Re: RC: Up Hill or Down

[David LeBlanc <dleblanc@mindspring.com>]

At 04:40 PM 1/9/00 EST, Tivers@aol.com wrote:
>In a message dated 1/9/00 12:00:51 PM Pacific Standard Time, CMKSAGEHIL 
>writes:

><< That's why I specified metabolic ease of going downhill vs. mechanical 
>ease.  Also, as I mentioned, horses can be taught to descend in a balanced 
>manner--the old concept that it is hard on the horse's front end to go 
>downhill is only true if the horse is NOT trained to be balanced going down>

>Incorrect. Basic physics. Also, balance has nothing to do with eccentric 
>muscle stress.

Actually, if you look at the static load on a horse standing on a hill
(aligned with the slope), you'll find that the proportion of the load on
the front is going to be a function of where the animal's center of gravity
is located.  If the horse lowers the back-end, it will carry more weight on
the rear legs.  Also, if the horse brings the back legs up under itself,
this also increases the loading on the rear legs.  Any time the load on
something isn't perfectly distributed, the support loading is going to be a
function of 2 things - the first is that the sum of the loads on the
supports must be equal to the total load (else it falls or flies), and that
the distance to the support from the center of gravity times the load on
the support must equal out, or the object will spin about the center of
gravity.  That's the picture from a statics engineering standpoint, and the
statics of a horse going downhill with a rider on it is anything but simple
(I wouldn't give this problem to students until they were through the first
1/2 of a good statics course).  Now when you account for the fact that the
whole thing is in motion, then we need to deal with dynamic loading, and
given that a horse's skeletal structure isn't remotely simple, it would
take me quite a while to cook up a numerical simulation that would give us
any really solid answers.

Incidently, not really understanding the dynamics of a system is why we
build bridges with a 'safety factor' of 10 - what it means is that we
really don't understand how the bridge really works, so if we add a lot of
extra steel and concrete, we hope it won't fall down. <g>

So anyway, what it boils down to is that Heidi's correct on this - the
horse can make adjustments that will change the loading between front and
back.  Since the way the horse carries itself does impact the loading
between front and back (if you're OK at trig and algebra, this can be
worked out), it is reasonable to assume that muscle stress must have
corresponding differences.

It's also true that if the horse tends to keep its back more level, the
rider's weight won't ride quite as far forward, and that will affect the
overall loading.

Now as to whether you should get off the horse and lead or zoom down the
hill is something I think is between you, your horse, and your respective
comfort levels.


David LeBlanc
dleblanc@mindspring.com


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Ridecamp is a service of Endurance Net, http://www.endurance.net.    
Information, Policy, Disclaimer: http://www.endurance.net/RideCamp   
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=