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Del
For
those of you that are curious about what other studies are being done in regards
to how our feet strike the earth check out this page and its links
www.uni-essen.de/~qpd800/research.html
. Some animated graphs that will amaze and entertain you.
Interesting fact:
The function of all of the muscles in the lower limb originating below
the knee is to move the foot. These muscles insert on any one or several of the
26 bones of the foot.
Mike
Douglas
I
can only offer what I have witnessed at beaches with regards to dominance. This
is hardly research in a controlled environment and the situation makes the
condition worse, (Having a subject traversing an inclined plane with
distractions both right and left) Because of this, It seems measuring from left
heel to left heel of a subject moving at a constant rate of speed and then doing
the same with the right yielded about 80% accuracy in dealing with dominance.
This is measuring people who were not caring anything, wearing just bathing
suits, not holding hands or compensating for their natural curving path.
(Measured during the wide curvature of their harmonic gate before walking into
the Ocean) Because of all these factors I stumbled upon a seemingly more
accurate measure of dominance provided the subject is on an ideal and consistent
tracking medium with a fairly level grade, and they are traveling at a constant
rate of speed with no burdens. This
situation rarely exists, I know. It seems the peaks formed at the back of the
heal are higher on the "punch" step. In wet Maine beach sand there is
also an accompanying wave behind the step as sand is pushed backward. While the
peak difference is usually between 1 and 2.5 millimeters in difference,
I can only say that the "feeler" step appears to throw a weaker wave,
having no way the measure it without destroying its original height. Toe blow
out
also seem different. Sand thrown from the toe of the dominant step seems to be
thrown as much as 5 mm more than the feeler, or non dominant side. To
check out this dominance thing even further, I went to a local Good Will Shop
and checked out the wear marks of all the foot wear. Out of 87 pair of
shoes 68 had dramatic wear on the right as compared to the left, while 16 had
dramatic wear on the left. The remainder had near identical wear. I
would have loved to see those three people making tracks on the beach. (Sort of
an informal control group) Still not sure about the mechanics of it all,
but that's what I have. I hope it can be of use to someone.
Del
Are
we forgetting what the original premise was?
Dominant STEP length being shorter. And the less dominant leg making a
longer step ... as small as 1/16"
In the BMP you will see that the STEP lengths of the left steps are all the same
length. The STEP lengths of the right steps are the same as each other ... but
they are longer than the left STEP. So in the BMP this walker would be
considered Left Dom. ?
They (left/right steps) are the same dimension on the upper 'STRAIGHT' Line of
travel as they are in the lower curved route of travel. But the difference in
length (STEPS) does not generate the turn. me pivoting the placement of the step
determines the line of travel.
Del
>If
the original premise was indeed that the dominant STEP being shorter affects
line of travel then I think you are entirely correct. I suspect >however,
that we are suffering from some rather basic differences in understanding
terminology. Specifically, based on my really sketchy notes, >what you are
calling STEP is what Tom Brown calls STRIDE, and what you are calling PACE,
Tom Brown calls TOTAL STRIDE. Furthermore, your bitmap (PACE2.BMP) labels the
distance corresponding
to PACE as "Left Side Stride" or "Right Side Stride". I
think we agree that it is possible for the PACE (TOTAL STRIDE) to be different
lengths, depending on whether you measure starting from the left heel or right
heel, but maybe I'm wrong about that too.
I agree... but find this is usually due to terrain features.
>That said, my assumption has been that the originally premise, whether it
was correctly stated or not, is that the PACE or TOTAL STRIDE, in the absence
of cues that keep the walker on course, will be shorter, on average, when
measured on the dominant side as compared to the other side. In other words,
the non-dominant foot moves a tiny bit further than the other foot when it
takes a step. In the presence of visual, auditory, or other cues, this
variation in the length of the PACE is really >easy for the body to
compensate for. We are after all talking about pretty small adjustments.
This is where I fall out of the boat again, Tstride ... ok
LRL Tstride or RLR Tsride for the sake of discussion. If "JOE" is
measured longer LRL stride than his RLR which dominance does he have?
Common terminology is always the first obstacle ... I am just surprised that
we are so far off.
Del
That
is how I would measure it also.
Assuming the Step (stride) length as the determination of limb dominance, but
as thorn posted yesterday Not the cause of the turn ... Can one have a longer
Right Step and still be Right dominant? The longer step due to some pathology
in the subjects gait.
Thorn
> the issue of dominance involves other subtleties. it can be observed by
looking at the longer stride, but what it does, being attached to a brain and
all, is cause someone who is walking to make decisions a certain way. a person
when going up a single step will prefer to step up with the dom leg, even if
adjusting his gate to do so.
long jumpers , hurtlers, and high jumpers take this to an extreme in
there sports jumping off the stronger leg. i've been around a lot o' track teams
so I know this.
so dominance refers not only to stride or step but to the way decisions are made
by a left or right dominant person. Observing people moving through the
landscape or following their tracks illustrates this the best.
i think DOT is maintained by pivoting the foot and this can be observed in the
pressure releases.
I’ll be
asking you biomechanics about these “pressure releases” next.
Del
I
am reading that Tom believes that you can have a RLR Total Stride a different
measurement than LRL TS measurement and this is the significant variable to a
dom induced turn or 'circling' and Thorn is sticking with the step length as the
significant variable to a dom induced turn or 'circling'.
We can probably agree that if a RLR TS measures shorter than a LRL TS then you
will find a difference in the step length. But let's look at this from a
different direction. What do we have to do to walk straight?
To walk straight each foot placement must be in line with your intended LOT and
even with that placement being good there may be an additional COG center of
gravity heel pivot to compensate for terrain. Then if your inner ear balance is
wacky your foot placement (although in the LOT) may be placed wide or long to
hold your balance. And I am sure that there are many more.
To borrow Thorn's picture we can see that pace measurement can be equal yet with
different step lengths
---------pace=38"-----------------
L
18"
R
20"
L
-----------pace=38"---------------
L
20 "
R
18"
R
But the pace can not be different with the same step lengths.
We can all agree that step lengths are not constant. Therefore paces are
not constant.
My question still is ... What can I see on the ground that would give me a 'high
level' of confidence that my subject will drift one way of the other in their
LOT so that I can increase my probability of finding his sign in a shorter
period of time? If I must track him over a long distance to establish 'limb
dominance', then the amount of time needed to do this maybe the time he needed
to die. This is just not good enough.
I
see two schools of thought:
1)
Limb dominance is seen when one step length is smaller than the other coupled
with other long range determinations. and
2)
When one total stride is
smaller than the other RLR or LRL coupled with other long range
determinations.
We can all agree that Leg Dominance has little to do with L/R handed nor L/R
legged ... Has anyone examined a dominant eye connection with Limb Dominance?
We can probably agree that if a RLR pace measures shorter than a LRL pace then
you will find a difference in the step length.
We can also probably all agree that step lengths are not constant. Therefore
paces are not constant.
We see that pace measurement can be equal yet with different step lengths
---pace=38"---
L 18" R 20" L
---pace=38"---
R 20" L 18" R
But the pace can not be different with the same step lengths.
But let's look at this from a different direction.
WHAT DO WE HAVE TO DO TO WALK STRAIGHT?
To walk straight each foot placement must be in line with
your intended DOT and even with that > placement being true and
straight< there may be an additional COG (center of gravity adjustments) heel
pivots to compensate for terrain.
Then if your inner ear balance is wacky ... your foot placement (although in the
DOT) may be placed wide or long to maintain your balance. And I am sure that
there are many more.
My question still is ... What can I see on the ground that would give me a 'high
level' of confidence that my subject will drift one way of the other in his/her
LOT so that I can increase my probability of finding his sign in a shorter
period of time? If I must track him over a long distance to establish 'limb
dominance', then the amount of time needed to do this maybe the time he needed
to die. This is just not good enough.
I do believe that there is a limb dom, but stride or step length are not the
evidence of it. Turning and circling seems to be ... but where does it come
from?
<<
My question still is ... What can I see on the ground that would give me a 'high
level' of confidence that my subject will drift one way of the other in his/her
LOT so that I can increase my probability of finding his sign in a shorter
period of time? If I must track him over a long distance to establish 'limb
dominance', then the amount of time needed to do this maybe the time he needed
to die. This is just not good enough.
I do believe that there is a limb dom, but stride or step length are not the
evidence of it. Turning and circling seems to be ... but where does it come
from? >>
I've been thinking about this and experimenting quite a bit since the discussion
started and I have been unable to conclude anything except that once you
determine which way the person tends to circle (not by looking at individual
tracks, pressure releases or stride lengths but by looking at the entire trail
over a long enough distance) he will continue to circle in that direction. If
there's another way it escapes me. My guess is that it's an unconscious habit
that people develop.
For an example of something similar: spread your fingers and then interlock them
with the palms of both hands coming together. Your fingers are now
alternately stacked, left little finger, right little finger, left ring finger,
right ring finger, etc. (I hope that's clear.) Notice which little finger is on
the bottom, "left" in my example. Now separate your hands and
interlock your fingers again, this time consciously choosing to put the *other*
little finger on the bottom. If you're like most people this will feel strange
compared to the way you have habitually done it without realizing.
Interesting
thoughts Carl,
Here is another thing that I have come up with I think it is a 'muscle' thing.
The dom leg being stronger and more concrete to its' placement, its' pitch, its'
direction.
Try this... with your stronger leg 'lock' you ankle with a negative pitch ...
your other leg leave 'normal' following the lead of your body swinging and
placing without trying to direct the direction of travel ... walking slowly and
safely .... see how the 'negative' pitch forces your direction of travel. Now
try locking your strong leg in a severe positive pitch and try it again ... does
it not 'pull' you in the direction of your dominant leg pitch?
>I
am reading that Tom believes that you can have a RLR Total Stride a different
measurement than LRL TS measurement and this is the significant variable to a
dom induced turn or 'circling' and Thorn is sticking with the step length
as the significant variable to a dom induced turn or 'circling'.
The more I reflect on this, the more I think that even though difference in RLR
and LRL total stride is a necessary condition of walking in a circle, this
difference is small, variable, and probably really difficult to measure
reliably. Furthermore, the difference only exists consistently if the walker is
in fact following an arc, in which case you can probably deduce dominance from
the direction of the track. Which leads to your question which still is ... What
can I see on the ground that would give me a 'high level' of confidence that my
subject will drift one way of the other in their LOT so that I can
increase my probability of finding his sign in a shorter period of time? If I
must track him over a long distance to establish 'limb dominance', then the
amount of time needed to do this maybe the time he needed to die. This is just
not good enough.
It seems to me that you answer your own question in concluding that you have to
establish "limb dominance". I am not sure that it is necessarily the
case that this will take a lot of time. This is well out of my range of
experience, but several people have come up with suggestions as to what might
help determine dominance, including differences between right and left prints
and what foot they favor going up, down, etc. And we have been going back and
forth on the question of what difference between right and left step length
means. After some very tentative, not at all conclusive experiments of my own, I
am leaning toward the belief that differences in step length may be reliable
indicators of dominance. What I seemed to observe is that a right leg dominant
person will have a shorter LR step than the RL step. I am still trying to sort
out in my own mind why this would make sense, so I am not going to speculate on
that now. And if I recollect, Thorny suggested that the opposite my be the case,
so I'm still very much open to any alternative views, particularly if they come
with intelligent explanations as to the cause.
Also, from your more recent post, I do believe that there is a limb dom, but
stride or step length are not the evidence of it. Turning and circling seems to
be ... but where does it come from?
you seem to have decided that step length is not a good indicator of dominance,
but I am not quite sure why.
In
any case, at best, dominance is most likely an indicator of a *tendency* to
drift to one side. All kinds of things, like terrain, significant landmarks,
etc. could override that tendency. I think that one of the stories that Tom
Brown tells related to the tendency to walk in a large circle concerns a search
for a small girl. I am pretty sure it's in one of his books, most likely The
Tracker. As I remember hearing it, the girl had wandered off into very thick
brush, and after a while of following her, Tom decided that he would be likely
to find her more quickly by going to the point where he figured her path would
intersect the trail or road. There were also a lot of semi-pertinent details,
like a police officer who was involved in this search, cigarettes, and the fact
that Tom was only 16 (or whatever) he was already too big to get through the
underbrush easily. The main points seem to me to be that the lost person was too
young to have many notions about how to navigate when she got lost, and that the
landscape was more or less uniform in vegetation and probably evenness of
terrain. This suggests to me that in more typical cases the tendency to drift in
a particular direction is only one of thousands of small pieces that can help
piece together the puzzle and help stay with the track.
To walk straight each foot placement must be in line with your intended LOT and
even with that placement being good there may be an additional COG center of
gravity heel pivot to compensate for terrain. Then if your inner ear balance is
wacky your foot placement (although in the LOT) may be >placed wide or long
to hold your balance. And I am sure that there are many more.
When I paddle a canoe, I can tell by watching the wake or sighting over the bow
that I am going slightly off course most of the time. All that I am suggesting
is that walking straight may involve continuous, usually small, adjustments to
compensate for the tendency (which you describe above) to diverge from a
perfectly true line.
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