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  • responses regarding forceplate slippage and targeting

    Good day,

    The following is a late posting of responses we received regarding the
    problem of slipping on the force plate and targeting during gait. Thank you
    sincerely for your responses and I hope this summary can serve others when
    dealing with the same problem.

    Dan K Ramsey

    MotorikLab Tel: +46 (0)8-517-77-503
    Astrid Lindgrens Barnsjukhus Fax: +46 (0)8-517-77-351
    Karolinska Institutet E-mail: Dan.Ramsey@kbh.ki.se
    S-171 76 Stockholm Lab: http://ikaros.f1.ki.se/motorlab/index.htm
    Sweden Profile: http://myprofile.cos.com/DRam
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    For targeting:
    After the subjects are comfortable on the walkway, we mark the starting spot
    for the subjects and instruct them to take the same first step on each trial
    (same foot, of course but same step length also). Consistency in the first
    step seems to help them maintain a consistent step length and hit the plate
    reasonably well. Most people seem to hit the plate well about 70 to 80% of
    the trials. Sometimes their stride changes and we adjust the starting point,
    perhaps up to 10 centimeters.

    Here is a protocol I have never tried but I'll bet it works well. After the
    subject practices and is comfortable on the walkway, mark the first three
    steps and instruct the person to hit these marks. You might have subject
    walk about five more steps before hitting the plate. I am sure this protocol
    will produce a high rate of succesful trials with limited targeting
    problems.

    For slipping:
    Paint the plate with some sandy paint. You can buy sand for paint in paint
    stores.

    Paul DeVita
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    We use both KISTLER and AMTI and occassionally run into some slipping for
    running/fast-walking trials. The force-plates are all in series and somewhat
    'disguised' with the tile patterns of the floor. One way we try to avoid
    targeting is by simply altering the subject's starting position by placing
    color-coordinated marks on both ends of the runway. With enough trials,
    clean force-plates hits can be achieved. There are also plate mats that can
    be utilized to maximize normal friction contacts.

    Arnel
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    We are in the process of completing a lab with a runway through it. The
    force plate has exactly the same surface as the runway. You might try
    Rekortan or Tartan or Mondo or any of the other commercial sport surfaces
    available in your area, and lay it not only on the platform but on the
    surrounding surface as well.

    You speak of targetting. Our runway situation is ideal as the platform is
    indistinguishable from the runway and the runway is real, for track
    athletes. Perhaps a covered floor would be real for your CP people too.

    Regards

    Doug
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    In our studies, we have the subject stand inside the force plate and then
    have them walk back - to whereever we want the starting position to be. One
    or two more small adjustments, and we begin data collection.

    Not much of a problem with targetting for us. The important thing is not to
    tell the subjects what you are doing. Keeping adjusting their starting
    position until they consistently land on the force plate (without looking
    down) as they walk over them. Then you can begin data collection.

    I hope this is helpful. I look forward to seeing what others have to say
    about their experiences.

    Raymond Chong, Ph.D.
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    I worked in the Biomehcanical Evaluation Lab. in Lansing, MI where patients
    of similar stature where dealt with there. The obstacle was over come with
    thin (not plush) carpeting. Ideally the carpet is laid down as tiles or
    squares and your force plate prefectly fits under a square of carpet. I
    hope this helps.

    Kitty Stabile
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

    We use for our portable walkway system an anti-slip floor covering called
    SureStep by Forbo (www.forbo.ch). I would consider it a very good compromise
    between "average" and "a little more" friction. We recommend to cut a gap
    around the force plate to prevent force shunt.

    There is a second possibility: use a "normal" floor covering with a gap for
    the normal applications and lay a large carpet (maybe rubber or similar)
    without gap on top of the plate when required. If the carpet is not too
    stiff, it doesn't require a gap. Of course the friction between floor cover
    and carpet is critical and keep in mind the slight cushioning effect.

    Forbo is in Sweden as well: http://www.forshaga.forbo.com

    Christian Calame
    -----------------------------------------------------------
    Mr. Christian Calame, Product Manager Biomechanics
    Kistler Instrumente AG Winterthur, P.O.Box 304,
    CH-8408 Winterthur, Switzerland
    Tel: +41 52 224 11 11, Fax: +41 52 224 14 14, Cell: +41 79 252 24 12
    E-Mail: christian.calame@kistler.ch, http://www.kistler.ch/biomech
    -----------------------------------------------------------
    =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
    Have you thought about using something like TUFF Skin? This is a spray
    used by athletic trainers when they tape ankles and other joints. This
    spray is very sticky and it can be applied directly to the participant's
    foot or shoe to increase your friction.

    Jeremy
    __________________________________________________ _____________________
    Dan K Ramsey

    MotorikLab Tel: +46 (0)8-517-77-503
    Astrid Lindgrens Barnsjukhus Fax: +46 (0)8-517-77-351
    Karolinska Institutet E-mail: Dan.Ramsey@kbh.ki.se
    S-171 76 Stockholm Lab: http://ikaros.f1.ki.se/motorlab/index.htm
    Sweden Profile: http://myprofile.cos.com/DRam
    __________________________________________________ ______________________

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