A cavity back iron type club head includes a striking plate having a substantially planar striking surface and a rear surface defining a thickness therebetween. The rear surface defines a striking plate rear cavity region. A perimeter support is coupled to a peripheral portion of the striking plate. The surface area of the striking surface is related to the club head loft angle by the equation SSA≥14.4(L)+2875, where SSA is the surface area of the striking surface in units of square-millimeters and L is the club head loft angle in units of degrees.

A golf practicing apparatus for providing a feedback with regard to a swing speed and form includes a hand portion, a strip portion, and a weight portion. The weight portion provides a signal when a player makes a swing with the apparatus and the signal indicates how the swing is made.

A portable golf swing exerciser includes: a main body of a shaft shape; a head shaft including a head, and one or more connection shafts, of which one end is detachably coupled to the head, and the other end is detachably coupled to a front end of the main body; and an antenna stick guide extended from or retracted into a rear end of the main body in a form of an antenna having multiple sections.

An equipment fitting system that measures swings by a user of different pieces of equipment with inertial sensors, and analyzes sensor data to recommend which piece of equipment is optimal for the user from among those tested. Illustrative applications include fitting of baseball bats and golf clubs. Swing metrics calculated from sensor data may include an acceleration metric, a speed metric, and a momentum metric; these metrics may be combined into a metrics score for each piece of equipment. Other factors may be included in an overall score, such as the user's subjective score for each piece of equipment, and ratings from experts or other consumers. Users may assign the relative importance for the different factors to calculate an overall equipment score.

Disclosed herein is an educational golf club comprising a shaft and a head, wherein the shaft has a weight increasing means disposed therein. The educational golf club according to the present invention is in a wide use since being adjusted in weight or length according to the user's height or age. Additionally, the educational golf club according to the present invention generates a hitting sound from the shaft realistically when the user hits the golf ball to arouse interest in golf.

A system that measures a swing of a bat with one or more sensors and analyzes sensor data to create swing quality metrics. Metrics may include for example rotational acceleration, on-plane efficiency, and body-bat connection. Rotational acceleration measures the centripetal acceleration of the bat along the bat's longitudinal axis at a point early in the rotational part of the swing; it is an indicator of the swing's power. On-plane efficiency measures how much of the bat's angular velocity occurs around the swing plane, the plane spanned by the bat and the bat's sweet spot velocity at impact. Body-bat connection measures the angle between the bat and the body tilt axis, which is estimated from the trajectory of the hand position on the bat through the swing; an ideal bat-body connection is near 90 degrees. These three swing quality metrics provide a simple and useful characterization of the swing mechanics.

A system that measures a swing of equipment (such as a bat or golf club) with inertial sensors, and analyzes sensor data to create a rotational profile. Swing analysis may use a two-lever model, with a body lever from the center of rotation to the hands, and an equipment lever from the hands to the sweet spot of the equipment. The rotational profile may include graphs of rates of change of the angle of the body lever and of the relative angle between the body lever and the equipment lever, and a graph of the centripetal acceleration of the equipment. These three graphs may provide insight into players' relative performance. The timing and sequencing of swing stages may be analyzed by partitioning the swing into four phases: load, accelerate, peak, and transfer. Swing metrics may be calculated from the centripetal acceleration curve and the equipment/body rotation rate curves.

A golf club head comprises a sole, a recessed sole port in the sole; and a rotatably adjustable sole piece adapted to be at least partially received within the sole port and comprising a central body having a plurality of contact surfaces adapted to contact the sole port and being offset from each other along a central axis extending through the central body of the sole piece. The sole piece can be positioned at least partially within the sole port at five or more rotational and axial positions with respect to the central axis, wherein at each rotational position, at least one of said contact surfaces of the central body contacts the sole port to set the axial position of the sole piece. The sole port and/or the sole piece can be generally pentagonal in shape.

A cavity back iron type club head includes a striking plate having a substantially planar striking surface and a rear surface defining a thickness therebetween. The rear surface defines a striking plate rear cavity region. A perimeter support is coupled to a peripheral portion of the striking plate. The surface area of the striking surface is related to the club head loft angle by the equation SSA≥14.4(L)+2875, where SSA is the surface area of the striking surface in units of square-millimeters and L is the club head loft angle in units of degrees.

A system that measures a swing of a bat with one or more sensors and analyzes sensor data to create swing quality metrics. Metrics may include for example rotational acceleration, on-plane efficiency, and body-bat connection. Rotational acceleration measures the centripetal acceleration of the bat along the bat's longitudinal axis at a point early in the rotational part of the swing; it is an indicator of the swing's power. On-plane efficiency measures how much of the bat's angular velocity occurs around the swing plane, the plane spanned by the bat and the bat's sweet spot velocity at impact. Body-bat connection measures the angle between the bat and the body tilt axis, which is estimated from the trajectory of the hand position on the bat through the swing; an ideal bat-body connection is near 90 degrees. These three swing quality metrics provide a simple and useful characterization of the swing mechanics.