Date of Award

2014

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Doctor of Philosophy

School

School of Exercise and Health Sciences

Faculty

Faculty of Health, Engineering and Science

First Supervisor

Associate Professor Angus Burnett

Second Supervisor

Dr Jodie Wilkie

Abstract

If golfers achieve long hitting distances whilst maintaining their accuracy they will gain a competitive advantage. To increase hitting distance, faster clubhead speed is required and this can potentially be achieved through a number of factors. Firstly, anthropometric factors such as height and physical factors such as trunk rotational power have been previously considered to be of importance. However, biomechanical factors such as; the X-factor (separation of the trunk-pelvis alignment when viewed in the transverse plane), have been a major focus of recent research. Further, the interaction of the golfer with the implement they hit with i.e. the golf club has also been examined in biomechanical studies. The broad aim of this doctoral research was to investigate how male high-level amateur golfers generate club head speed and this was examined in a series of five studies that examined technical and equipment factors.

The first study of this thesis (Study I) developed a valid three-dimensional Cardan / Euler model to examine the kinematics of the trunk and lower trunk during the golf swing. This validation study involved; developing and validating models and related algorithms as well as making comparisons to static and dynamic postures. It was concluded that a lateral bending / flexion-extension / axial rotation (ZYX) order of rotation was the most suitable to quantify the X-factor and lower trunk movement in the golf swing.

Previous research has shown conflicting relationships between golf swing kinematics (such as variables related to the X-factor) and clubhead speed, as well as what physical variables assist in generating clubhead speed. The second study of this thesis (Study II) had two aims.

The first aim was to determine whether significant between-club (driver and five-iron) differences existed for trunk and lower trunk kinematics as well as launch conditions. The second aim was to determine which anthropometric, physical and trunk and lower trunk kinematic variables were most strongly associated with clubhead speed. Fifteen high level amateur male golfers (2.5 ± 1.9 handicap) had their trunk and lower trunk three-dimensional kinematics data quantified using the methods developed in Study I. Nine significant (p < 0.002) between-club differences in swing kinematics were found; namely trunk and lower trunk flexion and lower trunk axial rotation, as well as ball velocity. Regression analyses explained 33.7 % and 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. No anthropometric (i.e. height) or physical (i.e. maximum trunk rotational speed) were associated with clubhead speed.

The low amount of variance explained by clubhead speed for the driver in Study II stimulated further investigation. Studies III and IV were designed to develop a method to locate the kick point during the golf swing and examine the effect of kick point location on swing parameters and their related launch conditions, respectively. Study III involved two phases, Firstly, the level of agreement between two methods of determining the static kick point was determined. This showed that an algorithm using three-dimensional locations of markers placed on the golf club was a valid method to determine the location of the static kick point. In the second phase of testing, this method was used to determine the location of the dynamic kick point during the golf swing. Excellent between-trial reliability was found for this method. Further, differences were found for the dynamic kick point location when compared to the static kick point location. The main objective of Study IV was to determine whether drivers fitted with shafts having high and low kick points would alter selected swing parameters, and related launch conditions. Twelve high level amateur male golfers (1.2 ± 1.8 handicap) had three shots analysed for each of two drivers fitted with “stiff” shafts but these drivers had differing kick point location. Stiffness profiles of these shafts were also measured. Five swing parameters and their related launch conditions were measured using a real-time launch monitor. The driver fitted with the shaft containing the high kick point displayed a more negative (steeper) angle of attack, a lower launch angle and an increased spin rate when compared to a driver fitted with a low kick point

In Study II, a relatively small amount of variance in clubhead speed was explained by the driver and it was the overall intention of the last study of this thesis (Study V) to attempt to explain more of this variance by examining both trunk and wrist kinematics. This was undertaken using two drivers containing differing kick point locations (low and high), with two separate regression models being produced. Twenty high-level amateur male golfers (1.9 ± 1.9 handicap) had their trunk and lower trunk three-dimensional kinematics data quantified as in Study II, but with the addition of a wrist segment. Four significant (p

In conclusion, the methods developed for this thesis to analyse golf swing kinematics revealed a greater insight into how highly skilled golfers produce clubhead speed. Particularly, the results from Studies II and V revealed significant associations between lower trunk related variables and clubhead speed when using different clubs (driver vs. fiveiron) and the same club fitted with two shafts of different kick point location (driver). Also, the methods developed in Studies III and IV to investigate dynamic shaft profiles (deflection) in the downswing provided possible explanations as to how shaft performance in the downswing can influence swing parameters and their related launch conditions at ball impact.

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