Tom Ivers wrote:
> Depends on the loading/exercise procedure. We have now run more than 2,000
> racehorses after a glycogen loading protocol and have zero reports of tying
> up. Perhaps it is different with endurance horses.
I guess this is one area where I personally would be extremely cautious
about comparing apples and oranges. From what I've read, endurance
horses deplete more glycogen through an endurance ride than do
racehorses during a race. 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. Especially when research does exist that at
least suggests glycogen loading in endurance horses may be
contraindicated.
> > 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.
> > 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. 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. 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---rather than try to "superfill" a gas tank before the
race, especially if doing so could harm him.
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.
>
> > 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. 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. I guess I just don't see a reason for glycogen-loading given
the potential risk.
Also, I would still be very cautious and conservative in relating
racetrack conditions to an endurance ride. There are just too many
differences that would injure an endurance horse. 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.
> >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.
>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.
(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.)
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.
Susan Evans