Mass and moment of intertia (MOI) are quantities that express a body’s tendency to resist linear and angular acceleration repsectively. Total club mass and MOI about the butt end of the club, therefore, have the potential to affect the ability of a golfer to accelerate the club during the downswing, which in turn could influence impact parameters such as clubhead and ball velocity. Previous studies, however, generally haven’t modified both mass and MOI independently nor have they explored their individual effects on the biomechanics of a golfer’s swing. There exisits an opportunity to optimise these parameters for an individual golfer in the custom fitting process but, to do this effectively, it is essential that the effects of mass and MOI on performance are repeatable over time and not just a quirk of a particular fitting session.

Aim

The aim of the project was to investigate the effect of independently modifying the mass and MOI of the whole golf club on golfer performance (clubhead delivery and ball launch) and swing kinematics (pelvis, thorax and lead/trail wrist kinematics). A further aim was to assess the test-retest reliability of the changes in performance with MOI.

Approach

  • Phase 1 – Repeat test sessions indoors with skilled golfers using three drivers of varying MOI (~ 200 kg∙cm2 increments), achieved through modifications in the position of a shaft mass. Clubhead delivery and ball launch measured using a Trackman 4 launch monitor.
  • Phase 2 – Indoor testing with skilled golfers using three driver conditions; a reference, increased mass (~ + 100 g) and increased MOI (~ 400 kg∙cm2) condition, achieved through modifying shaft mass and mass position, respectively. Two separate optoelectronic systems used to measure pelvis, thorax and lead/trail wrist kinematics (Vicon) and clubhead delivery (GOM); ball launch measured using a Trackman Pro 3e launch monitor. Discrete (t-tests) and continuous (SPM) statistical analysis techniques used to analyse the data on both a group and individual golfer basis.

Key Findings

  • Independently increasing golf club mass typically had a small, insignificant effect on both golfer performance and swing kinematics at the group level.
  • Increasing the MOI of the golf club was found to reliably decrease both clubhead and ball velocity.
  • Reductions in clubhead velocity, ball velocity and total spin rate due to MOI appeared to be primarily a result of a significant reduction in the angular velocity of the central pelvis and thorax segments leading up to, and/or at the time of impact.
  • At the individual level, golfer-specific changes in both performance and swing kinematics were observed when modifying the inertia of the golf club, suggesting that the optimum club design with respect to golf club inertia is also unique to each golfer.

Publications

Researchers

Josh Turner

Turner, J. (2021). The effect of golf club inertia on the golfer–club interaction. PhD Thesis.