with reference to fig1 a and 2b , the training aid indicated as a whole by the number 10 comprises a membrane 11 delimiting or defining a chamber 12 on the inside of the membrane . the membrane 11 is body having a wall that is made of a material impermeable to fluids . in one implementation , the membrane is made of a flexible material , such as a plastic . in other implementations , the membrane may be formed of polyvinyl chloride ( pvc ), polyurethane ( tpu ), synthetic rubber ( csm ), chlorosulfonated polyethylene ( cpse ), other polymeric materials or combinations thereof . in other implementations , the membrane 11 can be formed as a rigid , non - flexible body . the chamber 12 can be filled at least in part with a liquid l or small particles . the liquid can be water or other liquids with a similar viscosity . in other implementations , the liquid can have a higher viscosity and / or density than water . the small particles can be sand , or beads , pellets , balls , flakes , and / or pieces formed of a plastic material , a metal , a polyurethane , stone , glass , an elastomeric material , a thermoset material , and combinations thereof . the aid 10 can include a re - closable opening 13 to enable the liquid , the small particles , or combinations thereof to be added or removed from the chamber 12 of the membrane 11 . preferably , the remaining volume of the chamber 12 is filled with a gas g , for example compressed air . in other implementations , the gas may be ambient air , nitrogen or combinations thereof . the opening 13 is associated with a closure 14 positionable between a closed position and at least one open position . when closed , the closure 14 assists in sealing the chamber 12 . when opened , the liquid or particles can be added to or removed from the chamber 12 . preferably , the closure 14 is configured to be reclose - able so as to be opened and closed so as to allow the chamber to be filled or emptied several times . advantageously , the closure 14 can also be used to allow pressurized gas to be inserted into the chamber . in other implementations the closure 14 can be first and second spaced apart closures with the first closure configured for the adding or removal of the liquid or particles , and the second closure configured for adding or releasing gas into the chamber 12 . in one implementation , the membrane 11 is formed of a flexible material and can be shaped in such a way that , once the chamber 13 has been filled and sealed , the training aid takes on a specific shape for use . in the implementations illustrated in fig1 and 3 , the training aid can have , for example , an elongated tubular shape , more precisely a cylindrical shape . in other implementations , the aid 10 can be formed in other shapes , such as , for example , spherical , hemispherical , irregular , generally polygonal or combinations thereof . according to the invention , the membrane 11 is shaped in such a way that , once the chamber 12 has been filled and sealed , the training aid takes on a specific shape for use . in the implementations of fig1 and 3 , the training aid 10 has , for example , an elongated tubular shape , more precisely a cylindrical shape . the tension of the membrane 11 , and therefore the stiffness of the training aid 10 , can be regulated by increasing or decreasing the pressure of the gas in the chamber 12 . the tension of the membrane 11 , and therefore the stiffness of the training aid , can be regulated by increasing or decreasing the pressure of the gas in the chamber 12 . according to the invention , the chamber 12 comprises at least two compartments in fluid communication with one another . in the implementation of fig1 , the chamber 12 comprises three compartments 12 a , 12 b , 12 c , with the compartments separated by one or more walls 15 having one or more openings 16 to allow the liquid l to flow from one compartment 12 a , 12 b or 12 c to an adjoining compartment 12 a , 12 b or 12 c . in other implementations , the aid 10 may include 3 , 4 , 5 or more walls to defining 3 , 4 , 5 or more compartments . in practice , the wall 15 serves to limit the speed with which the fluid moves between the ends of the chamber , especially when the aid is moved quickly . in the implementation illustrated , the wall 15 comprises a lamina , the perimeter 15 a of which is connected to the inner surface 11 a of the membrane 11 . the lamina or wall 15 may be made of the same material as the membrane 11 or in another material . in the first case , the wall 15 or lamina can be thicker than the membrane 11 so as to have less flexibility and to give the aid greater stability when in use . alternatively , the lamina may be substantially rigid . suitable materials for the wall 15 include , for example , polycarbonate , polyethylene ( pe ), polyvinyl chloride ( pvc ), polypropylene , polymethylmethacrylate ( pmma ). polycarbonate , other polymeric materials or combinations thereof . the one or more openings 16 in the wall 15 enable the liquid to pass through the opening from one of the chambers 12 , 12 b or 12 c to another of the chambers 12 a , 12 b or 12 c . the openings 16 act as passages for the transfer of the liquid l between compartments . the size , number , and or position of the openings 16 in the wall 15 enable the flow of the liquid or particles to be controlled or governed . the total area of the openings with respect to the cross - section of the aid at the point where the wall is attached determines the speed at which the liquid can flow from one compartment of the chamber to another . the number of openings 16 and their size is chosen based on the damping effect one wishes to achieve on the liquid l inside the chamber 12 . in one implementation , each wall 15 defines a fluid passageway area that is composed of the collective area of the one or more openings 16 in the wall 15 or the porosity or permeability of the wall 15 . in one implementation , the fluid passageway ratio of the wall is the fluid passageway area over the surface area occupied by the wall 15 . in one implementation , the fluid passageway ratio is within the range of 0 . 5 and 3 . in another implementation , the fluid passageway ratio is within the range of 0 . 7 and 2 . the openings 16 , preferably , are circular in shape so as to avoid forces being concentrated on the edge of the openings , which could cause lacerations to the lamina . in other implementations , the openings can be form of other shapes such as polygonal , oval , irregular , or combinations thereof . advantageously , said openings 16 are distributed on the surface of the wall in such a way that the passage of the fluid is homogeneous and independent of the orientation of the aid in space . in the implementation illustrated , the openings 16 are arranged in a circular series around the axis of the tubular body . in alternative implementations , the wall 15 may be connected to the inner surface of the membrane only by one part of its perimeter . the passage of liquid may therefore be in the space between the wall and the inner surface of the membrane 11 . the wall may also comprise several separate laminas connected independently to the inner surface 11 a of the membrane 11 . in another implementation , the wall 15 may comprise a permeable , fibrous , natural or synthetic fabric . in this case also , by adopting a more or less permeable fabric , it is possible to vary the speed at which the liquid passes through the wall 15 to move from one compartment to another adjacent compartment . in another implementation , the wall may be formed partially of a permeable material and partially of a non - permeable material with or without openings . according to the invention , the chamber 12 may be provided with several walls 15 . in the implementation shown in fig1 , the walls 15 are arranged next to one another along the axis of the tubular body and parallel to one another . in his way , the damping effect on the inertia of the liquid is felt when the movement of the liquid l inside the chamber 12 takes place in a direction substantially parallel to the axis of the tubular body . in one implementations , the aid can include one or more handles or gripping members . in one implementation , there may be reinforcing strips 17 on the outer surface of the membrane 11 . preferably , said strips are placed on the membrane in the zone where the walls 15 are connected to the inner surface 11 a . the function of the strips is to make the membrane less deformable underneath as a result of the forces exerted on it by the walls when they are struck by the moving liquid . the training aid according to the invention is provided with gripping members 18 , such as handles or similar , for example , so that the aid can be grasped and moved when performing training exercises . in one implementation , the gripping members 18 can be a pair of spaced - apart handles to facilitate the grasping and maneuvering of the aid 10 . fig3 illustrates another implementation of the fitness training aid 10 . the chamber 11 can be provided with two spaced - apart transversely extending walls 15 within the chamber 12 , and a third wall 15 longitudinally extending between the first and second spaced apart walls 15 . the walls 15 can substantially perpendicular to one another . the training aid configured in such a way makes it possible to dampen the inertia of the liquid l when it moves around the chamber 12 , in different directions . starting from this implementation , it is possible to vary the number of walls 15 , arranging them partly parallel and partly transversal to one another . in other implementations , other numbers of walls or configurations of walls can be used to provide different properties , flow - rates , etc . of the liquid or particles within the membrane 11 . fig4 illustrates a training aid 10 where the membrane 11 , once it has been filled with the liquid l and the gas g , takes on a substantially spherical shape . in this implementation also , it is preferable to arrange at least two walls 15 transversal and intersecting with one another , so as to obtain a response from the aid that is as uniform as possible and independent of the grip position . the remaining characteristics of the training aid are the same as those described for the implementation shown in fig1 . while the preferred embodiments of the invention have been illustrated and described , it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention . one of skill in the art will understand that the invention may also be practiced without many of the details described above . accordingly , the present invention is intended to include all such alternatives , modifications and variations set forth within the spirit and scope of the appended claims . further , some well - known structures or functions may not be shown or described in detail because such structures or functions would be known to one skilled in the art . unless a term is specifically and overtly defined in this specification , the terminology used in the present specification is intended to be interpreted in its broadest reasonable manner , even though may be used conjunction with the description of certain specific embodiments of the present invention .
a fitness training aid including a flexible , impermeable membrane defining a chamber fillable at least in part with a first flowable material and at least in part with a second flowable material , at least closure coupled to the membrane , at least one gripping member coupled to the membrane , and at least one wall positioned within the chamber . the closure positionable between at least one open position enabling the first and / or second flowable materials to be introduced within the chamber , and a closed position that seals the first and / or second flowable materials within the chamber . the at least one wall and the membrane define at least first and second compartments within the membrane . the at least one wall enables fluid communication of the first and / or second flowable materials between the first and second compartments .