Patent Publication Number: US-10315086-B1

Title: Baseball and softball slide trainer

Description:
I. BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The Invention is an apparatus for training softball and baseball players in the proper technique for sliding into a base. The apparatus and method of the Invention allow a student softball or baseball player to overcome his or her fear of falling and fear of impact in a controlled, low-risk environment while learning the skills required to safely slide into a base. 
     B. Statement of the Related Art 
     In the games of baseball and softball, a properly executed slide makes it more difficult for a position player manning a base to tag a runner. Sliding into the base is a necessary skill for any accomplished softball or baseball player; however, many young players are reluctant to learn the skill due to the fear of pain and injury. Conversely, a young player may injure him- or herself by attempting to slide without instruction and without the skills to execute a slide safely. For these reasons, youth softball and baseball coaches are reluctant to train players to slide or to even set aside regular time for sliding practice, yet players are expected to slide in games when sliding situations arise. This lack of time spent sliding is in stark contrast to the many hours players routinely spend practicing hitting, throwing and catching. 
     In a foot-first slide, a player sprints toward the base along the baseline and assumes the ‘ FIG. 4 ’ position with one leg outstretched toward the bag and the knee of the other leg bent with the ankle of the second leg under the knee of the first leg. The player bends slightly at the waist and raises his or her head and hands. The player lands in front of the base on his or her bottom and second leg and slides in the dirt toward base. If the player is using proper form, the player&#39;s head and hands do not touch the ground. 
     The friction of the player&#39;s pants against the dirt slows the sliding player. If the player correctly gauges his or her initial speed and the rate of slowing during the slide, the player will stop while in contact with the base. If the player misjudges his or her speed, the player may stop short of the base or may slide past the base. If the player uses incorrect technique in the slide, the player may injure him or herself due to friction or impact. 
     Slide training apparatus are known in the art. U.S. Pat. No. 4,887,811 to Tresh issued Dec. 19, 1989, U.S. Patent Publication 2014/0051531 by Mazzocchi published Feb. 20, 2014 and the Schutt Slide-Rite 2.0 product marketed by Kranos Corporation, 710 South Industrial Drive, Litchfield, Ill. 62056 teach mats for slide training. The Schutt product is representative. The Schutt Slide-Rite 2.0 product utilizes a mat composed of fabric-covered foam to absorb the impact of a student landing on the mat. The Schutt Slide-Rite 2.0 foam is thick, at about 2.5 inches. The relatively deep penetration of the student into the Schutt foam causes substantial friction between the student and the Shutt mat, which reduces the slide of the student and may stop the slide prematurely. The thick foam is also bulky, and may present issues of storage and transportation. 
     The prior art does not teach the apparatus and method of the Invention. 
     II. BRIEF DESCRIPTION OF THE INVENTION 
     The apparatus of the Invention is an apparatus for teaching a baseball or softball player the safe and proper technique for sliding into a base. The apparatus comprises a resilient pad and a load-spreading member. The resilient pad is composed of a resilient material, such as open cell foam. The resilient pad absorbs the impact of a softball or baseball student, either small or large, landing on the mat. 
     The load-spreading member spreads the force of the student landing on the mat to a larger area and volume of the resilient pad than would be the case without the load-spreading member. The nature of open cell polymer foams is that the foam experiences nearly linear strain over a range of applied stress in compression. Because of the nearly linear stress/strain relationship of the open cell foam, the student landing on the load-spreading member on the resilient pad penetrates into the open cell foam less than would be the case without the load-spreading member. Because the student does not penetrate deeply into the foam on landing, use of the load-spreading member allows the thickness of the open cell foam to be less than would be the case without the load-spreading member. The open-cell foam also can be less dense and hence lighter and less expensive than would be the case without the load-spreading member. 
     The load-spreading member is disposed over all or a part of the top side of the resilient pad. The load-spreading member has a length and a width and is of at least an adequate size to transfer the force of the student landing on the load-spreading member to an adequate area and volume of the open cell foam to cushion the landing of the student and to prevent the student from fully crushing the open cell foam. 
     The resilient pad has a pad thickness, a crushed thickness and an expanded thickness. The ‘pad thickness’ is the thickness of the resilient pad normal to the top or bottom sides of the resilient pad. The ‘crushed thickness’ is the reduced thickness of the resilient pad when a force is applied to the pad normal to the top side of the resilient pad so that the pad will no longer experience resilient deformation in response to additional force. The ‘expanded thickness’ is the thickness of the resilient pad when the pad is not subjected to a force normal to the top of the resilient pad. Both the resilient pad and the load-spreading member have a stiffness, with the stiffness of the load-spreading member being greater than the stiffness of the resilient pad. The thickness and stiffness of the load-spreading member and of the resilient pad are selected so that the force applied by the student landing on the load-spreading member will compress the resilient pad to between the expanded thickness and the crushed thickness. The student landing on the load-spreading member will not compress the resilient pad to the crushed thickness. If the student misses the load-spreading member and lands directly on the resilient pad, the student may crush the resilient pad to the crushed thickness. 
     The apparatus of the Invention may include a base on the top side of the mat to provide a target for the student and to allow the student to gauge whether a slide is the correct distance or is long or short. The base may be removable and repositionable, as by hook-and-loop fasteners, to allow the student to learn different aspects of sliding technique and to practice different sliding scenarios. 
     In a first embodiment, the load-spreading member does not cover the entire top surface of the mat and instead defines a stripe in the longitudinal direction along the center of the top side of the resilient pad. The stripe defines the path along which the student will slide. The top side of the mat may define a frame into which the load-spreading member slides to releasably attach the load-spreading member to the mat. The frame holds the periphery of the load-spreading member. The surface of the load-spreading member is exposed through the frame. A fastener retains the load-spreading member in the frame. The resilient pad may feature a fabric cover between the resilient pad and the load-spreading member and the fabric of the fabric cover may define the frame. 
     To use the apparatus of the first embodiment, a user places a sliding sheet on top of the load-spreading member and on the mat at the location on which the student will land. The sliding sheet is separate from the mat and may be composed of any suitable material, such as cotton or synthetic sailcloth, polar fleece, terrycloth, woven or non-woven fabric, a calendared polymer or any other suitable flexible sheet material. The purpose of the sliding sheet is to prevent abrasion injuries to the student from sliding on the resilient pad and load-spreading member and to control the friction between the sliding sheet and the load-spreading member. The sliding sheet has a first side and a second side. The sliding sheet may exhibit a single material on both the first and second sides. Alternately, the sliding sheet may be composed of two different materials that are joined, as by sewing, so that the two opposing sides exhibit the two different materials. Where the sliding sheet exhibits two different materials, the user may select the sliding friction by selecting one of the sides of the sliding sheet on which to slide. 
     To use the Invention, the student will run in the longitudinal direction toward the mat and assume the figure-4 position. The student will land on the sliding sheet on the load-spreading member. The vertical force of the student landing on the load-spreading member causes both the load-spreading member and the resilient pad below the load-spreading member to resiliently deform, absorbing the impact and cushioning the student. The forward momentum to the student causes the student and the sliding sheet to slide on the load-spreading member in the longitudinal direction. 
     If the student is inaccurate in his or her aim and lands either wholly or partially off of the load-spreading member, the student will experience high friction from the resilient pad and thus slow very quickly. The student also may fully compress the resilient pad if the weight of the student lands off of the load-spreading member, causing the student a bump his or her bottom on the surface below the resilient pad. Because of the stress and strain characteristic of the foam, the student will nonetheless impact the surface below the pad with less force than if the resilient pad were not in place. Both of these events cause the student to quickly learn the importance of an accurate takeoff and landing. 
     While the student is sliding, the student is tempted put to his or her hands down for balance, which is not proper technique for safety. For the first embodiment, if the student puts his or her hands down while sliding, his or her hands will contact either the resilient pad or will contact the sliding sheet on top of the resilient pad. In either event, the friction caused by the student&#39;s hands or the sliding sheet will quickly slow the student, shortening the student&#39;s slide. The student quickly learns not to put his or her hands down. 
     For the first embodiment, a tough and durable fabric, such as a vinyl-covered fabric, woven nylon or other fabric or solid vinyl may cover the mat, including the resilient pad. The fabric may define a frame, open to the top side of the mat, configured to receive the load-spreading member and into which the load-spreading member slides. A strip of a suitable fastener, such as hook-and-loop fastener, may retain the load-spreading member in the frame. The frame covers the periphery of the load-spreading member and protects the student from possible injury caused by an edge defect that possibly may exist on the load-spreading member. The fabric frame also protects the student from a possible pinch injury if the student manages to place a finger between the resilient pad and the load-spreading member. The load-spreading member may extend for only a portion of the length of the mat because the student will not slide the entire length of the mat. 
     Rather than defining a frame, the fabric may cover the entire load-spreading member so that the sliding sheet slides on the fabric rather than on the load-spreading member. 
     The mat may be divided into sections that are hinged and that accordion-fold from an extended condition to a folded condition. In the folded condition, the sections are in a compact suitcase-shape for ease of carrying. Hook-and-loop fasteners, snaps, straps or any other suitable mechanism may retain the sections in the folded condition. Each of the sections has a width normal to the longitudinal axis of the resilient pad. The load-spreading member may be configured to have a length equal to or less than the width of the sections so that the load-spreading member may be stored between two of the sections when the sections are in the folded condition. 
     Alternative avenues to protect the student from edges of the load-spreading member include selecting a material for the load-spreading member that cannot have an edge defect, such as high-density foam. A second alternative is providing a load-spreading member that will not break to define edge defects and to blunt all edges of the load spreading member to eliminate edge defects. Another alternative is to protect the edges, as by burying the edges in the open-cell foam. Burying the edges in the open cell foam can also act to control the stiffness of the load-spreading member in the longitudinal direction, reducing movement of the mat in response to the friction of a sliding student. 
     The resilient pad optionally may include a second, denser resilient layer below the layer of open cell foam. The denser second resilient layer is selected so that the if the student misses the load-spreading member and lands on the resilient pad, or if the student otherwise fully compresses the open cell foam layer, then the downward motion of the student will be arrested by the denser second resilient layer rather than by a hard surface on which the pad rests. 
     A second embodiment of the Invention may include the load-spreading member extending the entire length of the resilient pad along the longitudinal axis. The resilient pad and the load-spreading member may be covered by the durable and abrasion-resistant fabric so that the student will slide on the fabric rather than on the load-spreading member. 
     A third embodiment of the Invention is similar to the second embodiment except that the load-spreading member covers the entire top side of the resilient pad, from edge to edge. Providing that the load-spreading member covers the entire top side of the resilient pad means that the student will slide wherever the student lands on the sliding mat and is not limited to a stripe down the center. Covering the entire top side of the resilient pad with the load-spreading member also means that the edges of the load-spreading member are widely separated and the student is unlikely to encounter any edge defects of the load-spreading member that may exist. Covering the entire top side also improves the stability of the apparatus because the mat has even less tendency to bunch and to be pulled along behind the student as he or she slides. The tough and durable fabric layer may cover the resilient pad or both the load-spreading member and resilient pad of the third embodiment. The fabric covering of the third embodiment further separates the student from any edge defects of the load-spreading member, providing addition safety to the student. 
     For each of the embodiments, the mat may be hinged to allow the mat to fold from and extended position to a folded position having a compact size for storage and transportation. Three or four sections that accordion-fold are believed to be suitable. As an alternative to the single, un-hinged load-spreading member of the first embodiment, separate load spreading member portions may be attached to some or all of the folding sections. At the intersection between the adjacent sections, the downstream load-spreading member portion will be sloped to well below the elevation of the adjacent upstream load-spreading member portion so that the weight of the sliding student will pass smoothly from one section and from one load-spreading member portion to the next. The sloping downstream load-spreading member eliminates the possibility that the sliding student might run into the end of the downstream load-spreading member portion. The load-spreading member portions may not extend along all of the sections because the student will not slide for the entire length of the mat. 
     For each of the embodiments, the sections may be of different thicknesses. For example, a first section may be the designated landing location for the student, who will then slide across the second section to the target base located on the third (or a fourth) section. Only the resilient pad of the first section need be adequate to absorb the force of the landing student. The second, third and fourth sections need provide only minimal cushioning to the student as the student slides on those sections. As an alternative, the second section also may feature resilient pads that will absorb the force of the landing student who misses the first section while the third and fourth sections provide minimal cushioning. 
     For the second and third embodiments, the resilient pad and the load-spreading member are attached one to the other by any suitable mechanism, such as by an adhesive or by stitching. The load-spreading member may be retained in position on the resilient pad by the fabric covering, avoiding the use of adhesive, stitching or other attachment mechanism. 
     For each of the embodiments, the thickness and the stiffnes of the open cell foam in compression may be selected so that if a baseball or softball player practicing a slide were to land on the resilient pad without the load-spreading member, the player&#39;s body would compress the pores of the open cell foam completely to the crushed thickness and allow the downward motion of the player&#39;s body to be stopped by the surface underneath the open cell foam. By including the load-spreading member, each of the embodiments prevents that occurrence and transfers the force of the student&#39;s landing to an adequately large area and volume of open cell foam so that the student&#39;s downward motion is stopped by the open cell foam and not by the surface supporting the open cell foam. 
     For each of the embodiments, the resilient pad may include a second denser resilient layer to arrest the downward motion of the student in the event that the student, particularly a large and heavy student, fully compresses a less-dense layer during landing. 
    
    
     
       III. BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first embodiment of the Invention. 
         FIG. 2  is a perspective view of the load-spreading member of the first embodiment. 
         FIG. 3  is a detail sectional view of the mat. 
         FIG. 4  is perspective view of the first embodiment with the load-spreading member and sliding sheet ready for use. 
         FIG. 5  is a plan view of the sliding sheet showing the first and second sides. 
         FIG. 6  is a perspective view of the first embodiment in a folded condition. 
         FIG. 7  is a perspective view of a second embodiment. 
         FIG. 8  is an end view of the second embodiment. 
         FIG. 9  is a perspective view of the second embodiment having a fabric cover. 
         FIG. 10  is an end view of the embodiment of  FIG. 9 . 
         FIG. 11  is a perspective view of a third embodiment. 
         FIG. 12  is an end view of the embodiment of  FIG. 11 . 
         FIG. 13  is a perspective view of the embodiment of  FIG. 11  with a fabric cover. 
         FIG. 14  is an end view of the embodiment of  FIG. 13 . 
         FIG. 15  is an end view of a load spreading member having exposed edges. 
         FIG. 16  is an end view of the load-spreading member having edges with a first configuration. 
         FIG. 17  is an end view of the load-spreading member having edges with a second configuration. 
         FIG. 18  is a detail sectional side view of a joint between a first and a second section having separate load-spreading members. 
         FIG. 19  is a second detail sectional side view of a junction between the second section of  FIG. 19  and a third section having separate load-spreading members. 
         FIG. 20  is a detail sectional view of a joint between a first and a second section having different thicknesses. 
         FIG. 21  is a detail sectional view of a joint between the second section of  FIG. 20  and a third section. 
     
    
    
     IV. DESCRIPTION OF AN EMBODIMENT 
       FIGS. 1 through 6  illustrate a first embodiment of the Invention.  FIG. 1  shows a mat  2  having four sections  4 . The mat defines a first end  6  and a second end  8 . The mat  2  also defines a top side  10  and a bottom side  12 . From  FIG. 3 , the mat  2  is a resilient pad  24  and includes a layer of a resilient material  26 , such as open cell foam  28 . A durable, abrasion-resistant fabric  18  may provide a cover  20  for the mat  2 . Vinyl-covered woven fabric having a weight of 18 ounces/yard has proven suitable in practice as the abrasion-resistant fabric  18 . 
     From  FIG. 1 , the top side  10  of the mat  2  defines a frame  14 , shown in detail cross section in  FIG. 3 . The frame  14  is configured to receive and retain a load-spreading member  16 , shown by  FIG. 2 . The load-spreading member  16  selectably slides into the frame  14  from the mat first end  6 . A fastener  22 , such as a hook-and-loop fastener, selectably retains the load-spreading member  16  in place on the mat top side  10 . The frame  14  retains the load-spreading member  16  in place during use of the Invention. As shown by  FIG. 3 , abrasion-resistant fabric  18  may be attached to the cover  20  to define the frame  14 . Any suitable attachment mechanism may attach the frame  14  to the cover  20 , such as stitching or adhesive. 
     As noted above, the purpose of the load-spreading member  16  is to support a student landing on the load-spreading member  16  and to spread the impact of the landing student to a relatively large area of the resilient material  26 . The use of the load-spreading member  16  allows use of a thinner, lighter and hence less expensive resilient material  26 , such as open cell foam  28 , than would otherwise be the case without the use of the load-spreading member  16 . Exposure of the relatively slippery load-spreading member  16  on the top side  10  of the mat  2  also allows a lower coefficient of kinetic friction between the sliding sheet  34  and the mat  2 , allowing an inexperienced student to slide more easily than would otherwise be the case. 
     The load-spreading member  16  is a relatively thin and relatively stiff solid polymer such as poly(methyl methacrylate), polyethylene, polypropylene, polycarbonate, polystyrene, fiber-reinforced resin, or any other suitable material that is selected to be relatively thin compared to its length and width, relatively stiff, resilient in flexure, impact resistant, and to transfer the impact load to the resilient pad  24 . Corrugated plastic sheet  30  composed of polypropylene that is 3/16 inches (4 mm) in thickness and with a weight of approximately 700 grams/square meter has proven suitable in practice for the load-spreading member  16 . The corrugated plastic sheet  30  features polypropylene top and bottom layers and has polypropylene webs interposed between the top and bottom layers. Suitable corrugated plastic sheets  30  are available from Boxforless.com, of 6836 Lankershim Blvd., North Hollywood, Calif. 91605. 
     A base  32  is disposed on the mat top side  10  at the mat second end  8 . The base  32  mimics the appearance of a baseball or softball base and provides the student with a sliding target. The base  32  can be moved to different locations on the mat top side  10  at the mat second end  8  to allow the student to practice different sliding scenarios. The base  32  is releasably attachable to the mat top side  10  by any suitable mechanism, such as hook-and-loop fasteners. 
     To use the Invention, a student runs in the longitudinal direction  44 , shown by  FIG. 4 , assumes the figure-4 position and lands on a sliding sheet  34  that is on top of the mat  2 .  FIGS. 4 and 5  show the sliding sheet  34 . The sliding sheet  34  has a first side  36  and a second side  40 . The sliding sheet  34  may display the same material on the first and second sides  36 ,  40 . Alternatively, the sliding sheet  34  may display a first material  38  on the first side  36  and a second material  42  on the second side  40 . The choice of materials for the first and second sides  36 ,  40  affects the coefficient of kinetic friction between the sliding sheet  32  and the load-spreading member  16  when the student is on the sliding sheet  34  and the sliding sheet  34  is sliding on the load-spreading member  16 . 
     Where the sliding sheet has two different materials  38 ,  42 , the first side  36  of the sliding sheet  34  has a first material  38  that is relatively slippery and that results in a relatively low coefficient of kinetic friction when a student is on the sheet  34  and the first side  36  of the sheet  34  is sliding on the load-spreading member  16 . The relatively slippery material of the first side  36  of the sliding sheet  34  allows the student to slide easily on the mat  2 . 
     The second side  40  of the sliding sheet  34  exhibits a second material  42  resulting in a higher coefficient of kinetic friction when the student is on the sliding sheet  34  and the second side  40  of the sliding sheet  34  is sliding on the load-spreading member  16 . The second material  42  is selected to approximate the higher friction experienced by the student sliding into an actual base on the dirt of an actual baseball or softball diamond 
     A sliding sheet  34  with the first side  36  composed of polyester polar fleece and the second side  40  composed of cotton terrycloth has proven suitable in practice where the load-spreading member  16  is composed of corrugated plastic  30  as described above on a mat  2  having a resilient pad  24  of open cell foam  28  that is 1.5 inches thick. The polyester polar fleece, a soft-napped insulating fabric, provides a relatively low coefficient of kinetic friction. The cotton terrycloth provides a relatively high coefficient of kinetic friction. For a two-sided sliding sheet  34 , a user can select a higher or lower coefficient of kinetic friction by selecting which side  36 ,  40  of the sliding sheet  34  is against the load-spreading member  16 . 
     The Inventor conducted experiments to determine appropriate coefficients of kinetic friction between the sliding sheet  34  and the mat  2 . The inventor prepared a test mat having a resilient pad composed of open cell foam that is 1.5 inches thick and enclosed in a cover composed of an abrasion-resistant vinyl-covered fabric of 18 ounces per square yard in weight. The Inventor secured a load-spreading member  16  to the mat  2 . The load-spreading member  16  was composed of 4 mm thick corrugated plastic  30 , as described above. The Inventor determined that the combination of load-spreading member  16  and mat  2  to be suitable for the purpose and to adequately cushion students of different weights landing on the load-spreading member  16  and mat  2 . The Inventor secured the load-spreading member  34  of corrugated plastic  30  to the mat  2  using a frame  14 , as described above. After experimentation, the Inventor determined that a sliding sheet  34  exhibiting a first side  36  of polar polyester polar fleece provided a suitable low sliding friction to allow an inexperienced student to easily slide while learning sliding technique. After experimentation, the Inventor determined that a sliding sheet  34  exhibiting a second side  40  of cotton terrycloth exhibited an adequately high sliding friction to adequately mimic the friction that a baseball or softball player would experience when sliding into an actual base in the dirt on an actual baseball or softball diamond. The Inventor then derived the coefficients of kinetic friction for each of those combinations. The following table presents the results of that derivation: 
                                                                 sliding               Weight       Force   sheet           Subject   (lbs.)   Force (N)   (lbs.)   material   μ = F/W                                                        1   77.2   130.92   29.43   first   0.381       2   49.4   83.5   18.77   first   0.380       3   153   251.34   56.5   first   0.369       1   77.2   165.9   37.29   second   0.483       2   49.4   97.98   22.03   second   0.446       3   153   282.56   63.52   second   0.415                    
Where:
 
a) the subject identifies the human test subject,
 
b) the weight is the measured weight of the human test subject,
 
c) the force (N) is the measured force in newtons required to maintain sliding movement of the sliding sheet  34  along the load-spreading member  16  on the mat  2  with the human test subject on the sliding sheet  34 ,
 
d) the force (lbs.) is the force (N) converted to pounds,
 
e) the sliding sheet  34  material  38 ,  42  is the material in sliding engagement with the load spreading member  16 . The first material  38  is polyester polar fleece. The second material  42  is cotton terrycloth.
 
e) μ is the coefficient of kinetic friction and in this instance is the dimensionless ratio of the force (lbs.) to the weight (lbs.).
 
     From these data, the Inventor concludes that an acceptable value for the coefficient of kinetic friction between the low-friction first material  38  and the mat  2  is less than or equal to 0.39. Any combination of materials and configurations of materials that results in a coefficient of kinetic friction of less than or equal to 0.39 will allow an inexperienced student to easily and safely slide while learning proper technique. The Inventor also concludes that from these data an acceptable value for the coefficient of kinetic friction between the high-friction second material  42  and the mat is greater than 0.39. Any combination of materials and configurations of materials that results in a coefficient of kinetic friction of greater than 0.39 will adequately approximate the friction that the student will experience when sliding into an actual base on an actual baseball or softball diamond. 
     Any configuration for the sliding sheet  34 , mat  2 , abrasion-resistant fabric  18 , load-spreading member  16 , resilient pad  24 , and thickness of the resilient pad  24 , that result in coefficients of sliding friction within the indicated ranges are contemplated by the Invention. 
       FIG. 6  illustrates that the sections  4  of the mat  2  fold to a suitcase-shape that is readily transportable and storable. The size of the load-spreading member  16  is equal to or less than the size of one of the sections  4  and so the load-spreading member  16  may be carried and stored between two adjacent folded sections  4  without extending beyond the edges of the folded sections  4 . The sections  4  may be retained in the folded condition by any suitable mechanism, such as hook-and-loop fasteners, snaps, straps, or any other mechanism known in the art.  FIG. 6  shows four sections  4  of the first embodiment, but the mat  2  may utilize any number of sections  4 , including one, two, three or more sections  4 . 
       FIGS. 7 through 10  illustrate a second embodiment of the Invention. In the second embodiment as shown by  FIGS. 7 and 8 , the load-spreading member  16  extends in a stripe  46  the length of the mat  2  and is exposed on the top side  10  of the mat  2 . In a modification of the second embodiment as shown by  FIGS. 9 and 10 , the top side  10  of the mat  2 , including the load-spreading member  16  is inside the cover  20  defined by the abrasion-resistant fabric  18 . A student using the second embodiment of  FIGS. 9 and 10  will slide on the abrasion-resistant fabric  18  rather than the load-spreading member  16 . In other respects, the mat  2  of the second embodiment of  FIGS. 7-10  functions in the same manner as the first embodiment. 
       FIGS. 11-14  show a third embodiment. In the third embodiment, the load-spreading member  16  extends from edge-to-edge on the mat  2 .  FIGS. 11 and 12  illustrate the load-spreading member  16  as extending the full length of the mat  2 , but the load-spreading member may extend less than the full length. Providing the load-spreading member  16  that extends edge to edge reduces the consequences to the student of missing a narrower load-spreading member  16 . Alternatively, the width of the mat  2  may be reduced to make the mat  2  more compact and easier to store and transport.  FIGS. 13 and 14  show that the mat  2 , including the load-spreading member  16 , may be enclosed within the cover  20  composed of the abrasion-resistant fabric  18 . In the instance of  FIGS. 13 and 14 , the sliding sheet  34  will slide on the abrasion-resistant fabric  18  rather than on the load-spreading member  34 . 
     For the second and third embodiments, the load-spreading member  16  is in one or more portions that cooperate to define the entire load-spreading member  16  when the sections  4  of the mat  2  are unfolded. As a result, the portions of the load-spreading member  16  stay with the sections  4  with which they are associated. FIGS.  15 ,  16  and  17  illustrate configurations of the load-spreading member  16  to reduce the likelihood that a student may come in contact with an imperfection in the edge of a load-spreading member  16  when sliding on the mat  2 .  FIG. 15  illustrates a load-spreading member  16  that is exposed on the top side of the mat  2  and that is configured so that the edges of the load-spreading member  16  cannot define an imperfection, such as by selecting a closed-cell foam for the load-spreading member  16  or by rounding the edges of the load-spreading member  16 .  FIG. 16  shows that the edges of the load-spreading member  16  may be oriented downward and buried in the resilient pad  24 .  FIG. 17  is similar to  FIG. 16  and shows a different configuration of the edges of the load-spreading member  16  and the resilient pad  24  so that a student cannot come in contact with the edges of the load-spreading member  16 . 
     In the second and third embodiments of  FIGS. 7-14 and 18-21 , the load-spreading member  16  is divided into portions  48  and each portion  48  may remain attached to its respective section  4  when the mat  2  is folded. As a result, when the mat  2  is in the extended condition there is an intersection between adjacent portions  48  of the load-spreading member  16 . The intersection of the adjoining load-spreading member portions  48  is configured so that the sliding student will not run into the end of a portion  48  of the load-spreading member  16  as the student slides from one section  4  to the next. 
       FIGS. 18-21  illustrate configurations to prevent the sliding student from running into the end of a load-spreading member portion  48 .  FIGS. 18 and 19  show the junctions between a first  52 , second  54  and third  56  sections  4  of a three-section mat  2 .  FIG. 18  shows two adjacent sections  4  that are hinged at the top side  10  by the abrasion-resistant fabric  18 . The thickness of the resilient pad  24  of the second section  54  is reduced at the junction between the two sections  52 ,  54  so that the sliding student will pass smoothly from the first section  52  to the second section  54  and from the upstream portion  48  of the load-spreading member  16  to the downstream portion  48 .  FIG. 19  shows the junction between the second section  54  of  FIG. 18  and the third section  56 .  FIG. 19  is similar to  FIG. 18 , except that the hinge between the adjacent sections  4  is on the bottom side  12 . To accordion fold, adjacent sections  4  are hinged on alternating sides. 
       FIGS. 20 and 21  also show the junctions between a first  52 , second  54  and third  56  section  4  of a three-section mat  2 .  FIG. 20  illustrates that different sections  4  may have different thicknesses.  FIG. 20  shows a first section  52  that is thicker than the second section  54 . The student will land on the first section  52 , which may be thicker to absorb the impact. The second and third sections  54 ,  56  may be thinner because those sections are only required to support the student while he or she is sliding.  FIG. 20  also shows that if the adjoining sections  52 ,  54  differ in thickness then the second section  54  may not require height compensation for the load-spreading member  16  to avoid the sliding student running into the edge of the load-spreading member portion  48 . 
       FIGS. 20 and 21  also illustrate that the resilient pad may be composed of more than one material, in this instance the first resilient material  26  and a second resilient layer  50 . The second resilient layer  50  cooperates with the resilient material  26  to define the resilient pad  24 . The second resilient layer  50  may be selected to be relatively stiff so that if a student fully compresses the first resilient material  26  on landing, the impact of the student is nonetheless cushioned by the second resilient layer  50  rather than stopped by an unyielding floor or other hard surface below the mat  2 . 
       FIG. 20  and  FIG. 21  also show that adjacent sections  52 ,  54 ,  56  are hinged on alternating sides, with the first and second sections  52 ,  54  of  FIG. 20  hinged at the top side  10  and the second and third sections  54 ,  56  of  FIG. 12  hinged at the bottom side  12 . As noted above, to successfully accordion fold, adjacent sections  4  are hinged on alternating sides  10 ,  12 . 
     The following is a list of the numbered elements.
     Mat  2     Mat section  4     Mat first end  6     Mat second end  8     Mat top side  10     Mat bottom side  12     Frame  14     Load-spreading member  16     Abrasion-resistant fabric  18     Cover  20  for the mat   Fastener  22     Resilient pad  24     Resilient material  26     Open cell foam  28     Corrugated plastic sheet  30     Base  32     Sliding sheet  34     First side  36     First material  38     Second side  40     Second material  42     Longitudinal direction  44     Stripe  46     Portion  48  of the load-spreading member  16     Second layer  50  of the resilient pad  24     First section  52     Second section  54     Third section  56