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Skilled Golfers Wanted

Project Title: Comparison of golf swing characteristics between two weight shift styles

Golf swing

The Biomechanics Laboratory at Texas Woman’s University-Denton Campus is seeking potential research participants (male skilled golfers) for a golf research study with intention to investigate the effects of weight shift on various kinematic and kinetic downswing characteristics.

This is a motion analysis study in which your swing trials will be captured real-time with an optical motion capture system (see the figure on the left). The time commitment for this single data collection session study will be approximately 1.5 hours.

The participation in the study is completely voluntary and you may choose to withdraw from the study at any time during the course of the study. You will be asked to perform multiple trials of swing using three different clubs (driver, 5-iron, and pitching wedge) with our reflective marker system for motion capture.

In order to qualify for the current study you must meet the following minimum criteria:

  • Male golfer
  • Five years or more golf experience
  • Posted handicap of 3 or less
  • Between 19 and 40 years of age
  • Injury-free

There will be no monetary compensation for participation in this study. The benefit for you, the participant, will be an opportunity to participate in a motion capture-based research and a copy of the final study report/publication, which may assist you in better understanding your swing. If you are interested, you will also have a chance to view your computerized swings.

Here are some more details of the research procedures:

  • All testing will take place at the Motion Analysis Laboratory, TWU Denton campus.
  • You will be asked to wear black spandex shorts and shirt for motion capture purposes.
  • Your mass (weight), height, age, and experience will be recorded.
  • You will be provided with a participant preparation room to change clothes and get ready.
  • For the purposes of motion capture, a total of 70 small (1-cm diameter) reflective markers will be placed on specific body landmarks, some over the clothes (e.g. pelvis) and some directly on the body (e.g. arms), using double-sided tape: 5 on the pelvic area, 11 on thetrunk, 4 on the head, 20 on the arms, 16 on the legs, 9 on the club, and 5 on the ball plate.
  • You will be asked to perform swings on the force plates covered with artificial grass. The force plate will measure the forces acting between your feet and ground (see the figure on the left).
  • You will be asked to perform 5 good swing trials in each club condition. You will be given instruction before each trial.

If interested in this study, please do not hesitate to contact the principal investigator by using the following information:

Kihoon Han, doctoral student
(940) 595-6961

Weight Shift

So what is weight shift? Weight shift in golf means lateral motion of the weight center (center of mass; COM) away from or toward the target during the swing. During the backswing golfer’s body COM (including the club) moves toward the trail leg (away from the target), whereas it moves toward the lead leg (toward the target) during the downswing.

Weight shift style

Depending on the degree of deviation from the initial CM position at address, weight shift styles can be classified into two main categories: unrestricted weight shift (UWS) and centered pivot (CP) (see the figure on the left). In the CP style, the trail-side (backswing) and lead-side (downswing) maximum deviations of the COM from the initial position (broken line in the figure) are similar in magnitude. The UWS style, however, shows larger trail-side deviation from the initial COM position. Although the lateral head displacement during the backswing is a good indicator of your weight shift style, you will be assigned to a specific style based on your maximum COM deviation values.

Functional Swing Plane and Body Motion Planes

Functional swing plane

The functional swing plane (FSP) is the motion plane of the clubhead during the execution phase of the downswing (Mid Downswing to Mid Follow-through; see the figure on the left). The FSP is obtained by mathematically fitting the clubhead trajectory to a plane. The motion planes of important body points such as the arm joints can be identified in a similar way by fitting the trajectories of the body points to respective planes. Body motion planes are often defined for the entire downswing (Top of Backswing to Mid Follow-through). The FSP and body motion planes visualize the motion of the clubhead and body points. Weight shift style can change the properties (orientation and curvature) of the FSP and body motion planes.

Ground Reaction Force and Center of Pressure

Ground reaction force

Ground reaction force (GRF) is the reaction to golfer's force action to the ground. Force plates are used to measure the foot-ground interaction, one for each foot. GRFs can be analyzed for each foot or as combined force. The figure on the left shows both individual GRFs and the combined GRF (black arrows). GRF is an important external force in golf as the angular momentum of the body-club system is generted through the foot-ground interaction using the GRF.

A concept often misunderstood by many golf professionals is center of pressure (COP). COP is the application point of the GRF and shouldn't be used as an indicator of weight shift. Weight shift means displacement of the COM, not COP. Weight shift style can drectly affect the GRF and COP  patterns and eventually the angular momentum profile.


page last updated 12/8/2015 12:44 PM