Re: Re: Up Hill or Down

["Duncan Fletcher" <dfletche@gte.net>]

Whose on first, Tom. Some of your comments are aimed at posts other mine. If
you are taking issue with the degree to which a trotting horse can actually
keep a level back (and whether the gait in that situation is a true trot),
that is open to debate. But if you questioning the physics presented about
the load on the legs of a static horse, it is not. More details below, with
my appologies to digest users.

Duncan Fletcher
dfletche@gte.net

----- Original Message -----
From: <Tivers@aol.com>

> In a message dated 1/10/00 7:32:44 PM Pacific Standard Time,
dfletche@gte.net
> writes:
>
> << > Well, you're on to the next question already. We still don't have a
>  > definitive statement from the horseman-observer that a horse standing
on a
>  > sloping plane, nose down, receives more weight on the forelegs--before
any
>  > contortions take place.
>
>  If the horse stands with legs square underneath on a slope, then CG moves
>  forward and more load is carried by the fores. But horses adjust
>  (contortions is a loaded word ->
>
> A bit like flat earther, eh? How do you like the word hypocrite?

If you believe that load on a leg is dependent ONLY on CG and not on where
each and every leg is relative to CG, then flat earther is the correct term.
The placement of the hind legs does effect load on the front legs even if CG
remains the same relative to the front leg. If you are questioning to what
degree and underwhat circumstances (gait, slope, etc.) and horse is able to
actually keep his back level, that is open to debate.

> > all athetes contort) to the environment. I
>  don't stand on a 12/12 pitch (45 degree) roof the same way I stand on the
>  ground. Neither do horses move on hills the same way they move on level
>  ground.>
>
> Horses are quadrupeds--this is easily seen in the wild, although I hear
tell
> they often become bipeds when properly TRAINED by intelligent and
experienced
> horsewomen.

No argument, but I have seen horses drop their butt going down hill. Now I
am not prepared to argue one way or another to what degree they can do this
under various gaits and slopes. But they do adjust their body to the slope.
It was a mistake for me to use 45 degrees in the above anology, because I
doubt anyone is riding 45 degree slopes.

>  >Once that is established, simply, without any
>  > formularific obfucation, then we can proceed to the second assertion,
that
>  > the horse is capable of countering the effects of gravity by crouching
>  lower
>  > behind, as, it is said, by moving his rear legs forward--that is moving
>  mass
>  > forward, underneath his body.
>
>  He is not moving mass - he is moving his legs forward. >
>
> Legs with no mass. Interesting concept--indeed, a very complex calculus.

If you looked further down in the passage, you will note in your subsequent
question that I aknowledged an insignificant forward movement of CG. What
percentage of the horse's weight is in the hind legs (Without getting into
the math needed to calculate this, remember that the biggest part of the
mass is at the top of the leg which moves very little and the the lower part
of the leg which has the lowest part of the mass is the part that moves)?
The effect can be ignored (just as you ignore whatever minor fiber
impurities are in you carbo charge). Again, the other question as to the
circumstance in which a horse can accomplish this is the real debate.

> >That does 2 things.
>  Assuming for the moment that the legs are straight, the top line is
sloped
>  to the rear in reference to the slope>
>
> Forget reference to the slope. Now you're sidestepping the issue--the
horse
> is still canted downhill, receiving more load on the forelegs--attempting
to
> lessen that extra load, granted, but not negating it.

Nope, under that assumption I am agreeing with you.

>  >and will be somewhat more level in
>  relationship to gravity thus preventing that forward movement of CG of  a
>  horse standing square on the slope.>
>
> You must have come into the argument late. Heidi didn't say "more" level,
she
> said "level". And you hopped right on board and "did the math" for her.
> Duncan bought it.

I (Duncan, whose post you are answering) jumped into this (and David did the
math), because you were making your argument on the basis that load on the
front legs is not effected by placement of the rear legs and is dependent
only on location of CG.  I was trying to straighten the physics out so you
could focus on your real issue which is that the horse is not capable of
keeping a level back at the trot on a slope. I would not care to defend
level in an absolute sense. I certainly see them drop their butt by keeping
their legs further forward - as to degree, gait, and slope measurements, I
haven't observed enough.

>  >(Actually he will probably not keep his
>  legs quite as straight thus lower his back more). Because his legs (base
of
>  support) are move forward, the load is somewhat transferred to the hind.>
>
> What's all this hedging with "somewhats" and "mores"? Thought you did the
> math and proved me wrong without even rising from your computer desk.
> Remember, you are the horseman and astute observer and I am the flat
earther.

Careful, no one suggested that the load is transferred entirely off the
front legs. Somewhat is exactly what the math showed (which was posted by
David, not me). But it does show a decrease in front leg load.

>  >
>  > Looking at the second aspect, hoping beyond hope that elementary
physics
>  > remains as it has been for at least the past two weeks, let's
investigate
>  the
>  > crouching phenomenon.
>  >
>  > If the horse's forefeet are sitting 24" lower than his hind feet, and
if
>  the
>  > mass of the hind legs must move forward to accommodate a 24" crouch, a}
>  can
>  > it be done and, b} where does the center of mass go and, c) how does
this
>  > affect the stride efficiency and, d) is this compensation, if it can
>  possibly
>  > exist, healthy?
>
>  >a) yes>
>
> Picture, please. Anyone. Anywhere. Defend the scintillating math!

I would not care to suggest however that the gait would be a trot.

>  >b) very minor movement forward (for all practical purposes no change -
not
>  much weight in the leg) - but the base of support is moved forward at a
much
>  greater rate.>
>
> An inch is worth a mile? How many inches to overcome the effects of a 45
> degree incline in an 8' horse? Do the math, puleeeeze! And please count
the
> weight of the legs for something--make it easy on yourself and call it 50
> lbs.

OK. Assuming a 1050 lb horse with 50 lbs of rear leg. If the CG (except the
rear legs which is centered over the hinds) is 1 foot behind the fores and 3
feet in front of the hinds then the fores will support 750 lb and the hinds
300 lbs. The overall CG (including the rear legs) will be 13.71 inches
behind the fores. If you move the rear legs foward 1 foot the CG moves
forward by 0.57 inches (and this assumes the whole leg moves forward, not
just the hoof). But the base of support also moves forward and the total
load on the fores is 667 lb and and load on the hinds is 383 lbs.

As for 45 degree slopes, I would question whether anyone here has ridden one
of any significant length. I only know of couple of ski trails in this
country that approach 45 degrees. (it does make a nice easy number for
calculations). I will point out that at 45 degrees if one assumes that the
CG is 2 feet above the slope (and CG is less than 2 feet from the fores) and
the horse keeps the same position as it had on level ground with respect to
the slope, the CG has moved in front of the horse's fores and it is toppling
over on its nose.

>  >c) compared to level ground, decreases. But nobody said that they could
go
>  downhill with the same efficency as on the level.>
>
> Stride efficiency, I'm talking about. Heidi says her horses show up at vet
> checks refreshed after downhill speed--metabolic efficiency, she infers. I
> dispute the safety of such maneuvers, and that's where stride efficiency
> comes in. If the horse has to levitate its forelimbs to do this magic
trick,
> then the hind end, particularly the semitendinosus/suspensory, hocks and
> stifles receive exta punishment. But I don't think the horse can do it,
> anyway. I think, instead, he'll come down hard on the forelegs--unless he
is
> actually sliding down the hill on his hinds--and that would not be a trot.
> But, hey, I'm perfectly willing to believe a picture. Anybody? Anywhere?

And here is where your argument really lies. Not my expertise. But I my
understanding is that horses can shift their weight to the rear, even on
level ground and that is generally beneficial. That is not to say that in
the extreme it may not be.

>
>  >d) is a riders weight healthy for a horse, is racing healthy, is me
carrying
>  a 40 lb backpack healthy, is life healthy?>
>
> Are your bridges healthy? Is this what you say to the inspector when he
tells
> you your design has nothing to do with reality? "Aw, people are killed
waling
> across the street."  6th grade debate tactic--you're learning bad lessons
> from some of the group.

I don't build bridges. But I confess my answer was a bit flip. The question
should be not whether it is healthy, but to what degree is the risk
increased. Certainly moving weight fore to aft will decrease risk to the
fore and increase it on the hind. I don't pretend to have any real answers.
I will note that the whole point of military dressage was in part to get the
horse to shift his weight to the rear by getting the hinds up underneath and
that this was done in part to keep the horses sound. Whether this and old
wifes (or old military) tale I will leave to others.

> > It certainly requires much
>  stronger muscles (paticularly hind). I will leave it to those better
trained
>  to get into more depth on that question.>
>
> Dropping back to punt? Three failed ends around and you're going to punt?
> This close to the goal line? You've got Duncan convinced. And Heidi loves
> your math. Finish it out and show me how you can eliminate extra stress on
> the forelegs going downhill. According to you, it's extremely elementary.
> Only flat earthers can't figure it out. According to Heidi, only easily
> beatable morons can't accomplish this.

I am Duncan (and Heidi loves Dave's math), but my input was on the physics,
not the Ultimate Question.

>  > I'd love to see a trotting horse moving down a significant incline with
a
>  > level back, first. I can envision a horse sliding down a hill on his
hind
>  > legs, front in the air, in order to achieve a level back--but not a
horse
>  at
>  > a trot.
>
>  I will leave this to others - my Peruvians don't generally trot. My guess
is
>  that the back is probably not level, but lower than parallel with the
slope.
>  And if the slope is steep the gait is probably more of a 2 beat shuffle
>  without much if any suspension - but I am now into speculation.>
>
> You've been into speculation from the git-go, Pard. If the back is not
level,
> then the horse is taking more weight in front.

That depends on leg position. If the leg position changes, it may not.
Again, relative leg load is dependent on CG AND the position of each and
every leg to that CG. Reposition one leg and the load on the other 3 will
change as well as the one that is repositioned. For a horse whose back is
parallel to the slope and who repositions his legs further forward, the net
result and whether it favors fore or hinds depends on how much he moves his
hinds forward and how steep the slope. If he does drop his butt and the
horse is level with respect to gravity, the answer is easy.

> And if a hind leg and a fore
> leg are on the ground at the same time, going downhill, then there must be
an
> incline to the back of the horse. I know of no gait where there isn't
overlap
> between at least one foreleg and one hind leg--do you? Unless the horse
> becomes a biped, as Heidi suggests and you have speculated.

Or the horse understrides.

>  > All I need is a picture of this being done and I'll concede the entire
>  point.
>  >
>  > ti
>
>  Duncan Fletcher >>
>
> Actually, I've got a couple of pictures: Roy Rogers and Triigger; the Lone
> Ranger and Silver. Is that the way Pasos move? I thought they were more
like
> eggbeaters.

The fino fino gait of the Paso is a very understrided gait. The corto and
largo are not. The paso llano of the Peruvian is not understrided, but does
include a swimming motion from the shoulder.

>
> ti
>




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