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RE: [RC] weight divisions - heidi

Since energy expended is a function of work performed and horses are,
from a mechanical movement standpoint, an assortment of levers and
pulleys, the amount of work required to move the mass forward is as much
a function of how those levers and pulleys work in relation to each
other as it is the static value of the mass.


Kat is on the right track here, but one thing no one has mentioned is
the absorbed energy in a system of springs that is reused on the next
stride.  The suspensory apparatus in horses is particularly efficient
in absorbing the energy of the landing phase of a stride and
translating that energy back into the departure stage of the next
stride.  Because of this, it takes far less "work" or calories to
initiate strides once the progression has started.

Imagine a slinky.  It will travel several "steps" even on the level
before it winds down, purely from stored energy in the spring itself. 
With the help of gravity, it will go down steps virtually forever,
since the additional energy of losing elevation is enough to maintain
the motion.  

Or think of a trampoline, and how effortless it is to jump high and
continue to jump high, once you've gotten started.  The rubber absorbs
the energy and gives it back to the next jump.

Because the suspensory mechanisms in the horse work this same way, it is
not valid to calculate the energy expended by using formulas written for
direct lifting or pulling.  I can't remember the estimates of how much
less work is involved due to the spring-like action of the suspensory
apparatus, but it is considerable.  Perhaps some of the university
folks who deal with this can offer some numbers...

Heidi


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