;s body on the flat massage surface, which has reduced friction as described hereinabove, allows the body and the spine to straighten due to the impact of gravity on the body. Specifically, as explained hereinabove, the massage surface  806  is constructed such that the ball transfer units  10  are attached to the brackets  200  without limiting the movement of ball bearings  130  or of motion transfer ball  140 , and each motion transfer ball  140  is capable of omnidirectional movement irrespective of movement of other ball transfer units. When the torso of user  810  is placed on the massage surface  806 , relative motion of the ball transfer units  10  results in spreading out of the mass of the user&#39;s torso on the massage surface  806 , or stretching the user&#39;s torso, in a similar manner to that of rolling out dough on a surface dusted with flour. When using massage table  800 , simply turning the body of user  810  body on its side, on its stomach or on its back, you can achieve such a stretching effect for all areas of the spine and surrounding the spine. 
     Additionally, carrying a traditional massage, applied by a massage therapist or other person while user  810  lies on massage table  800 , may enhance the stretching effect described above. This may be due to the fact that, as a result of the massage, the muscular framework surrounding and supporting the spine will relax, and slight pressure applied to the body during the massage promotes even greater spreading of the body and the spine along the table surface. Consequently, decompression of the spine will increase. 
     Furthermore, each of the ball transfer units  10  may function as an individual massage point, in part due to the fact that the motion of motion transfer ball  140  of each ball transfer unit  10  is capable of omnidirectional rotation independent of the motion of any other ball or ball transfer unit. As such, when the torso of user  810  is placed on the massage surface  806 , each ball transfer unit provides a separate massage point, such that a massage of multiple points, similar to a “shiatzu massage” occurs in parallel. 
     In some embodiments, the massage table  800 , and specifically the massage surface  806 , may further include one or more vibrational elements and a control mechanism for adjusting the amplitudes and periods of vibration of the vibrational elements. Vibration of the ball transfer units  10  during placement of the user&#39;s body thereon may further decompress the spine, and enhance the muscle relaxation effects of the massage. 
     In some embodiments, the planar massage surface  806  may be replaced by a convex massage surface, similar to that shown in  FIGS. 7A and 7B . A convex massage surface allows for a greater stretching force due to stretching of the muscles to conform to the shape of the surface, and as a result, to a higher degree of decompression of the spine. Additionally, on a convex massage surface, it is possible not only to straighten the spine, but also to bend the spine in a desired direction. 
     In some embodiments, a physical activity may be performed on the massage table, the physical activity including at least one of massage, sports exercise, medical exercise, muscle rehabilitation exercise, joint rehabilitation exercise, spinal decompression, and post-traumatic rehabilitation. The reduced friction provided by the massage surface may enable the user to invest less force in such physical activity, thereby resulting in the user achieving a greater range of motion and/or conserving more energy while carrying out the physical activity. 
       FIGS. 9A and 9B  are schematic illustrations of using a convex massage barrel  900  constructed according to the present invention, to stretch the hip joints of a human subject straddling the massage barrel and to stretch the spine of a subject lying on the massage barrel. 
     As seen, convex massage barrel  900  is formed of a base frame  902  including frame walls, each including a quadrilateral portion  904 , and a convex portion  906 . Mounted onto the convex portion  906  of the base frame  902  is a massage surface  908 , including a plurality of ball transfer unit blocks  300 , substantially as described hereinabove with respect to  FIGS. 7A and 7B . Massage barrel  900  is particularly characterized in having substantially large curvature of convex portion  906 . In some embodiments, the radius of curvature of convex portion  906  is in the range of 10 to 20 inches. 
     Turning specifically to  FIG. 9A , a user  910   a  is straddling massage surface  908 , such that the hips of the user engage massage surface  908 , and the user&#39;s legs hang down alongside quadrilateral portion  904 . In this position, the user&#39;s hip joints are stretched. This is particularly due to the fact that the reduced friction allows the user&#39;s legs to extend downward with gravity, without the user having to apply force to overcome the friction between the massage barrel and his body. Additionally, if weights are placed on the legs, and the user swings the legs back and forth, no burden is applied to the legs while restoring and strengthening ligaments and muscles that ensure the operability of the hip joint. 
     In  FIG. 9B , a user  910   b  is lying over the barrel such that his torso is aligned with the massage surface  908 . It is appreciated that placing a user&#39;s body on a strongly curved surface, such as massage surface  908 , greatly increases the degree of decompression action on the spine relative to when using a flat massage surface, regardless of whether the user is on his stomach, back, or side. Stretching of the spine on such a curved surface, even without additional load (known as passive stretching), also provides greater decompression of the spine than when using a massage surface having lower curvature. Performance of physical exercises on massage barrel  900 , when the body is forced from a curved positon to a horizontal position by forces of the muscles, or when the body bends in the opposite direction to the curvature of the barrel  900  (as in a sit-up), is designed to reinforce and/or fix the effect of decompression of the spine, and to strengthen the muscular corset surrounding the spine. 
     The reduced friction of massage surface  908 , stemming from use of ball transfer units, is advantageous when using a massage barrel for similar reasons to those described hereinabove with respect to  FIG. 8 , such as for the effect of spreading out the spine, and for the creation of multiple pressure points. 
       FIGS. 10A and 10B  are schematic illustrations of using a massage surface, constructed according to the present invention, for performing exercises and stretching the spine of a human subject against gravity, where in  FIG. 10A  the massage surface is convex, and in  FIG. 10B  the massage surface is flat. 
     As seen in  FIG. 10A , an exercise machine  1000 , which may, for example, be a “Swedish wall”, has a convex surface  1002  which is elevated from the ground by a base portion  1004 . A massage surface  1006 , similar to the massage surfaces of  FIGS. 6A to 7B , is disposed on a portion of convex surface  1002 . Attached to a bottom surface  1008  of base portion  1004  are a plurality of loads or anchors  1010 , which may be held or manipulated by a user. 
       FIG. 10B  illustrates massage table  1020  which includes a flat table  1022  mounted onto a base portion  1024  via an elevation mechanism  1025 . Table  1022  is substantially similar to table plate  804  of  FIG. 8 , and includes a planar massage surface  1026 , which may be similar to massage surfaces  600  of  FIGS. 6A and 6B . In some embodiments, table  1022  includes first and second ends  1030   a  and  1030   b , and an L-shaped leg rest  1032  is connected to second end  1030   b , and hangs downwardly therefrom. 
     The elevation mechanism  1025  is adapted to elevate at least a portion of table  1022  relative to base portion  1024 , and may be hydraulic, pneumatic, or any other suitable type of elevation element. In the illustrated embodiment, table  1022  is elevated such that first end  1030   a  engages the base portion  1024 , and leg rest  1032  is elevated in the air above the base portion. As such, in the embodiment of  FIG. 10B , table  1022  is slanted relative to base portion  1024 . Free standing weights, such as kettle ball  1034 , dumbbells, or other weights may be disposed adjacent massage table  1020  for use during treatment thereon. 
     Exercise machine  1000  of  FIG. 10A  and massage table  1020  of  FIG. 10B  are used in a similar manner. A user  1040  lies on convex surface  1002  or on an upper surface of table portion  1022 , such that at least a torso thereof is disposed on the massage surface  1006  or  1026 . In the embodiment of  FIG. 10A , the user  1040  lies on the surface  1002  such that the head thereof is disposed higher than the knees, whereas in the embodiment of  FIG. 10B , the user lies on the surface  1022  such that the head of the user  1040  is disposed lower than the knees of the user, and the user is facing “down-hill” on the device relative to the horizontal plane. 
     The devices of  FIGS. 10A and 10B  are designed for passive (no added load) and active (with added loads) decompression of the spine and restoration of the mobility of the musculoskeletal system. Using the devices  1000  and  1020 , stretching and/or decompression of the spine is achieved by placing the human body on the reduced friction surface defined by massage surface  1006  or  1026 , while the reduced friction surface is inclined relative to the horizontal plane. The body of the user  1040  is fixed to the inclined surface, for example by holding anchors  1010  of device  1000  of  FIG. 10A , or by anchoring the shins of the user to the leg-rest  1032  of massage table  1020  of  FIG. 10B . Such fixation does not allow the user to slip along the reduced friction surface  1006  or  1026  under the gravitational force, while assisting in stretching the spasmodic muscles and decompressing and/or stretching the spine and joints. The degree of stretching and decompression can be adjusted by adjusting one or more of the following:
     an angle of inclination of reduced friction surface on which the human body is placed—this adjusts the passive decompression; and   a load pulling down any part of the body below the point at which the body is fixed to the inclined surface—this adjusts active decompression.   

     Various physical exercises may be carried out on the devices of  FIGS. 10A and 10B , when the user&#39;s body is downwardly inclined and vertical loads are removed from the spine and joints may include:
     pull ups when holding an anchor, such as anchors  1010 ;   lifting the legs and bending the torso, as illustrated by dashed lines in  FIG. 10A ;   flexion and extension of the torso; and   hand work with free loads, such as kettlebells or dumbbells  1034  illustrated in  FIG. 10B .   

     More generally, at a time when the spine and joints are in a stretched state, any additional decompression action exerted or carried out helps to restore the mobility of the musculoskeletal system. 
     Reference is now made to  FIGS. 11A and 11B , which are schematically represent the human spine in the compressed state and in the stretched (decompressed) state, respectively. Comparison of  FIG. 11A , in which the user&#39;s torso is inclined and the spine is well stretched, to  FIG. 11B , in which the user&#39;s torso is horizontal, or laying on a flat surface, and the vertebrae of the spine remain very close to one another, illustrates the advantages of using the systems of  FIGS. 10A and 10B  for spinal decompression, as compared to using a massage table having a flat surface, such as the massage table of  FIG. 8 . 
     While the disclosed technology has been taught with specific reference to the above embodiments, a person having ordinary skill in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the disclosed technology. The described embodiments are to be considered in all respects only as illustrative and not restrictive. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. Combinations of any of the methods and apparatuses described hereinabove are also contemplated and within the scope of the invention.