The influence of golf club shaft stiffness on clubhead kinematics at ball impact

The role of shaft stiffness on the golf swing is not well understood. Studies in which golfers hit balls with clubs of varying shaft flex have reported changes in ball distance. The results of mathematical models suggest that shaft stiffness affects only the orientation of the clubhead at impact, not the speed of the clubhead, but there are no experimental results validating these findings. The purpose of this study was therefore to experimentally examine the influence of shaft stiffness on clubhead kinematics at ball impact. Forty golfers hit 10 balls with each of five drivers varying in shaft stiffness from 'Ladies' to 'Extra-Stiff', in a double-blind study design. The motions of three reflective markers attached to the clubhead were captured with a high-speed motion analysis system. At ball impact, shaft stiffness had a statistically significant influence on clubhead speed for 27 subjects, on loft angle for 11 subjects, and on lie angle for all 40 subjects. No effect was observed on face angle, in to out path angle, or attack angle. These results show that shaft stiffness can affect ball launch conditions by altering clubhead speed and/or loft angle.     

Understanding the role of shaft stiffness in the golf swing

Theoretically, shaft stiffness can alter shot distance by increasing clubhead speed or altering clubhead orientation at impact. A 3D forward dynamics model of a golfer and flexible club simulated the downswing. A genetic algorithm optimized the coordination of the model’s muscles (four torque generators) to maximize clubhead speed. The maximum torque output and maximum rate of torque development from the torque generators were varied to simulate the swing of golfers that generate different clubhead speeds. Four shafts of varying stiffness (flexible, regular, stiff, and completely rigid) were entered into these simulations to examine the role that shaft flexibility had on clubhead speed and orientation at impact. Shaft stiffness was found to have a meaningful effect only on clubhead orientation (dynamic loft and dynamic close) at impact. There was no evidence to support the premise that matching the stiffness properties of the shaft with the golfer would improve clubhead speed.     

Influence of shaft length on golf driving performance

The aim of this study was to determine how shaft length affects golf driving performance. A range of drivers with lengths between 1.168 m and 1.270 m, representing lengths close to the 1.219 m limit imposed by R&A Rules Limited (2008), were assembled and evaluated. Clubhead and ball launch conditions and drive distance and accuracy were determined for seven category 1 golfers (handicaps 0.21 +/- 2.41) who performed shots on a purpose-built practice hole. As shaft length increased from 1.168 m to 1.270 m, initial ball velocity increased (+ 1.8 m/s, P < 0.01). Ball carry (+ 4.3 m, P = 0.152) also increased, although not significantly so. Furthermore, as shaft length increased, for all club comparisons there was no decrease in accuracy. Ball launch conditions of spin components and launch angle remained unaffected by shaft length. Launch angle increased (0.8 degree, F = 1.074, P = 0.362) as driver shaft length increased. Our results show that clubhead and ball velocity together with ball carry tended to increase with no loss of accuracy.     

The influence of shaft stiffness on potential energy and puck speed during wrist and slap shots in ice hockey

The purpose of this study was to explore the relationship between hockey stick shaft stiffness and puck speed with mechanical energy considerations during stationary wrist and slap shots. Thirty left-handed pro-model composite hockey sticks, submitted by eleven hockey stick manufacturers, were subjected to a mechanical cantilever bend test to determine the shaft stiffness of each stick. Eight sticks representing the entire spectrum of stiffnesses were then used by five elite male hockey players to perform stationary wrist and slap shots in a laboratory setting. Eight infra-red high-speed digital video cameras were used to capture shaft deformation and puck speed. A second mechanical test then replicated the loading patterns applied to each stick during shooting. Force-deformation data from this test were used to determine the shaft stiffness and potential energy storage and return associated with each stick during shooting. The results of this study suggest that shaft stiffness has an influence on puck speed in wrist but not slap shots. During a wrist shot, a given player should realise higher puck speeds with a stick in which they store increased elastic potential energy in the shaft. In general, flexible sticks were found to store the most energy. However, how the athlete loads the stick has as much influence on puck speed as stick construction. Energy considerations were unable to explain changes in puck speed for the slap shot. For this type of shot it is the athlete and not the equipment influencing puck speed, but the governing mechanisms have yet to be elucidated.     

The effects of conscious processing on golf putting proficiency and kinematics

Researchers have suggested that skill performance deteriorates when people try to exert conscious control over automatic actions. Unfortunately, little is known about the effects of different types of conscious processing on skilled performance by expert athletes. We conducted two experiments to address this issue. Experiment 1 investigated the influence of a specific form of conscious control (making technical adjustments to a stroke) on the putting skills of expert golfers. The expert golfers maintained putting proficiency (i.e. number of putts holed) when making technical adjustments. However, this form of conscious processing altered the timing and consistency of golfers' putting strokes. Experiment 2 compared the influence of technical adjustments and conscious monitoring (paying attention to the execution of the stroke) on expert golfers' putting skills. Technical adjustments had no disruptive influence on expert golfers' putting proficiency but did reduce the consistency of their strokes. However, conscious monitoring was found to impair putting proficiency. The implications of the work for theory and future work are discussed.     

Numerical study on the wrist action during the golf downswing

The purpose of this paper was to examine whether the ball position and wrist action (different types of torque application) could be optimised to increase the horizontal golf club head speed at impact with the ball. A two-dimensional double pendulum model of the golf downswing was used to determine to what extent the wrist action affected the club head speed in a driver, and how this affected the optimum ball position. Three different patterns of wrist actions (negative, positive, and negative-positive torque at the wrist) were investigated; and two criteria (maximum and impact criteria) were used to assess their effectiveness in terms of the maximum horizontal club head speed, and the club head speed as the shaft becomes vertical when viewed ‘face-on’. The simulation results indicated that the horizontal club head speed at impact could be increased by these patterns of wrist actions and the optimum ball position could be determined by the impact criterion. Based on the analysis of the energy flow from the input joints of shoulder and wrist to the arm and club head, the way the wrist action affects the club head speed has been discussed. The sensitivity of the results to small changes in model parameter values and initial conditions was investigated. The results were also examined under different torque patterns.     

Variability in clubhead presentation characteristics and ball impact location for golfers' drives

The purpose of the present study was to analyse the variability in clubhead presentation to the ball and the resulting ball impact location on the club face for a range of golfers of different ability. A total of 285 male and female participants hit multiple shots using one of four proprietary drivers. Self-reported handicap was used to quantify a participant's golfing ability. A bespoke motion capture system and user-written algorithms was used to track the clubhead just before and at impact, measuring clubhead speed, clubhead orientation, and impact location. A Doppler radar was used to measure golf ball speed. Generally, golfers of higher skill (lower handicap) generated increased clubhead speed and increased efficiency (ratio of ball speed to clubhead speed). Non-parametric statistical tests showed that low-handicap golfers exhibit significantly lower variability from shot to shot in clubhead speed, efficiency, impact location, attack angle, club path, and face angle compared with high-handicap golfers.     

Assessment of planarity of the golf swing based on the functional swing plane of the clubhead and motion planes of the body points

The purposes of this study were (1) to determine the functional swing plane (FSP) of the clubhead and the motion planes (MPs) of the shoulder/arm points and (2) to assess planarity of the golf swing based on the FSP and the MPs. The swing motions of 14 male skilled golfers (mean handicap = -0.5 +/- 2.0) using three different clubs (driver, 5-iron, and pitching wedge) were captured by an optical motion capture system (250Hz). The FSP and MPs along with their slope/relative inclination and direction/direction of inclination were obtained using a new trajectory-plane fitting method. The slope and direction of the FSP revealed a significant club effect (p < 0.001). The relative inclination and direction of inclination of the MP showed significant point (p < 0.001) and club (p < 0.001) effects and interaction (p < 0.001). Maximum deviations of the points from the FSP revealed a significant point effect (p < 0.001) and point-club interaction (p < 0.001). It was concluded that skilled golfers exhibited well-defined and consistent FSP and MPs, and the shoulder/arm points moved on vastly different MPs and exhibited large deviations from the FSP. Skilled golfers in general exhibited semi-planar downswings with two distinct phases: a transition phase and a planar execution phase.     

Dynamic strain profile of the ice hockey stick: comparisons of player calibre and stick shaft stiffness

The goal of this research was to develop a method to quantify the dynamic strain profile (DSP) of an ice hockey stick shaft and assess the potential influence of player skill and stick shaft stiffness on DSP during slap (SS) and wrist shots (WS). Seventeen adult males performed shots with two different stick stiffness’ on synthetic ice. Subjects were subdivided as high (HC) and low calibre (LC). Dependent measures included strain measures from five strain gauge pairs along the shaft length recorded at 10 kHz. In general, this approach was sufficiently sensitive to clearly distinguish between shot types (strains SS > WS), player calibre (strains HC > LC) and stick models (strain flex77 > flex102) as well as to identify within stick deflection differences along the shaft. This strain based analysis has a time and spatial resolution undetected by common motion capture based systems.     

Understanding the mechanisms of shaft deflection in the golf swing

An understanding of shaft dynamics during the golf swing was gained through a series of theoretical simulations, using a 3D forward dynamics model. By resolving the resultant force applied at the grip end of the club into a tangential and a radial (centripetal) component, the mechanisms of shaft deflection were quantified. It was determined that radial force plays an important role in producing the toe-down and lead-deflections recorded in all golf swings made with a driver. However, the simulations also revealed that the recoil of the shaft, from its previously toe-up and lag deflected position during the downswing (due to tangential forces), plays at least an equally important role in determining the position and orientation of the clubhead at impact. It was further demonstrated that, due to the influence of the radial force component, maximum kick velocity is reached after the clubhead has passed beyond the neutral shaft position.     

Inter-joint coordination between hips and trunk during downswings: Effects on the clubhead speed

Understanding of the inter-joint coordination between rotational movement of each hip and trunk in golf would provide basic knowledge regarding how the neuromuscular system organises the related joints to perform a successful swing motion. In this study, we evaluated the inter-joint coordination characteristics between rotational movement of the hips and trunk during golf downswings. Twenty-one right-handed male professional golfers were recruited for this study. Infrared cameras were installed to capture the swing motion. The axial rotation angle, angular velocity and inter-joint coordination were calculated by the Euler angle, numerical difference method and continuous relative phase, respectively. A more typical inter-joint coordination demonstrated in the leading hip/trunk than trailing hip/trunk. Three coordination characteristics of the leading hip/trunk reported a significant relationship with clubhead speed at impact (r < ?0.5) in male professional golfers. The increased rotation difference between the leading hip and trunk in the overall downswing phase as well as the faster rotation of the leading hip compared to that of the trunk in the early downswing play important roles in increasing clubhead speed. These novel inter-joint coordination strategies have the great potential to use a biomechanical guideline to improve the golf swing performance of unskilled golfers.     

The static and dynamic stiffness behaviour of composite golf shafts and their constituent materials

Golf shafts are normally characterised using static or quasi-static tests, yet the golf swing itself is dynamic. The purpose of this research was to determine whether stiffness properties obtained from these tests can be used when modelling the dynamic behaviour of golf shafts made from carbon fibre reinforced polymer (CFRP). Three shafts, matched for all properties except shaft flex, were subjected to human swing testing by 12 skillful players whilst strains were recorded. Peak principal strains as well as strain rates increased as shaft flex decreased (p < 0.001). CFRP flat panels with lay-ups similar to those contained in the shafts were constructed and tested statically and at strain rates between 10⁻⁴ and 4 s⁻¹. Some level of strain-rate dependency was found for these panels, but only for strain rates exceeding those seen during a swing, which suggests that static material tests are appropriate for measuring the dynamic stiffness of golf shafts.     

The effect of alterations in foot centre of pressure on lower body kinematics during the five-iron golf swing

ABSTRACT

The research aimed to evaluate the effects of an intervention aimed at altering pressure towards the medial aspect of the foot relating to stability mechanisms associated with the golf swing. We hypothesised that by altering the position of the foot pressure, the lower body stabilisation would improve which in turn would enhance weight distribution and underpinning lower body joint kinematics. Eight professional golf association (PGA) golf coaches performed five golf swings, recorded using a nine-camera motion analysis system synchronised with two force platforms. Following verbal intervention, they performed further five swings. One participant returned following a one-year intervention programme and performed five additional golf swings to provide a longitudinal case study analysis. Golf performance was unchanged evidenced by the velocity and angle of the club at ball impact (BI), although the one-year intervention significantly changed the percentage of weight experienced at each foot in the final 9% of downswing, which provided an even weight distribution at BI. This is a highly relevant finding as it indicates that the foot centre of pressure was central to the base of support and in-line with the centre of mass (CoM), indicating significantly increased stability when the CoM is near maximal acceleration.     

Repeatability of three-dimensional thorax and pelvis kinematics in the golf swing measured using a field-based motion capture system

Field-based methods of evaluating three-dimensional (3D) swing kinematics offer coaches and researchers the opportunity to assess golfers in context-specific environments. The purpose of this study was to establish the inter-trial, between-tester, between-location, and between-day repeatability of thorax and pelvis kinematics during the downswing using an electromagnetic motion capture system. Two experienced testers measured swing kinematics in 20 golfers (handicap < or =14 strokes) on consecutive days in an indoor and outdoor location. Participants performed five swings with each of two clubs (five-iron and driver) at each test condition. Repeatability of 3D kinematic data was evaluated by computing the coefficient of multiple determination (CMD) and the systematic error (SE). With the exception of pelvis forward bend for between-day and between-tester conditions, CMDs exceeded 0.854 for all variables, indicating high levels of overall waveform repeatability across conditions. When repeatability was compared across conditions using MANOVA, the lowest CMDs and highest SEs were found for the between-tester and between-day conditions. The highest CMDs were for the inter-trial and between-location conditions. The absence of significant differences in CMDs between these two conditions supports this method of analysing pelvis and thorax kinematics in different environmental settings without unduly affecting repeatability.     

Effects of pelvis-shoulders torsional separation style on kinematic sequence in golf driving

The golfer’s body (trunk/arms/club) can be modeled as an inclined axle-chain system and the rotations of its parts observed on the functional swing plane (FSP) can represent the actual angular motions closely. The purpose of this study was to investigate the effects of pelvis-shoulders torsional separation style on the kinematic sequences employed by the axle-chain system in golf driving. Seventy-four male skilled golfers (handicap ≤ 3) were assigned to five groups based on their shoulder girdle motion and X-factor stretch characteristics: Late Shoulder Acceleration, Large Downswing Stretch, Large Backswing Stretch, Medium Total Stretch, and Small Total Stretch. Swing trials were captured by an optical system and the hip-line, thorax, shoulder-line, upper-lever, club, and wrist angular positions/velocities were calculated on the FSP. Kinematic sequences were established based on the timings of the peak angular velocities (backswing and downswing sequences) and the backswing-to-downswing transition time points (transition sequence). The backswing and transition sequences were somewhat consistent across the groups, showing full or partial proximal-to-distal sequences with minor variations. The downswing sequence was inconsistent across the groups and the angular velocity peaks of the body segments were not significantly separated. Various swing characteristics associated with the separation styles influenced the motion sequences.     

国际金融危机对中美高尔夫运动的影响

通过对中国高尔夫运动的发展变化与美国国家高尔夫基金会公布数据的比较发现:国际金融危机导致美国高尔夫运动整体下滑,而中国高尔夫球场和高尔夫球员数量反而高速增长,高尔夫球场经营出现了两极分化趋势.高尔夫运动发展阶段、球场开发模式以及高尔夫产业政策的不同是中关高尔夫运动受金融危机影响差异的主要原因.     

Effects of the rider on the linear kinematics of jumping horses

This study examined the effects of the rider on the linear projectile kinematics of show-jumping horses. SVHS video recordings (50 Hz) of eight horses jumping a vertical fence 1 m high were used for the study. Horses jumped the fence under two conditions: loose (no rider or tack) and ridden. Recordings were digitised using Peak Motus. After digitising the sequences, each rider's digitised data were removed from the ridden horse data so that three conditions were examined: loose, ridden (including the rider's data) and riderless (rider's data removed). Repeated measures ANOVA revealed significant differences between ridden and loose conditions for CG height at take-off (p < 0.001), CG distance to the fence at take-off (p = 0.001), maximum CG during the suspension phase (p < 0.001), CG position over the centre of the fence (p < 0.001), CG height at landing (p < 0.001), and vertical velocity at take-off (p < 0.001). The results indicated that the rider's effect on jumping horses was primarily due to behavioural changes in the horses motion (resulting from the rider's instruction), rather than inertial effects (due to the positioning of the rider on the horse). These findings have implications for the coaching of riders and horses.     

论木球与高尔夫

从术球与高尔夫的起源、技术特征、运动特点、心理特点等方面进行比较分析,旨在为术球在国内乃至世界各地进一步推广和发辰提供参考。     

Stressors, social support, and effects upon performance in golf

In this study, we extended the work of Rees and Hardy (2004) by examining the main and stress-buffering effects of social support upon sports performance in a different context, using a different outcome measure, and a specific time-frame. A high-level performance sample of 117 male golfers (mean age 24.8, s = 8.3) completed measures of social support and stressors before competitions. Performance outcome was recorded. Moderated hierarchical regression analyses revealed significant (P < 0.05) main effects for stressors upon performance in 8 of the 11 models tested (R2 = 0.08 - 0.21). Over and above the variance accounted for by stressors, there were significant (P < 0.05) main effects for social support upon performance in all models tested (DeltaR2 = 0.10 - 0.24). In all models, stressors were associated with worse performance, whereas social support was associated with better performance. There were no significant interactions (stress-buffering effects). Main effects for social support upon performance suggest that social support may have aided performance directly, regardless of the level of stress.