What is best cut-off frequency in club swing of pro-golfer

[Hyun-Seob, Lee]

I experimented about club swing of pro-golfer by 3D Motion analysis system and get the raw data with markers coordinates.

In post-process, what is best cut-off frequency?

Generally, Gait is 6Hz. In golf?

I appreciate to any information which are an article and your opinions.

[Allan Carman]

Re: What is best cut-off frequency in club swing of pro-golfer

I collected 3D motion of a professional golfer some years ago for animation purposes. I am sure it was captured at 200Hz. The interesting thing was that if a Butterworth low pass filter was applied to the 3D coordinate data the golf club would shorten as swing speed increased. Starting at the correct length at the beginning of the swing but shorten as the swing speed progressed (the golf club head moving up and closer to the hands, being shortest at the bottom of the swing such that the head would pass over where the golf ball would have been) and then lengthen again as the swing slowed down. I don't remember if the 3D coordinate data of the club head was filtered at all. If it was the cut off frequency would have been relatively high. So if you do filter 3D data check the club length and motion of the club head.

Cheers
Allan

[Hyun-Seob, Lee]

Re: What is best cut-off frequency in club swing of pro-golfer

Thanks to Allan Carman.

I appreciating your advice. Your mentions are helping to me.
I will experiment with your method to my data.

Hyun-Seob Lee

[Chris Kirtley]

Re: What is best cut-off frequency in club swing of pro-golfer

The optimal cutoff frequency in gait is actually 6*natural frequency (i.e. the stride frequency). This just happens to be about 1 Hz for freely selected cadence (60 strides/min, or 120 steps/min). But it would be, e.g. 6*1.5 = 9 Hz for gait at a stride frequency of 1.5 Hz or 90 strides/min (cadence of 180 steps/min). I suspect this is a general relation for cyclical activities. In golf, I guess the natural frequency would be the swing frequency: you could estimate this from the time taken to swing the club. Of course, a residual analysis would be even better, and it might be interesting to compare the two approaches.

[Hyun-Seob, Lee]

Re: What is best cut-off frequency in club swing of pro-golfer

Thank to Kirtley!

Your post has been helpful to me. and Thanks for your explanation again.
I have a question about 6*natural frequency. Why to six times a natural frequency? Is it related to the nyquist frequency? What is mean number 6?
Natural frequency of golf swing * 6 = best frequency for golf ?
please explain to me detailly.

[Chris Kirtley]

Re: What is best cut-off frequency in club swing of pro-golfer

As I recall, the 6*stride freq number was empirically determined by David Winter using a residual analysis of gait kinematics filtered at various frequencies (his 1974 paper, I think?). Nothing to do with Nyquist - it's really about the harmonics of the signal - there is very little signal (and therefore mainly noise) after the 6th harmonic. As I say, this may be specific to gait, but I suspect is a more general characteristic of human movement.

We had a discussion about this on BIOMCHL in 1996:

http://www.clinicalgaitanalysis.com/faq/cutoff.html

... and Peter Sinclair helpfully supplied an Excel spreadsheet for residual analysis:

http://www.clinicalgaitanalysis.com/tools

... although these articles sound a note of scepticism about the approach:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.231.1647&rep=rep1&type=pdf

http://www.humankinetics.com/acucustom/sitename/Documents/DocumentItem/2387.pdf

[Hyun-Seob, Lee]

Re: What is best cut-off frequency in club swing of pro-golfer

Thanks very much! Kirtley.

Your kind response is help to me. I will read contents that you have presented above.

[Wadim Korneew]

Re: What is best cut-off frequency in club swing of pro-golfer

I appreciating your advice. Your mentions are helping to me.