fig2 a shows an item of sports equipment which is particularly designed for sliding on snow or ice . the sports equipment comprises a front portion 10 and a rear portion 20 which are configured to be elongated and the longitudinal axes of which are approximately aligned . the front portion 10 comprises a raised shovel 12 which points in the direction of motion . the front portion 10 and the rear portion 20 are respectively formed as snow sliding boards , in particular in the shape of skis . as shown in fig2 a to 2 d , the ends 11 , 22 of the front portion 10 and rear portion 20 which point towards each other are disconnected , but could be connected to a pivoting joint 40 in the form of a hinge , as shown in fig2 d . the pivoting joint can in principle also be formed in another of the ways described in this document . the sports equipment shown in fig2 d is in principle structured in the same way as the sports equipment from fig2 a to 2 c . the front portion 10 and the rear portion 20 can be elastically deformed transverse to their longitudinal axis , i . e . about their transverse axis . the first portion 10 and the second portion 20 are connected by means of a crosspiece 30 , the flexural rigidity of which about the transverse axis is significantly greater than that of the first and second portions 10 , 20 , such that the crosspiece 30 can also be referred to as rigid . the crosspiece 30 is fastened to the first portion 10 and the second portion 20 by means of pivoting joints 13 , 23 . the pivoting joints 13 , 23 therefore form bearings for the crosspiece 30 , which are in principle torque - free , on the first portion 10 and the second portion 20 . if desired , a moment could be transmitted from the crosspiece 30 to the front and / or rear portion 10 , 20 by a spring member arranged on the pivoting joints . a damping member could also be provided which acts kinematically between the crosspiece 30 and the front portion 10 and / or rear portion 20 and damps pivoting movements between the crosspiece 30 and the front portion 10 and / or between the crosspiece 30 and the rear portion 20 . fig2 b shows the sports equipment from fig2 a when under a load during turning . the lateral edges which laterally enclose the sliding surfaces 14 , 24 of the first and second portions 10 , 20 conform to the motion curve , thus elastically bowing the first portion 10 and the second portion 20 such that the sliding surfaces 14 , 24 are convex . the deformation is caused by the centrifugal force f which the user of the sports equipment exerts on the crosspiece 30 . the skier wears a ski boot which is fastened to the crosspiece 30 by means of a binding ( not shown ). since the force f is arranged in the middle between the front joint 13 and the rear joint 23 , it is distributed uniformly between the joints 13 , 23 , wherein the force f / 2 acts on each of the joints . the line of application of the forces f / 2 passes through the respective design point k of the front and rear portions 10 , 20 . if a moment is applied to the crosspiece 30 , it is not relayed to the front and rear portions 10 , 20 . only the forces at the pivoting joints 13 , 23 change . if the skier shifts their centre of gravity towards the rear ( fig2 c ), the line of application of the force f moves further towards the rear and therefore nearer to the joint 23 . the joint 23 is therefore under the load of a force 3 f / 4 , while the front joint 13 is only under the load of a force f / 4 . despite the shift in the line of application of the force , a moment is not transmitted from the crosspiece 30 to the rear or front portions 10 , 20 . the forces at the front joint 13 and the rear joint 23 also pass through the design point k of the front portion 10 and rear portion 20 under these load conditions . this ensures that the edge of the front portion 10 and rear portion 20 remains constantly conformed to the motion curve and does not rise up . it can be seen from fig2 d that the crosspiece 30 is connected to the front portion 10 by a pivoting joint 13 which only permits a pivoting movement about one axis which is parallel to the transverse axis . the crosspiece 30 is also connected to the rear portion 20 by the joint 23 . the joint 23 exhibits two pivoting axes which are parallel to each other and parallel to the transverse axis . an intermediate piece is arranged between the two pivoting axes and performs a pivoting movement relative to the rear portion 20 and the crosspiece 30 when the rear portion 20 performs a pivoting movement relative to the crosspiece 30 . the intermediate piece serves as a length compensator when the front portion 10 is pivoted relative to the rear portion 20 by means of the hinge 40 . fig3 shows an alternative item of sports equipment in the form of a roller skate which comprises a boot for accommodating a foot . a first pivoting joint 13 for a front mount 10 and a second pivoting joint 23 for a rear mount 20 are arranged on the lower side of the boot . the front mount 10 and the rear mount 20 can be pivoted in relation to the boot , the rigid sole of which forms a crosspiece 30 , by means of the pivoting joints 13 , 23 . the front mount 10 comprises two bearings which each rotatably support a roller 15 relative to the front mount 10 . the rear mount 20 comprises two bearings which each rotatably support a roller 25 relative to the rear mount 20 . the mounts 20 , 10 are disconnected , but could for example be connected via a joint as described in this document ; alternatively or additionally , they could be connected via a spring and / or damping element . the four rollers 15 , 25 shown in fig3 are arranged in alignment in the longitudinal direction of the crosspiece 30 , i . e . in the middle beneath the boot , as can be seen from the lateral view in fig3 . with conventional inline skates , so - called grinding occurs during turning , wherein usually four or five rollers arranged in a straight line are moved along the motion curve , generating a relatively high degree of abrasion on the rollers . the arrangement in accordance with the invention remedies this , since the rollers 25 of the rear mount 20 can conform to the motion curve independently of the rollers 15 of the front mount 10 . the same applies to the mount 10 . as can be seen from fig3 , the front mount 10 and the rear mount 20 can only be pivoted about one axis , i . e . the transverse axis , which is parallel to the rotational axes of the rollers 15 , 25 . if the front mount 10 and rear mount 20 are connected by means of a pivot bearing 40 , as shown for example in fig2 d , the rear mount 20 is preferably connected to the crosspiece 30 by a joint 23 which permits length compensation . such a joint is for example shown in fig2 d . the joint 23 exhibits two pivoting axes which are parallel to each other and parallel to the transverse axis . an intermediate piece is arranged between the two pivoting axes which performs a pivoting movement relative to the rear portion 20 and the crosspiece 30 when the rear portion 20 performs a pivoting movement relative to the crosspiece 30 . the intermediate piece serves as a length compensator when the front portion 10 is pivoted relative to the rear portion 20 by means of the hinge 40 . fig4 a and 5 show a cross - section transverse to the longitudinal axis of a sliding board or ski , for example the ski from fig1 a to 1 c or the portions 10 , 20 in fig2 a to 2 d , which are referred to in the following as the ski 100 , wherein “ ski ” is to be understood to also mean a sliding board in general . the ski 100 comprises an upper side which is preferably formed by a faceplate 150 and arranged facing away from a sliding surface 160 on the lower side of the ski 100 . a patterned element can be arranged on the upper side and / or the faceplate 150 can comprise a patterned element . the sliding surface 160 is laterally enclosed or defined in the longitudinal direction of the ski 100 by an engaging edge 130 on each side , which is preferably formed as a steel edge . reference is additionally made to the engaging edge or steel edge described in this document . the engaging edge 130 comprises a multitude of perforations 131 which are arranged such that they are spaced from each other by a grid spacing r ( fig4 c ). the steel edges 130 are fastened directly to a lower tension - compression belt 120 via a connecting layer 135 , namely on the lower side of the lower tension - compression belt 120 , i . e . the side which points towards the sliding surface 160 . the steel edges 130 and the connecting layer 135 each comprise perforations 121 which are congruent with the perforations 131 of the lower tension - compression belt 120 . the perforations 121 are arranged along the longitudinal direction of the ski 100 in the peripheral region of the tension - compression belt 120 . the perforations 121 , 131 , which are formed as elliptical holes whose main axes point in the direction of the longitudinal direction of the ski 100 , therefore form a passage between the upper side of the tension - compression belt 120 and the lower side of the engaging edge 130 . the engaging edge 130 is shown to be approximately l - shaped , wherein one limb is parallel to the tension - compression belt 120 and the other limb is approximately perpendicular to the first limb . the perpendicular limb preferably forms the sharpened edge which can engage with the ground surface when the ski 100 is in use . the connecting layer 135 can for example be an adhesive . an upper tension - compression belt 110 is arranged between the upper side of the ski 100 and the lower tension - compression belt 120 in relation to the height of the ski 100 . the lower tension - compression belt 120 is arranged between the upper tension - compression belt 110 and the sliding surface 160 in relation to the height of the ski 100 . the upper tension - compression belt 110 comprises a multitude of perforations 113 which can be configured as elliptical holes with a main axis extending in the longitudinal direction of the ski 100 . the upper and lower tension - compression belts 110 , 120 are each arranged such that they are spaced from a neutral fibre when the ski 100 is flexed about a flexing axis transverse to the longitudinal direction and parallel to the sliding surface 160 , wherein the neutral fibre is arranged between the upper tension - compression belt 110 and the lower tension - compression belt 120 . the embodiment shown in fig5 substantially differs from the embodiment shown in fig4 a only in that instead of being separate from each other , the upper and lower tension - compression belts 110 , 120 are connected to each other , namely via one or more connecting portions 115 which extend through the neutral fibre and are preferably formed from the same material as the upper and lower tension - compression belts 110 , 120 . the upper tension - compression belt 110 and the lower tension - compression belt 120 and the connecting portion 115 are formed from one part in the embodiment from fig5 . in the embodiment from fig4 a , the upper tension - compression belt 110 and the lower tension - compression belt 120 are formed by separate parts . the connecting portion 115 is preferably arranged at an angle of between 45 ° and 90 ° in relation to the upper tension - compression belt 110 and the lower tension - compression belt 120 and likewise comprises perforations 116 which can be shaped in the same way as the perforations of the upper and lower tension - compression belts 110 , 120 . a plastic 140 which is injected by means of an injection - moulding method is injected around the upper tension - compression belt 110 and the lower tension - compression belt 120 . the plastic is preferably a thermoplast such as for example polyethylene . the plastic can be provided in a foamed or unfoamed form . other suitable plastics are for example thermoplasts which are fibre - reinforced , for example glass fibre reinforced . examples of these include polyamide 6 plastics and polyamide 12 plastics which are reinforced with glass fibres . the fibres can for example be short fibres exhibiting a length of for example 0 . 1 to 1 mm or long fibres exhibiting a length of for example 1 to 50 mm . plastics which contain long and short fibres can still be injection - moulded . the fibres can be inorganic or organic reinforcing fibres . the plastic 140 is additionally arranged or injected in the perforations 111 , 113 , 121 , 123 and 131 . this results in a substantially shear - resistant connection between the tension - compression belts 110 , 120 , the edges 130 and the plastic 140 . in other words , the plastic 140 , the upper tension - compression belt 110 , the lower tension - compression belt 120 and the edges 130 form a material composite . the area moment of inertia or the flexural resistance of the ski 100 about the aforementioned flexing axis can for example advantageously be adjusted in the design of the ski 100 by the distance between the tension - compression belts 110 , 120 and the neutral fibre and by the cross - section of the tension - compression belts 110 , 120 . the plastic 140 can form the upper side of the ski 100 . if a faceplate 150 is used , the faceplate can for example comprise projections ( not shown ) around which the plastic 140 is likewise injected , such that a firm bond between the plastic 140 and the faceplate 150 results . these or other projections ( not shown ) of the faceplate 150 can serve as spacers for the upper tension - compression belt 110 , such that the plastic 140 can be dispersed between the faceplate 150 and the upper tension - compression belt 110 . the upper tension - compression belt 110 ( fig4 a , fig5 ) can comprise an opening 112 which is formed as a hole in the planarly formed tension - compression belt , as shown for example in fig4 . the opening 112 exhibits a larger cross - section than the perforations 111 and 113 . the opening 112 is arranged approximately in the middle , i . e . within the middle third , in relation to the front and rear ends of the ski 100 . in this example , the opening is likewise elliptical , wherein the main axis points in the longitudinal direction of the ski 100 . fig4 c shows a lower tension - compression belt 120 in which the front end is arched upwards and forms a tip of the ski . the rear end of the tension - compression belt 120 is likewise arched upwards slightly , though not as much as the front end . it can be seen in fig4 c that each of the left - hand and right - hand peripheral region of the tension - compression belt 120 comprises a multitude of perforations 121 which are arranged such that they are spaced from each other by one or more grid spacings r in the longitudinal direction of the ski 100 and are for example arranged not more than 2 mm from the lateral edge of the lower tension - compression belt 120 , in order to advantageously establish a mechanical connection with the injection - moulded plastic . a multitude of uniformly distributed perforations 123 are arranged between the perforations of the left - hand and right - hand side and are arranged in a distribution up to the region of the upwardly arched front end of the lower tension - compression belt 120 . the openings arranged in the upwardly arched region or tip of the ski , which are larger than the perforations 123 , 121 , can on the one hand save weight in this region and on the other hand can reduce the strength in this region , since somewhat lower mechanism demands are made on the arched region or tip of the ski . the openings can therefore be larger than or exhibit a different shape to the perforations arranged between the arched region or tip of the ski and the rear end of the ski 100 . fig4 d shows the left - hand and right - hand edges 130 for the ski 100 from fig4 a or fig5 , which exhibit a smaller width , extending transverse to the longitudinal direction of the ski 100 , than the lower tension - compression belt 120 and comprise a multitude of perforations 131 which are arranged in a distribution in the longitudinal direction of the edges 130 or the longitudinal direction of the ski 100 and are spaced from each other by one or more grid spacings r . the perforations 131 are arranged such that they are congruent with the perforations 121 of the lower tension - compression belt 120 .
an item of sports equipment to be fastened to a person &# 39 ; s foot , the sports equipment including a rolling or sliding member by which the sports equipment can be rolled or slid along a ground surface , wherein the rolling or sliding member includes a front portion and a rear portion , wherein the front portion includes a roller or a sliding surface for the ground surface , and the rear portion includes a roller or a sliding surface for the ground surface , wherein the front portion and the rear portion are connected to a crosspiece .