Teach-in '99 on Toe Clearance: What people said...

Why is clearance so small?
The answer I believe is for efficiency. If walking is so important and
is needed so much to hunt and gather it must expend the least amount of
energy as possible. The way to do this is to have as least amount of
floor clearance as possible. If there was more clearance it would
require much more active contraction of the limb about to swing. i.e.
hip, and knee flexion and ankle dorsiflexion. When you do see someone
today with this type of gait, they are the ones you expect to suffer
from back pain.

Was man's clearance always so small?
I believe not. I believe that early man probably walked with much more
back flexion. (although I have forgotten any anthropology I once knew)
Also if you look at those pictures you sent this early man walked with
an abducted gait. He might have had an inability to utilize his first
MPJ (hallux limitus) and had to walk so he could clear the mpj that he
couldn't in the sagittal plane. This also might have caused some
increased flexion at the hip and knee as well.

Why does clearance become even smaller in the elderly?
As we get older we start to loose the ability to have a single limb
stance with heel off. If you watch the way an elderly person walks
especially one who is fixed in back flexion, you will see that the heel
of the stance foot does not come off of the ground before the other heel
strikes. This is for stability.

Henry


In contemplating your question as to the major contributor of clearance
in swing, as an orthotist, I must clinically consider all three of those
you listed.  Let me explain.
If I have a patient come to me for an AFO (ankle foot orthosis) due to
drop foot, formerly, I used to lick my chops and think how easily this
case will be.  I'll put a solid ankle AFO on this person and they will
effortlessly walk away into the sunset.  We now will have acheived toe
clearance.  In those early days, I would fit the orthosis and anxiously
wait the results as the patient tried out the orthosis.  Often times all
would go well.  Other times I ws frustrated.  Suddenly I realized it
wasn't just dorsiflexion.  PROXIMAL STRENGTH IS THE ISSUE HERE.  Those
who were not successful most often had hip flexor weakness.  Quads may
have been ok but not the hips.  My point is that all three are
components to this puzzle.  I can do more orthotically if I have hips
and dorsis but poor quads.  However take my hip flexors away and I
really have trouble orthotically trying to acheive clearance.  That is
why working with a PT as we have in our facility is so important to good
orthotic management of the LE.
Hope to hear from others.

Regards,
Gilbert L. Gulbrandson, C.O.


I agree with Henry, efficiency is the best explanation for the very small
clearances of the toes during swing phase of walking gait.  In fact, during
slow motion video of walking, I often would use the ability of the subject's
hallux to only clear the ground by a few millimeters in teaching the idea of
gait efficiency to podiatry students.

Animals, including humans, have a remarkable ability to find the most
efficient way to move from point A to point B.  It seems to be a tendency
for all animal species to conserve energy during most activities.  Reducing toe
clearance during swing phase is likely much more energy efficient than
increasing toe clearance and therefore, a much more economical strategy of
moving from point A to point B.

I suspect that the proprioceptive mechanisms present within our lower
extremities allow us to "sense the ground with our toes" to improve
efficiency without causing injury (stubbing a toe and tripping).  It is
quite amazing.  It almost seems, at times, like the toes have eyes to only clear
the ground by the bare minimum during midswing.

Excellent question.

Cheers,

Kevin

Kevin A. Kirby, D.P.M.
Assistant Clinical Professor of Biomechanics
California College of Podiatric Medicine

Private Practice:

2626 N Street
Sacramento, CA  95816
Voice:  (916) 456-4768   Fax:  (916) 451-6014
      Kevkirby@aol.com


Always been fascinated with this particular topic.

Unfortunately there was no one around to capture the early walking style
and although the footprints look familiar it may be cautionary not to
assume too much  familiarity.

Throughout history  the gait patterns of the privilaged classes have
altered to fit  social mores. The introduction of the fashion heel (for
males) for example  in the seventeenth and eighteenth centuries made
mincing gait the norm for the best part of a century . Similarly in  the
fifteenth and sixteenth century Venice , the wearing of chopines or high
platforms caused changes to body  deportment necessitating  the
introduction of walking stick as a fashion accessory. In pre-revolution
France, books on ettiquette  clearly outline  the importance of the short
step style (for females) brought on by wearing tight fitting high heel
shoes . The classic sado-ritualistic example is of course  foot binding in
China, this practice  lasted a millenium.

My point being although the physical parameters may be governed by
anthrompometry, there is still a wide variation in individual gait
interpretation.

Cheers
Cameron

Cameron Kippen
        e-mail:rkippenc@alpha2.curtin.edu.au
Department of Podiatry                                  Tel:
+61-08-9-266-3675
Curtin University of Technology                 Fax: +61-08-9-266-3679
Shenton Park, WA 6008
Australia

Since Cleopatra first stuck nugget sized diamonds between her toes and Mata
Hari bound her ankles with sapphire-encrusted sandals, every hedonistic
phase of fashion, whether the Naughty Nineties  or the Roaring Twenties,
indulged in sumptuous, visually edible footwear.
                                                                Linda
O'Keeffe


I just looked at Chris's animation which fascinates me. I have one question
though: Can you deduct from the 2 cm clearance on a flat floor that
clearence is also this small when a subject is negotiating arbitrarily
uneven ground? It would have been great to see a similar animation of this
latter situation.
Best regards
Rolf
_____________________________________________________________
Rolf Moe-Nilssen, MS, PT, Research fellow, Division of Physiotherapy Science,
Department of Public Health and Primary Health Care, Faculty of Medicine,
University of Bergen, Ulriksdal 8c, N-5009 Bergen, Norway,
email: rolf.moe-nilssen@isf.uib.no voice:+47 55 58 61 70, fax:+47 55 58 6130

 I suspect that most people will say "efficiency/energy conservation"
-
there's no reason for the body to lift the toe any higher then necessary to
clear the ground and there's an energy expense if you do.  I would doubt
that your 117,000 year old individual walked much differently from any of us,
given the same terrain.

        I think that, in general, people "learn" the environment pretty
quickly.  For instance, try running across extremely broken, and uneven, terrain.  Many
people who enjoy orienteering and hashing do this all the time, yet very few
of them fall over or even change their stride much.  Presumably they have a
greater toe clearance in the rougher terrain, yet they adapt quickly and
don't appear to walk any differently when they return to civilization.

        It might make an interesting study - take a number of subjects and
measure their toe-clearance in your gait lab.  Then send them off for either a two
mile run on the pavement or a two mile run over broken terrain.  Re-measure
their toe clearance as they return.

        Alternatively you could make your gait lab conform to the real world
and do a few tests with the odd door-mat, carpet and children's toys littering the
calibration area and see what happens to the toe clearance...

Best Regards,
Edmund Cramp,
Motion Lab Systems, Inc.
4326 Pine Park Drive, Baton Rouge, LA  70809  USA
+1 225 928-4248 (voice, 2 lines) and +1 225 928-0261 (fax) Note - New
Area Code effective April 1999!
My email address is eac@emgsrus.com <mailto:eac@emgsrus.com>  - web site
is http://www.emgsrus.com


The toe clearance allows people to safely navigate in the environment.
>From my point of view, the low cost energy is usually part of any kind
of everyday's tasks. The purpose is mainly to optimise the production
of the required response at each body level to accommodate to the
immediate environment. When performing a so called fundamental task
such as walking or ongoing over a non-complex obstacle, the central
nervous system (cns) uses inputs from vision to produce a strategy
suitable to accomplish the task. In doing so, the cns must cope with
several factors such as physical fitness (fatigue...), psychological
state (fear of falling...), disorders, experience of the task, etc.
McFadyen has qualified tasks such as obstacle avoidance as
anticipated locomotor adjustment (ALA). Studies by Lee, Michel
Laurent... suggested the possibility for the visual system (optical
flow) to trigger the ALA. So when a task is performed often enough, a
raw strategy is somehow stored. When the situation requires it, this
raw strategy is triggered and there's an online optimization of the
parameters required to perform the task. The observable low toe
clearance could be the result of this optimization.

A. Niang
PhD student in clinical science
Sherbrooke, Quebec


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