Patent Publication Number: US-7713180-B2

Title: Partially stabilized exercise device with valve mechanism

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 10/718,005, filed Nov. 19, 2003 now abandoned, and entitled “PARTALLY STABILIZED EXERCISE DEVICE”. U.S. patent application Ser. No. 10/969,539, filed Oct. 20, 2004, and entitled “PARTIALLY STAIBILIZED EXERCISE DEVICE,” which is abandoned, is incorporated herein by reference in its entirely. 
    
    
     BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     The present invention relates generally to exercise equipment. More specifically, embodiments of the present invention relate to exercise devices, such as stability balls, that enhance the user&#39;s exercise by destabilizing the user. 
     2. The Related Technology 
     Over the years those engaging in physical fitness exercises have used a variety of different ways to achieve their desired exercise goals. For example, individuals exercise by carrying out routines using their own weight for resistance, such as push-ups and sit-ups. To meet their exercise needs, exercisers have also used hand weights and/or devices that use a system of cables, pulleys, weights, springs, and/or resilient 
     Recently, however, those engaging in physical fitness activities have recognized the value of exercise devices that place the user in an unstable position. One such device is a stability ball, also known as an exercise ball or Swiss ball. 
     The stability ball is a large flexible ball that is used to create instability during an exercise routine. As the unstable user exercises, he or she exercises his or her core muscles to maintain balance during the exercise routine. For instance an exerciser can lie on the stability ball while exercising with hand weights. The instability of the ball requires the user to flex and exert core body muscles to maintain balance while performing the hand weight exercise. Instead of simply exercising a targeted group of muscles, the exerciser on a stability ball also uses core or stabilizing muscles, particularly those in the abdominal region. Stability balls are known to develop balance and stability by exercising the core body muscles. 
     One problem with stability balls, however, is that stability balls have a tendency to move or roll relative to an underlying support surface. While it is desirable for the stability ball to create instability in an exerciser, it is undesirable for the stability ball to randomly move or roll relative to the support surface. For example, a stability ball that is instable with respect to the support surface tends to roll out of position unless the user is continuously in contact with it. A user can become occupied with maintaining the position of the ball, thus detracting from the core body training experience. 
     A particularly advantageous solution for stabilizing a stability ball is to place a small amount of sand or other filler material in the ball. One difficulty with placing a filler material in a stability ball is that traditional valves make it difficult to inject the filler into the ball. Furthermore, valves currently in use with stability balls prevent certain grains of filler from being placed in the ball due to grain size. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the present invention overcome various aspects of the aforementioned problems by providing an exercise device, such as a stability ball, that is at least partially stabilized with respect to a support surface and that can be easily filled with a filler material. 
     In an exemplary embodiment, the partially stabilized exercise device includes a removable valve main body that allows a filler material to be easily placed in the inflatable bladder through a large aperture in the bladder. Once the filler material is in the inflatable bladder, the valve main body is fitted into the large aperture in the bladder. The aperture in the bladder and a portion of the valve main body are configured to engage to form a seal. 
     The valve main body also includes a small aperture for inflating the bladder with air. Any valve of a suitable size can be used in the valve main body. For example, a suitable valve includes a channel that is occluded using a stem plug. 
     Upon inflation, the bladder forms a stability ball or similar shaped device. In one embodiment, the exercise device has a diameter greater than 15 cm and its thickness, surface area, and dimensions are configured to support the weight of a user exercising thereon. 
     A loose filler is disposed within the exercise device. The filler is a flowable material that can move inside the ball when the ball is moved. For example, the filler can be a material such as sand that flows on the inner surface of the ball in the event that the ball is moved, such as when the ball is rolled along a floor. 
     The weight of the filler is selected according to the size of the ball and the desired stability. Generally the more voluminous the ball the more filler that can be utilized to stabilize the exercise device with respect to the support surface. In one embodiment, the ratio of the weight of the filler to the diameter of the ball is in a range from about 3.5 grams/cm to about 35 grams/cm. In another embodiment, the ratio is in the range from about 10 grams/cm to about 25 grams/cm. In yet another embodiment, the ratio is about 15 grams/cm to about 20 grams/cm. In another embodiment, the amount of filler is related to the volume of the inflated bladder. For example, in one embodiment the ratio of the weight of the filler to the volume of the ball is in a range from about 2 grams/liter to about 26 grams/liter. In another embodiment, the ratio is from about 6 grams/liter to about 20 grams/liter. In yet another embodiment, the ratio is from about 10 grams/liter to about 16 grams/liter. 
     The filler is selected to flow on the interior surface of the ball. The amount of filler in the ball is relatively small such that it forms a small pile or layer at the bottom of the ball. This small amount of weight, however, is effective for minimizing unwanted movement of the ball on a flat surface. However, the amount of filler utilized is sufficiently small that it does not appreciably affect the instability that a user experiences when exercising or balancing on the ball. 
     The improved exercise device of the present invention advantageously provides a bladder that is instable with respect to a user but stabilized with respect to a surface. The stability of the exercise device with respect to the surface allows a user to place the stability ball at a desired location without the ball moving or rolling away. This feature frees the user to attend to other devices and/or matters without needing to prevent movement or rolling of the ball. 
     In one embodiment, the stability ball of the present invention has a small amount of filler so that the overall operability of the ball during exercises is largely unchanged, while the unwanted movement of the ball is minimized when the ball is not in use. The forces exerted by the user on the ball are much greater than the resistance to rotation created by the filler. Consequently, the user&#39;s stability on the ball and exercise benefits provided by the ball are essentially unaffected by the filler. As such users of the stability ball of the present invention can perform all the beneficial exercises associated with other stability balls. 
     The valve mechanism of the present invention facilitates the placement of the filler material in the stability ball. The large aperture in the bladder allows the filler material to be easily placed in the stability ball, while the small aperture in the valve main body allows the stability ball to be easily inflated with air. By providing a two aperture system, the stability ball can be easily filled by someone other than the manufacturer, such as a retailer, wholesaler, or even the user. Because the stability ball can be easily filled with filler material, the stability ball can be manufactured and then shipped to another location before the filler material is placed in the ball. Shipping the stability ball without the filler material can significantly reduce shipping costs. 
     The present invention also includes methods for depositing the filler (e.g., sand) in the inflatable bladder. In an exemplary embodiment forced air is used to assist depositing a proper amount of filler in the bladder. The stability ball is inflated or partially inflated as the air and filler (e.g., sand) are forced into the ball. Once the filler is deposited in the bladder, the air can be released to compress the ball for packaging and/or shipping. Depositing the filler using forced air significantly reduces the time it takes to insert the filler through the valve. The methods of depositing the filler material in the inflatable bladder are advantageous because they allow the stability ball to be shipped without the filler material to reduce the weight during shipping, thereby saving costs. 
     These and other features of the present invention will become more fully apparent from the following description and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates a perspective view of an exemplary exercise device of the present invention; 
         FIG. 2  shows a cross-section elevational view of the exercise device of  FIG. 1 ; 
         FIG. 3A  shows a cross-section elevational view of the exercise device of  FIG. 1 , prior to movement of the ball; 
         FIG. 3B  shows a cross-section elevational view of the exercise device of  FIG. 3A , undergoing movement; 
         FIG. 3C  shows a cross-section elevational view of the exercise device of 
         FIG. 3A , after the exercise device has undergone movement and come to rest; 
         FIG. 4A  shows a perspective view of the exercise device of  FIG. 1  having a translucent bladder; 
         FIG. 4B  shows a perspective view of the exercise device of  FIG. 4A  in a larger size and having more filler therein; 
         FIG. 4C  shows a perspective view of the exercise device of  FIG. 4B  in a larger size and having more filler therein; 
         FIG. 5  shows an exerciser performing sit-ups on the exercise device of  FIG. 1 ; 
         FIG. 6  shows an exerciser using a cable exercise device while sitting on the exercise device of  FIG. 1 ; 
         FIG. 7  shows a perspective view of an exemplary exercise device in which some filler particles stick to an inner bladder wall; 
         FIG. 8  shows a perspective view of an exemplary exercise device in which a bottom portion is defined by a thicker portion of the exercise device; 
         FIG. 9  shows a perspective view of an exemplary exercise device in which a bottom portion is defined by a bowl portion coupled to an inner wall of the exercise device; 
         FIG. 10  shows the exerciser of  FIG. 5  exercising on the bladder of  FIG. 8 ; 
         FIG. 11  shows the exerciser of  FIG. 6  exercising on the bladder of  FIG. 9 . 
         FIG. 12  shows a partial exploded view of the valve and bladder of the exercise device of  FIG. 1 ; 
         FIG. 13A  shows an exploded cross sectional view of the valve and bladder of the exercise device of  FIG. 1 ; 
         FIG. 13B  shows a cross sectional view of the bladder and valve of  FIG. 12  with the valve main body seated in the bladder; 
         FIG. 13C  shows a cross sectional view of the bladder and valve main body of  FIG. 12  with the stem plug seated in the valve main body; 
         FIG. 14  shows the bladder of  FIG. 1  being filled with a mixture of air and filler that is being injected through an aperture in the valve main body using air pressure; and 
         FIG. 15  shows a schematic drawing of a forced air system that creates a vacuum to cause the filler to mix with the air stream. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     I. Introduction and Definitions 
     The present invention relates generally to partially stabilized exercise devices. The exercise devices are partially stabilized using a small amount of filler. The present invention allows the bladder to be easily filled by (i) providing separate apertures for injecting filler and air into the bladder, and/or (ii) by injecting a mixture of filler and air into the bladder using air pressure. 
     The present invention also includes kits that allow a user to fill the bladder with filler and/or to fill the bladder with air. The kits typically include a small pump such as a hand or foot pump that can be used to force air into the bladder. 
     In one embodiment, the exercise device is stabilized with respect to a support surface. By being stabilized with respect to the support surface, rolling, rotation along the support surface, or other movement of the exercise device is minimized. Such movements can be referred to as rotation along a surface and should not be considered as limiting as to the type or nature of movement of the bladder. For simplicity, the exercise device will be referred to as a “stability ball,” or simply a “ball.” The term stability ball is used to generally describe the exercise devices that relate to the present invention and can be used to refer to a variety of types and configurations of balls including an exercise ball, Swiss Ball, physioball, fitness ball, yoga ball, Pilates Ball, etc. Furthermore, those skilled in the art typically refer to the size of a stability ball by its diameter as measured in centimeters. For ease of understanding, the disclosure herein follows this convention of measuring stability balls by their diameter in centimeters. 
     Various ratios disclosed herein are calculated based on the diameter, volume, or other parameter of a bladder inflated to its normal operating pressures. The size of the bladder inflated to normal operating pressures can be substantially similar to the size of the bladder at the point where the bladder has sufficient air pressure such that it does not significantly deflected under its own weight. 
     Calculations made herein also assume that the inflated bladder has a spherical shape. This convention is used for the ease of describing the invention and is in no way a limitation on the shape of the invention. Those skilled in the art will recognize that the diameter of a sphere is easily converted to and from volume by the equation 4/3πr 3 . Where size of a non-spherical bladder is relevant, the diameter of that bladder should be determined by taking the volume of the non-spherical bladder and calculating its diameter as if it where a sphere. 
     II. Inflatable Bladder and Filler 
     With reference now to  FIGS. 1 and 2 , in an exemplary embodiment, a stability ball  10  has an inflatable bladder  12  that defines a chamber. In one exemplary implementation, bladder  12  can be inflated and deflated through valve mechanism  14 . Stability ball  10  also includes a small amount of filler  16  disposed within bladder  12 . 
     Bladder  12  can be inflated with air, for example, using a pump. The air can be any gaseous substance. The amount of air pressure in the bladder can vary according to personal preferences. The air pressure should be sufficient to support the weight of the user thereon. A user&#39;s weight is sufficiently supported by bladder  12  so long as when the user is positioned thereon bladder  12  flexes only so far such that at least a portion of the user&#39;s weight is directly supported by bladder  12  rather than by the underlying support surface. Further reference herein to bladder  12  assumes that bladder  12  is inflated. 
     Bladder  12  is sufficiently large for a user to perform exercises utilizing bladder  12 . In one embodiment the diameter of the ball is in the range of about 15 cm to about 115 cm, e.g., about 23 cm to about 105 cm. Typically, bladder  12  is utilized by a user by performing exercises thereon. 
     Examples of useful sizes of bladders include spherical bladders  12  that have diameters of approximately 23 cm, 35 cm, 45 cm, 55 cm, 65 cm, 75 cm, 85 cm, 95 cm, and 105 cm. These sizes can be determined based on the age, size, and/or experience of the user. For example, typically, for an adult the bladder is about 55 cm to about 75 cm in diameter, whereas youth sizes can typically begin at about 35 cm in diameter. 
     The stability ball  10  of the present invention can also have a non-spherical shape. Non-spherical shapes include various shapes such as elliptical, egg-shaped, and bi-lobed. In particular, stability ball  10  can be any shape that has some degree of curvature such that a user will be at least partially destabilized when positioned thereon. The curvature also causes instability of the ball with respect to the support surface. In other words, stability ball  10 , however shaped, should still have a limited degree of as movement when a user rests or lies thereon. 
     To keep the weight of stability ball  10  at a minimum, bladder  12  can be made from a thin, lightweight and sturdy material such as, for example, polyvinyl chloride. In one embodiment, bladder  12  is formed from a burst resistant material such as a material comprising primarily polyvinyl chloride in combination with other materials, compounds, or the like. Generally the lighter and stronger the material, the more suitable the material is for forming bladder  12 . To be suitable for exercising thereon, bladder  12  resists bursting under pressures exerted by a user thereon. Example burst weights include weights from 200 to 1000 lbs. Ideally, these weights take into account both the weight of the user as well as additional weight apparatus the user holds during an exercise routine. The texture, flex, and cost of the bladder material parameters can be selected to allow for such weights and pressures, In one embodiment, the outside surface of the ball is grip textures. Other materials can be selected or added to those disclosed herein to enhance structural integrity as desired. Those skilled in the art will recognize that bladder  12  can be formed from any one of a number of materials. 
     In an exemplary embodiment, filler  16  is deposited within bladder  12  by way of valve mechanism  14 . Filler  16  can be a particulate, e.g., a fluidly moving particulate, or other material, such as a dense or loose material that can flow on the inner surface  18  of bladder  12 . Suitable fillers include sand, weighted beads, gel, water, and the like. Filler  16  forms a small pile or layer on the bottom of inner surface  18 . The small amount of filler  16  is sufficient to weight stability ball  10  and provide a small amount of resistance against rolling. 
     The amount of filler  16  utilized with respect to the overall volume of the bladder can be selected to provided desired results. In one embodiment, the volume of the filler is less than about 75 percent of the overall volume of the bladder. In another embodiment, the volume of the filler is less than about 50 percent of the overall volume of the bladder. In another embodiment, the volume of the filler is less than about 25 percent of the overall volume of the bladder. In another embodiment, the volume of the filler is less than about 10 percent of the overall volume of the bladder. In another embodiment, the volume of the filler is less than about 5 percent of the overall volume of the bladder. In another embodiment, the volume of the filler is less than about 1 percent of the overall volume of the bladder. In one embodiment, the volume of the filler is approximately 0.5 percent of the overall volume of the bladder. In one embodiment, the volume of filler relative to the overall volume of the bladder is dependent on the type of filler utilized. For example, in one embodiment in which the filler comprises sand the volume of the filler is approximately 0.5 percent of the overall volume of the bladder. 
       FIGS. 3A-3B  show the rotation of an exemplary stability ball  10  with filler disposed therein. As shown in  FIG. 3A , initially stability ball  10  is at rest and filler  16  is disposed in the bottom thereof. As shown in  FIG. 3B , as stability ball  12  begins to roll along a support surface, the friction between inner surface  18  and filler  16  causes filler  16  to move with bladder  12 . The weight of filler  16 , applied to inner surface  18  through friction, causes stability ball  18  to resist rotation. In order for stability ball  10  to roll, the rotational force applied to ball  10  must be greater than the rotational resistance created by filler  16 . By resisting rotation of the ball, unexpected movement of the ball is minimized providing predictability of the location of the ball. This allows users to exercise in the vicinity of the ball while enjoying a safe periphery around the ball. This can be advantageous in certain circumstances in which the stability balls are utilized. For example, in aerobics or cross-training routines in which the ball is intermittently utilized and/or where exercisers are moving in the proximity of the ball. 
     As shown in  FIG. 3B , if a sufficiently large rotational force is applied to stability ball  10 , ball  10  rotates from the position in  FIG. 3A  to the position in  FIG. 3C , despite the presence of filler  16 . Filler  16  is a particulate such as sand or other material that can flow on inner surface  18 . Since filler  16  is loose, gravity causes filler  16  to flow toward the bottommost portion of bladder  12 . 
     As shown in  FIG. 3C , once stability ball  10  has come to rest, filler  16  is again positioned at the bottom of bladder  12 . While  FIGS. 3A-3C  show filler  16  flowing directly on the inner surface of a single layered bladder, it should be understood, that bladder  12  can have multiple layers. 
     In one embodiment, the amount of filler  16  is selected to have as little weight as possible and still prevent unwanted ball movement. Existing stability balls are subject to unwanted movement for a variety of reasons including manufacturing imperfections in the ball, imperfections in the floor or support surface, and air currents in the exercise room. The amount of filler in stability ball  10  only needs to produce enough resistance against rotation to overcome the slight forces that cause unwanted movements. Because the forces that cause unwanted rotation are generally relatively small, stability ball  10  generally requires only small amounts of filler. In other words, filler  16  and ball  10  can be configured for a certain degree of “rotational resistance,” which is a threshold force required to rotate or move the stability ball a given amount. Thus, for ball  10  to move or rotate, the rotational force applied to ball  10  must be greater than the rotational resistance provided by filler  16 . 
     One will appreciate, therefore, that the stability ball  10  can be configured for greater or lesser stability by varying the size, weight, amount, etc. of filler  16  as discussed above. For example, adding filler  16 , or using a heavier filler  16 , can increase the rotational resistance. On the other hand, reducing the amount of filler  16 , or using a lighter filler  16 , can decrease the rotational resistance. However designed, the filler&#39;s  16  rotational resistance minimizes unexpected movement of the stability ball  10 , providing the stability ball  10  with an added sense of stability in one location, as well as enhancing the predictability of the stability ball  10 . Furthermore, the ball&#39;s resistance to rotation can vary depending on a particular user&#39;s likes or dislikes. therefore, additional weight can be added to the ball as desired. 
     At least one advantage of minimizing unexpected or unwanted stability ball  10  movement is that users can exercise in the vicinity of the stability ball  10 , while enjoying a safe periphery around the stability ball  10 . This can be particularly advantageous in circumstances such as in aerobics or cross-training routines, where the stability ball  10  is intermittently utilized and/or where exercisers are moving in the proximity of the stability ball  10 . At least a second advantage of this minimization is that users can safely exercise on the stability ball  10  without repeatedly having to adjust the location or orientation of the stability ball  10 . 
       FIGS. 4A-4C  show additional exemplary implementations of a stability ball  10 , albeit in progressively larger sizes both for the stability ball  10  and bladder  12 , as well as for the filler  16 . These larger sizes can be based on ultimately desired weights, after the filler  16  has been added. 
       FIGS. 4A-4C  show stability ball  10  in progressively larger sizes. In one embodiment, the weight of the filler utilized is in the range of about 28 grams to about 6.8 kilograms. In one embodiment, the weight of the filler is in the range of about 28 grams of a pound to about 4.55 kilograms. In another embodiment, the weight of the filler is in the range of about 681 grams to about 1.36 kilograms. In yet another embodiment, the weight of the filler is dependent on the type of filler utilized. By way of example, in one embodiment a 23 cm diameter ball has a filler weight of about 113 grams. In another example, a 65-75 cm diameter ball has a filler weight of about 1.13 kilograms. 
     Filler  16   a - 16   c  disposed in the respective balls of  FIGS. 4A-4C  increase in weight as the ball size increases. In one embodiment, the amount of weight of the filler utilized is dependent on the size of the bladder. In an exemplary embodiment, the weight of filler  16  disposed in bladder  12  increases with diameter by about 3.5 grams/cm to about 35 grams/cm. In another embodiment, the weight to diameter ratio is in the range of about 10 grams/cm to about 25 grams/cm. In another embodiment, the weight to diameter ratio is from about 15 grams/cm to about 20 grams/cm. 
     In another embodiment, the amount of filler is related to the volume of the inflated bladder. For example, in one embodiment the ratio of the weight of the filler to the volume of the ball is in a range from about 2 grams/liter to about 26 grams/liter. In another embodiment, the ratio is from about 6 grams/liter to about 20 grams/liter. In yet another embodiment, the ratio is from about 10 grams/liter to about 16 grams/liter. 
     The amount of filler  16  disposed in bladder  12  can depend on the users&#39; preferences. Thus, a number of stability balls having the same diameter can have different weights. In yet another, the amount of filler is calculated based on another parameter of the bladder. Examples of other parameters can include the weight of the ball, the type of material utilized, the thickness of the material, the type of filler utilized, or the like. 
     In yet another embodiment of the invention, filler  16  is colored and bladder  12  is translucent such that the color of filler  16  can be detected. The color of filler  16  corresponds to the weight of the filler such that a user can readily identify a particular stability ball among a selection of stability balls. The color of filler  16  can also correspond to the size of bladder  12  such that a user can readily identify a particular sized stability ball. In another embodiment, the color of the filler  16  is selected to correspond to the color of a semi-translucent and colored ball. In yet another embodiment, glitter is utilized alone or in combination with another filler. In yet still another embodiment, indicia are utilized with the balls to indicate the weight of the exercise ball or other parameter of the ball. This can be useful where stability balls of different weights are utilized for resistance during an exercise routine. 
     III. Performing Exercises on Partially Stabilized Exercise Device 
     The stability ball of the present invention can be used for numerous activities including all activities performed by a conventional stability ball.  FIG. 5  illustrates a user performing sit-ups using stability ball  10  of the present invention. As the user prepares to perform a given exercise the stability ball remains in position on the support surface due in part to the presence of filler  16 . If the user has his or her hands occupied with hand weights for example, the user need not worry about controlling stability ball  10  prior to positioning himself or herself thereon. 
     Once positioned on stability ball  10 , the user performs exercises to develop core muscles involved in stabilizing the user&#39;s body. The forces of the user&#39;s body on stability ball  10  are so much greater than the resistance provided against rotation provided by filler  16  that the user&#39;s actions are substantially uninhibited by filler  16  disposed within bladder  12 . Thus, as the user performs exercises, stability ball  10  only changes position when caused to be moved by the user. 
       FIG. 6  illustrates the advantages of stability ball  10  of the present invention when used in combination with a cable exercise device  20 . The user positions stability ball  10  and then grasps handles  22   a  and  22   b . While the user grasps handles  22   a  and  22   b , stability ball  10  remains in position due to the presence of filler  16  disposed therein. The user positions himself or herself on stability ball  10  and uses core muscles to stabilize himself or herself as he or she pulls on handles  22   a  and  22   b . Since filler  16  helps to stabilize the stability ball  10  in a certain position, the user can expend energy on core muscles to stabilize himself or herself as he or she pulls on handles  22   a  and  22   b , and need not worry about the stability ball  10  moving in an unwanted manner. 
     A variety of other types and configurations of exercises can be utilized with stability balls of the present invention. For example, a smaller stability ball having a diameter of 23 cm can be placed between the legs of the exerciser to perform certain stability and other types of exercises. The filler minimizes movement of the stability ball when the user places the ball on a support surface during rest or at the completion of the exercise routine. 
     In still another embodiment, as shown in  FIG. 7 , colored filler  16   d  can be used that at least partially adheres, at least momentarily, to the inner surface  18  of the bladder  12 , which, in this embodiment is preferably light permeable (e.g., transparent or translucent). The filler can adhere to the inner surface  18  due to forces such as, for example, electrostatic forces. In such a case, at least a portion of the filler  16   d  sticks to the inner walls  18  of bladder  12 , thereby adding more visual appeal to the light permeable stability ball  10  when the filler  16   d  is colored, or glittering. One can appreciate, therefore, that a manufacturer and/or user may employ a wide range of fillers  16   d  to indicate a host of properties associated with the stability ball  10  and/or to make the ball more visually appealing. 
     IV. Alternative Embodiments of Exercise Devices 
     In yet additional embodiments, the stability ball  10 , as described herein, can be further configured so that the ball  10  has a designated upper portion and a designated lower portion. In one embodiment, the lower portion of the bladder is configured such that it is the natural tendency of the lower portion to rest adjacent the support surface, such as a floor, while the upper portion is positioned away from and above the support surface. 
     For example, in the exemplary embodiment shown in  FIG. 8 , the stability ball  10   a  has a designated lower portion  26   a  of the bladder  12  that is defined in part by a thicker, and hence heavier, portion  12   a  of the bladder  12  wall than the remaining portions or walls of the bladder  12 . The heavier weight of the stability ball  10   a  at one end, i.e., the lower portion  26   a , ensures that the stability ball  10   a  rests in a specific position. If lower portion  26   a  is rotated off the support surface, absent an external force, gravity causes the lower portion  26   a  to rotate until it rests on the surface. In an exemplary embodiment, the extra weight of thicker portion  12   a  is the minimum amount of weight necessary to resist unwanted rotation such as rotation caused by slightly uneven surfaces or air currents in a room. 
     In one embodiment, thicker portion  12   a  is formed as part of bladder  12 . For example, during the manufacture of bladder  12 , thicker portion  12   a  can be a thicker gauge of the same material forming the rest of bladder  12 . In another embodiment, thicker portion  12   a  is a separate material weight that has been formed onto or inserted into or fixed to a particular location of lower portion  26   a . For example a pouch having a material such as sand can be fixed to the inside surface of lower portion  26   a  or inserted in a pocket of material of lower portion  26   a.    
     Similarly, as shown in  FIG. 9 , the stability ball  10   b  can be further configured so that a ringed, or lipped, portion  13  defines a bowl portion  12   b  on lower portion  26   b . In one embodiment, bowl portion  12   b  may comprise a ringed, or lipped, upper area  13  and a thicker bottom area such as thicker area  12   a  shown in  FIG. 8 . However, in other embodiments, the bowl portion  12   b  comprises only a ringed, or lipped, upper area  13  without a thicker portion such as thicker area  12   a.    
     The ringed, or lipped, portion  13  of the bowl portion  12   b  can be formed with the bladder  12  during bladder formation. Alternatively, the ringed, or lipped, portion  13  can be formed from a separate material, inserted, and fixed into a specific point of lower portion  26   b . In any case, the bowl portion  12   b  adds weight to lower portion  26   b  of the stability ball  10   b , and/or gathers the filler  16   e  in a relatively defined area. In particular, the ringed portion  13  of the bowl portion  12   b  can cause filler moving within the ball  10   b  to gather within the bowl portion  12   b . Bowl portion  12   b  is yet another way of increasing the resistance to movement of the stability ball. One can also appreciate that filler  16   e  is not necessary, depending on the thickness, orientation, and stability of the thicker portion and the ringed, or lipped, area of the bowl portion  12   b.    
       FIGS. 8 and 9  show stability balls  10   a  and  10   b  in a natural position. The natural position is the position that gravity will cause the ball to assume in the absence of other significant forces, such as an exerciser pushing the ball. In  FIGS. 8 and 9 , stability balls  10   a  and  10   b  are in the natural position such that upper portions  24   a  and  24   b  respectively, is positioned away from and above a support surface. Thicker portion  12   a  and bowl portion  12   b  create a natural tendency for the lower portions  26   a  and  26   b  respectively, of each ball to rest adjacent the support surface. 
     In one embodiment, the stability ball  10   a  shown in  FIG. 10  has a lower portion  26  that has a natural tendency to assume a natural position, such as by having a thicker wall  12   a  as shown in  FIG. 8 . The ball  10   b  shown in  FIG. 11  has a lower portion  26   b  that has a natural tendency to assume a natural position by having a bowl portion  12   b , as shown in  FIG. 9 .  FIGS. 10 and 11  each show a user supported on an upper portion  24   a  and  24   b  respectively, while the lower portion  26   a  and  26   b  respectively is adjacent a support surface.  FIG. 11  shows a user on an upper portion  24   b  while a bowl portion  12   b  of bottom portion  26   b  is adjacent the support surface. 
     As shown in  FIGS. 10 and 11 , the bladder of a ball having a lower portion with a thicker wall and/or a bowl portion can support a user exercising thereon when stability ball  10  is in the natural position. Thus,  FIGS. 8A and 8B  show examples of bladders supporting users exercising on the upper portion of the respective bladders while the ball is in the natural position. 
     V. Valve Mechanisms for Filling the Bladder with a Filler 
     The exercise devices of the present invention also include a valve mechanism for placing filler into the bladder. The filler material can be more easily deposited in the bladder by either providing a large aperture in the bladder and/or by using a mixture of forced air and filler material. 
     In an exemplary embodiment, the stability ball includes a first aperture for introducing a filler into the bladder and a second aperture for filling the bladder with air. By using two different sizes of aperture, the apertures can be optimized for placing filler and air into the bladder. 
       FIGS. 12 and 13A  show an exemplary valve  14 , which enables the placement of both filler and air into bladder  12  of stability ball  10 . The valve  14  comprises a valve main body  30  that can be received in large aperture  28  to plug aperture  28 . Valve main body  30  has a small aperture  34  that can receive stem plug  32  to plug aperture  34 . 
     Large aperture  28  allows a filler material to be easily placed in bladder  12 . In an exemplary embodiment large aperture  28  has a diameter between about 1 cm and about 3 cm, e.g. between about 1.25 cm and about 1.75 cm. 
     The stability ball also includes a smaller aperture  34  for inserting air. In an exemplary embodiment, smaller aperture  34  has a diameter between about 0.5 cm to about 1.0 cm. Smaller aperture  34  can be configured to receive standard air nozzles such that the stability ball can be filled using a variety of air compressors. 
     As shown in  FIGS. 12 and 13B , large aperture  28  is configured to receive valve main body  30 . Bladder  12  has a tubular wall  36 . Aperture  28  is defined by wall  36 , which is sized to receive valve main body  30  in a snug fit. Valve main body  30  includes a insert portion  38  that is substantially the same size or slightly larger than the inside diameter of wall  36 . Insert portion  40  can be made from a resilient material such that valve main body  30  can be pressure fitted into aperture  28 . The force of the resilient material of valve main body  30  provides friction that inhibits the valve main body from being accidentally removed. The pressure between valve main body  30  and aperture  28  forms a seal that prevents air and the filler from escaping between valve main body  30  and aperture  28  when valve main body  30  is seated in aperture  28 . Valve main body  30  can also include a rim  40  that prevents valve main body  30  from passing completely through aperture  28 . Wall  36  can be more rigid than the remainder of bladder  12  in order to make placement of the valve more convenient. 
     In a preferred embodiment, wall  36  comprises a smooth plastic material that can form a good seal with valve main body  30 . As shown in  FIG. 13B , wall  36  can be a separate piece from the remainder of bladder  12 , in which case wall  36  is made from a material that can adhere to the remainder of bladder  12 . In an alternative embodiment, wall  36  can be made from the same material as other portions of bladder  12  such that wall  36  is continuous with the remainder of bladder  12 . 
       FIG. 13C  shows the valve with stem plug  32  inserted into aperture  34  to close aperture  34 . Stem plug  32  is configured to be slidably received in aperture  34 . Stem plug  32  includes a protruding ring  42  that extends circumferentially about stem plug  32 . Ring  42  is configured to be substantially the same size or slightly wider than the diameter of aperture  34 . As stem plug  32  is inserted into aperture  34 , ring  32  engages the inside surface of valve main body  30  to form a seal between stem plug  32  and valve main body  30 . When rim  44  is seated against valve main body  30 , ring  42  of stem plug  34  is disposed within aperture  34  and forms a seal to prevent air and filler from escaping from the bladder. Stem plug  32  includes rim  44 , which prevents stem plug  32  from passing completely through aperture  34 . 
       FIGS. 1-4  and  12 - 14  thus illustrate examples of a bladder assembly comprising a bladder  12  having a first aperture  28  and a valve  30 . The bladder assembly thus has first and second apertures  28 ,  34 . First aperture  28  and second aperture  34  are capable of being selectively opened and closed to allow a filler material and air to be inserted into the bladder assembly. 
     The present invention also includes other valve mechanisms that provide a first aperture size for depositing a filler material in a stability ball and a second size of aperture for inserting air. For example, in an alternative embodiment, the two sizes of aperture are provided by two separate apertures in the bladder of the stability ball. In addition, other closure and sealing mechanisms can be used with the valve mechanism of the present invention. For example, standard valves that can be opened with a needle can also be used with the present invention. 
     Bladders having the foregoing valve mechanisms can also be included in kits that allow a user or distributor to inject the sand following manufacturing. In this embodiment, the bladder can be shipped empty and the sand is injected by the user or distributor. A hand or foot pump can be included in the kit to allow the user to inflate the bladder. 
     VI. Methods For Placing the Filler in the Bladder 
     A variety of methods using various apparatuses can be utilized to introduce the filler into bladder  12 . For example, in one embodiment, a funnel is utilized to pour the filler through aperture  28 . 
     In a preferred embodiment, a pressurized air stream is used to inject the filler material into the bladder. Filler materials that are injected using a pressurized air stream can be introduced into the bladder at a faster rate and/or through a smaller aperture than filler that is poured. By injecting the filler material using a pressurized air stream, the filler can be injected through the same aperture as the air, thus eliminating the need for separate apertures for introducing the filler and the air; although a separate aperture for injecting the filler can be used if desired. Once the desired amount of filler is injected into the bladder, the bladder can be deflated for packaging and/or shipping. 
     The pressurized air stream can be generated using any air compressor system. Air compressor systems are known to those skilled in the art and typically include pumps, air tanks, hoses, and air nozzles to create an air stream. The air nozzle allows an air stream to be directed in a desired direction. 
       FIG. 14  shows an exemplary setup for injecting a mixture of air and filler into bladder  12 . Funnel  46  includes a tapered conical section  48  and an outlet  50 . Outlet  50  is position aperture  34 . Funnel  46  is partially filled with filler and an air nozzle  52  is partially submerged in the filler such that the air stream ejected there from is below the level of the filler. The air stream is also directed toward outlet  50  of the funnel  46 . As the air stream passes through the filler, a mixture of filler and air is formed. The force of the air carries the filler into bladder  12 . 
     In an alternative embodiment, the filler can be mixed with the air using a vacuum created by a pressurized air stream.  FIG. 15  shows an air stream  52  that is forced down passageway  54 . Air stream  54  passing by hollow tube  56  creates a vacuum in hollow tube  56 . Hollow tube  56  is also in fluid communication with reservoir of filler  58 . Filler from reservoir of filler  58  is sucked into air stream  52  through the vacuum in hollow tube  56 . The mixed air stream is injected into the bladder  12  through aperture  34 . Alternatively, the mixture of sand and air can be injected through aperture  28  ( FIG. 12 ). 
     By injecting the filler into the bladder, substantial time can be saved in filling the bladder. Furthermore, the bladder can be easily filled with filler at a location different than where the bladder is manufactured. This allows the bladder to be manufactured and shipped without the filler thereby reduce shipping costs. 
     The present invention can be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.