toe off and foot-ground contact
Louisa & Titus
I have received several responses. I would like to apologize for and
clarify some confusion in my original posting. The subjects in my study
walked on a smooth surface. No force plate was involved due to the
limited resource in our lab for gait analysis. My interest is on the
swing phase only and thus my computer program does not take the ground
reaction force into account. This is one of the reasons why I want to
have a precise toe-off and foot ground contact. I did use the ankle
angle to identify (peak plantarflexion for toe-off and peak dorsiflexion
for heel strike). However, the toe off that I identify from observation
tended to occur 2 to 3 frames consistently earlier than when I use the
peak plantarflexion to identify. After I reviewed the tape,
surprisingly, subjects continued to plantarflex after toe off for a
period of 2 to 3 frames. (that's why I think my observation may not be
too inaccurate!!)
Further suggestion will be greatly appreciated.
The following is my original posting
Louisa
I am doing a 2-D gait study. The purpose is to look at the kinetic
pattern of the lower limb during the swing phase in children by running
inverse dynamic. During filming, subjects walked barefooted and there
was no light sensor attached to the sole of foot for indicating toe-off
& foot ground contact.I did observe & record down the frame # for
toe-off and ground contact during digitizing. Now I would like to know
if I could determine when toe-off and foot ground contact occur from
the data itself rather from my observation (which I think may not be
inaccurate though). Unfortunately, I did not have a marker on the toe. I
had the markers on the MT joint of the 5th toe, ankle and heel for the
foot movement.So when the Y coordinate of MT joint of the 5th toe is
right above zero, the forefoot is still on the ground.
Does anybody have a good idea as to how I determine these two events
from the data of MT joint of the 5th toe, ankle and heel.
Any idea will be greatly appreciated
Louisa Law MEd
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Dr. Chris Kirtley (Kwok Kei Chi)
After Jim Richards correctly pointed out that toe velocity is a better
signal than acceleration to indicate toe-off, I thought I'd better go
back and look at this again. By chance, there was a typhoon this
weekend, so I had plenty of time to make a summary of all the different
possibilities at:
http://guardian.curtin.edu.au/cga/faq/toe-off.html
or http://www.polyu.edu.hk/cga/faq/toe-off.html
or http://www.univie.ac.at/cga/faq/toe-off.html
Thanks to Jim for correcting me!
Best wishes,
Chris
--
Dr. Chris Kirtley MD PhD
Dept. of Rehabilitation Sciences
The Hong Kong Polytechnic University
Hong Kong
Special Administrative Region of The People's Republic of China
Tel: +852 2766 6755 (lab 4830) Fax: 2764 1435
Home: http://www.polyu.edu.hk/~rs/kirt/index.htm
PolyU Gait Lab: http://www.rs.polyu.edu.hk/gaitlab
Clinical Gait Analysis: http://www.polyu.edu.hk/cga
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