Described is an apparatus for practicing a golf swing in either an indoor or outdoor environment. The apparatus includes a frame with a leg portion, a rebounding surface, an arm with a cord that is secured to golf ball, and a mat. A golfer can practice a golf swing by striking the ball secured to the cord, and receives instantaneous feedback based on the ball's trajectory, sound produced when the ball hits the rebounding surface, and divot markings imprinted on the mat.

The disclosure relates to an irreversible dosimetric shock-detection substrate as well as related articles and methods. The shock-detection substrate incorporates a plurality of microcapsules serving as an irreversible means for detecting impact on the substrate. A shock above a characteristic threshold level experienced by the substrate induces an irreversible detectable change associated with the microcapsules upon shock-induced rupture. The irreversible detectable change provides a tamper-proof and non-electronic means for detecting a shock or impact. The shock-detection substrates can be incorporated into a variety of articles and used in a variety of settings, for example to monitor personal safety, to monitor article integrity, to monitor the end of the useful life of the shock-detection substrate itself, or in any other setting where it is desirable to irreversibly detect and/or localize a shock event.

Techniques are disclosed for systems and methods to provide golf training. A golf training system includes a monolithic platform having a first recessed portion, a first swing insert, and a second swing insert. The swing inserts are configured for interchangeably engaging the first recessed portion, which may position a top surface of the swing inserts substantially flush with a top surface of the platform. A golf training apparatus of the golf training system includes a monolithic platform having a first recessed portion and a second recessed portion, the second recessed portion positioned substantially opposite from the first recessed portion. The apparatus includes a first swing insert and a second swing insert. The swing inserts include an anchor support by way of a midpoint portion and an end portion. The end portion includes an end width greater than a midpoint width of the midpoint portion.

A golf club head includes a top portion, a sole portion opposite the top portion, and a striking face configured to impact a golf ball. The striking face includes a face center and a variable thickness distribution such that the club head exhibits an Expected COR value of not less than 0.810, the Expected COR value being determined based on the following relationship

[00001]$\mathrm{Expected}.Math..Math.\mathrm{COR}=\underset{i=1}{\overset{n}{.Math.}}.Math.\underset{j=1}{\overset{m}{.Math.}}.Math.p_{\mathrm{ij}}*c_{\mathrm{ij}}$

The variable c.sub.ij corresponds to an average COR value associated with bin and the variable p.sub.ij corresponds to a bin-specific impact probability value. And the club head exhibits a characteristic time no greater than 257 microseconds.

A golf tee has a contact alert material encapsulated therein. The golf tee includes a top portion with top, side and bottom walls fixedly attached to a shaft that terminates into a point appointed to be inserted into a ground surface. A cavity is formed between the top, side and bottom walls of the top portion. A contact alert material is encapsulated within the cavity and is composed of a combustible material that generates a spark on impact. The contact alert material is appointed to generate the spark during a golf swing when a golf club strikes the ball and the side walls. The alert is provided immediately as instantaneous feedback during the golf swing adapted to thereby improve muscle memory required to reliably replicate a proper golf swing.

A processing device includes an operation circuit that determines based on a first signal a swing start time, the first signal being acquired from a sensor that is attached to a striking member for striking a to-be-struck object by being swung and that detects deformation of the striking member when the striking member is swung. An absolute value of a difference between a reference value and a value of the first signal is defined as a first difference value. The operation circuit executes a first determination step in which an impact time is determined based on one or more times at which the first difference value becomes greater than or equal to a first determination value.

A golf club set includes at least one first golf club whose loft angle is not less than 46 degrees and less than 56 degrees, and at least one second golf club whose loft angle is not less than 56 degrees and less than 60 degrees. The first and second golf clubs each comprise a face provided with score lines each formed by a groove having a groove bottom and a pair of opposite grooves walls which are inclined at an inclination angle with respect to a normal direction to the face so that the groove width between the opposite grooves walls is increased from the groove bottom toward the face. The inclination angle of the groove walls of the score lines of the first golf club is in the range from 28 to 42 degrees. The inclination angle of the groove walls of the score lines of the second golf club is in the range from 23 to 37 degrees and smaller than that of the first golf club.

A golf club head includes a top portion, a sole portion opposite the top portion, and a striking face configured to impact a golf ball. The striking face includes a face center and a variable thickness distribution such that the club head exhibits an Expected COR value of not less than 0.810, the Expected COR value being determined based on the following relationship: $\mathrm{Expected}\mathrm{COR}=\underset{i=1}{\overset{n}{.Math.}}\underset{j=1}{\overset{m}{.Math.}}{p}_{\mathrm{ij}}*c_{\mathrm{ij}}$
The variable c.sub.ij corresponds to an average COR value associated with bin i, j, and the variable p.sub.ij corresponds to a bin-specific impact probability value. And the club head exhibits a characteristic time no greater than 257 microseconds.

A club mountable golfing aid is operable to indicate to a golfer a location at which a training golf ball contacts a striking surface of the club mountable golfing aid when the club mountable golfing aid is mounted on a golf club. The club mountable golfing aid includes an attachment mechanism that is configured to mount the club mountable golfing aid to a head of a golf club. The club mountable golfing aid includes the striking surface. The striking surface covers at least a portion of the face of the golf club when the club mountable golfing aid is mounted on the head of the golf club. The striking surface is operable to attach to and retain a training golf ball at about a point of contact between the striking surface and the training golf ball when a golfer strikes the ball.

Described is an apparatus for practicing a golf swing in either an indoor or outdoor environment. The apparatus includes a frame with a leg portion, a rebounding surface, an arm with a cord that is secured to golf ball, and a mat. A golfer can practice a golf swing by striking the ball secured to the cord, and receives instantaneous feedback based on the ball's trajectory, sound produced when the ball hits the rebounding surface, and divot markings imprinted on the mat.