An Instrumented Grip Handle for Golf Clubs to Measure Forces and Moments Exerted by Each Hand During Swing Motion

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An instrumented grip handle was designed to simultaneously measure the forces and moments exerted by each hand on the handle during golf swing. Eleven pairs of strain gages were attached on the surface of an aluminum bar inserted under separated grip covers. The device was calibrated under static conditions and revealed good agreement between applied and calculated loads. The output of the sensors was converted into forces and moments by resolving static equilibrium equations. A professional golf player participated in this study and performed golf swings with several clubs. Reflective-markers on the body segment endpoints and on the clubs were captured by VICON motion system with 8 cameras operating at 250Hz. The results obtained in this study were: (1) long axial load of shaft affected the sensor coefficients of the device, and (2) internal forces and moments that do not cause the motion of the club were observed in the swings.

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... Strain gauges and pressure sensors can be used to measure the contact forces and moments exerted by the golfer on the grip. Koike et al. [37] reported good agreement between these measurements and values calculated using inverse dynamic models (Sect. 3.1). ...
A narrative review of dynamic models of golf phenomena is presented, as well as current technologies for measuring the motions of a golfer, club, and ball. Kinematic and dynamic models of the golf swing are reviewed, including models with prescribed motions or torques as inputs, and predictive dynamic models that maximize an objective (e.g., driving distance) to determine optimal inputs or equipment designs. Impulse–momentum and continuous contact dynamic models for clubhead–ball and ball–ground impacts are described. The key observations from 172 cited references are extracted and presented, along with suggestions for future research.
... Both Suzuki et al. [21] and Nesbit [22] claim that highly skilled golfers can use joint torque profiles that influence shaft deflection in a way that allows an efficient utilisation of energy stored in the shaft. Koike et al. [23] measured a golfer's torque and force inputs to the shaft directly using an instrumented grip. They only presented preliminary results for one scratch golfer, but the trend for the wrist torque to drop towards a zero or negative torque within the last 0.05 s of the downswing can also be observed in their results. ...
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There is much debate around the role of shaft stiffness in the dynamic response of the club shaft during the golf swing. This study used a novel complex analysis to investigate within- and between-golfer differences in shaft strain patterns for three shaft stiffnesses. Twelve right-handed male golfers, with a handicap less than or equal to five, hit six shots with three driver clubs which differed only in shaft stiffness. Clubs were instrumented to record the shaft strain in the lead/lag and toe/heel directions. The analysis combined these perpendicular components into a single complex function, which enabled the differences between two swings to be characterised by a scale and a rotation component. Within-golfer strain patterns were found to be significantly more consistent than between-golfer, p < 0.01. Whilst some golfers displayed more similar patterns than others, there were no clear groups of golfers with similar patterns of shaft strain. Between the clubs, shaft strain patterns differed in the scale component, p < 0.01, rather than the rotation, p = 0.07.
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The role of the shaft in the golf swing has been the subject of scientific debate for many years but there is little consensus regarding the effects of altering shaft bending stiffness. The aim of this thesis was to determine and explain the effects of changes in shaft stiffness on body kinematics, shaft strain and key performance indicators including club head speed, impact location on the club face and launch conditions. For this purpose, three clubs matched in all properties but shaft bending stiffness (l-flex (217 cpm), r-flex (245 cpm) and xflex (272 cpm)) were instrumented with strain gauges. In an initial study, seventeen male golfers (handicap 1.8 ±1.9) tested these clubs, but no shaft effects on body kinematics, club head speed and ball launch conditions were identified. A follow-up study involved twenty skilled players (handicap 0.3 ±1.7), testing only the l- and x-flex clubs. Two optical motion capture systems were used to determine wrist angular kinematics, club head presentation and the ball‟s impact location on the club face. There was an effect of shaft stiffness on ball and club head speed, both of which increased by 0.7 % for the l-flex club (p = 0.008 and < 0.001, respectively). Two factors contributed to these increases: (i) a faster recovery of the l-flex shaft from lag to lead bending just before impact (p < 0.001); (ii) an increase of 0.5 % in angular velocity of the grip of the l-flex club at impact (p = 0.005). A difference in angular wrist kinematics between the two clubs was identified for two swing events and may have contributed to the increase in angular velocity. The face angle (p = 0.176) and the ball‟s impact location (p = 0.907 and p = 0.774) were unaffected by changes in shaft stiffness. Decreases in shaft stiffness were associated with significantly more shaft bending at the transition from backswing to downswing (p < 0.001), but the amount of lead bending at impact was found to be largely unaffected by shaft stiffness. The test protocol from the follow-up study was repeated using a golf robot, confirming the results for ball speed and wrist kinematics if the impact speed was set to replicate the mean club head speed achieved by the human players. Results from this thesis contradict the conventional view that reducing shaft stiffness leads to an increase in lead bending at impact and, consequently, to an increase in ball launch angle. Overall, these results suggest that it is unlikely that changes in overall shaft stiffness in themselves have a marked effect on driving performance.
The purpose of this study was to examine whether, in theory, the clubhead speed at impact could be increased by an optimally timed wrist torque, without jeopardizing the desired club position at impact. A 2-D, three-segment model comprising torso, left arm, and golfclub was used to model the downward phase of the golf swing. Torque generators that adhered to the activation and force-velocity properties of muscle were inserted at the proximal end of each segment. Separate simulations were performed, with the wrist joint generator enabled then disabled. The results from these simulations showed that significant gains in clubhead speed (≈9 %) could be achieved if an active wrist torque was applied to the club during the latter stages of the downswing. For a swing that produced a clubhead speed of 44 m/s (≈99 mph), the optimal timing for the activation of wrist torque occurred when the arm segment was approximately 30° below a horizontal line through the shoulder joint. The optimal activation time for the joint generators was very much dependant on the shape of the torque profiles. The optimization process confirmed that maximum clubhead speed was achieved when the torque generators commenced in sequential order from proximal to distal.
Current marketing of golf clubs places great emphasis on the importance of the correct choice of shaft in relation to the golfer. The design of shafts is based on a body of received wisdom for which there appears to be little in the way of hard evidence, either of a theoretical or experimental nature. In this paper the behaviour of the shaft in the golf swing is investigated using a suitable dynamic computer simulation and by making direct strain gauge measurements on the shaft during actual golf swings. The conclusion is, contrary to popular belief, that shaft bending flexibility plays a minor dynamic role in the golf swing and that the conventional tests associated with shaft specification are peculiarly inappropriate to the swing dynamics; other tests are proposed. A concomitant conclusion is that it should be difficult for the golfer to actually identify shaft flexibility. It is found that if golfers are asked to hit golf balls with sets of clubs having different shafts but identical swingweights the success rate in identifying the shaft is surprisingly low.