A rubber composition for a tennis ball includes a base rubber and a filler having a degree of flatness DL of not less than 50, the degree of flatness DL being obtained by dividing an average particle diameter D.sub.50 (m) of the filler by an average thickness T (m) of the filler. An amount of the filler per 100 parts by weight of the base rubber is not less than 1 part by weight and not greater than 150 parts by weight. A gas permeability coefficient GPS and a loss tangent tan S of the rubber composition and a gas permeability coefficient GPL and a loss tangent tan L of a rubber composition obtained by replacing the filler with kaolin clay having a degree of flatness DL of 20 satisfy (1): GPL/GPS1.02 and (2): |tan Ltan S|0.03. A tennis ball 2 includes a core 4 formed using the rubber composition.

A rubber composition for a tennis ball includes a base rubber and a filler having a degree of flatness DL of not less than 50, the degree of flatness DL being obtained by dividing an average particle diameter D.sub.50 (m) of the filler by an average thickness T (m) of the filler. An amount of the filler per 100 parts by weight of the base rubber is not less than 1 part by weight and not greater than 150 parts by weight. A gas permeability coefficient GPS and a loss tangent tan S of the rubber composition and a gas permeability coefficient GPL and a loss tangent tan L of a rubber composition obtained by replacing the filler with kaolin clay having a degree of flatness DL of 20 satisfy (1): GPL/GPS1.02 and (2): |tan Ltan S|0.03. A tennis ball 2 includes a core 4 formed using the rubber composition.

A training/practice/amusement projectile comprises a ball with optimal baffling and rebounding characteristics for play and training of hand-eye coordination and motor skills. The ball generally includes a combination of bounce and baffling elements. In one embodiment the bounce and baffling elements respectively comprise densely packed loops of filament, and individual filament strands of lesser density, both radiating from a core of the ball. A novel method of fabrication includes winding wider and narrower loops of filament, bundling same together at a cinched core, and then cutting the wider loops to form the strands radiating outward inched core to impart a generally spherical outer shape to the ball.

An aqueous adhesive for a tennis ball includes rubber latex and a sulfenamide-based vulcanization accelerator. When a solid content in the aqueous adhesive is measured at a temperature of 150 C. by a curelastometer, a 10% torque time t10 is preferably not shorter than 3 minutes and preferably not longer than 15 minutes, and a ratio (t10/t90) of the 10% torque time t10 to a 90% torque time t90 is preferably not less than 0.60 and preferably not greater than 0.95. A tennis ball includes a hollow core obtained by two semi-spherical half cores being adhered by using the aqueous adhesive.

An aqueous adhesive for a tennis ball includes rubber latex and a sulfenamide-based vulcanization accelerator. When a solid content in the aqueous adhesive is measured at a temperature of 150 C. by a curelastometer, a 10% torque time t10 is preferably not shorter than 3 minutes and preferably not longer than 15 minutes, and a ratio (t10/t90) of the 10% torque time t10 to a 90% torque time t90 is preferably not less than 0.60 and preferably not greater than 0.95. A tennis ball includes a hollow core obtained by two semi-spherical half cores being adhered by using the aqueous adhesive.

A gravity training ball includes a ball core unit having a predetermined weight specification, a buffer unit covering the ball core unit and made of a material having a shock absorbing effect, and an outer cover unit covering said buffer unit. The outer cover unit includes an outer cover layer covering the buffer unit.

Systems and methods for tracking a sports ball assembly in real time during a sporting event are disclosed. A structure of the sports ball assembly is also disclosed. The sports ball assembly comprises at least one electronic circuit embedded or attached to a sports ball. The sports ball assembly is in network communication with a server processor via at least two receivers within a sports arena. The sports ball assembly generates and transmits UWB data packets comprising movement-related data for the sports ball assembly in real time at a predetermined rate. The at least two receivers receive the UWB data packets and transmit to the server processor with time stamps. The server processor is operable to determine a movement of the sports ball assembly based on the UWB data packets and the time stamps received from the at least two receivers.

Systems and methods for tracking a sports ball assembly in real time during a sporting event are disclosed. A structure of the sports ball assembly is also disclosed. The sports ball assembly comprises at least one electronic circuit embedded or attached to a sports ball. The sports ball assembly is in network communication with a server processor via at least two receivers within a sports arena. The sports ball assembly generates and transmits UWB data packets comprising movement-related data for the sports ball assembly in real time at a predetermined rate. The at least two receivers receive the UWB data packets and transmit to the server processor with time stamps. The server processor is operable to determine a movement of the sports ball assembly based on the UWB data packets and the time stamps received from the at least two receivers.

A tennis ball may include a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm and a textile layer covering the spherical hollow core

The present disclosure provides for various objects (weights, playing apparatuses, balls, clothing, etc.) that have liquid disposed in them to assist in building and strengthening small muscle fibers and/or nerves. The various objects can include weights, playing apparatuses such as objects that can be swung in sports, balls, and clothing or other objects that can be worn by humans or other animals. The objects include fluid paths and redirections walls disposed within the fluid paths to direct fluid flow to particular areas within the objects. The designated areas to where fluid flow is directed aid in development of small muscle fibers and/or nerves due to the fluid sloshing around at those particular locations. Methods of making and using the various objects disclosed are also provided.