Shaft flex has been shown to affect driving distance in a subject specific manner. However, the dynamic role of the flexible shaft has not been adequately described, and so it cannot be predicted which golfers should be matched with which flex. Therefore, the main purposes of this investigation were to determine the influence of shaft flex on the dynamics of the clubhead at ball impact, to identify the mechanisms by which shaft flex influences the dynamics of the clubhead at ball impact, and to objectively match golfers with the appropriate shaft flex required for maximum driving distance.

The results of this study indicate that shaft flex significantly influences clubhead speed at impact for most golfers. Changes seen in driving distance with different flexes are likely due to this effect. The mechanism by which this influence occurs includes both altering the swing speed of the player and the kick velocity of the shaft. However, shaft flex does not change clubhead speed in all golfers. For those that it does, there is not one flex which results in maximum clubhead speed for everyone.

These subject specific effects were found to be dependent upon how the player loads the club during the swing. Specifically, whether the player has positive or negative shaft kick velocity at impact, and whether the majority of shaft deflection occurs at the top of the backswing or during the downswing. These factors influence the player's swing speed and shaft kick velocity, which in turn dictate the clubhead speed at impact.

By identifying these key characteristics of the club loading pattern, it is possible to predict, on average, whether shaft flex will have an influence on the player's clubhead speed, and if so, whether they should be matched with a flexible or stiff shaft. With the implementation of a system that suitably measures shaft deflection during the swing, this information has the potential to help clubfitters match individual golfers with the appropriate shaft flex required to maximize clubhead speed at impact.