Different centre of pressure patterns within the golf stroke I: Cluster analysis.

Weight transfer research in the golf swing has produced conflicting and inconclusive results. A limitation of previous studies is the assumption that only one swing "style" exists within the golf swing. If different styles, or movement strategies, exist and if the different styles are analysed together in a single group, statistical errors will result. The aim of this study was to determine if different weight transfer styles exist in the golf swing by applying cluster analysis to centre of pressure (CP) patterns in the direction of hit (CPy) and to evaluate cluster analysis issues. Sixty-two professional to high handicap golfers performed simulated drives, hitting a golf ball into a net, while standing on two force plates. Centre of pressure position relative to the feet (CPy%) was quantified at eight swing events identified from 200-Hz video. Cluster analysis identified two major CPy% styles: a "Front Foot" style and a "Reverse" style. Both styles began with CPy% positioned evenly between the feet, moved to the back foot during backswing, and then forward during early downswing. Beyond early downswing, the Front Foot group continued to move CPy% to the Front Foot through to ball contact, while the Reverse group moved CPy% towards the back foot through ball contact and follow-through. Both weight transfer styles were evident across skill levels from professional to high handicap golfers, indicating that neither style was a technical error. Cluster analysis should include hierarchical and non-hierarchical clustering and use objective measures combined with theoretical assessment to determine the optimal number of clusters. Furthermore, a number of validation procedures should always be used to validate the solution.