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View Full Version : Re: Anthropometric scalability question - Push/Pull Fo rces



Greiner, Thomas M. Ph.d.
07-29-2004, 12:22 AM
There are no valid scaling methods available to transform a 50th percentile
person to a 5th percentile person. The reason for this is that the concept
of a "5th percentile person" is neither biologically nor statistically
valid.

Look on the charts of anthropometric values that contain percentile ranges.
If you put together a person who possessed the 5th percentile values for
stature, and weight, and finger breadth, and arm length, etc it is very
unlikely that would produce a body shape that could exist. And if it did
exist, the frequency of that combination of anthropometric values in the
population would be much rarer than 5%. Do a quick check. How many people
in the survey have both the 5th percentile stature and 5th percentile body
weight? The answer you come up with will be no where close to 5 percent of
the population.

This is a common error that shows up in human engineering applications. It
is also an example of how a little knowledge coupled with misapplication of
statistical and biological principles can be a very dangerous thing.

The data that you are looking for would have to be based upon a survey of
push/pull forces for women. You could derive a meaningful estimate of the
population 5th percentile value, and for than value only, from sample
distribution in that survey.

Thomas M. Greiner, Ph.D.
Associate Professor of Anatomy
Department of Basic Sciences
New York Chiropractic College
Seneca Falls, NY 13148-0800 USA

Office Phone: (315) 568-3183
Gait Lab Phone: (315) 568-3150
Fax: (315) 568-3017
Email: tgreiner@nycc.edu



> -----Original Message-----
> From: Matt Kuklis [SMTP:Matt_Kuklis@HILL-ROM.COM]
> Sent: Thursday, July 29, 2004 8:59 AM
> To: BIOMCH-L@NIC.SURFNET.NL
> Subject: [BIOMCH-L] Anthropometric scalability question - Push/Pull
> Forces
>
> Group,
>
> A colleague and I are working on a project to try to understand a
> comfortable range of push/pull forces that a 5th percentile female can
> endure. We have found many tables of forces published by many individuals
> mostly to do with maximum endurance forces for various push/pull
> exercises. We found a decent representation of our application in
> Dreyfuss' "Measure of Man and Woman". However, the forces given are for a
> 50th percentile male. Dreyfuss gives a male to female scaling factor of
> 2/3; we've also seen scaling factors around 1/2. We are interested in the
> 5th percentile female as I have mentioned.
>
> Is there any such scaling factor/conversion that can take data (in
> particular push/pull forces) from one segment of the population (based on
> percentile) to another (e.g., is there a conversion to take data from 50th
> percentile to 5th percentile)?
>
> Short of doing our own study, is there a better way to get the data more
> directly? For instance, is there a more gold-type standard/study of
> push/pull forces for various exercises (i.e., forearm/shoulder in
> different orientations; sitting versus standing, etc.)?
>
> A summary of responses will be posted. Please indicate if you would like
> your name removed from the summary posting.
>
> Thank you for any information.
>
> Matt Kuklis
> Biomechanical Engineer
> Hill-Rom Co., Inc
>
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