Golf club fitting device, method and program

Abstract

To provide a fitting device for highly accurately selecting a golf club suited to a golfer.SOLUTION: A fitting device includes an acquisition part, a calculation part and a determination part. The acquisition part acquires measurement data obtained by measuring swing motion of a golf club by a golfer with a measuring instrument. The calculation part calculates a first swing index relating to a degree of torsion of a golf club during the swing motion based on the measurement data. The determination part determines an optimal club length, the length of the golf club suited to the golfer, according to the size of the first swing index.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a fitting device, a fitting method, and a fitting program for selecting a golf club suitable for a golfer. [Background technology]

[0002] Conventionally, various fitting methods have been proposed in which a golfer is made to try a test club, the motion is measured by a measuring device, and a golf club suitable for the golfer is selected based on the measurement data. As one of these, Patent Document 1 discloses a fitting method for selecting a golf club shaft suitable for a golfer. Specifically, in Patent Document 1, based on the measurement data of the test club, an optimal stiffness index indicating the stiffness of a shaft suitable for the golfer is determined together with an optimal ease of swing index of a golf club suitable for the golfer. Then, after fixing the head, a shaft that matches the optimal ease of swing index and the optimal stiffness index as closely as possible is extracted from a large number of shafts registered in a database. Such a method is highly expected as a technology for improving the accuracy of shaft fitting. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-170105 A Summary of the Invention [Problem to be solved by the invention]

[0004] According to the method of Patent Document 1, it is possible to narrow down the shafts and, in turn, the golf clubs that match the optimal swing ease index and the optimal stiffness index as much as possible, but different shaft length options may be prepared in order to adjust the club length of the golf club. Therefore, there has been a demand for a method that can select a golf club with a length more suitable for a golfer from the golf clubs narrowed down by the conventional method, not limited to the method disclosed in Patent Document 1. This also applies to the case where shafts and golf clubs suitable for a golfer are not narrowed down by any method and an attempt is made to select a shaft or golf club suitable for the golfer.

[0005] An object of the present invention is to provide a fitting device, method, and program for accurately selecting a golf club having a length suitable for a golfer. [Means for solving the problem]

[0006] A fitting device according to a first aspect includes an acquisition unit, a calculation unit, and a determination unit. The acquisition unit acquires measurement data obtained by measuring a swing motion of a golf club by a golfer using a measuring device. The calculation unit calculates a first swing index related to a degree of twisting of the golf club during the swing motion based on the measurement data. The determination unit determines an optimal club length, which is a length of the golf club suitable for the golfer, according to a magnitude of the first swing index.

[0007] A fitting device according to a second aspect is the fitting device according to the first aspect, wherein the determination unit compares the first swing indicator with a predetermined first threshold, and if the first swing indicator is equal to or greater than the first threshold, determines that the optimal club length is the first club length.

[0008] A fitting device according to a third aspect is the fitting device according to the second aspect, wherein the determination unit compares the first swing indicator with a predetermined second threshold value smaller than the first threshold value, and if the first swing indicator is equal to or smaller than the second threshold value, determines that the optimal club length is a second club length longer than the first club length.

[0009] A fitting device according to a fourth aspect is a fitting device according to any one of the first to third aspects, wherein the measurement data includes an angular velocity at a grip end of the golf club, and the first swing indicator is calculated based on an angular velocity about an axis parallel to a shaft of the golf club.

[0010] A fitting device according to a fifth aspect is the fitting device according to the fourth aspect, wherein the first swing index is an average value or an integral value of the angular velocity during a downswing.

[0011] A fitting device according to a sixth aspect is a fitting device according to any one of the first to fifth aspects, further comprising a selection unit that selects at least one of a golf club that best matches the optimum club length and a shaft to be included in the golf club.

[0012] A fitting device according to a seventh aspect includes an acquisition unit, a calculation unit, a determination unit, and a selection unit. The acquisition unit acquires measurement data obtained by measuring a swing motion of a golf club by a golfer using a measurement device. The calculation unit calculates a first swing index, a second swing index, and a third swing index related to the swing motion based on the measurement data. The determination unit determines an optimal club length that is a club length suitable for the golfer according to the magnitude of the first swing index, determines an optimal swing ease index that is an index of ease of swing of a golf club suitable for the golfer according to the magnitude of the second swing index, and determines an optimal stiffness index that indicates stiffness of the shaft suitable for the golfer according to the magnitude of the third swing index. The selection unit selects at least one of a golf club that best matches the optimal swing ease index, the optimal stiffness index, and the club length and a shaft to be included in the golf club. The first swing index is an index related to the degree of twisting of the golf club during the swing motion.

[0013] A fitting device according to an eighth aspect includes an acquisition unit, a calculation unit, a determination unit, and a selection unit. The acquisition unit acquires measurement data obtained by measuring a swing motion of a golf club by a golfer using a measurement device. The calculation unit calculates a first swing index, a second swing index, and a third swing index related to the swing motion based on the measurement data. The determination unit determines an optimal club length that is a club length suitable for the golfer according to the magnitude of the first swing index, determines an optimal characteristic index that indicates a characteristic of a specific part of the golf club suitable for the golfer according to the magnitude of the second swing index, and determines an optimal stiffness index that indicates stiffness of the shaft suitable for the golfer according to the magnitude of the third swing index. The selection unit selects at least one of a golf club that best matches the optimal characteristic index, the optimal stiffness index, and the club length and a shaft to be included in the golf club. The first swing index is an index related to the degree of twisting of the golf club during the swing motion.

[0014] A fitting device according to a ninth aspect is the fitting device according to the seventh or eighth aspect, wherein the measurement data includes an angular velocity at a grip end of the golf club, and the first swing indicator is calculated based on the angular velocity about an axis parallel to a shaft of the golf club.

[0015] A fitting method according to a tenth aspect includes the following steps (1) to (3). (1) A step of acquiring measurement data obtained by measuring a swing motion of a golf club by a golfer using a measuring device. (2) calculating, using a computer, a first swing index relating to the degree of twisting of the golf club during the swing motion based on the measurement data; (3) determining an optimal club length that is suitable for the golfer in accordance with the magnitude of the first swing indicator;

[0016] A fitting method according to an eleventh aspect causes a computer to execute the following steps (1) to (3). (1) A step of acquiring measurement data by measuring a golfer's swing motion of a golf club using a measuring device. (2) calculating, using a computer, a first swing index relating to the degree of twisting of the golf club during the swing motion based on the measurement data; (3) determining an optimal club length that is suitable for the golfer in accordance with the magnitude of the first swing indicator; Effect of the Invention

[0017] According to a first aspect of the present invention, a first swing index that indicates the degree of twisting of a golf club is calculated based on a measurement value of the golf club. Then, an optimum club length that is a length of a golf club suitable for a golfer is determined according to the first swing index. In other words, since the optimum club length suitable for the golfer is determined based on the characteristics of the golfer's swing motion, a golf club having a club length suitable for the golfer can be accurately selected.

[0018] According to a seventh aspect of the present invention, a first swing index, a second swing index, and a third swing index are calculated based on measurements of a golf club. Then, an optimum club length, which is a length of a golf club suitable for a golfer, is determined according to the first swing index, an optimum swing ease index, which is an index of the ease of swing of a golf club suitable for a golfer, is determined according to the second swing index, and an optimum stiffness index, which indicates the stiffness of a shaft suitable for a golfer, is determined according to the third swing index. Then, at least one of a golf club and a shaft to be included therein that best matches the optimum swing ease index, the optimum stiffness index, and the optimum club length is selected. The first swing index represents the degree of twisting of the golf club. This narrows down golf clubs suitable for a golfer from various points of view, so that a golf club can be selected with high accuracy.

[0019] According to an eighth aspect of the present invention, a first swing index, a second swing index, and a third swing index are calculated based on measurements of a golf club. Then, an optimum club length, which is the length of a golf club suitable for a golfer, is determined according to the first swing index, an optimum characteristic index representing the characteristic of a specific part of the golf club suitable for the golfer is determined according to the second swing index, and an optimum stiffness index indicating the stiffness of a shaft suitable for the golfer is determined according to the third swing index. Then, at least one of a golf club and a shaft to be included therein that best matches the optimum characteristic index, the optimum stiffness index, and the optimum club length is selected. The first swing index represents the degree of twist of the golf club. This narrows down golf clubs suitable for a golfer from various points of view, allowing the golf club to be selected with high accuracy. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a fitting system including a fitting device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a functional block diagram of the fitting system. [Diagram 3] FIG. 2 is a diagram illustrating an xyz local coordinate system based on the grip of a golf club. [Figure 4] 11 is a flowchart showing the flow of a fitting process. [Diagram 5] (A) Address state, (B) Top state, (C) Impact state, (D) Finish state. [Figure 6] 11 is a flowchart showing the flow of a first index calculation step. [Figure 7] FIG. 13 is a diagram for explaining a method for deriving the top time. [Figure 8] 11 is a flowchart showing the flow of an optimum club length determination process. [Figure 9] 11 is a graph showing differences in the waveform of angular velocity ωz due to differences in swing behavior. [Figure 10] FIG. [Figure 11] A conceptual diagram of the double pendulum model. [Figure 12] Another diagram conceptually explaining the double pendulum model. [Figure 13] FIG. [Figure 14] FIG. 13 is a diagram showing an average model region. [Figure 15] Diagram explaining the International Flex Code (IFC). [Figure 16] 4A to 4C are diagrams illustrating a method for measuring the bending rigidity of a shaft. [Figure 17] A diagram explaining the bending of a shaft during a swing. [Figure 18] 13 is a diagram for explaining an angle serving as a first swing indicator according to a modified example. FIG. [Figure 19] 13 is a diagram showing a space indicating a second swing indicator divided into divided regions corresponding to optimal shaft weight bands. FIG. [Figure 20A] FIG. 13 is a diagram showing a space showing a first swing indicator divided into divided regions corresponding to optimal shaft weight bands for a particular flex. [Figure 20B]FIG. 13 is a diagram showing a space showing a first swing indicator divided into divided regions corresponding to optimal shaft weight bands for different flexes. [Figure 20C] FIG. 13 is a diagram showing a space showing a first swing indicator divided into divided regions corresponding to optimum shaft weight ranges for yet another flex. [Figure 21A] Conceptual diagram showing torsional rotational movement. [Figure 21B] A conceptual diagram showing the rotational movement of a push. [Figure 22] FIG. 13 is a diagram showing the flow of exception handling. [Figure 23A] FIG. 11 is a diagram comparing test shot results of an embodiment and a comparative example by a golfer. [Figure 23B] FIG. 11 is a diagram comparing test shot results of the embodiment and the comparative example by different golfers. [Figure 23C] FIG. 11 is a diagram comparing test shot results of the embodiment and the comparative example by still another golfer. [Figure 23D] FIG. 11 is a diagram comparing test shot results of the embodiment and the comparative example by still another golfer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A golf club fitting device, method, and program according to an embodiment of the present invention will be described below with reference to the drawings.

[0022] <1. Outline of fitting system configuration> 1 and 2 show the overall configuration of a fitting system 100 (hereinafter also simply referred to as "system 100") equipped with a fitting device 2 according to this embodiment. The fitting device 2 is a device for selecting a golf club 4 suitable for a golfer G based on measurement data obtained by measuring the swing motion of the golf club 4 by the golfer G. In this embodiment, the swing motion is measured by a sensor unit 1 attached to the grip 42 of the golf club 4, and the fitting device 2 and this sensor unit 1 constitute the system 100.

[0023] Below, the configurations of the sensor unit 1 and the fitting device 2 will be described, and then the flow of the fitting process will be described.

[0024] <1-1. Sensor unit configuration> As shown in FIG. 1 and FIG. 3, the sensor unit 1 is attached to an end of a grip 42 of a golf club 4 on the opposite side to a head 41, and measures the behavior of the grip 42. The golf club 4 is a typical golf club, and is composed of a shaft 40, a head 41 provided at one end of the shaft 40, and a grip 42 provided at the other end of the shaft 40. The shaft 40 according to this embodiment is a carbon shaft. The sensor unit 1 is small and lightweight so as not to interfere with the swing motion. As shown in FIG. 2, the sensor unit 1 according to this embodiment is equipped with an acceleration sensor 11, an angular velocity sensor 12, and a geomagnetic sensor 13. The sensor unit 1 is also equipped with a communication device 10 for transmitting measurement data by these sensors 11 to 13 to an external fitting device 2. In this embodiment, the communication device 10 is wireless so as not to interfere with the swing motion, but may be connected to the fitting device 2 in a wired manner via a cable.

[0025] The acceleration sensor 11, the angular velocity sensor 12, and the geomagnetic sensor 13 respectively measure grip acceleration, grip angular velocity, and grip geomagnetism in an xyz local coordinate system based on the grip 42. More specifically, the acceleration sensor 11 measures grip acceleration a in the x-axis, y-axis, and z-axis directions. x ,a y ,a z The angular velocity sensor 12 measures the grip angular velocity ω x ,ω y ,ω z The geomagnetic sensor 13 measures the grip geomagnetic field m in the x-axis, y-axis, and z-axis directions. x ,m y ,m zare measured. These measurement data are acquired as time-series data with a predetermined sampling period Δt. The xyz local coordinate system is a three-axis orthogonal coordinate system defined as shown in FIG. 3. That is, the z-axis coincides with the direction in which the shaft 40 extends, and the direction from the head 41 to the grip 42 is the positive direction of the z-axis. The x-axis is oriented as close as possible to the toe-heel direction of the head 41, and the y-axis is oriented as close as possible to the normal direction of the face surface of the head 41.

[0026] In this embodiment, the measurement data from the acceleration sensor 11, the angular velocity sensor 12, and the geomagnetic sensor 13 are transmitted in real time to the fitting device 2 via the communication device 10. However, for example, the measurement data may be stored in a storage device within the sensor unit 1, and after the swing motion is completed, the measurement data may be retrieved from the storage device and passed to the fitting device 2.

[0027] <1-2. Configuration of fitting device> The fitting device 2 is a general-purpose computer as hardware, and is realized as, for example, a desktop computer, a notebook computer, a tablet computer, a smartphone, or the like. As shown in FIG. 2, the fitting device 2 is manufactured by installing a fitting program 3 according to this embodiment (hereinafter, also simply referred to as "program 3") in a general-purpose personal computer. The program 3 is acquired by the fitting device 2 from a computer-readable recording medium 20 such as a CD-ROM, or via a communication network such as a local area network (LAN) or the Internet connected to the communication unit 25. The program 3 is software for analyzing a swing motion based on the measurement data sent from the sensor unit 1, and outputting information to assist in selecting a golf club 4 suitable for the golfer G. The program 3 causes the fitting device 2 to execute operations to be described later.

[0028] The fitting device 2 includes a display unit 21, an input unit 22, a storage unit 23, a control unit 24, and a communication unit 25. These units 21 to 25 are connected via a bus line 26 and can communicate with each other. In this embodiment, the display unit 21 is configured with a liquid crystal display or the like, and displays information to be described later to the user. The user here is a general term for anyone who requires the fitting results, such as the golfer G himself / herself, his / her instructor, a golf club salesperson, etc. The input unit 22 can be configured with a mouse, a keyboard, a touch panel, etc., and accepts operations from the user on the fitting device 2. The communication unit 25 is a communication interface that enables communication between the fitting device 2 and an external device, and receives data from the sensor unit 1.

[0029] The storage unit 23 is composed of a non-volatile storage device such as a hard disk. In addition to storing the program 3 in the storage unit 23, the measurement data sent from the sensor unit 1 is saved. In addition, the storage unit 23 stores correspondence data 28, a head database (DB) 27, and a shaft database (DB) 29. The correspondence data 28, which will be described in detail later, is data that is defined for each of various models (series) of the golf club 4 and indicates conditions for determining an optimal ease of swing index. Similarly, the head DB 27, which will be described in detail later, is a database in which information indicating the specifications of a large number of heads 41 is stored in association with information specifying the type of head 41.

[0030] The control unit 24 can be composed of a CPU, a ROM, a RAM, etc. The control unit 24 reads and executes the program 3 in the storage unit 23, thereby virtually operating as an acquisition unit 24A, a grip behavior derivation unit 24B, a shoulder behavior derivation unit 24C, a calculation unit 24D, a determination unit 24E, a selection unit 24F, and a display control unit 24G. Details of the operation of each unit 24A to 24G will be described later.

[0031] <2. Fitting process> Next, there will be described the fitting process executed by the system 100. As shown in FIG. 4, the fitting process according to this embodiment is made up of the following 11 steps (S1 to S11). (S1) Grip acceleration a in the xyz local coordinate system x ,a y ,a z , grip angular velocity ω x ,ω y ,ω z and grip geomagnetic field m x ,m y ,m z Measurement process to measure the measurement data (S2) Grip angular velocity ω z A first indicator calculation step of calculating a first swing indicator from (S3) An optimal club length determination step for determining an optimal club length based on the first swing index. (S4) The measurement data in the xyz local coordinate system obtained in the measurement process is converted into the grip acceleration a X ,a Y ,a Z and grip angular velocity ω X ,ω Y ,ω Z The first transformation step converts the grip velocity v in the XYZ global coordinate system into X ,v Y ,v Z is also derived.) (S5) Behavior of grip 42 in the XYZ global coordinate system (grip angular velocity ω X ,ω Y ,ω Z and grip speed v X ,v Y ,v Z ) into the behavior of the grip 42 within the swing plane P (described later). (S6) A shoulder behavior deriving process for deriving a pseudo shoulder behavior of the golfer G in the swing plane P based on the behavior of the grip 42 in the swing plane P. (S7) Based on the behavior of the grip 42 and the pseudo shoulder behavior within the swing plane P, a second swing indicator (in this embodiment, an arm output power P1_AVE , Club input power P2_ AVE and head speed V h ) A second index calculation step (S8) Based on the second swing indicator, a swing ease indicator suitable for the golfer G (in this embodiment, the swing moment of inertia I S An optimal swing ease determination step for determining an optimal swing ease index (in this embodiment, an optimal swing MI) (S9) A third index calculation process for calculating third swing indexes (first to fourth feature amounts F1 to F4 in this embodiment, which will be described later) based on the measurement data (S10) An optimal stiffness determination step of determining an optimal stiffness index (in this embodiment, an EI distribution, which will be described later) indicating the stiffness of the shaft 40 suitable for the golfer G based on the third swing index. (S11) An optimum club selection process for selecting a golf club 4, particularly a shaft 40, that matches the optimum swing ease index, the optimum stiffness index, and the optimum club length. These steps will be described in order below.

[0032] The XYZ global coordinate system is a three-axis Cartesian coordinate system defined as shown in Figure 1. That is, the Z axis is a vertical direction from bottom to top, the X axis is a direction from the back to the stomach of the golfer G, and the Y axis is a direction parallel to the ground plane from the ball hitting point to the target point.

[0033] <2-1. Measurement process> In the measurement step (S1), the golf club 4 with the sensor unit 1 described above is swung by the golfer G. The golf club 4 swung in the measurement step is one of two test clubs. These test clubs are different types of golf clubs, and in this embodiment, one is a professional golf club (hereinafter, professional model club) and the other is a golf club suitable for average users (hereinafter, average model club). In this embodiment, the professional model club is heavier than the average model club. Which test club is swung in the measurement step is determined based on the preference, experience, etc. of the golfer G.

[0034] Next, the grip acceleration a during the swing motion of the golf club 4 as described above x ,a y ,a z , grip angular velocity ω x ,ω y ,ω z and grip geomagnetic field m x ,m y ,m z The measurement data is measured by the sensor unit 1. This measurement data is transmitted to the fitting device 2 via the communication device 10 of the sensor unit 1. Meanwhile, on the fitting device 2 side, the acquisition unit 24A receives this data via the communication unit 25 and stores it in the storage unit 23. In this embodiment, time-series measurement data is measured at least from address to impact.

[0035] The swing motion of a golf club generally proceeds in the order of address, top, impact, and finish. Address refers to the initial state in which the head 41 of the golf club 4 is located near the ball, as shown in Fig. 5(A), and top refers to the state in which the golf club 4 is taken back from the address and the head 41 is swung up to the maximum, as shown in Fig. 5(B). Impact refers to the state at the moment when the golf club 4 is swung down from the top (downswing) and the head 41 collides with the ball, as shown in Fig. 5(C), and finish refers to the state in which the golf club 4 is swung forward after the impact, as shown in Fig. 5(D).

[0036] In the measurement process, it is preferable that the golf club 4 is test-hit a number of times, preferably five times or more. In this case, the average value of the measurement data is calculated and can be used in the subsequent calculations. In addition, in order to remove abnormal values ​​due to mis-shots, measurement errors, etc., the standard deviation σ of the measurement data is calculated, and if all the measurement data does not fall within the average value ±k·σ (k is a constant), a message requesting additional measurement or redoing the measurement may be displayed on the display unit 21. Note that the average value of the measurement data itself is not used, but rather a processed value calculated based on the measurement data (for example, arm output power P1_ AVE , Club input power P2_ AVE and head speed V h ) may be calculated. When calculating the average value of the processed values, the reliability of the data can be checked based on the standard deviation σ.

[0037] <2-2. First index calculation process> Hereinafter, the first index calculation step (S2) will be described with reference to FIG. x ,ω y ,ω z Based on the measurement data, a first swing indicator SW1 is calculated. The first swing indicator SW1 is an indicator that indicates the degree of twisting of the golf club 4 during a swing motion, in other words, the rotational movement of the twisting around the shaft axis of the golf club 4 (see FIG. 21A). In this embodiment, as the first swing indicator SW1, a grip angular velocity ω z The average value of the above is calculated. The first swing index SW1 is an index for determining the optimum club length in a process described later. The reason why an index representing such a degree of twist is calculated as an index for determining the optimum club length will be described later.

[0038] Specifically, first, the acquisition unit 24A acquires the grip angular velocity ω x ,ω y ,ω z The time-series measurement data is read out (step S21).

[0039] Next, the grip behavior deriving unit 24B calculates the grip angular velocity ω x ,ω y ,ω z Based on the measurement data, the top time t i and the time of impact t t (Step S22). i There are various known methods for deriving the grip angular velocity ω y In the waveform of the grip angular velocity ω y The timing when the sign of changes from negative to positive, i.e., ω y The timing when ω = 0 is defined as the top timing. y From the measurement data, ω y The time when = 0 is the top time t i The time of impact is specified as t t Since various methods are known for deriving the grip angular velocity ω, detailed description will be omitted. In this embodiment, the grip angular velocity ω is calculated according to the method described in Japanese Patent No. 6059878. x ,ω y ,ω z Based on the measured data, the impact time t t is derived.

[0040] In step S23, the calculation unit 24D calculates the top time t i from impact time t t Grip angular velocity ω up to z In this embodiment, the grip angular velocity ω is calculated according to the following formula: z The average value is calculated.

number

[0041] That is, the first swing index SW1 of the present embodiment is i from impact time t tGrip angular velocity ω in the section up to z The first swing indicator SW1 is calculated by dividing the integral value of the absolute value of by the period from the top to the impact. However, the first swing indicator SW1 is not limited to this. i from impact time t t Grip angular velocity ω in the section up to z When the calculated first swing indicator SW1 is stored in the RAM or the storage unit 23, the first indicator calculation process ends.

[0042] <2-3. Optimal club length determination process> Hereinafter, with reference to FIG. 8, an optimum club length determination step (S3) for determining an optimum club length based on the first swing indicator SW1 calculated in the first indicator calculation step will be described. In this embodiment, according to the magnitude of the first swing indicator SW1, any one of the basic club length, the first club length shorter than the basic club length, and the second club length longer than the basic club length is determined as the optimum club length. Each club length is determined in advance, and the basic club length is, but is not limited to, for example, 45.25 inches. In addition, the first club length is, but is not limited to, for example, 44.75 inches, and the second club length is, but is not limited to, for example, 45.75 inches. Note that the method of measuring the club length may be defined based on the 60-degree method or the heel-end method as long as it is unified among the many shafts 40 registered in the shaft DB 29. The method of measuring the club length in this embodiment is based on the heel-end method.

[0043] In step S31, the determination unit 24E determines whether the first swing index SW1 is greater than or equal to a predetermined first threshold value TH1 (SW1 ≧ TH1). The first threshold value TH1 is a value predetermined based on a large number of experimental data or the like, and may be stored in the storage unit 23 or may be incorporated into the program 3. In the present embodiment, TH1 is determined to be 250. When the determination unit 24E determines that SW1 ≧ TH1, the process proceeds to step S32. On the other hand, when the determination unit 24E determines that the first swing index SW1 is less than the predetermined first threshold value TH1, that is, SW1 < TH1, the process proceeds to step S33.

[0044] In step S32, the determination unit 24E determines the optimal club length to be a first club length shorter than the basic club length. Then, the optimal club length determination process ends.

[0045] In step S33, the determination unit 24E determines whether the first swing index SW1 is less than or equal to a predetermined second threshold value TH2 (SW1 ≦ TH2). The second threshold value TH2 is, like the first threshold value TH1, a value predetermined based on a large number of experimental data or the like, and may be stored in the storage unit 23 or may be incorporated into the program 3. In the present embodiment, TH2 is determined to be 75. When the determination unit 24E determines that SW1 ≦ TH2, the process proceeds to step S34. On the other hand, when the determination unit 24E determines that the first swing index SW1 exceeds the predetermined second threshold value TH2, the process proceeds to step S35.

[0046] In step S34, the determination unit 24E determines the optimal club length to be a second club length longer than the basic club length. Then, the optimal club length determination process ends.

[0047] The process when the first swing index SW1 exceeds the second threshold value TH2 and is less than the first threshold value TH1 (TH2 < SW1 < TH1) is the process of step S35. In step S35, the determination unit 24E determines the optimal club length to be the basic club length. Then, the optimal club length determination process ends.

[0048] As described above, the fact that the optimal club length can be determined based on the first swing parameter SW1 has been confirmed by experiments conducted by the inventors. The inventors had many golfers try out the golf club 4 with the sensor unit 1, and measured the grip angular velocity ω z As a result, as shown in FIG. 9, the grip angular velocity ω z It was found that there is a significant difference in the waveforms of the two. For the sake of convenience, only representative examples of the two are shown in Fig. 9. The inventors have found that the first swing index SW1 of each golfer tends to be distributed among a group that uses a lot of rotational motion, a group that uses standard rotational motion, and a group that uses almost no rotational motion.

[0049] The inventors had 10 golfers who use a lot of rotational movements, that is, those who had a significantly large first swing index SW1, try hitting the ball with the golf club 4 of the first club length, and compared the distance of the ball and the directionality of the trajectory (less deviation from left to right) with those of the test hit with the golf club 4 of the basic club length. As a result, for all 10 golfers, the test hit with the golf club 4 of the first club length showed either a longer maximum distance with almost no change in directionality, or improved directionality with almost no change in maximum distance.

[0050] Furthermore, the inventors had seven golfers who hardly used rotational motion, i.e., those with a significantly small first swing index SW1, try hitting the ball with the golf club 4 of the second club length, and compared the distance and trajectory directionality (less deviation from left to right) of the ball with those of the test hit with the golf club 4 of the basic club length. As a result, for the six golfers, the test hit with the golf club 4 of the second club length showed either a longer maximum distance with almost no change in directionality, or an improved directionality with almost no change in maximum distance.

[0051] The above experimental results are believed to be due to the following reasons. In a swing motion with a lot of rotational movement and a large degree of twisting, it is relatively difficult to perform the turning motion of the golf club 4 (see FIG. 17(2)). However, using a relatively short golf club 4 makes the turning motion easier and improves the swing. Also, in a swing motion with extremely little rotational movement and a small degree of twisting, the turning motion of the golf club 4 is relatively easy, so there is a tendency for the golf club 4 to turn over too much. However, using a relatively long golf club 4 prevents the golf club from turning over too much and improves the swing.

[0052] <2-4. First conversion process> In the first conversion step (S4), a process is performed to convert the measurement data in the xyz local coordinate system into values ​​in the XYZ global coordinate system. In this process, the grip behavior derivation unit 24B converts the grip angular velocity ω x ,ω y ,ω z and grip acceleration a x ,a y ,a z The time series measurement data of the grip angular velocity ω in the XYZ global coordinate system from address to impact X ,ω Y ,ω Z and grip acceleration a X ,a Y ,a Z The grip behavior deriving unit 24B converts the grip acceleration a X ,a Y ,a Z By integrating the time series data of the grip velocity v in the XYZ global coordinate system from address to impact, X ,v Y ,v Z The specific calculation method is described in detail in Patent Document 1, and therefore will not be described here.

[0053] <2-5. Second conversion process> In the second conversion step (S5), a process is performed in which the behavior of the grip 42 in the XYZ global coordinate system calculated in the first conversion step is converted into the behavior of the grip 42 in the swing plane P. In this embodiment, the swing plane P is defined as a plane that includes the origin of the XYZ global coordinate system and is parallel to the Y axis and the shaft 40 at the time of impact (see FIG. 10). In the second conversion step, the grip behavior derivation unit 24B converts the grip velocity v X ,v Y ,v Z and grip angular velocity ω X ,ω Y ,ω Z The grip velocity v projected onto the swing plane P pX ,v pY ,v pZ and grip angular velocity ω pX ,ω pY ,ω pZ The specific calculation method is described in detail in Patent Document 1, and therefore will not be described here.

[0054] <2-6. Shoulder behavior derivation process> In the shoulder behavior deriving process (S6), the grip behavior (grip speed V GE and grip angular velocity ω pX ), a process is performed to derive a pseudo shoulder behavior within the swing plane P. In this embodiment, the behavior of the golf club 4 is analyzed based on a double pendulum model shown in FIG. 11, in which the shoulder of the golfer G and the grip 42 (or the wrist of the golfer gripping it) are nodes, and the arms of the golfer G and the golf club 4 are links. The shoulder behavior deriving unit 24C calculates, as the shoulder behavior, angular velocity ω1 around the shoulder (angular velocity of the arm) within the swing plane P from the top to the impact. A specific calculation method is described in detail in Patent Document 1, and therefore a description thereof will be omitted here.

[0055] <2-7. Second index calculation process> In the first index calculation step (S7), a process of calculating a second swing index is performed based on the behavior of the grip 42 and the behavior of the shoulder. The second swing index is a feature amount that characterizes the swing motion of the golfer G for determining an optimal swing ease index. In the present embodiment, the calculation unit 24D calculates the arm output power P1_ AVE , Club input power P2_ AVE and head speed V h Here, the second swing index is calculated based on a new XY coordinate system in the swing plane P shown in FIG. 12. The paper surface of FIG. 12 is equal to the swing plane P. The X-axis of the new XY coordinate system in the swing plane P is equal to the Y-axis of the above-mentioned XYZ global coordinate system, and the Y-axis of the new XY coordinate system is the axis obtained by projecting the Z-axis of the XYZ global coordinate system onto the swing plane P. Arm output power P1_ AVE , Club input power P2_ AVE and head speed V h The specific calculation method is described in detail in Patent Document 1 and JP2017-217324A, which is a prior art document by the present applicant, so the description will be omitted here.

[0056] As explained in JP 2017-217324 A, the arm output power P1_ AVE In other words, it is an index that indicates the strength with which the golfer G cocks the club during the swing motion. AVE In other words, it can be said that the force with which the golfer G releases the cock during the swing motion.

[0057] <2-8. Process for determining optimal swing ease> In the optimal ease of swing determination step (S8), an optimal ease of swing index is determined based on the second swing index calculated in the second index calculation step. A specific procedure for determining the optimal ease of swing index is described in detail in Patent Document 1, and therefore will be briefly described below for reference. Here, the optimal ease of swing index is an optimal swing MI, and the optimal swing MI is the swing moment of inertia I of the golf club 4 suitable for the golfer. SThis refers to the swing moment of inertia I s is the moment of inertia around the shoulders during a swing, and in this embodiment, is defined according to the following formula. I s =I2+m2(R+L) 2 +I1+m1(R / 2) 2 Here, I2 is the moment of inertia around the center of gravity of the golf club 4, and is predefined as a specification of the golf club 4. m2 is the mass of the golf club 4. R is the arm length of the golfer G, and in this embodiment, R=60 cm (constant). However, it may be the distance R (see FIG. 11) between the shoulder and the grip 42 from the top to the impact in the swing plane P, which is calculated in the process of the shoulder behavior derivation step (S6). Also, L is the distance from the grip 42 to the center of gravity of the golf club 4, and is predefined as a specification of the golf club 4. Furthermore, m1 is the mass of the arm of the golfer G, and is automatically calculated, for example, by inputting the weight of the golfer G before starting the analysis and multiplying the input weight by a predetermined coefficient. For each golfer G, the weight of the arm is the same even if the golf club 4 is changed. Therefore, for the sake of simplicity, in this embodiment, the swing moment of inertia I s is calculated according to the following formula, omitting the moment of inertia for the rotation of the arm. I s =I2+m2(R+L) 2 By the way, I S The parameters m2, I2, and L that determine the swing moment of inertia I S These are also the specifications of Golf Club 4.

[0058] When the test club test-hit in the measurement process is a professional model club, the determination unit 24E determines the arm output power P1_ AVE and club input power P2_ AVE The point showing this is P1_ AVE -P2_ AVEThe optimal swing MI band is determined depending on which area in space it is plotted in. AVE -P2_ AVE Information identifying the boundaries L1 to L4 that divide the space, and data defining the correspondence between the divided areas A1 to A5 divided by the boundaries L1 to L4 and the optimal swing MI band are stored in the memory unit 23 as correspondence data 28.

[0059] In addition, when the test club test-hit in the measurement process is an average model club, the determination unit 24E determines the arm output power P1_ AVE , Club input power P2_ AVE and head speed V h The point showing the arm output power P1_ shown in Figure 14 AVE -Club input power P2_ AVE - Head speed V h The optimal swing MI zone is determined depending on which area in the space it is plotted in. However, for simplicity, in FIG. 14, the head speed V h The axis representing the arm output power P1_ is omitted. AVE -Club input power P2_ AVE The plane is shown. P1_ AVE -P2_ AVE Information specifying the boundaries L5-L6 that divide the space, and data defining the correspondence between the divided regions B1-B3 divided by the boundaries L1-L6 and the optimum swing MI band are stored in the storage unit 23 as correspondence data 28. Note that, although the correspondence data 28 is shown as data separate from the fitting program 3 in FIG. 2, it may be incorporated in the program 3.

[0060] <2-9. Third indicator calculation process> Hereinafter, a third indicator calculation step (S9) for calculating a third swing indicator based on the measurement data obtained in the measurement step will be described. The third swing indicator is a feature amount that characterizes a swing motion of a golfer G for determining an optimal stiffness indicator. In this embodiment, first to fourth feature amounts F1 to F4 described later are calculated as the third swing indicator.

[0061] In order to understand the first to fourth feature quantities F1 to F4, it is important to first understand the optimum stiffness index. The optimum stiffness index is an index indicating the stiffness of the shaft 40 suitable for the golfer G, and in this embodiment, the stiffness of the shaft 40 is evaluated as a distribution of bending stiffness at a plurality of positions of the shaft 40 (hereinafter, EI distribution). The EI distribution according to this embodiment is quantitatively expressed using numerical values, and more specifically, is calculated using the International Flex Code (IFC). Therefore, this IFC will be described first. Note that the IFC is a known index indicating the characteristics of a shaft that has been widely proposed by the present applicant, and has already been described in detail in various documents, including Patent Document 1, for example. Therefore, it is not necessarily necessary to explain it again here, but it will be described here for reference.

[0062] As shown in FIG. 15, the IFC is a code in which the bending stiffness of the shaft 40 at four positions H1 to H4 along the extension direction of the shaft 40 is expressed by a single digit number from 0 to 9, and these four numbers are arranged along the extension direction of the shaft 40. More specifically, four measurement points H1 to H4 are defined in this order from the butt end to the tip end of the shaft 40 at approximately regular intervals. For example, a point 36 inches from the tip end of the shaft 40 can be set as measurement point H1, a point 26 inches can be set as measurement point H2, a point 16 inches can be set as measurement point H3, and a point 6 inches can be set as measurement point H4. Then, bending stiffness values ​​(hereinafter, EI values) J1 to J4 at each of these four measurement points H1 to H4 are measured.

[0063] EI value (N m) at each measurement point H (H1 to H4) on the shaft 40 2) can be measured by various methods, for example, as shown in FIG. 16 using an Intesco 2020 type measuring instrument (maximum load 500 kgf). In this measurement method, the shaft 40 is supported from below by two support points 111 and 112, and the deflection amount is measured when a load F is applied from above to a measurement point H. The distance (span) between the support points 111 and 112 can be, for example, 200 mm, and the measurement point H can be the midpoint between the support points 111 and 112. More specifically, with the supports 114 and 115 supporting the support points 111 and 112 fixed, the indenter 113 is moved downward at a constant speed (for example, 5 mm / min) at the measurement point H. Then, when the load F reaches 20 kgf, the movement of the indenter 113 is stopped, and the deflection amount (mm) of the shaft 40 at this moment is measured, and this deflection amount is expressed as an EI value (N·m 2 ) to

[0064] Next, the EI values ​​J1 to J4 at the four measurement points H1 to H4 are converted into 10-level rank values ​​K1 to K4, respectively. Specifically, the rank values ​​K1 to K4 can be calculated from the EI values ​​J1 to J4 according to the following conversion tables (Tables 1 to 4) for the measurement points H1 to H4, respectively (the converted rank values ​​are shown in the IFC column in Tables 1 to 4). The four rank values ​​K1 to K4 thus assigned to the measurement points H1 to H4, respectively, are arranged so that the value corresponding to the butt side is on the left and the value corresponding to the tip side is on the right. The four-digit code thus obtained is the IFC. In the IFC, the larger the value of each digit, the higher the rigidity at the corresponding position. [Table 1] [Table 2] [Table 3] [Table 4]

[0065] In the third index calculation step, the calculation unit 24D calculates the first to fourth feature amounts F1 to F4. In this embodiment, the first to fourth feature amounts F1 to F4 are calculated based on the optimal EI values ​​J1 to J4 that are suitable for the golfer G, respectively. S1 ~J S4 , and the optimum rank value K1 to K4 suitable for the golfer G. S1 ~K S4 Therefore, in this embodiment, the first to fourth feature amounts F1 to F4 are the optimal EI values ​​J S1 ~J S4 A feature quantity having a correlation with is selected. In this embodiment, the following indices are used as the first to fourth feature quantities F1 to F4, but any other feature quantity can be used as the third swing index as long as it is correlated with the optimal stiffness index.

[0066] The first feature F1 is the angular velocity ω y For example, the angular velocity ω y and the angular velocity ω 50 ms after the top y It can be expressed as the sum of

[0067] The second feature F2 is the angular velocity ω y The angular velocity ω y The second feature F2 is the average value of the angular velocity ω y Find the point at which is maximum, and calculate the angular velocity ω y It is calculated by dividing the cumulative value of by the time from the top to this point.

[0068] The third feature F3 is the angular velocity ω y The angular velocity ω from the time when it becomes maximum to the time of impact y The third feature F3 is the average value of the angular velocity ω y The angular velocity ω from the point where it is maximum to the impact y The cumulative value of yIt is calculated by dividing the time from when the force is at its maximum by the time to impact.

[0069] The fourth feature F4 is the angular velocity ω y is the average value of the angular velocity ω from the top to the impact. y It is calculated by dividing the cumulative value by the time from the top to impact.

[0070] During a swing motion, the shaft 40 of the golf club 4 is bent due to the inertia of the head 41, which is relatively heavy, at the tip of the golf club. This bending does not occur at the same place on the shaft 40 throughout the entire swing process, but is transmitted from the grip side to the tip side of the shaft 40 from the top to the impact, as shown in Fig. 17. In other words, as the swing progresses from the top to the impact, the position of the bending in the shaft 40 moves from the grip side to the tip side of the shaft 40.

[0071] More specifically, when the golfer takes the ball back from the address and reaches the top (the point indicated by (1) in FIG. 17), a bend occurs in the shaft 40 near the grip. Then, when the golfer makes a turn and reaches the beginning of the downswing (the point indicated by (2) in FIG. 17), the bend moves slightly toward the tip of the shaft 40. Furthermore, when the golfer's arms become horizontal (the point indicated by (3) in FIG. 17), the bend moves toward the tip of the shaft 40 rather than the center. Then, just before impact (the point indicated by (4) in FIG. 17), the bend moves to the vicinity of the tip of the shaft 40.

[0072] Therefore, the first to fourth feature amounts F1 to F4 can be calculated in the first to third sections from near the top to near the impact during the swing motion, respectively. The first to third sections are sections along the time course in this order, and may or may not overlap with each other.

[0073] <2-10. Optimal stiffness determination process> In the optimal stiffness determination step (S10), the determination unit 24E determines the second swing index (the first to fourth feature amounts F1 to F4) and the optimal stiffness index (the optimal EI value J S1 ~J S4 ) according to a predetermined approximation formula that expresses the correlation with the optimal stiffness index (optimum EI value J S1 ~J S4 The approximation equation according to this embodiment is a linear approximation equation and is expressed as follows: J S1 =a1·F1+b1 J S2 =a2·F2+b2 J S3 =a3·F3+b3 J S4 =a4·F4+b4

[0074] The determination unit 24E determines the optimal EI value J by substituting the first to fourth feature amounts F1 to F4 calculated in the second index calculation process into the approximation formula. S1 ~J S4 In addition, the determination unit 24E calculates the optimal EI value J according to the conversion tables of Tables 1 to 4 described above. S1 ~J S4 Each of these is the optimal rank value K S1 ~K S4 Convert to.

[0075] In the above formula, a1 to a4 and b1 to b4 are constants obtained by regression analysis from the results of many experiments conducted in advance, and are values ​​stored in the storage unit 23 in advance. The experiment can be performed as follows, for example, as in Patent Document 1. That is, first, many golfers are asked to swing multiple golf clubs, and the flight distance, the direction of the ball (left / right deviation), and the ease of swinging by a sensory test are quantified. Then, a golf club suitable for each golfer is determined from the numerical values, and the EI value of the golf club is set as the optimal EI value for the golfer. In addition, the first to fourth feature values ​​F1 to F4 of each golfer are calculated in the same manner as above. After the experiment, a1 to a4 and b1 to b4 are calculated by performing regression analysis on the data of the first to fourth feature values ​​F1 to F4 and the optimal EI value for many golfers.

[0076] In order to obtain a more reliable approximation, the values ​​of a1 to a4 and b1 to b4 can be changed according to conditions. For example, when the head speed V h In one example, the experimental data is classified according to the head speed range (for example, 45 m / s or more, 41 to 45 m / s, 41 m / s or less), and the above approximation formula is created for only data belonging to the same classification, and a1 to a4 and b1 to b4 are determined in advance. Then, in the optimum stiffness determination step, h It is determined which head speed range the head speed belongs to, and an optimum stiffness index is calculated using an approximation formula corresponding to the head speed range.

[0077] <2-11. Optimal club selection process> Through the above steps S1 to S10, the optimum club length, the optimum swing ease index (optimum swing MI band) and the optimum stiffness index (optimum EI value J S1 ~J S4 , the optimal rank value K S1 ~K S4 ) is determined, the selection unit 24F executes an optimum club selection step (S11). In this step, a shaft 40 (hereinafter, a recommended shaft) suitable for the golfer G is identified from among the many shafts registered in the shaft DB 29. In addition, as a result of the fitting, a golf club 4 (hereinafter, a recommended golf club) suitable for the golfer G is also identified.

[0078] In this embodiment, first, the selection unit 24F determines the type of head 41 (hereinafter, recommended head) to be used for the recommended golf club. The type of the recommended head can be determined by a fitting process not described in this specification, or can be determined by asking the user questions via the display unit 21 and the input unit 22 to select a preferred head 41. The selection unit 24F then reads out information indicating the specifications of the recommended head from the head DB 27, and also reads out information indicating the specifications of all shafts 40 registered in the shaft DB 29. The information indicating the specifications of the head 41 registered in the head DB 27 includes the manufacturer, model number, weight, etc. Meanwhile, the information indicating the specifications of the shaft 40 registered in the shaft DB 29 includes the manufacturer, model number, EI values ​​J1 to J4 and rank values ​​K1 to K4 (IFC) at four positions H1 to H4, the weight, flex, torque, flex, length, and center of gravity position of the shaft 40, etc. The selection unit 24F selects from this information the swing moment of inertia I of the golf club 4 when each shaft 40 is combined with the recommended head. S is calculated, and the golf club 4 (hereinafter, the first narrowed-down golf club) and the shaft 40 (hereinafter, the first narrowed-down shaft) included therein whose value belongs to the optimum swing MI zone are specified. Note that there are usually a large number of first narrowed-down golf clubs and shafts.

[0079] Next, for each of the first narrowed-down shafts, the selection unit 24F selects the rank values ​​K1 to K4 of the shaft and the optimum rank value K determined in the optimum stiffness determination step. S1 ~K S4 The degree of agreement between the shafts is calculated, and a shaft having a high degree of agreement is identified as the second narrowed-down shaft. The degree of agreement can be calculated, for example, according to the following formula 25, and the smaller the value, the higher the degree of agreement.

number

[0080] Only one shaft may be specified as the second narrowed-down shaft, or multiple shafts may be specified. In addition, a predetermined number of shafts having a relatively high degree of matching among the first narrowed-down shafts may be specified as the second narrowed-down shafts, or all shafts having a degree of matching equal to or higher than a certain level may be specified.

[0081] Next, the selection unit 24F calculates the club length of the golf club 4 when each second narrowed-down shaft is combined with the recommended head from the information included in the head DB 27 and the shaft DB 29, and specifies a shaft whose value matches or is closest to the optimal club length determined in the optimal club length determination step (S3). Since the club length usually includes the length from the reference point on the head side to the grip cap line of the grip, the selection unit 24F calculates the club length of the golf club 4 when each second narrowed-down shaft is combined with the recommended head, taking into account the length of the grip part. The selection unit 24F selects the specified shaft as the recommended shaft. The selection unit 24F also selects the golf club 4 when the recommended shaft is combined with the recommended head as the recommended golf club.

[0082] The display control unit 24G refers to the shaft DB 29 and causes the display unit 21 to display information indicating the type of the recommended shaft as well as information indicating the specifications of the recommended shaft (including the IFC value). Furthermore, the display control unit 24G causes the display unit 21 to display the optimum club length, optimum swing MI band, and optimum rank value K of the golfer G. S1 ~K S4 on the display unit 21. The display control unit 24G also displays information indicating that the recommended golf club is a golf club that combines a recommended shaft and a recommended head on the display unit 21. This allows the user to know the type of golf club 4 and shaft 40 that is suitable for the golfer G, as well as the club length, IFC value, optimal swing MI band, and optimal rank value K of the golf club. S1 ~K S4 You can find out.

[0083] <3. Features> According to the system 100 of this embodiment, a recommended golf club suitable for golfer G, including, for example, a head 41 preferred by golfer G, is selected based on the measurement data by the common sensor unit 1. The recommended golf club is a golf club that matches or has a high degree of match with the optimum club length, optimum swing ease index, and optimum stiffness index. In other words, a golf club suitable for golfer G is selected from the viewpoints of club length, swing MI zone, and IFC, so that a highly accurate fitting can be performed.

[0084] <4. Modifications> Although several embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible without departing from the spirit of the present invention. For example, the following modifications are possible. In addition, the gist of the following modifications can be combined as appropriate.

[0085] <4-1> In the above embodiment, in the optimum club selection step (S11), first, the swing moment of inertia I S The golf clubs or shafts included therein whose values ​​belong to the optimal swing MI band are narrowed down, then the shafts matching the optimal stiffness index are narrowed down, and finally the golf clubs or shafts included therein whose values ​​match the optimal club length are identified. However, the golf clubs or shafts do not have to be narrowed down in this order. For example, first the golf clubs or shafts included therein whose values ​​match the optimal club length are narrowed down, then the shafts matching the optimal stiffness index are narrowed down, or the swing moment of inertia I S The golf clubs or shafts included therein whose values ​​belong to the optimum swing MI zone may be narrowed down.

[0086] <4-2> In the system 100 of the above embodiment, fitting of the club length, fitting of the swingability, and fitting of the rigidity are performed together. However, the system 100 can be configured as a system that omits fitting of the swingability and fitting of the rigidity and simply fits only the club length. That is, the system 100 may be configured to determine the optimum club length based on the first swing index SW1 in steps S1 to S3, and then select a golf club that matches the optimum club length in the optimum club selection step (S11). In this case, the selection of the golf club can be performed, for example, by first determining a recommended head as in the above embodiment, and specifying as the recommended shaft a shaft 40 such that the club length of the golf club 4 when combined with the recommended head matches or is closest to the optimum club length. Also, for example, data on the combination of the head 41 and the shaft 40 fixed in advance in the memory unit 23 may be stored, and a golf club combined with the head 41 and the shaft 40 that matches or is closest to the optimum club length may be selected in step S11. Furthermore, the fitting of the club length based on the first swing parameter SW1 may be combined with either the fitting of the ease of swinging or the fitting of the stiffness, or with fitting by another method.

[0087] <4-3> In the above embodiment, the optimum swing MI band is finally determined in the optimum swing ease determining step (S8). However, in the optimum swing ease determining step (S8), an optimum characteristic index that represents the characteristics of a specific part of the golf club 4 suitable for the golfer G may be determined from the optimum swing MI. For example, the weight (optimum shaft weight) of the shaft 40 of the golf club 4 that is finally suitable for the golfer G may be determined as the optimum characteristic index, and in the optimum club selecting step (S11), the optimum shafts may be narrowed down based on the optimum shaft weight. In this case, the second swing index (P1_ AVE , P2_ AVE , and V hThe optimal swing MI may be calculated directly from the second swing index by calculating and storing in advance a multiple regression equation with the optimal swing MI as an explanatory variable and the optimal swing MI as a response variable. By determining in advance the correspondence relationship between the optimal swing MI and the optimal shaft weight range as correspondence data, the correspondence data can be collated and the optimal shaft weight range can be determined from the calculated optimal swing MI. Here, the swing moment of inertia I S is the total value of the swing moment of inertia of the head 41, the swing moment of inertia of the shaft 40, and the swing moment of inertia of other parts (grip 42, ferrule, etc.). Therefore, when the swing moment of inertia of other parts is stored in the storage unit 23, the swing moment of inertia I of the entire golf club 4 is calculated by referring to this data. S A recommended shaft and a recommended head can be selected so that the weight range of the shaft 40 and the grip 42 suitable for the golfer G, the weight range of the golf club 4 excluding the head 41, etc. may be determined as the optimal characteristic index from the correspondence with the optimal swing MI, in addition to the shaft weight range. That is, the specific part of the golf club 4 may be the shaft 40, the shaft 40 and the grip 42, and the part of the golf club 4 excluding the head 41. The correspondence data may be prepared for each type of head 41, or may be data that does not depend on the type of head 41.

[0088] In the above embodiment, in the optimum stiffness determination step (S10), the optimum rank value K S1 ~K S4(IFC) was determined, but instead, the flex (optimum flex) of the shaft 40 of the golf club 4 suitable for the golfer G may be determined. The method of determining the optimum shaft weight and optimum flex, and the method of selecting the shaft 40 based on the optimum shaft weight and optimum flex are described in detail in Patent Document 1, and therefore the description will be omitted here. Finally, from among the shafts 40 that match the optimum shaft weight and optimum flex, a shaft 40 that realizes the optimum club length may be selected as the recommended shaft. Alternatively, from among the golf clubs 4 that match the optimum club length, a shaft 40 that includes a shaft 40 that matches the optimum shaft weight and optimum flex may be selected as the recommended golf club.

[0089] <4-4> In the above embodiment, the sensor unit 1 having three sensors, an acceleration sensor, an angular velocity sensor, and a geomagnetic sensor, is used as a measuring device for measuring the swing motion of the golfer G, but the measuring device may have another configuration. For example, the geomagnetic sensor may be omitted. In this case, it is possible to convert the measurement data from the xyz local coordinate system to the XYZ global coordinate system by a statistical method. Since such a method is a publicly known technique (refer to JP 2013-56074 A if necessary), a detailed description is omitted here. Alternatively, a three-dimensional measuring camera may be used as the measuring device. Since a method for measuring the behavior of a golfer, a golf club, and a golf ball using a three-dimensional measuring camera is also publicly known, a detailed description is omitted here. Furthermore, when a three-dimensional measuring camera is used, the process of converting the measurement data from the xyz local coordinate system to the XYZ global coordinate system may be omitted, and the behavior of the grip in the XYZ global coordinate system may be directly measured.

[0090] <4-5> In the above embodiment, the optimum swing ease index is calculated as an example. However, the optimum swing ease index may be calculated for various other indexes that represent the ease of swinging the golf club 4. For example, the weight m2 of the golf club 4 (strictly speaking, if the mass is m2, the weight is m2g (g is the acceleration of gravity), but for simplicity, both are expressed as m2 here), the moment of inertia around the grip end I G , and the moment of inertia around the center of gravity I2 are also indices that indicate the ease of swinging the golf club 4, and an optimal ease of swing index may be calculated for these indices. Also, a plurality of optimal ease of swing indexes may be calculated, and fitting may be performed based on all of these optimal ease of swing indexes. For example, the optimal swing MI, the moment of inertia around the grip end suitable for the golfer I G (hereinafter, optimum grip end MI), moment of inertia I2 around the center of gravity suitable for the golfer (hereinafter, optimum center of gravity MI), and weight m2 of the golf club 4 suitable for the golfer (hereinafter, optimum club weight) may all be calculated, and a shaft 40 of the golf club 4 that meets these four conditions may be searched for in the shaft DB 29. G are the parameters of the golf club 4. m2, I2, L and I G The method of determining the optimum club weight or the optimum grip end MI based on the above is described in detail in Patent Document 1, so the description will be omitted here.

[0091] <4-6> In the above embodiment, the arm output power P1_ is used as the second swing index for determining the optimal swing ease index. AVE , Club input power P2_ AVE and head speed V h The above three were used in combination. However, the present invention is not limited to this example. For example, the swing index P1_ AVE Only, P2_ AVE You can use only (P1_ AVE ,V h ), (P2_ AVE ,V h ), (P1_ AVE ,P2_ AVE) may also be used.

[0092] <4-7> In addition, the optimal swing ease index is the above-mentioned club weight m2, the moment of inertia around the grip end I G Various indices can be set, such as the optimal swing MI, the moment of inertia around the center of gravity I2, etc., but any indices can be set as the second swing indices as long as a certain relationship (correlation) is recognized between these optimal swing ease indices. For example, the arm energy E exerted by the golfer during the swing motion AVE , E1, total shoulder torque T ti and average shoulder torque T AVE can be used as the second swing indicator. ti and T AVE is an index that represents the torque around the shoulders that is exerted by the golfer during the swing motion. AVE , E1, T ti and T AVE The calculation method of is described in detail in Patent Document 1. In addition, the arm energy E AVE , average shoulder torque T AVE and head speed V h are calculated, and these indicators E AVE , T AVE , V h The procedure for calculating the optimum club weight range (hereinafter, optimum weight band) or the optimum swing MI band depending on the golfer's swing is described in detail in Patent Document 1, and therefore will not be described here.

[0093] Furthermore, the following index described in Patent Document 1 can also be used as the second swing index. (1) Angle θ1 between shaft 40 and Z axis of global coordinate system (below grip) at the time of top (see FIG. 18) (2) Angular velocity ω2 of the golf club 4 around the grip 42 during the swing motion (=grip angular velocity ω pX ) average (3) Maximum value of angular velocity ω2 from the top to impact (4) Grip speed V from the top to the impact GE The average value of (5) Grip speed V from the top to the impact GE Maximum of (6) Distance D of grip 42 traveled between the top and impact (7) Cock release timing r and the difference between the impact time (the cock release timing t r can be defined as the timing when the release speed of the cock angle θ2 between the arm and the shaft 40 increases and the energy of the arm begins to change into the energy of the shaft 40. (8) Cock release timing r The cock angle θ2 between the arm and the shaft 40 at (see Figure 18) (9) Downswing time, i.e., the time from the top to impact (10) The integral value of torque T2 from the top time to the time when torque T2 around grip 42 reverses sign.

[0094] <4-8> In the above embodiment, the bending stiffness is evaluated as the stiffness of the shaft, but instead, the torsional stiffness may be evaluated. The value of the torsional stiffness (hereinafter, GJ value) can also be measured or calculated at multiple positions along the extension direction of the shaft 40. That is, the distribution of the torsional stiffness at multiple positions along the extension direction of the shaft 40 may be taken as the stiffness of the shaft. In this case, a GJ value (optimum GJ value) suitable for the golfer G is determined as the optimum stiffness index, and any index that is recognized to be correlated with the optimum GJ value can be used as the third swing index for determining the optimum GJ value. For example, the following index as described in JP 2014-212862 A can be used as such a third swing index.

[0095] (1) Grip angular velocity ω y Grip angular velocity ω per unit time from when is maximum to impact x The magnitude of change in (2) Grip angular velocity ω near the top z Change in (3) When the grip angular velocity is ω y The grip angular velocity ω z The magnitude of change in

[0096] In this modified example, an approximation equation expressing the relationship between the third swing index and the optimal GJ value is calculated in advance through experiments and stored in memory unit 23, so that the optimal GJ value can be determined from the second swing index based on the measurement data obtained in the measurement process.

[0097] Furthermore, in the above embodiment, instead of the stiffness distribution at multiple positions of the shaft 40 suitable for the golfer G, the flex, kick point or torque of the shaft 40 suitable for the golfer G may be determined as the optimum stiffness index. Note that the torque is an index representing the torsional stiffness of the entire shaft 40.

[0098] <4-9> In the above embodiment, the optimum stiffness index determination step (S10) is performed after the optimum swing ease index determination step (S8), but the method of narrowing down the shafts 40 and golf clubs 4 is not limited to this. For example, the optimum shaft weight band can be calculated directly according to the magnitude of the second swing index. For example, as shown in FIG. 19, P1 - AVE -P2_ AVE (-V h ) The space may be divided into regions to define regions corresponding to optimal shaft weight bands, and the definition information may be stored in advance as correspondence data replacing the correspondence data 28 in Fig. 2. In this case, the optimal characteristic index may be derived depending on which region the second swing index derived in the second index calculation step belongs to.

[0099] In addition, as the correspondence data, for each optimal flex, a second swing index space (e.g., P1_ AVE -P2_ AVEData specifying a boundary line dividing the golf club head (plane) into each optimum shaft weight band may be calculated and stored in advance. The narrowing down of the shafts 40 or golf clubs 4 based on the optimum club length may be performed before or after narrowing down of the shafts 40 that match the optimum flex and belong to the optimum shaft weight band.

[0100] For example, FIG. 20A shows data for determining the optimum shaft weight band when the optimum flex is "X", FIG. 20B shows data for determining the optimum shaft weight band when the optimum flex is "S", and FIG. 20C shows data for determining the optimum shaft weight band when the optimum flex is "SR". That is, first, the optimum stiffness index is determined, and the corresponding correspondence data is selected. Then, based on the selected correspondence data, the optimum shaft weight band is determined according to the magnitude of the second swing index. According to this method, the optimum shaft weight band can be directly calculated from the second swing index without determining the optimum swing ease index, and the recommended shaft can be determined by prioritizing the optimum stiffness index over the optimum shaft weight band.

[0101] <4-10> In the above embodiment and modified examples, in order to further improve the accuracy of fitting, if the second swing indicator exists near the boundary between a plurality of regions defined by dividing the space representing the second swing indicator, boundary processing may be performed to modify the previously mentioned optimal swing MI zone and optimal shaft weight. The optimal shaft weight is, for example, the weight of a shaft that exists in the optimal shaft weight zone and matches or has the closest flex to the optimal flex, and if there is one such shaft, the weight of that shaft can be set as the optimal shaft weight. Also, if there are multiple such shafts, for example, when the type of head 41 is fixed, the swing moment of inertia I of the golf club 4 as a whole can be set as the optimal shaft weight. S For example, the second swing index may be set to a weight of the shaft such that P1_ AVE -P2_ AVE (-V hIf the second swing indicator is within a threshold distance from the upper boundary of any of the divided regions in the space, the determination unit 24E may correct the previously determined optimum swing MI zone to an optimum swing MI zone of a next higher zone, or adjust the previously determined optimum shaft weight to be increased by a predetermined amount (for example, 2.5 g). AVE -P2_ AVE (-V h ) If the distance is within a threshold value from the lower boundary line of any of the divided regions in the space, the determination unit 24E may modify the previously determined optimal swing MI band to the optimal swing MI band of a region one level lower, or may adjust the previously determined optimal shaft weight to decrease it by a predetermined amount (e.g., 2.5 g).

[0102] <4-11> In the modified example 4-10, the boundary process for determining the optimum club index more accurately was described, but the exception process according to this modified example is also a process for determining the optimum club index more accurately. In the above embodiment, the analysis was performed within the swing plane P when calculating the second swing index, but the above-mentioned second swing index P1_ AVE ,P2_ AVE The indices shown in the modified examples 4-7 and 4-8 are indices that represent the two-dimensional swing motion of the golfer G projected onto the swing plane P. However, the actual swing motion is performed three-dimensionally. The exception processing according to these modified examples is processing for reducing errors due to two-dimensional analysis and improving the accuracy of the optimum club indicators.

[0103] In the exception processing according to this modification, an index indicating a rotation movement that does not appear on the swing plane P and an index indicating a cocking movement (hereinafter referred to as a cocking index) are derived in addition to the above-mentioned second swing index. The rotation movement that does not appear on the swing plane P can be evaluated by an index indicating a twisting rotation movement (see FIG. 21A) around the shaft axis of the golf club 4 projected on the swing plane P, that is, the first swing index SW1, or an index indicating a rotation movement (see FIG. 21B) of the golf club 4 in a direction (push direction) jumping out of the swing plane P (hereinafter referred to as a push index). Some golfers G obtain head speed by such a rotation movement. Some golfers G obtain head speed by a cocking movement in the latter half of the downswing, but the overall image of such a cocking movement is not necessarily projected on the swing plane P. In the exception processing described here, the optimum swing ease index and the optimum shaft weight can be derived with high accuracy even for such golfers G.

[0104] As an example, the following describes the exception processing that is applied when the optimum shaft weight band is determined as in Fig. 19. A specific processing flow is as shown in Fig. 22. The exception processing shown in Fig. 22 is executed after the optimum shaft weight is determined according to the judgment criteria (boundaries L7-L10 of divided areas C1-C5) shown in Fig. 19.

[0105] In step S71, the calculation unit 24D derives an index (torsion index) that represents the rotational movement of the twist around the shaft axis of the golf club 4. If the first index calculation step (S2) has already been performed, the first swing index SW1 calculated there can be used as the twist index, and if the first index calculation step has not yet been performed, the twist index can be calculated according to the definition of the first swing index SW1 described above. Next, the determination unit 24E determines the head speed V hIt is determined whether the torsion index is within a predetermined range and the torsion index is equal to or greater than a predetermined value. If these conditions are met, the optimum shaft weight is adjusted to be increased by a predetermined amount (step S72). On the other hand, if these conditions are not met, the process proceeds to step S73.

[0106] In step S73, the calculation unit 24D calculates the push indicator based on the measurement data. h It is determined whether or not the ω of the top is within a predetermined range, the push index is equal to or greater than a predetermined value, and the previously determined optimum shaft weight is within a predetermined range. If these conditions are met, the previously determined optimum shaft weight is adjusted to be increased by a predetermined amount (step S74). On the other hand, if these conditions are not met, the process proceeds to step S75. Note that the case where the push index is equal to or greater than a predetermined value is, for example, when the ω of the top x ≧0, and ω from the top to the impact y Average value of / ω from top to impact x The average value of ≧1.5 is satisfied.

[0107] In step S75, the calculation unit 24D calculates the cock index based on the measurement data. The cock index is, for example, y And, ω y ω from the time when y The head speed V h is within a predetermined range, the cock index is equal to or greater than a predetermined value, and the previously determined optimum shaft weight is within a predetermined range. If these conditions are met, the previously determined optimum shaft weight is adjusted to increase by a predetermined amount (step S76).

[0108] When the above steps are completed, the exception processing ends. This exception processing and the boundary processing of the modified example 4-10 are both processing for determining the optimum swing ease index and the optimum shaft weight range with higher accuracy, and both processing can be combined. In this case, it is preferable to execute this exception processing after the boundary processing.

[0109] <4-12> In the above embodiment, the first swing index SW1 calculated in the first swing index calculation step (S2) is compared with the first threshold value TH1 and the second threshold value TH2, and the optimum club length is determined to be one of the basic club length, the first club length, and the second club length according to the comparison result. However, the optimum club length to be determined may be two types, or may be four or more types, and the number of threshold values ​​of the first swing index SW1 may be increased or decreased accordingly. Also, in the above-mentioned optimum club length determination step (S3), either step S31 and step S32 or step S33 and step S34 may be omitted. Specifically, the determination unit 24E may be configured to determine the optimum club length as the first club length when the first swing index SW1 is equal to or greater than the first threshold value TH1, and to determine the optimum club length as the basic club length otherwise. Also, the determination unit 24E may be configured to determine the optimum club length as the second club length when the first swing index SW1 is equal to or less than the second threshold value TH2, and to determine the optimum club length as the basic club length otherwise. EXAMPLES

[0110] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0111] <Example> The fitting method (comparative example) of Patent Document 1 was applied to a plurality of golfers, and the fitting method (example) according to the above embodiment was also applied.

[0112] In the comparative example, the swing moment of inertia I SAmong the golf clubs that belonged to the optimal swing MI zone of each golfer and had the IFC shaft that best matched the optimal stiffness index, one was selected as the recommended golf club. The club length of the recommended golf clubs was the basic club length (45.25 inches). Then, each golfer was asked to test hit several balls using the recommended golf club, and the flight distance and left / right deviation of the hit ball were measured.

[0113] In the method of the embodiment, in addition to the optimum swing MI zone and the optimum stiffness index, the optimum club length suitable for each golfer was also determined as in the above embodiment. Then, for golfers whose optimum club length was determined to be the first club length (44.75 inches) or the second club length (45.75 inches), the swing moment of inertia I S The golf club that belongs to the optimal swing MI zone of each golfer, has an IFC shaft that most closely matches the optimal stiffness index, and further has a club length customized to the optimal club length was determined as the recommended golf club. Then, the golfer was asked to test hit several balls using the recommended golf club, and the flight distance and left / right deviation of the hit ball were measured.

[0114] 23A-D are diagrams comparing the measurement results of the flight distance and left-right deviation of the recommended golf club according to the embodiment and the comparative example for each golfer who was recommended a club length other than the basic club length in the embodiment. FIG. 23A is an example of a golfer who was recommended a golf club of the first club length in the embodiment because the first swing index SW1 was equal to or greater than the first threshold value of 250 deg / s. As can be seen from FIG. 23A, the recommended golf club according to the comparative example had a sufficient flight distance, but the recommended golf club of the basic club length tended to cause the ball to deviate to the left, suggesting that the ball was likely to be caught too much. In this regard, the recommended golf club according to the embodiment stabilized the direction of the ball while maintaining a constant flight distance, and the left-right deviation was improved. FIG. 23B is an example of another golfer who was recommended a golf club of the first club length in the embodiment. As can be seen from FIG. 23B, in this example, the maximum flight distance was significantly increased in the test shot using the golf club according to the embodiment.

[0115] FIG. 24C is an example of a golfer for whom a golf club with a second club length was recommended in the embodiment because the first swing index SW1 was equal to or less than the second threshold value of 75 deg / s. As can be seen from FIG. 24C, there was almost no difference in the degree of left-right deviation between the recommended golf club according to the comparative example and the recommended golf club according to the embodiment, but the maximum flight distance was significantly increased in the test shot using the golf club according to the embodiment. FIG. 24D is an example of another golfer for whom a golf club with a second club length was recommended in the embodiment. As can be seen from FIG. 24D, the left-right deviation was relatively stable in the test shot using the golf club according to the embodiment, and the maximum flight distance was significantly increased.

[0116] From the above results, it was found that the recommended golf club selected by the method of the embodiment allows a more preferable swing compared to the recommended golf club selected by the method of the comparative example. In other words, it was confirmed that the method of the embodiment can recommend a golf club more suitable for a golfer. [Explanation of symbols]

[0117] 1. Sensor unit (measuring device) 2 Fitting device 3. Fitting Program 4. Golf Clubs 24A Acquisition Department 24B Grip behavior derivation part 24C Shoulder behavior derivation part 24D calculation section 24E Decision section 24F Selection Section 40 Shaft 41 Head 42 Grip

Claims

1. An acquisition unit that acquires measurement data obtained by measuring a swing motion of a golf club by a golfer using a measuring device; a calculation unit that calculates a first swing index related to a degree of twist of the golf club during the swing motion based on the measurement data; a determination unit that determines an optimal club length, which is a length of the golf club suitable for the golfer, according to a magnitude of the first swing indicator; Equipped with the determination unit compares the first swing indicator with a predetermined first threshold, and when the first swing indicator is equal to or greater than the first threshold, determines that the optimum club length is a first club length that is shorter than a basic club length; When the first swing indicator is less than the first threshold, the determiner compares the first swing indicator with a predetermined second threshold which is smaller than the first threshold, and when the first swing indicator is equal to or smaller than the second threshold, determines that the optimum club length is a second club length which is longer than the basic club length; When the first swing indicator is less than the first threshold value and greater than the second threshold value, the determination unit determines that the optimum club length is the basic club length. Fitting device.

2. The measurement data includes an angular velocity at a grip end of the golf club, and the first swing indicator is calculated based on the angular velocity about an axis parallel to a shaft of the golf club. The fitting device according to claim 1 .

3. The first swing indicator is an average value or an integral value of the angular velocity during a downswing. The fitting device according to claim 2 .

4. A selection unit for selecting at least one of a golf club that best matches the optimum club length and a shaft to be included in the golf club; Further comprising: A fitting device according to any one of claims 1 to 3.

5. An acquisition unit that acquires measurement data obtained by measuring a swing motion of a golf club by a golfer using a measuring device; a calculation unit that calculates a first swing index, a second swing index, and a third swing index related to the swing motion based on the measurement data; a determination unit which determines an optimum club length which is a club length suitable for the golfer according to a magnitude of the first swing indicator, determines an optimum swing ease index which is an index of ease of swinging a golf club suitable for the golfer according to a magnitude of the second swing indicator, and determines an optimum stiffness index which indicates stiffness of a shaft of a golf club suitable for the golfer according to a magnitude of the third swing indicator; a selection unit that selects at least one of a golf club that best matches the optimum swing ease index, the optimum stiffness index, and the optimum club length and a shaft to be included in the golf club; Equipped with the first swing indicator is an indicator related to a degree of twisting of the golf club during the swing motion, the determination unit compares the first swing indicator with a predetermined first threshold, and when the first swing indicator is equal to or greater than the first threshold, determines that the optimum club length is a first club length that is shorter than a basic club length; When the first swing indicator is less than the first threshold, the determiner compares the first swing indicator with a predetermined second threshold which is smaller than the first threshold, and when the first swing indicator is equal to or smaller than the second threshold, determines that the optimum club length is a second club length which is longer than the basic club length; When the first swing indicator is less than the first threshold value and greater than the second threshold value, the determination unit determines that the optimum club length is the basic club length. Fitting device.

6. An acquisition unit that acquires measurement data obtained by measuring a swing motion of a golf club by a golfer using a measuring device; a calculation unit that calculates a first swing index, a second swing index, and a third swing index related to the swing motion based on the measurement data; a determination unit which determines an optimum club length which is a club length suitable for the golfer according to a magnitude of the first swing indicator, determines an optimum characteristic indicator which indicates a characteristic of a specific part of a golf club suitable for the golfer according to a magnitude of the second swing indicator, and determines an optimum stiffness indicator which indicates stiffness of a shaft of the golf club suitable for the golfer according to a magnitude of the third swing indicator; a selection unit for selecting at least one of a golf club that best matches the optimum characteristic index, the optimum stiffness index, and the optimum club length and a shaft to be included in the golf club; Equipped with the first swing indicator is an indicator related to a degree of twisting of the golf club during the swing motion, the determination unit compares the first swing indicator with a predetermined first threshold, and when the first swing indicator is equal to or greater than the first threshold, determines that the optimum club length is a first club length that is shorter than a basic club length; When the first swing indicator is less than the first threshold, the determiner compares the first swing indicator with a predetermined second threshold which is smaller than the first threshold, and when the first swing indicator is equal to or smaller than the second threshold, determines that the optimum club length is a second club length which is longer than the basic club length; When the first swing indicator is less than the first threshold value and greater than the second threshold value, the determination unit determines that the optimum club length is the basic club length. Fitting device.

7. The measurement data includes an angular velocity at a grip end of the golf club, and the first swing indicator is calculated based on the angular velocity about an axis parallel to a shaft of the golf club.

7. A fitting device according to claim 5 or 6.

8. A step of acquiring measurement data obtained by measuring a swing motion of a golf club by a golfer using a measuring device; calculating, using a computer, a first swing index relating to a degree of twist of the golf club during the swing motion based on the measurement data; determining an optimum club length that is suitable for the golfer according to a magnitude of the first swing indicator; Including, The determining step includes comparing the first swing indicator with a predetermined first threshold, and determining that the optimum club length is a first club length that is shorter than a basic club length when the first swing indicator is equal to or greater than the first threshold; If the first swing indicator is less than the first threshold, the determining step includes comparing the first swing indicator with a second threshold that is less than the first threshold, and determining that the optimal club length is a second club length that is longer than the base club length if the first swing indicator is equal to or less than the second threshold; If the first swing indicator is less than the first threshold and greater than the second threshold, the determining step determines that the optimum club length is the base club length. Fitting method:

9. A step of acquiring measurement data obtained by measuring a swing motion of a golf club by a golfer using a measuring device; calculating a first swing index related to a degree of twist of the golf club during the swing motion based on the measurement data; determining an optimum club length that is suitable for the golfer according to a magnitude of the first swing indicator; Run the following on your computer: In the determining step, the computer compares the first swing indicator with a predetermined first threshold, and when the first swing indicator is equal to or greater than the first threshold, determines that the optimum club length is a first club length that is shorter than a basic club length; If the first swing indicator is less than the first threshold, the computer, in the determining step, compares the first swing indicator with a predetermined second threshold that is less than the first threshold, and if the first swing indicator is equal to or less than the second threshold, determines that the optimal club length is a second club length that is longer than the basic club length; If the first swing indicator is less than the first threshold and greater than the second threshold, the computer determines in the determining step that the optimum club length is the base club length. Fitting program.

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