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Acceleration and Shaft Fitting

accelgraph_300Swing tempo is one of the most misunderstood topics in shaft fitting. There have been numerous prior discussions on this issue in the golf press. Unfortunately, these discussions while recognizing the importance of acceleration in the shaft fitting process arrived at less than desirable conclusions due to misunderstanding the nature of a golfer's acceleration and swing variations.

The common practice today is to use a meter to register the highest rate of speedceleration during the swing. This rate is then compared to a pre-determined rate that represents an average speed. If the swing speed exceeds the pre-determined rate, a stiffer shaft flex will be recommended. If not, a softer flex will be recommended.

The error in this theory lies in its failure to understand that acceleration pattern is a much better parameter to use for shaft fitting. Golfers generate countless acceleration patterns. Most of the time, the acceleration is not consistent through out the entire swing. When considering swing tempo in the fitting process, we need to understand the nature of the acceleration and to consider its relevance.

The followings are 4 common types of swing tempo:

Smooth Tempo
The ideal type of swing tempo is one that accelerates gradually from 11 o'clock position to 6 o'clock impact position. Fitting a golfer with a smooth acceleration could be based primarily on swing speed. The selection of a softer flex is not necessary because the swing speed at impact is derived gradually and smoothly.

Delayed Release
Professional golfers and well-known teachers have been using and advocating a golf swing with a delayed release between the 7 and 8 oÕclock position. This type of swing generates an increase in accelerating from 7 oÕclock position to ball impact. Upon observing this type of tempo, a club fitter should consider increasing the stiffness and lowering the torque of the recommended shaft.

Early Release
Opposite of the delayed release is one that achieves an early peak of acceleration between 10 and 11 o'clock hand position. This is most common among younger golfers or golfers with excessive over swing. Frequently an early releaser loses his momentum prior to impact. If the peak acceleration is the only perameter used as a fitting factor, the result will naturally be quite erroneous. In this case, swing speed at impact can be an effective perameter for fitting.

Half Swing
Increased acceleration at the last quarter of the swing is also common among senior golfers. This is largely due to senior golfersÕ inability to complete a full swing. However, even with a swing from 9 oÕclock position to impact, most male senior golfers are still generating a swing speed of no less than 85 mph speed. In this instance, the acceleration will be substantially higher than an equal speed generated by a full swing. Most frequently, the 85-mph speed is generated with excessive hip and leg motion. In either scenario, a stiffer and lower torque shaft will prove to be more accurate and predictable than a lighter, softer and higher torque shaft.

Quick Way to Measure Swing Tempo
If you do not have an instrument to measure swing tempo, your own eyes and ears can be used to determine the subtle difference between high and low of a golfer's acceleration.
We recommend that you do the following:

  • Note the highest point of the upswing in terms of clock position
  • Divide the downswing into 2 parts. The portion from 12 o'clock to 8 o'clock is the first half. The portion from 8 oÕclock to impact is the second half.
  • Note the difference in speed between the first half and the second half.
  • If the second half is noticeably faster than the first half, recommend a stiffer, lower torque, or even heavier shaft.
  • If not, recommend a shaft flex basing on swing speed.

Conclusion
The popular practice of shaft fitting based on the highest acceleration rate is not technically sound. Strong acceleration at the last quarter of the swing justifies using stiffer, lower torque or even heavier shafts. In this article, we have tried to focus the discussion on acceleration. However, acceleration is not the only factor to consider in shaft fitting. Swing variation is equally, if not more, important than acceleration in the shaft selection process.