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Using Center of Pressure Data to Diagnose and Train Early Extension

57p_sc_earlyextensionEarly Extension is the most common swing characteristic in golf.  It is defined by TPI as “any forward movement of the lower body towards the ball on the backswing or downswing.”  Of the 90,000 golfers that TPI has analyzed, 67% had early extension.

The majority of TOUR players do not early extend, although some do.  For many amateurs, early extension can be responsible for a two-way miss and significant loss of speed.

Ground mechanics play an important role in diagnosing and training early extension.  In the video below, we summarized a training session that Lance Gill led at an educational event co-hosted by K-Vest and BodiTrak at Egoscue near San Diego.  The focus of the event was to share practical ways that instructors could incorporate technology into their lessons or drills.  Lance demonstrated how a simple medicine ball drill could help a student improve their posture and correct a movement tendency (without any cueing), using visual biofeedback as reinforcement.


image-1image-1-1You’ll see Lance taking his client Elliot through the medicine ball drill at the 2:14 mark of the video.  Notice that the trace immediately becomes more linear when the med ball is introduced.  Linear isn’t always better, but for the purpose of this lesson, it’s a desired outcome.  What’s more interesting is that it improved without any cueing from Lance.  We’ll dive into the drill more in the next few weeks, but, essentially what’s happening is that the weight of the medicine ball is causing Elliot to engage his core in a way that encourages him to maintain his posture.  By maintaining core engagement, Elliot keeps his pelvis from compensating by moving toward to ball.

jason-day-traceIt’s important to note that a center of pressure trace that gets to the toes of the lead foot doesn’t necessarily always indicate early extension.  For example, check out this trace on the right.  The trace moves from fore-foot of the trail leg towards the toes of the lead foot before ending in the heel.  Does it look like early extension?  Potentially.  Is it a problem?  Not for Jason Day, the man who the trace belongs to.

If you just looked at Jason Day’s trace, you might guess that he early extends severely because the pressure goes to his toes.  However, Day’s COP traveling toward the toe of his lead foot is not a representation of his center of mass, but rather a representation of how hard he is pushing into the ground, away from the ball, from the ball of his lead foot.  This is a classic example of center of mass vs center of pressure.

Hopefully this provides some clarity on what we can learn from COP data when working with a student who exhibits early extension.  For more on early extension, check out this clip from our Golf Ground Mechanics certification program which features Mark Blackburn discussing early extension: http://boditraksports.com/kc/boditrak-ground-mechanics-early-extension/