Re: RC: RE: Fwd: physiology of weight

[Truman Prevatt <tprevatt@mindspring.com>]

Mike Sofen wrote:

> I have to simply smile at all of this.
>
> Remember the old chicken and egg story - are fewer heavy weights "winning"
> events because their horses can't handle it or is it because fewer
> heavyweights enter the events or even try for a top ten?  Are heavyweight
> riders selecting "appropriately sized" mounts or going with a good looking
> but underbuilt horse?  Are the "overwhelming majority of events being won by
> arab and arab crosses" being won because there are only a handful of
> non-arab breeds even entering the event?  There are SO many places where we
> simply don't have the right kind of data from which to draw conclusions like
> these.
>
> There is no question in my mind that carrying a heavier rider has to consume
> more energy from the horse.  My ONLY question is this - does it really
> (scientifically) affect the outcome of an event when ALL mitigating factors
> are compensated for?  In a sense, a single weight National Championship
> would give us that kind of data.
>

Mike you have just answered your own question. Work required is directly
proportional to mass - that's high school physics. It takes twice the work to
carry a 220 pound rider than it does a 110 pound ride. Since the conversion of
chemical energy to mechanical energy (which is how the body works) is not 100%
efficient, maybe 50%, the other portion of the energy is converted to heat. This
heat has to be dissipated. So a horse carrying a 220 pound rider has to
dissipate twice the heat as a horse carrying a 110 pound ride. Here is where
Howard may have had a good point but didn't know it :-), in the humidity it is
harder to dissipate heat than in arid and semi-arid climates. So the heat
dissipation related to weight differences may in fact be slightly bigger issue
in the East than the West, but I doubt it.

The more heat required to be dissipated the more sweat, the more electrolytes
lost, the higher the stress on the metabolic system. So I would say from a
string of conclusions using no more than high school physics, there is a
significantly higher stress level on a horse carrying 220 pounds vs 110 pounds.

On question, how do you compensate for the "mitigating factor" of a horse
carrying a heavier weight producing more heat in proportion of the weight
carried?

Cheers,
Truman