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Del Wong
07-30-2003, 05:19 PM
Dear all,
Thank you for the replies and below is the summary about the impact velocity of
walk and run.
And any discussion or suggestions are welcome.

Del Wong

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I don't know about any published work however, Nike as a new pedometer that
uses an accelerometer attached to the shoe. You may be able to get the data
through them.

Good Luck
Josh

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You might investigate David Winter's work and particularly his texts. He and
his colleagues have published velocity data of the foot and points nearby.


Paul DeVita, Ph.D.

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A little obscure but has the data averaged over ~15 subjects:

The Biomechanics and Motor Control of Human Gait, David A Winter, University
of Waterloo Press, about 1985, not sure though.

More easily found and has data from at least one subject in appendices:

The Biomechanics and Motor Control of Human Movement, David A Winter, Wiley
Interscience, 19890

Finally, I think he has some articles with these data but I am not sure
which ones.


Paul DeVita, Ph.D.

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The downward velocity of the heel just before impact ranges from
0.4 to 1.1 m/s. Apparently the impact velocity in walking can be
higher than in running (Aerts & DeClercq, 1993). Impact velocity
has a major influence on impact peak force in mechanical tests,
but in human subject experiments the correlation seems to be not
very strong (Uwe Kersting showed me some interesting data last
week on this topic).

There is a technical issue also. Motion data is usually low-pass
filtered before calculating velocities. This causes a "temporal blurring",
and you get a velocity that is an average over a finite time period
rather than the true instantaneous velocity. If the low-pass filter is
10 Hz, this blur can be 100 ms long (see Chris Kirtley's postings
last month on the impoulse response of low-pass filters). At impact,
the velocity changes very quickly, from 1 m/s to zero, and these values
all go into the blurred average. This can cause impact velocities to be
underestimated by as much as 50%. We found that impact velocities are
in fact more accurate without low-pass filtering, even at a video frame
rate of 240 fps. So if you find studies where impact velocities are
reported, it is good to keep this in mind and carefully read the Methods
section.

Reference
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Aerts P, De Clercq D (1993) Deformation characteristics of the heel
region of the shod foot during a simulated heel strike: The effect
of varying midsole hardness. J Sports Sci 11:449-461.

--

Ton van den Bogert

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just a very quick and incomplete answer:
we had published a running analysis providing at
least the vertical touch down velocity of the ankle in
(BIBTEX format)

@Article{Guenther2002a,
author = {G{\"u}nther, M. and Blickhan, R.},
title = {{Joint stiffness of the ankle and the knee in
running}},
journal = {{Journal of Biomechanics}},
year = 2002,
volume = 35,
number = 11,
pages = {1459-1474}
}

Best regards,
Michael.

--
Michael G"unther



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