Devices systems and methods are disclosed. Among other things, the devices systems and methods can facilitate ergonomic gripping of a handle; conform to the shape of a wrist; enhance golf techniques or performance; enhance racket sport technique or performance; protect a head of a user engaged in contact sports or other hazardous activities; identify concussions, in some cases in substantially real time; provide sterilization of garments; control surgical robots; allow for medical treatment of multiple subjects without disrobing; provide biometric or other data; and/or be used to train muscles or body parts for, for example, performing specified tasks using a body part.

A ball bat includes a handle, a barrel attached to or continuous with the handle, and a tamper-evident section positioned in the barrel. The tamper-evident section may include a layer of foam material or another suitable material positioned within a wall of the barrel between an inwardly facing surface and an outer layer of the wall. The outer layer of the wall may be positioned to deform to indicate a condition of the tamper-evident section. In some embodiments, the wall is formed from a composite material. In other embodiments, the wall may include a metal alloy material and the outer layer may include a composite material. The foam material may have a compression value greater than that of a softball.

A golf club includes a golf club head, a shaft adapter secured within a hosel of the golf club head, and a shaft secured within the shaft adapter. The golf club shaft is formed from a fiber reinforced polymer and extends along a longitudinal axis between a tip end and a grip end. The golf club shaft includes a tip end section, a grip end section, and a tapered section between the tip end section and the grip end section. The tapered section of the shaft includes a reference portion within the upper half that has a frustoconical shape with a near-constant taper rate, and a narrowed portion within the lower half. The narrowed portion is recessed relative to a reference surface extrapolated from the frustoconical shape.

A bendable core insert configured for manufacturing a golf-club shaft. The bendable core includes a bendable relief tube having a first end attached to a top coupling tube and a second end attached to a bottom coupling tube. The bendable relief tube, the top coupling tube, and the bottom coupling tube have respective channels that are aligned to form a continuous channel through opposing ends of the bendable core insert. The length of the bendable core insert corresponds to a length of a corresponding segment of the golf-club shaft. The bendable relief tube is configured to be bent in one or more directions to define a bend profile of the corresponding segment of the golf-club shaft.

A variable stiffness striking implement, such as, for example, a ball bat typically used in baseball, softball, or rubber ball. The striking implement, preferably has a separate barrel and handle. A wedge and joint attached directly to the handle or indirectly to the handle using an interface portion engage the interior surface of the barrel. Most preferably, the wedge and joint are molded about the interface portion and a handle preform is then inserted into the intention of the interface portion and the handle is then molded. Wedge hardness is selectable and a stiffness member may also be employed. Stiffness member hardness may be selectable or may be adjustable by varied adjustment of a cap in relation to the barrel. Alternatively, the cap may not be adjustable in relation to the barrel so that a selected stiffness member hardness is fixed.

A shaft 6 includes a tip end Tp and a butt end Bt. If a shaft length is defined as Ls, a distance between the butt end Bt of the shaft and a center of gravity G of the shaft is defined as Lg, and a ratio of the distance Lg to the shaft length Ls is defined as a ratio of the center of gravity of the shaft, then the ratio of the center of gravity of the shaft is equal to or less than 47%. The shaft length Ls is equal to or less than 991 mm. If a forward flex is defined as F1 (mm) and a backward flex is defined as F2 (mm), a flex point ratio C1 of the shaft calculated by the following formula (1) is equal to or less than 39%:

C1=[F2/(F1+F2)]100](1).

A rod-like object for ball games 1 usable for a ball games or practice thereof, the rod-like object 1 comprising a grip 20 on a proximal end side of an elongated main body 10, the main body 10 comprising a first flexible part 12 in which primary deflective deformation occurs along a first imaginary plane, a second flexible part 14 that is provided more toward the proximal end side than the first flexible part 12 is and in which principal deflective deformation occurs along a second imaginary plane, and a highly rigid part 19 interposed between the first flexible part 12 and the second flexible part 14, the first imaginary plane and the second imaginary plane intersecting each other, and the highly rigid part 19 having a flexural rigidity in a direction of the first imaginary plane that is equal to or greater than a flexural rigidity of the second flexible part 14 in the same direction and a flexural rigidity in a direction of the second imaginary plane that is equal to or greater than a flexural rigidity of the first flexible part 12 in the same direction.

The present invention provides a high-balance-point shaft capable of increasing ball speed. A golf club shaft formed by laminating fiber-reinforced resin, wherein the balance point obtained by formula below is set to be 53% or higher; and the kickpoint obtained by formula below is set to be 44% or higher.

A variable stiffness striking implement, such as, for example, a ball bat typically used in baseball, softball, or rubber ball. The striking implement, preferably has a separate barrel and handle and includes a variable stiffness assembly which results in the user being able to adjust stiffness. This is accomplished by the user selecting a stiffness member having a desired hardness and inserting the selected stiffness around the handle and abutting the end of the barrel closest to the handle end and using a cap to hold the stiffness member in place, or, if desired by the user, the striking implement may be used without a stiffness member.

A shaft insert (or external connecting segment) with greater flexibility than the substrate shaft allowing for a more flexible zone in an area of separation between two separated portions of the substrate shaft. The flexible connection is intended to be installed between two segments of the separated substrate shaft primarily on a golf putter with the flexible connection within 5 inches of the base of the club in total compliance with USGA (United States Golf Association) Rule 2, Appendix II. 2. b. requiring any change from the continuous shaft be within 5 inches of the club base. The shaft flex connection is designed to be symmetrical around its cross section with equal flexibility and torsional displacement in all directions in compliance with USGA Rule 2, Appendix 2. c. requiring golf shafts to be equally flexible with equal torsional displacement in all directions. The preferred embodiment of the invention utilizes a flexible tube for which the outside diameter is slightly smaller than the inside diameter of the substrate shaft. The substrate shaft is separated at the top of the hosel of the club and joined by fixing the tube (with epoxy or other adhesive) in each section of the separated sections of the substrate shaft whereby the separation is maintained at a fixed distance by installing an O ring or other spacer over the insert tube and between the two segments of the substrate shaft.