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Dan Ramsey
11-10-2000, 08:17 PM
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
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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
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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
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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
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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.
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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
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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
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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
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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
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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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