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  • Re: footwear stability

    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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