The influence of golf shaft stiffness on grip and clubhead kinematics

The purpose of this study was to investigate the influence of shaft stiffness on grip and clubhead kinematics. Two driver shafts with disparate levels of stiffness, but very similar inertial properties, were tested by 33 golfers representing a range of abilities. Shaft deflection data as well as grip and clubhead kinematics were collected from 14 swings, with each shaft, for each golfer using an optical motion capture system. The more flexible shaft (R-Flex) demonstrated a higher contribution to clubhead speed from shaft deflection dynamics (P < .001), but was also associated with significantly less grip angular velocity at impact (P = .001), resulting in no significant difference in clubhead speed (P = .14). However, at the individual level, half of the participants demonstrated a significant difference in clubhead speed between shafts. The more flexible shaft was also associated with significantly different magnitudes of head rotation relative to the grip. More specifically, both bend loft (P < .001) and bend lie (P < .001) were greater for the R-Flex shaft, while bend close (P = .017) was greater for the stiffer (X-Flex) shaft. However, changes in grip orientation resulted in no significant differences in face orientation, between the shafts, at impact.     

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.     

The influence of golf shaft torque on clubhead kinematics and ball flight

ABSTRACT

The purpose of this study was to investigate the influence of shaft torque (torsional rigidity) on clubhead kinematics and the resulting flight of the ball. Two driver shafts with disparate levels of torque, but otherwise very similar properties, were tested by 40 right-handed golfers representing a range of abilities. Shaft deflection data as well as grip and clubhead kinematics were collected from 14 swings, with each shaft, for each golfer using an optical motion capture system. Ball flight and additional clubhead kinematics were collected using a Doppler radar launch monitor. At impact, the high torque shaft (HT) was associated with increased delivered loft (P = .028) and a more open face (P < .001) relative to the low torque shaft (LT). This resulted in the HT shaft being associated with a ball finishing position that was further right (P = .002). At the individual level, the change in face angle due solely to shaft deformation was significantly higher for the HT shaft for 25/40 participants. Although shaft twist was not directly measured, it was logically deduced using the collected data that these outcomes were the result of the HT being twisted more open relative to the LT shaft at impact.     

Three-dimensional trunk kinematics in golf: between-club differences and relationships to clubhead speed

The aims of this study were (i) to determine whether significant three-dimensional (3D) trunk kinematic differences existed between a driver and a five-iron during a golf swing; and (ii) to determine the anthropometric, physiological, and trunk kinematic variables associated with clubhead speed. Trunk range of motion and golf swing kinematic data were collected from 15 low-handicap male golfers (handicap = 2.5 ± 1.9). Data were collected using a 10-camera motion capture system operating at 250 Hz. Data on clubhead speed and ball velocity were collected using a real-time launch monitor. Paired t-tests revealed nine significant (p ≤ 0.0019) between-club differences for golf swing kinematics, namely trunk and lower trunk flexion/extension and lower trunk axial rotation. Multiple regression analyses explained 33.7–66.7% of the variance in clubhead speed for the driver and five-iron, respectively, with both trunk and lower trunk variables showing associations with clubhead speed. Future studies should consider the role of the upper limbs and modifiable features of the golf club in developing clubhead speed for the driver in particular.     

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.     

A preliminary investigation of trunk and wrist kinematics when using drivers with different shaft properties

It is unknown whether skilled golfers will modify their kinematics when using drivers of different shaft properties. This study aimed to firstly determine if golf swing kinematics and swing parameters and related launch conditions differed when using modified drivers, then secondly, determine which kinematics were associated with clubhead speed. Twenty high level amateur male golfers (M ± SD: handicap = 1.9 ± 1.9 score) had their three-dimensional (3D) trunk and wrist kinematics collected for two driver trials. Swing parameters and related launch conditions were collected using a launch monitor. A one-way repeated measures ANOVA revealed significant (p ≤ 0.003) between driver differences; specifically, faster trunk axial rotation velocity and an early wrist release for the low kick point driver. Launch angle was shown to be 2° lower for the high kick point driver. Regression models for both drivers explained a significant amount of variance (60–67%) in clubhead speed. Wrist kinematics were most associated with clubhead speed, indicating the importance of the wrists in producing clubhead speed regardless of driver shaft properties.     

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 R&;A Rules Limited. 2008. Rules of golf, St. Andrews: R&;A Rules Limited, The Royal and Ancient Golf Club of St. Andrews.  [Google Scholar]), 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°, 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.     

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.     

Examining the influence of grip type on wrist and club head kinematics during the golf swing: Benefits of a local co-ordinate system

Wrist movements have been identified as an important factor in producing a successful golf swing, with their complex motion influencing both club head velocity and orientation. However, a detailed analysis of wrist angles is lacking in the literature. The purpose of this study was to determine kinematics across wrists and club head characteristics during the golf swing under weak, neutral and strong grip conditions. Twelve professional male golfers executed 24 shots using a driver under three grip conditions. A six degrees of freedom analysis of the hand with respect to the distal forearm was performed using a 10-camera three-dimensional motion capture system. Differences in joint angles were explored using repeated measures ANOVAs at key swing events (onset, top of backswing and impact), in addition club head velocity and clubface angle at impact were also explored. Main findings revealed significant differences in flexion/extension and internal/external rotation for both wrists at all swing events, whereas fewer significant interactions were found in ulnar/radial deviation across grips for both wrists at all events. Clubface angle only differed significantly between the weak and the strong and neural grips, presenting a more ‘open’ clubface to the intended hitting direction. This study is the first to explore tri-planar wrist movement and the effect of different grips, such analysis has implications for coaching knowledge and practice and should inform future research into different aspects of skill, technique analysis and may inform injury mechanisms/prevention.     

The effects of conscious processing on golf putting proficiency and kinematics

Abstract

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.     

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.     

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

Previous studies on overarm throwing have described a proximal-to-distal segmental sequence. The proximal segments reached their maximal linear velocities before the distal ones. In handball, no study has demonstrated this sequence from the upper torso to the wrist, although a recent study did present a different organization. The aim of this study was to analyse the throwing arm segmental organization during handball throwing. We found that the maximal linear velocity of the shoulder occurred after the maximal linear velocity of the elbow. Moreover, the maximal angular velocity of the upper torso occurred later than that of the elbow. Hence, contrary to other disciplines, the rotation of the upper torso was not suddenly stopped just after the forward arm motion was initiated. These results may apply to handball in general or be specific to the population of handball players studied. It may be advisable in future studies to include international players.     

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.     

Effects of fatigue on golf performance

The purpose of this study was to determine if body position, weight transfer, and/or pelvis/trunk rotations changed as a result of a golf specific fatiguing protocol and whether these changes affected resultant club head velocity at impact and shot consistency. Six male golfers and one female golfer participated in the study, who had a mean age, height, and body mass of 23.9 +/- 3.9 years, 177.4 +/- 4.9 cm, and 75.3 +/- 9.9 kg, respectively. Path analysis was used to determine the relationships between fatigue, biomechanical variables, and resultant club head velocity at impact and shot consistency. In the statistical models representing the effects of biomechanical variables calculated at the top of the swing and ball contact, golf specific fatigue was associated with a 2.0% and 2.5% reduction in the club head velocity and a 7.1% and 9.4% improvement in the shot consistency, respectively. These data suggest that golf specific fatigue was not related to the initial lower body sagittal plane angles at address nor was simulated golf specific fatigue related to peak transverse plane pelvis and trunk rotational velocities (or their timings) in a manner that indicates a relationship to resultant club head velocity and shot consistency.     

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.     

Effects of forefoot bending stiffness of badminton shoes on agility,comfort perception and lower leg kinematics during typical badminton movements

This study investigated whether an increase in the forefoot bending stiffness of a badminton shoe would positively affect agility, comfort and biomechanical variables during badminton-specific movements. Three shoe conditions with identical shoe upper and sole designs with different bending stiffness (Flexible, Regular and Stiff) were used. Elite male badminton players completed an agility test on a standard badminton court involving consecutive lunges in six directions, a comfort test performed by a pair of participants conducting a game-like practice trial and a biomechanics test involving a random assignment of consecutive right forward lunges. No significant differences were found in agility time and biomechanical variables among the three shoes. The players wearing the shoe with a flexible forefoot outsole demonstrated a decreased perception of comfort in the forefoot cushion compared to regular and stiffer conditions during the comfort test (p < 0.05). The results suggested that the modification of forefoot bending stiffness would influence individual perception of comfort but would not influence performance and lower extremity kinematics during the tested badminton-specific tasks. It was concluded that an optimisation of forefoot structure and materials in badminton shoes should consider the individual’s perception to maximise footwear comfort in performance.