Re: RC: Re: Re:overweight an issue? - Weight vs. lean mass

[Tivers@aol.com]

In a message dated 7/26/00 12:44:37 PM Pacific Daylight Time, 
suendavid@worldnet.att.net writes:

<< > RWR? Might help my slow thinking process if you avoid acronyms.
 
 Rider weight ratio.  Sorry, didn't think it was a leap.>

I tend to detest jargon in all its forms. Just a quirk in my personality.
 
 
 
 > Is that another word for "in a catabolic state"?
 
 Same thing.  Burning lean muscle mass.>

Can it be found in a medical dictionary? Or was it a spur of the moment 
creation like RWR?
 
 
 >
 >  >and has burned up its own
 >  lean muscle mass and glycogen stores---thus, less motor available and a
 >  smaller fuel tank.  The horse runs out of glycogen and into metabolic
 >  trouble, and now "mpg" *has* made a difference.>
 >
 > Don't get the "mpg" reference here. I am now deeply confused.
 
 A horse with a small rider is going to burn fewer calories per miles to
 cover the same number of miles.  The same horse with heavy rider is going to
 burn more calories per mile.  Thus the smaller load is more efficient, in
 that they're burning less fuel to go 100 miles.>

Thank you.

>  But the assumption has been
 that with a large load,  the horse doesn't have the onboard fuel capacity to
 go just as far.  This study says they do, assuming the horse is in good body
 condition.>

I don't think that you can come to that delusion. Just look at what you said. 
You're saying that the same horse, fat as a hog--or whatever you consider 
"condition" to be--will carry a 150 lb rider or a 250 lb rider "just as far". 
Just so you can't deny you ever said it, please read the quote taken directly 
from your most recent post, above. You may not have meant to say that, but 
you did. I'm taking the time to read your words carefully and take them at 
their face value without adding any wild extrapolations. And what you said 
above is clearly, on the face of it, untrue. And it is the same thrust you 
made at the very beginning of this discussion. It's an oversimplification and 
stretchy extrapolation of your data. Clarity of thought is reflected in 
clarity of expression.
 
 >Now let's say the same horse is excessivly thin--I called it cachexic, you
 called it in a catabolic state.>

"Excessively thin" is not the same as catabolic. "Fuel depleted" is akin to 
catabolic. And this is where the intramuscular triglycerides come in--you 
tend to confuse body fat with muscle-stored fat. Body fat is costly to burn, 
IMTGs (note I referenced the acronym immediately above--the polite way uf 
using them) are very efficient to burn. 


 > Same thing---the horse hasn't been getting
 enough calories and so to fuel the energy demand during conditioning, he's
 been burning up his own lean muscle mass.> 

Maybe, maybe not. You certainly can't tell by looking at the horse.


  >He might be aerobically fit as
 hell, but the lean muscle isn't there to support it and actually drive the
 horse forward.  The net effect is that he has the same muscle mass available
 as a horse with considerably less conditioning>>

Whoops, lost me there in that last sentence. First sentence says "muscle mass 
isn't there", second sentence says "same muscle mass available..." Less 
conditioning doesn't necessarily equate with reduced muscle mass. 

->--plus, less potential muscle
 glycogen storage available (at least, hypothetically, none of this is
 proven, but I'm working on it). >

Let's call it substrate availability, in order to cover all the bases.

 >Now you put the heavyweight rider on this
 thin, catabolic horse.  He's burning more calories per mile because of the
 extra weight, but the critical factor is that now he has *less lean muscle
 available and less glycogen onboard*---hence, he's relying more heavily on
 anaerobic metabolism, reaches fatigue and glycogen depletion faster and is
 going to be the first to get into metabolic trouble. >>

Whoa! You didn't mean "anaerobic metabolism" did you? 

 >Under THOSE
 circumstances, the size of the rider matters, because it directly affects
 the calories required for each mile of trail.>

The size of the rider matters under ALL conditions. Period. Obviously. The 
sentence above suggests it matter only under those circumstances. Clearly 
incorrect. 
 
 >Therefore, my hypotheses is that body fat is not an indication of
 triglycerides available onboard for fatty acid oxidation---even a skeletal
 horse still has sufficient body fats, 7-8% I think.  What I'm saying is that
 condition score is an indicator of the catabolic or anabolic state of the
 horse, and whether the horse had had sufficient substrates to sufficiently
 build lean muscle mass and store liver and muscle glycogen. >

Catabolic and anabolic states are moving targets--you can't look at a horse 
and say that he is in either state. It could be that a skinny horse was in a 
catabolic state two weeks ago, but not today. It could also be that the plump 
horse is catabolic right now, but not yesterday. Or it could be that the 
skinny was never, ever catabolic for any extended period. You just can't draw 
those conclusions from eyballing a horse--and this is a gigantic mistake some 
endurance vets are making. Big stupid mistake that has hurt at least one 
horse I'm familiar with.  

 >Without taking
 that into account, trying to draw conclusions about the effect of rider
 weight is just barely skimming the surface of a very deep pond.>

Well, what can I say here that won't offend? Actually, better just leave the 
pointed metaphor alone. 
 
 
 >Susan G

ti
 
  >>