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jcgonzalez88
09-28-2000, 07:16 PM
Here is a summary of all the answers I got concerning the measurement of
footwear stability.

Thanks to all answerers


-----Original Message-----

Can anyone direct me to information (references) regarding any
method to measure footwear stability. I am interested on methods to
measure footwear stability in tests with subjects (using force plates,
pressure insoles, etc.) and machine testing of shoes. Any information
would be appreciated and I will post a summary of replies if anyone is
interested.
__________________________________________________ _________

Sam Lee:

I don't have any references handy, but I do have an intensive interest
in
athletic footwear and foot&ankle biomechanics.

First of all, I think you need to precisely define what it is you mean
by
stability. I presume you mean the general industry paradigm of rearfoot

in/eversion, in which case I might suggest employing a video analysis to

measure frontal plane tibiocalcaneal angle: two markers on the Achilles
tendon to represent the lower leg axis and two markers on the heel to
represent the shoe/foot (of course, there's some discrepancy there, with

movement of the foot within the shoe). Stability could then be
quantified
by the maximum angle achieved during stance phase; higher angle, less
stability.

My second thought would be to use the center-of-pressure output from the

force plate (XY coordinates in horizontal plane) to quantify the path of
the
foot. If you could compare the dynamic curves, a more medial route
would
represent more instability.

Finally, you might be able to use insole pressure distribution to
quantify
peak pressures underneath the heel.

Of course, there's the difficulty in accounting for whether subjects
tend to
run differently in different types of shoes in response to the different

proprioception...

Samuel Lee, M.Sc.
Research Engineer
Hospital for Special Surgery
Department of Biomechanics & Biomaterials
New York, N.Y. 10021 U.S.A.
(212) 774-2382
LeeS@HSS.edu

__________________________________________________ _________

Paul Bourassa:

I can refer you to a basic mechanical model for stability. It is given
in
particular in the book by T.R.Tauchert '' Energy principles in
structural
mechanics'' Mc Graw Hill 1974. You may see a vertical rod of length L
attached to the ground through a coil spring of rigidity K and being
subject to a vertical force Q. The critical charge Qo = k/L. We have
measured (many years ago, the torsional stiffness of various joging
shoes,
using a home made test^platform.
We have written a french report for the provincial government. The study

was supported for one year only and we did not pursue our research.
Further
study, I feel, could be done from that starting model. One could devise
more complex model eventually, using for instance finite elements and so

on. I Hope this will be useful, Au revoir, Hasta la vista..

Paul Bourassa,
genie mecanique, Sherbrooke Universidad,
Canada.

__________________________________________________ ____________

Martyn Shorten:

Except for rearfoot stability of running shoes, there is no real
consensus about how footwear stability should be
measured.

The frontal plane motion of the foot/ankle complex has often been used
as a measure of stability in running
shoes. Most labs uses some variation on a "rearfoot motion protocol",
although the link between rearfoot motion
and injury mechanics is unclear. ASTM Standard F1833-97 "Standard Test
Method Comparison of Rearfoot
Motion Control Properties of Running Shoes." is a consensus standard
describing the fundamentals of the
protocol. The standard is available on the internet from
http://www.astm.org.

The following references also provide a good introduction:

(1) Clark, T.E., Frederick, E.C., and Hamill, C.L., "The Study of
Rearfoot Movement in Running," in E.C. Frederick
(Ed.), Sport Shoes and Playing Surfaces, Champaign, IL, Human Kinetics
Publishers, 1984,pp. 166-189.

(2) Edington, C.J., Frederick. E.C., and Cavanagh, P.R., "Rearfoot
Motion in Distance Running," in P.R. Cavanagh
(Ed) Biomechanics of Distance Running, Champaign, IL, Human Kinetics
Publishers, 1990, pp. 135-164.

__________________________________________________ ___________

Susan Stacpoole-Shea:

How you measure footwear stability depends on what you mean by
"stability".
If you are interested in the stability inherent within the
construction/design of the shoe, then material testing with eg: Instrong
or
MTS machines would be valuable. However, if you are interested in the
foot,
stance or gait stability of patients or research subjects, then I would
suggest in-shoe pressure testing with either a Pedar or F-scan in
combination with 3D video and force plate data. I have used several
systems
and they all have different advantages depending upon your question.

There are many references that deal with stability especially related to
the
study of falling in the aging population. Most falls studies include
factors
that influence falling including floor surfaces and footwear.

A starting point for reading into this area would be the book by Craik
and
Oatis, Clinical Gait Analysis. There are also many research papers by B.

Nigg on shoe testing, both construction and dynamic.

Cheers,

Susan Stacpoole-Shea
Clinical and Research Podiatrist
Ballarat Health Services and University of Ballarat, School of Human
Movement and Sport Sciences.
Ballarat, Victoria, Australia
susan@shea.com.au

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