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[RC] Rider Weight - katswig@xxxxxxxxxxxxx

Truman said:

Bottom line is examples of "I saw a 350 pound rider
riding a 14 hand Paso" has no meaning as to the ability
of the population of horess (or Pasos for that matter)
carry more than 15, 20, or 65 percent of their body weight.
After all not many people ride horses that belong in the
records books. One rat experiments only tells you want one
rat did. Two rat experiements only tell you what two rats
did and uncontrolled experiments are not any better as far
as measuring properties of a population.

Since it is individual horses that carry weight and not populations of
horses that do, Truman, has, in fact, got this completely backwards.  As is
evidenced by Trumans's stated example of "I saw a 350 pound rider riding a
14 hand Paso," and his assertion that this doesn't mean that every horse
(or even every Paso for that matter) can do the same, almost everybody
should agree that there is huge variation among individual horses with
respect to how much weight they have the ability to carry (begging the
question entirely of exactly how "ability to carry" is being defined,
which, BTW, is NOT an irrelevant question).  Considering the fact that
there is huge variation in the population, what percentage of its totally
body weight, the "average" that the entire population can carry becomes
almost totally irrelevant.  With such huge variation (some horses are so
badly put together and/or are already so lame that they don't have the
ability to carry ANY additional weight so the percentage for them is 0%),
one MUST look at the individual to determine what percentage of its body
weight it can safely carry. It doesn't really matter what percentage of its
body weight the other guy's horse can carry, nor does it matter what the
average horse can carry.  Making decisions based on averages is rarely ever
a good idea; doing so when the variation in a population is so huge is
absolutely nuts.

The fact that there are examples of horses that have "safely carried" as
much as 40% of their body weight for huge distances over long periods of
time is not irrelevant.  What it does is highlight the existence of the
huge variation in the population so that people can understand that they
had better look at their own horse rather than at some mythical "average"
horse, since that horse doesn't exist. :) Or if it does, and we could find
it, my horse probably isn't it.

The second misnomer is there is really a "lightweight
250 pound rider." Two hundred fifty pounds is 250 pounds.
Good saddles will help but still won't reduce the weight
the horse is holding above the ground. The horse has to
carry 250 pounds. The ability of the rider to ride balanced
will help the horse - just as it will for a 100 pound rider
- but it will not make the weight any less - the horse is
still hold up 250 pounds.

And this statement is pure hogwash.  It only comes close to being true if
the horse never moves (although the weight distributing effect of a saddle
still has an effect, even on a stationary horse, since any structure is
only as strong as its weakest link, if you distribute the weight that is
put on each link, you have increased the ability to the entire structure to
bear the load); however, since (I think) that when people ask "how much
weight can my horse safely carry" are not asking how much weight they can
put on their stationary horse, discussing static load is almost irrelevant
(it is only relevant to the extent that static load affects the dynamic
load, which also varies hugely).

I SHOULDN'T need to explain to Truman the difference between a static load
and a dynamic load (if I understand correctly, Truman is a physicist both
by training and by profession so he understands the difference just fine);
however, since most people on this list are not physicists (which I am not
either, by training I am an engineer not a physicist), I will try to give a
simple example (using a horse) to help people understand.

Since almost everybody on this list is a horse person, most of them also
know that when a horse canters (and when it trots if it is truly trotting),
that there is a point of time during each stride when all four feet are off
the ground (in horse parlance, this is called the moment of suspension). 
Obviously, when all four feet of the horse are off the ground, the horse is
not "holding up" ANY weight, no matter how much it or its rider weighs;
when the horse reaches to top of its arc (from having pushed up off the
ground with its legs just before gravity brings it down), the horse and its
load is "weightless."  Equally as obviously, the horse cannot do this
forever (which is why it is called a "moment" of suspension).  

When and how a horse comes down from its moment of suspension and how much
force is exerted on the structures of the horse as it does so varies VERY
much dependent upon how much momentum the horse has and in which
directions, on where its feet are in relation to its center of gravity, and
how it uses its own shock absorbers (i.e. its joints) to absorb and/or
diffuse these forces..........(it depends on so many things they can't be
listed).

Not only does the ability to do this vary hugely from horse to horse (even
horses of exactly the same static weight), depending upon its build and its
experience, the ability of a rider (even riders of exactly the same static
weight) to alter how the horse does this also varies hugely.

There IS such a thing as a horse that is "light on its feet" and there is
such a thing as a rider that is "light on a horse," and it has everything
to do with how the horse carries its dynamic load and to what extent it can
reduce its dynamic load by carrying it "better."  And while the physics of
it are EXTREMELY complicated (it is so complicated, in fact, that Physics
1A rarely ever goes into very much detail with respect to calculating
dynamic loads), when talking about the loads on horses that are expected to
carry the load forward (not just hold the load up), it is the only physics
that is relevant.

So, contrary to Truman's assertion, the examples of "I saw a 350 pound
rider riding a 14 hand Paso" has a great deal of meaning.  What one rat did
tells you that you had better look at your rat and not the average rat
(especially since nobody has even done a study to determine what the
average rat can do).

And contrary to Truman's assertion that "the ability of the rider...will
not make the weight any less," the ability of the rider can have a
substantial effect on how much weight a horse is carrying (and how much it
varies during the course of every stride); although, I assert that this
ability has less to do with "riding in balance" so that the rider's weight
doesn't interfere with the way the horse carries its weight, and has much
more to do with the ability of the rider to IMPROVE the way a horse carries
its own weight.  Good riders don't just stay out of their horse's way, they
also affect the way the horse uses itself so that the horse itself becomes
"lighter on its feet."  And some of the ways to do this is to tell the
horse where to put its feet and when and also to warn the horse in advance
of any change it needs to make, so that the changes can be made more
"smoothly."

The bottom line is there is so much variation among both horses and riders
(even horses and riders of exactly the same static weight) such that the
question, "What percentage in static load of its body weight can the
average horse carry?" is almost totally irrelevant.  It varies between 0%
and 50%.  And one of the big reasons for this is that static load and
dynamic load are only very loosely related (and are not perfectly
correlated) to each other; and the higher the speeds, the looser this
relationship gets.

All of this also entirely begs the question of fuelling the effort over
time.  However, the ability to fuel the effort over time varies hugely from
horse to horse. And how the effort is fueled over time varies depending on
how much time we are talking about here (just how long is the effort? so in
determining this we don't get to ignore the question of what is meant by
ability).  

And if we try to evaluate the ability of a horse to fuel the effort over
time, we can't even use the extremely complicated physics of calculating
dynamic loads, we have to look at invisible metabolics.  

But make no mistake, a great deal of the calculation of a horse's ability
to carry weight over time (even if that time is only the 2 minutes it takes
to run the Kentucky Derby) is a function of that individual's ability to
store fuel and to mobilize it for consumption during the effort.

kat
Orange County, Calif.


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