<< I guess this is one area where I personally would be extremely cautious
about comparing apples and oranges. >>
We're talking about muscle cells and glycogen depletion.
> From what I've read, endurance
horses deplete more glycogen through an endurance ride than do
racehorses during a race.>
Depends on which muscle cells you're talking about. Racehorses deplete
different muscle cells than do endurance horses. From what I've read,
endurance horses return from their events with very little depletion of the
cells that racehorses typically deplete. Can provide references if you wish.
> Also, racehorses are depleting glycogen
at a much faster rate than do endurance horses, and under greatly
different conditions. IMHO, assuming that what will work for racehorses
will also work for endurance horses is a good way to kill or injure
endurance horses.>
This is not coherent thinking. You've gone from the specific to the general
and then injected emotionalism. Not a worthwhile humble opinion.
> Especially when research does exist that at
least suggests glycogen loading in endurance horses may be
contraindicated.>
Cites, please. I've not encountered this literature. The human science, along
with studies on a number of species, supports carbohydrate loading and
carbohydrate support during extended exercise bouts.
> > David Snow (an equine exercise
> physiology god who produces a ton of research on this kind of thing)
> told me at AESM last year that glycogen storage is considerably higher in
horses than in humans, that glycogen storage concentrations in
a normal horse is equivalent to that in a "loaded" human athlete.>
> This should tell you something--horses are more dependant on stored
glycogen
> than humans.
>Then if horses have already adapted themselves to store maximum amounts
of glycogen, I guess I would argue alot more for the benefits of
glycogen loading in humans than in horses, although I don't argue with
any demonstrated benefits in racehorses.>
You said "maximum", Snow said "more". There's a major difference in those two
concepts.
> > Also that repletion after exercise is much slower (up to 92 hours) in
horses than it is in humans, which is why horses cannot compete as
often as humans after competitions that totally deplete glycogen
stores.
> Again, the importance of glycogen availability.
>>Guess I'm being dumb---what does that have to do with glycogen loading
before an endurance event? The horse is already fully loaded.>>
Again, an error in thinking. The storage of more glycogen in equine muscle
does not lead to the conclusion that the muscle cells is "fully loaded". It
is not.
> Any
multi-day rider will tell you that endurance horses ridden sensibly will
go out and do 50 a day for five days straight and get stronger every
day, demonstrating that the horse did not deplete 100% of his glycogen
stores, as he would be incapable of "filling his tank" before the next
day.>
Now you're off science and into conjecture. Fatigue in muscle cells occurs
long before 100% depletion. As little as a 10% depletion in a muscle cell
will cause slower contraction (fatigue). During time off, glycogen repletion
takes place in a number of ways, including feed intake and liver neogenesis.
>> Guess I would lean a lot more towards making sure a horse ate at
every opportunity during the day---thus filling his tank a bit
>>continuously>>
This is effective.
>>---rather than try to "superfill" a gas tank before the
race, especially if doing so could harm him.>>
This is the humble opinion appearing again. If you can demonstrate this
assertion with cites, I'll defer. Otherwise, it's just talk. If this opinion
is true, then the horse is unique among mammals.
>> Again, I could see alot more advantage to superfilling a horse's gas
tank if he was only going to sprint a relatively short distance, ie
quarter to a mile or so.>>
Actually, as far as the literature is concerned, there is far more validity
in glycogen loading the long distance athlete. I stumbled upon the effect
with sprinting racehorses by accident. Up to that point, all the science said
that glycogen loading was worthless in sprinters. However, some recent work
has also demonstrated its effectiveness in human sprinters and weightlifters.
>
> > In Dr.
> Snow's opinion, all that is required in endurance horses is a normal
> high-energy diet>>
>
> Doesn't compute from the above observations.
>>I don't understand why? A high energy diet provides glucose and
therefore glycogen, which an endurance horse normally keeps stored at
normally very high levels without any extra help. Seems like providing
a diet that supplies the required substrate would be a fairly
straightforward management strategy.>>
What is the required substrate for, say, 50 miles? And what is the level of
locally available substrate that will guarantee no fatigue? I submit that no
one knows the answer to either question. Certainly no one knows in
racehorses.
> Plus an elite endurance horse
would already have even higher stored glycogen concentrations, since
Arabians have the highest average popluation of slow-twitch muscle
fibers (storing more glycogen), and have specifically been conditioned
so that the muscle fiber increases it's normal glycogen storage
capacity.
ST muscle cells store more glycogen? Never heard that before. Any
conditioning, sprint or endurance, that depletes muscle cells of glycogen
will result in increased glycogen storage.
> I guess I just don't see a reason for glycogen-loading given
the potential risk.>
Again, the humble opinion. Please document this "risk". Snow? Where? I've
read every paper Snow ever wrote. I'll go back and read his latest stuff over
the weekend to see if I encounter any hind of the "death by carbohydrate
loading" you're referring to--or even tying up via carbo loading. Meanwhile,
you can speed my search by pointing out the papers where this "danger" is
mentioned.
>Also, I would still be very cautious and conservative in relating
racetrack conditions to an endurance ride.>
So would I.
> There are just too many
differences that would injure an endurance horse. >
For example? You're making assumptions here that have no specific reference
to fact or experience. Athletics is a continuum of performance demands and
metabolic requirements. You're injecting emotion into an argument that
originated as a discussion of the usefullness of a technique that has been
successfully and safely applied to rats, mice, racehorses, humans (endurance
and sprinting) and may just have application in horses going long and slow.
All I'm saying is that nobody knows. Teddy says her horse was "too much on
the iron" with her protocol. You're saying that Snow says they'll tie up with
his protocol (although he's never documented that, as far as I know). Were
Snow's horses too much on the iron and Teddy's tied up in a knot? Don't think
so. Does glycogen loading benefit an endurance horse--nobody has the foggiest
idea. Aren't you the least bit curious?
>Energetics, kinetics,
biomechanics, everything is different. Treating an endurance horse like
a racehorse would injure the endurance horse, and doing vice versa would
injure the racehorse.>
Again, humble opinion. Please state the circumstances or literature that have
led you to this conclusion. Seems to me there are a few endurance horses that
were once racehorses--or did they all die on the trail? For my part, I can
tell you that racehorses could stand a hell of a lot more exercise of the
kind that endurance horses get--without falling down dead. In fact, there
have been several champion racehorses produced in Australia that have
routinely delivered 20 miles a day. Stanerra won the Japan Cup coming off a
base of 15 miles daily. How many endurance horses train 15-20 miles every day
for, say, six months?
> >and to avoid efforts at glycogen-loading per se, as
> > tying up has invariably been a factor time and again in research
trials.>
> Is this published data? What was the loading/exercise protocol?
>>Of course it's published research. Protocol varied from project to
project as tying up was an unwanted nuisance variable, not the focus of
the study. Check your database, there's been alot of stuff in ENPS for
years and years.>>
I'll check. You check. Author, paper, publisher, date, sample quote on this
specific. Let's see how many we can find.
>The situation is entirely different, so probably the effects are entirely
different, as well.>>
> Mebbe, mebbe not. My opinion: there is no equine exercise physiology god.
>> It's just my personal opinion of a very well-respected and knowledgable
researcher. As far as I'm concerned, anyone who has produced the reams
of truly excellent and statistically impeccable research that Dr. Snow
has deserves my unqualified respect and admiration. Anyone else can
decide for themselves, of course.>>
Dr. Snow has been wrong in the past, as have we all, and as will we all. As
soon as one begins True Believing, one stops thinking.
>(P.S. I argue with Dr. Snow, too. That's what happens when your
research advisor/role model is a pushy, opinionated
veterinarian/researcher who encourages insurrection in the ranks.)>
In that case, I take back what I just said about True Believing.
> We
> know next to nothing about equine exercise physiology in relation to
optimum
> performance/conditioning in the various events of the equine athlete.>
>No, but we've got a helluva start.
We're at least 20 years behind the human science--but we are catching up
because some researchers have leapfrogged those who insist on reinventing the
exercise physiology wheel for horses. Snow is of that school, in my opinion.
The Swedes, Kansas, Louisiana, some Aussies and others are doing more leading
edge research--Persson's group has actually revolutionized Standardbred
racing.
Again, for the record, in the final analysis it is not the physiologists who
innnovate in sport, it is the coach and the athlete. The physiologists follow
along behind, picking up the pieces of shattered theories.
>> Susan Evans
>>
Tom Ivers