ridecamp@endurance.net: A fresh start, please?

A fresh start, please?

Susan F. Evans (suendavid@worldnet.att.net)
Sat, 19 Apr 1997 21:10:11 -0700


Maybe it's just our personalities, but we sure do seem to have a
difficult time discussing things. May we please try again? I don't
have any hidden agendas in saying what I have to say, and all I want is
to present a sometimes differing perspective so everyone on the list can
make an educated decision. If anyone else has something to add/disagree
with/debate, and I learn something new, then that's gravy.

I realize you are a busy man, so maybe you just missed the first
paragraph of my insulin post regarding feeding carbs to horses. I won't
re-print it here, but I do wish you'd take a look at it in the
archives if you have a minute. I thought I stated as plainly as I could
that I respected other people's opinions and experiences, that I didn't
have a corner on Truth more than anyone else and that everyone should do
whatever works best for them, regardless of my or anyone else's views or
conclusions (which, in essence, agrees with your own statement of "what
works is real"). I'm doing my best not to jam my opinions down anyone
else's throats, and if my style of writing seems to you to be hysterical
and doom-shouting, well, I apologize that I seem to be doing such a poor
job of communication. I'm really just trying to present other data
presented in various journals.

If you disagree with me, Tom, by all means I would like to hear about it
and why, and maybe everyone can learn something. I appreciate that you
have far more experience than I, but won't you admit that the (formal)
education I have is at least legitimate and more recent than yours?
This is NOT meant to be a one-ups-manship zing!!! Maybe I do have
access to some data that you don't, only because I can use the
university journal libraries and because I have alot of professors that
point things my way, often from journals that aren't directly related to
eq ex phys. And, because as a student, I have to spend alot of time
reading the research, while you have a business to run.

Please, I'm not playing comparison games, I'm just pointing out that
maybe EVERYONE can gain if you and I can cut each other a little slack
and assume that no one's trying to be hysterical, predict falling off of
ears or the End of Life As We Know It, and if you are calling me a clown
or a moron, maybe it's just because I have not expressed myself well
enough, and so to you, I do sound like an idiot. If you want me to see
your point of view, please explain to me my errors in logic. I'm
honestly willing to listen if you are.

That said, hopefully you are still reading. Below are my comments and
questions regarding your responses/disagreements with my original post.
I hope to hear from you soon.

Susan Evans

> Note: we're talking about a maximum individual dose of 4 ounces of medium and
> long chain carbohydrates <snip> Carbo jolt? Big whack
> of sugars? Four ounces is a measuring cup, not a bucket.

I was purposely being ambiguous in my amounts regarding carbs because 1)
all of the published research used differing amounts of carbohydrates
for different studies, so I was unable to be specific in
quantities. Also, the source of carbs differed, as did other aspects of
protocol. The commonality between them was that the carbohydrate was
fed in varying doses and "excessive", or "a large amount" differed from
horse to horse. Certainly you'd agree that what may be a normal meal
for one horse would be too much for another. Also, I was grouping
together grain-based carbohydrates and glycogen-loader-based
carbohydrates. What I ambiguously called a "big whack" was simply
referring to an excess of some form of sugar.

2) You have indeed mentioned that your glycogen loader is fed in 4 oz,
but beyond that, I don't think I've seen an exact protocol for feeding
it for several days in advance, and when the final dose is fed. Also, I
admit total ignorance as to what the ingredients are and how they will
enter the system. I did not mean to imply that 4 oz of carbo-loader is
necessarily excessive, I was only trying to point out that excessive
amounts of ANY sugar may have adverse effects---no falling off of ears,
no abrupt and agonizing death. Just not the effect you may be looking

> The author above is talking about pre-event carbohydrate feeding. A tricky
> problem, but not anything that will precipitate the End of the World as We
> Know It.

Then I apologize if I misunderstood your protocol. I was apparently
mistakenly under the impression that you fed the carbo-loader sometime
before (as in semi-immediately) before the event. This was based on
your discussions that a horse will get snoozy after a carbo meal and you
should have him moving before this snooziness. I would very much
appreciate a detailed explanation of your recommended protocol to clear
up the confusion.

Hypoglycemia, by the way, is not the same as "fasted glucose
> levels". Hypoglycemia is dangerously low blood sugar. None of the references
> are talking about this condition subsequent to carbohydrate intake.

Actually, one of the references were quite clear in stating that during
exercise, the blood glucose levels were below fasting levels, and they
did refer to them as hypoglycemia. Again, this low glucose condition
occurred during strenuous exercise, not just because they had been fed

> And she's not talking about during-event supplementation when she mentions
> the studies above.

That's true. I was only discussing carbohydrates immediately before the

Both carbo loading (also known as glycogen loading) and
> carbohydrate intake during longer events have been shown, with no doubt
> whatsoever, to be ergogenic in athletic events from sprints to marathons.

I agree with you. Which is why my recommendations included small
amounts of carbohydrates during the ride, especially for the longer

> Pre-race sugar dosing has also been demonstrated to have ergogenic effects
> under some circumstances--but it's very tricky to get the timing right.

Which leads to the question---wouldn't it have far more benefits for TB
racing under anaerobic conditions than it would for endurance horses who
must rely much more heavily on lipolysis? I agree with you that keeping
as much glucose in the system is helpful for any performance horse. But
my thought is that an amount of carbohydrates that would excessively
elevate blood insulin is going to have more disadvantages (through
suppressing fat utilization) than through the advantage of supplying
more plasma glucose. I would appreciate your comments, especially
regarding timing, as that seems to be what we are primarily disagreeing

> >>If you could time that big burst of energy after a carbo-load to
> coincide with the onset of the exercise bout,>>
> There is no big burst of energy after a single dose of carobhydrate or after
> carbhydrate loading. Horses and humans feel good, but there is no mythical
> "sugar high".

This is not a challenge, Tom, just questions---isn't blood glucose going
to sharply increase at some point after carbohydrate ingestion and
before insulin levels react, depending on how soluble the sugar source
is? (I was under the possibly false impression that the glycogen
boosters you recommend are highly soluble---please clarify. Isn't a
markedly higher plasma glucose level going to result in a higher
available energy level? I have never done this myself, but I thought
several people on the list had reported "riding rockets" after a feed of
soluble carbohydrates. I was under the impression that the horses
"feeling good" had been taken to a new high. I guess I'm confused as to
exactly what you are trying for in feeding a glycogen-booster. Are you
only trying to increase pre-exercise glycogen levels? Or boost blood
glucose levels during the event itself, in effect supplementing the
amount of glucose being supplied by the liver? Again, I guess an
explanation of your protocol and timing would be helpful.

> Well, here's what actually happens with a single dose:
> Whether you feed grain or sugar, you're going to get a spike in blood glucose
> at 1 1/2 to two hours from the time of feeding. That is, a horse that began
> fasted, with a 70 blood sugar, will demonstrate a 120 or 130 blood sugar
> after a meal of grain. A dose of sugar might increase the spike to 140 or
> 150--the highest I've seen is in the 160s.
> The fitter the horse, the lower the blood glucose response to carbohydrate
> ingestion. A very fit horse may move as little as 10 points in blood sugar.

Why would this be? (And I'm challenging you, just asking) Is this
because the fitter horse has better adapted himself to utilizing glucose
and packing the glucose off to glycogen storage? If so, then wouldn't
it follow that the fitter horse also has the more immediate insulin
response? How would you consider this as a factor to immediately
subsequent exercise?

> At any rate, all horses, no matter what the dose, demonstrate the same kind
> of curve--a rapid or gradual drop from the initial peak (the higher the peak
> the faster the drop)

I guess this is what concerns me. I assume you agree that the drop is
glucose levels is in reaction to the insulin response. If a horse
(say a somewhat unfit one that is going to experience a higher peak
and faster drop) were to undergo a rapid drop in glucose as part of the
insulin response, AND that horse was exercising at a rate that was
demanding more glucose, not less, AND the insulin presence was
inhibiting the utilization of fat as a fuel source, don't you think this
horse is going to have more trouble maintaining the performance level
than he would if he had not received carbohydrate supplementation?
Again, maybe this scenario would be avoided entirely through the right
timing which avoided exercise during the rapid glucose drop.

> Somewhere along the down curve there comes the "post Thanksgiving dinner
> naptime" reaction--the horse, if left in his stall with no exercise, becomes
> snoozy for an hour or so. You don't want a racehorse to be snoozy, so the
> final dose of a glycogen loader has to be given with proper timing, and that
> timing can vary with the horse.

How do you find out what this timing is? Is it qualitative or

Smaller doses of carbohydrates in the midst
> of exercise should not need much in the way of timing.

Yup, I agree.

> During the 80s, at the racetrack, veterinarians were tubing large quantities
> of sugar and sodium bicarbonate into the horses, because of the dramatically
> improved performance seen with this draconian measure.

The improvement were
> more dramatic if the treatment was accompanied with insulin. Horses didn't
> die, or become sick--they kicked butt.

Well, I agree with you, pretty draconian. Do you know what the "large
quantities of sugars" were, source and amount? Does this differ from
the glycogen booster you advocate? Do you ascribe the improved
performance more to increased glycogen stores (and I can only imagine,
talk about mega-amounts of glucose being forced into storage) or to the
increased pH levels as a result of the bicarb?

> Anyway, single dose is not what I've been talking about. I'm talking about
> glycogen loading over a 4-day period, and/or smaller doses of carbs spread
> throughout the event--both of which will benefit the endurance horse without
> having its ears fall off.

Again, I admit ignorance of your exact recommended protocol. If dosing
with the glycogen loader product does not take place just several hours
before the event, then of course none of my arguments regarding insulin
response would apply, as the glucose curves have already been and gone.
However, I have seen over the years alot of riders giving thier horses
a large amount of grain before the start and it was this scenario that I
was discussing, probably more so, than I was regarding the glycogen

Which leads me to my next question---if your protocol leads to simply
glycogen loading for several days before the ride, what is the advantage
of the glycogen-loader over plain old grain? It seems to me that once
the carbohydrate (whatever it's source) has been broken down in the
body, it's all just glucose. Are the advantages because it is possibly
more cost-efficient, more convenient, or am I missing some physiological

Glycogen loading is a well-known term to anyone
> involved in exercise science and has always referred to the loading period,
> not to a single dosing. Susan's CarboBlast, or whatever she wants to call it
> is not something that is done in any professional or Olympic level athletics
> that I know of.

Me neither. Again, I apologize if I am confused about your dosing
protocol. I'm relieved to hear that it is NOT single-dosing immediately
prior to exercise.

SFE wrote:
> >>Endurance horses, on the other hand, exercise primarily at sub-maximal,
> aerobic levels for very extended periods of time with only with
> occasional and short rest periods. His energy source is therefore
> PARTIALLY from carbohydrates, but PRIMARILY from metabolism of fat
> stores. Carbos are of more importance than fats for the first few miles
> of a ride, as it takes awhile for lipolysis (fat mobilization) to get
> going, but every distance rider knows that endurance races can be lost,
> but not won, in the first few miles.>>

ti wrote:
> The above is, simply, untrue. Fat burns "on the flame of glycogen".

I agree, but there is alot of variability of how much fat and how much
glycogen, depending on intensity of exercise, as measured by
steady-state RQ values.

There is
> a point where fat metabolism exceeds glucose/glycogen metabolism during
> athletic performance, in human marathons for example, but this is at "the
> wall"--about 18 miles into a 26 mile marathon--at theis point, the runner
> must slow down, must rapidly build body temperature, and must rapidly become
> dehydrated--all due to the the near-exclusive use of fat for muscular fuel.

I'm unfamiliar with human/marathon physiology and so am unfamiliar with
"hitting the wall". However, in horses, I do know exercise levels with
an RQ of less than 1.0 are going to be burning more fat than glycogen as
a fuel source. This is well established. At resting levels, the RQ
value is around .70, and the reliance is primarily on fat metabolism,
though of course not exclusively.

I think you yourself have estimated 60% VO2 max to be a businesslike
canter, somewhere around a 3:30 mile? Endurance horses are going quite
a bit slower than that canter (most of the time, except for the front
runners, hotshoes and runaways), so oxygen consumption must be less than
60% VO2max. What would you say---40-50% VO2max? Rose reported that
endurance horses with rider during a 80 km (50 mile) ride exercised at
30-60% VO2max. I have a hard time believing that a horse exercising at
only 50% VO2max is going to have an RQ over 1.0, therefore that horse
must be relying quite a bit more on fat metabolism than glucose (notice
I said more, not entirely). What would you estimate the RQ would be of
a horse at 50% VO2max? .75? .80? Around this range, according to
Zuntz and Schumberg (sorry, this just from a xeroxed journal
reprint I was given, I don't have the entire reference), the horse would
be burning between 15.6 - 33.4% carbohydrates and 66.6 - 84.40% fats.
There's some evidence that horses on a high-fat diet shift the RQ even a
bit more towards fats and away from carbohydrate dependence, but so far,
I don't think anyone's really figured it out.

So I agree with you that you don't want to get a horse totally
glycogen-depleted, AND that you should try and start a horse out with as
much glycogen on board as possible, but I also think it's a mistake to
rely on glycogen more than fats during an endurance ride, but fat is
going to be the fuel source in greater usage. I would appreciate your

> One should remember, though, that human marathoners are performing at a much
> higher exercise intensity than equine endurance competitors. They'll cover 26
> miles in 90-odd minutes. Normally, a horse moves twice as fast as a human
> with less of a metabolic challenge. If 50-milers were completed in 3 hours,
> they'd be taken at about half the intensity as human marathons.

I guess I'd like to see what the average VO2max values are for a
marathon runner exercising at this speed. We did measure some values
for an Olympic-calibre distance runner over in the human performance lab
(see, I poke my fingers into _everyone_ else's pie at Cal Poly) and got
alot of VO2 measurement, but he sure as hell wasn't running at 30.6 km
per hour.

> One of the problems with products like Gatorade (electrolytes and glucose
> dissolved in water) when used with hard working athletes is that they can
> cause nausea because they are too concentrated. Body fluids have been drawn
> away from the gut and into the peripheral tissues to support the work being
> done, and when a high concentration fluid hits the gut, it wants to draw even
> more fluid from the gut lining--that's trouble. Eating anything under those
> conditions is also a problem. However, it is unlikely that endurance horses
> are working hard enough to experience harm from food intake during the actual
> event. If they were, then usefullness and comfort in carbohydrate intake
> during the event would then likely become a factor of dilution.

I agree with you here, although I think sometimes heat and dehydration
add significantly to the stress load in some horses. IMO, food
(both forage and additional carbohydrates, though I prefer a
moderate to moderate-high glycemic index source vs. high glycemic
source) during the ride is extremely beneficial, assuming the gut
remains moving. And if the gut slows down, then grass or hay is still
good, I would then just back off on the carbohydrate.

> Still, glycogen loading is a protocol that includes no carbhohydrate intake
> within five hours of the beginning of the event (we're using long-chain
> sugars in our race horses in order to back clear away from short-term blood
> glucose upsets). It stacks muscle cells with fuel for several days prior to
> the event, with a final dose early in the morning on the day of competition.

Then clearly I misunderstood your protocol, for which I apologize. I am
still rampantly opposed to soluble carbohydrate meals (assuming we're
talking an appreciable amount for that horse) immediately prior to a
ride, for the same reasons you have (short-term blood glucose upsets).

> Before closing, let me tell you about one, honest to God danger in feeding
> carbohydrates of any kind. Once in a while you're going to encounter a horse
> that is temporarily hypoglycemic. That is, demonstrates a blood glucose of 30
> (you'll never see such a number after a "huge whacky jolt" of sugar). This
> horse will get shakey for an hour after a big dose of any carbohydrate. These
> horses are few and far between, but the way to avoid encountering them at all
> is to feed the way you'll hear all vets advise--many smaller feedings vs a
> couple-three big feedings.

Though I have no firsthand experience with these kinds of horses (what's
causing the severe hypoglycemia? A pancreas running amok?), I would
definitely agree that small, frequent meals are preferable to the
couple-three big feedings which, unfortunately, are the way alot of
horses are managed.

> Meanwhile, we don't know yet what benefits to endurance horses might be
> achieved in well-thought-out manipulations of diet, prior to, and during,
> competition. Careful exploration of the possibilities by those with the
> intellect, the courage, and the desire for knowledge necessary, will benefit
> us all if the information is reported back.

I agree, and would love to see some funding for such a study. Despite
my preference for controlled studies and statistics, I am
perfectly aware that ALOT of the ideas for research (at least in ex
phys) comes from the anecdotal/field experience folks. It's a symbiotic
relationship---you (meaning the field coaches and trainers, etc.) notice
the trends and effects and we (meaning the research community) validate
it as right or wrong, and by how much. Sometimes it works the other way
around, and we measure a bunch of things and notice an effect that we
weren't expecting that still benefits the entire field.

I don't think you and I are all that far apart in what we believe, Tom.
Maybe we can both learn something, eh? Whaddaya think?

Actually, it won't benefit us all
> because there are those who will find your experiences meaningless and
> irrelevant--and who will feign moral indignation at your having dared to seek
> information on your own.

Well, it ain't me. Really.

I look forward to your comments.

Susan Evans

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