Steve R. Otto

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

Abstract 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 participants 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.

Ball launch conditions for skilled golfers using drivers of different lengths in an indoor testing facility

Abstract The displacement of the golf ball struck by a driving club is affected by several player characteristics and equipment parameters and their interrelationships. Some modelling and simulation studies have shown a relationship between shaft length and clubhead speed, supported by a few experimental studies. The aim of the present study was to examine the relationship between driver length and ball launch conditions in an indoor test facility using a ball launch monitor. Nine males considered to be skilled golfers participated in the study. Four driving clubs of total length 117, 119, 124, and 132 cm were assembled from commercially available components and were used to strike golf shots while initial ball velocity, backspin rate, and launch angles were measured. Statistical analysis identified a significant difference in initial launch speed due to club length, a significant difference between participants, but no difference between the trials for a given golfer. A positive trend was noted between backspin and launch angle for all four clubs, and significant inverse associations between initial launch speed and backspin rate and launch angle. However, the combined launch conditions associated with increasing length were not considered optimal, with uncontrolled swingweight and moment of inertia effects considered to be limiting factors.

Determination of the swing technique characteristics and performance outcome relationship in golf driving for low handicap female golfers

Abstract Previous studies on the kinematics of the golf swing have mainly focused on group analysis of male golfers of a wide ability range. In the present study, we investigated gross body kinematics using a novel method of analysis for golf research for a group of low handicap female golfers to provide an understanding of their swing mechanics in relation to performance. Data were collected for the drive swings of 16 golfers using a 12-camera three-dimensional motion capture system and a stereoscopic launch monitor. Analysis of covariance identified three covariates (increased pelvis–thorax differential at the top of the backswing, increased pelvis translation during the backswing, and a decrease in absolute backswing time) as determinants of the variance in clubhead speed (adjusted r 2 = 0.965, P < 0.05). A significant correlation was found between left-hand grip strength and clubhead speed (r = 0.54, P < 0.05) and between handicap and clubhead speed (r = −0.612, P < 0.05). Flexibility measures showed some correlation with clubhead speed; both sitting flexibility tests gave positive correlations (clockwise: r = 0.522, P < 0.05; counterclockwise: r = 0.711, P < 0.01). The results suggest that there is no common driver swing technique for optimal performance in low handicap female golfers, and therefore consideration should be given to individual swing characteristics in future studies.

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°, 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.

Validation of a Full-Body Computer Simulation of the Golf Drive for Clubs of Differing Length

The aim of the present study was to validate a full-body computer simulation of a golfer’s swing for driving clubs. An elite male golfer performed 24 shots in a laboratory, comprised of 8 trials using each of three drivers of different shaft length (46″, 48″, & 50″). A 5-camera MACTM system operating at 240 Hz collected kinematic data which was subsequently used to drive the model utilising ADAMS/LifeMOD software. Additional skin markers were used for model validation. A large-scale musculoskeletal human model was constructed, with a parametric model of a driver. Inverse and forward dynamics calculations were performed with the imported experimental motion data in order to generate model movement. A commercially available launch monitor recorded experimental eclubhead and launch conditions. There was a very high level of agreement (r=0.995) between experimental kinematic data and the predicted trjectory splines of the model. There was also a high level of correlation (r=0.989) between the model predicted mean values for clubhead speed and the experimental values for each of the club lengths, both demonstrating increased clubhead velocity as club length increased. Muscle contraction force output by the model showed a significant difference (p≤0.001) between driver simulations, demonstrating its capability to illustrate the link between gross muscle force production and club length, as evidenced by the increased force output for the longest shafted club.

Effects of golf shaft stiffness on strain, clubhead presentation and wrist kinematics

The aim of this study was to quantify and explain the effect of shaft stiffness on the dynamics of golf drives. Twenty golfers performed swings with two clubs designed to differ only in shaft bending stiffness. Wrist kinematics and clubhead presentation to the ball were determined using optical motion capture systems in conjunction with a radar device for capturing ball speed, launch angle, and spin. Shaft stiffness had a marginally small effect on clubhead and ball speeds, which increased by 0.45% (p < 0.001) and 0.7% (p = 0.008), respectively, for the less stiff club. Two factors directly contributed to these increases: (i) a faster recovery of the lower flex shaft from lag to lead bending just before impact (p < 0.001); and (ii) an increase of 0.4% in angular velocity of the grip of the lower flex club at impact (p = 0.003). Unsurprisingly, decreases in shaft stiffness led to more shaft bending at the transition from backswing to downswing (p < 0.001). Contrary to previous research, lead bending at impact marginally increased for the stiffer shaft (p = 0.003). Overall, and taking effect sizes into account, the changes in shaft stiffness in isolation did not have a meaningful effect on the measured parameters, for the type of shaft investigated.

The relationships between driver clubhead presentation characteristics, ball launch conditions and golf shot outcomes

The purpose of this study was to analyse the effects of clubhead presentation on golf ball launch conditions and the subsequent shot outcome. Clubhead presentation was measured using a three-dimensional motion capture system for both male and female golfers across a range of skill levels. A Doppler radar was used to track the golf ball during its flight, yielding speed, launch angles, spin rate and distance. Importantly, the measurements of clubhead and ball quantities were taken independently so that any inter-relationships could be evaluated without recourse to any preconceived models. This article provides values for the median launch conditions and shot outcome, and the associated variability in these quantities for golfers was grouped by handicap category and gender. It was shown that the variability in certain outcome quantities was more linked to golfing ability than others. Linear regression was used to demonstrate that differences in clubhead presentation resulted in changes to ball launch conditions as one might expect from physical analysis. Furthermore, the link between the variability in clubhead presentation and the variability in shot outcome was demonstrated. In particular, the importance of impact location variability in determining launch angle and total distance variability was shown.

Material and surface effects on the spin and launch angle generated from a wedge/ball interaction in golf

Backspin rate and friction coefficients have been studied for a range of commercially available wedges and multi-piece golf balls using a mechanical golfer and a modified pin-on-disc tester. Analysis of shot characteristics for wedges with three different surface roughness values and two golf ball types (two-piece ionomer covered and three-piece polyurethane covered) was carried out using the mechanical golfer, whilst pin-on-disc testing was performed to determine the friction coefficient between the different golf ball covers (with a range of hardness values) and steel discs with a range of surface roughness values seen for different wedges. It was found that the polyurethane covered balls (lower hardness) showed greater backspin than the ionomer covered balls (higher hardness), and showed higher friction values during the pin-ondisc testing.During the mechanical golfer tests, however, it was observed that the ionomer covered balls showed an increase in friction coefficient for increasing surface roughness, although the effect of differences in cover material types was greater than that of surface roughness variation for the same cover material within the range of commercially available wedge face surface roughnesses.

Iron Golf Club Striking Characteristics for Male Elite Golfers

Ball launch condition data and clubhead data were measured in order to gain an understanding of the striking characteristics associated with a group of elite golfers using different iron golf clubs. Ten right-handed male golfers were used as subjects (handicap −0.5±1.7). The testing was carried out in a dedicated indoor golf facility. Each golfer hit eight shots with each of four of his own iron clubs (3-iron, 5-iron, 7-iron and pitching wedge). Launch conditions and clubhead data were measured using a stereoscopic high-speed camera system. The mean club head speeds for the group decreased and the mean clubhead angle of attack increased as the club became more lofted. The more lofted clubs produced a higher mean spin rate and higher mean launch angle. Whilst these findings are as expected, the study is novel in providing a scientific database for the competences with irons associated with this elite skill level. It also validates the choice of a single subject that may be used in the future construction of a simulation model designed to investigate iron club striking properties.

Differences in the structure of variability in ground reaction force trajectories provide additional information about variability in the golf swing

The study presents a novel application of measures of the structure of variability to ground reaction force trajectories and highlights the use of such measures to provide valuable information about coordination of the golf swing. The variability and regularity of ground reaction force trajectories were quantified for iron and driver shots from three participants with different skill levels. Pointwise median absolute deviation was used to indicate the variability of ground reaction force trajectories across their length, and two alternative methodologies, sample entropy and cross-sample entropy, were used to determine their regularity. For both driver and iron shots, results showed that while there was no difference in the magnitude of variability between any of the participants, there were differences in the structure of this variability. In general, the ground reaction force of the highest skilled participant was significantly more regular than that of the lesser skilled golfers. However, differences occurred across the various components of ground reaction force. Thus, entropy measures can provide additional valuable information concerning dissimilarities among golfers of various skill levels and may indicate differences in neuromuscular system coordination during the golf swing. This study highlights the importance of considering the structure of variability, as well as its magnitude, and describes methods which could be applied to further investigations.