in the Performance Horse: New Trails to Safety and Performance
by Tom Ivers
Through evolution, the equine athlete has been highly
tuned to the importance of plant carbohydrates. The horse
prefers timothy to steaks, and we are not surprised. In
research, and in conditioning our athletes, we've seen
that carbohydrate supply is critical for equine athletes.
We've known that muscles depleted of carbohydrate-derived
glycogen stop functioning and die. We know that carbohydrate-derived
blood glucose can drop so low that the central nervous
system ceases functioning, with coma and death as a consequence.
Indeed, without glucose in the blood and glycogen in the
muscle, the horse cannot function, despite large stores
of fat and plenty of protein in the lean muscle mass.
We've seen hard working horses that are fed too few carbohydrates;
they lose lean muscle mass as they attempt to supply working
energy by tearing down (catabolizing) their own flesh.
And since grade school we've known that carbohydrates
in the form of sugars and starches are digested to form
simple sugars, readily available energy that powers every
organ in the body. How much more can we learn about this
basic, simple fuel food?
Plenty. World-wide research with carbohydrates in athletes
continues to produce exciting and very useful findings.
For example, we now know that sugar is the most anabolic
substance available to athletes. Many of you will immediately
think of anabolic steroids - testosterone and testosterone-like
substances - as the primary anabolic agents. They aren't.
Those substances are anti-catabolic; they prevent some
tissues from being broken down as the body goes through
its normal protein turnover. The result is a gain in lean
muscle mass. The actual tissue building occurs due to
another hormone, Insulin Growth Factor I (IGF-I)
As you know, athletes proceeding through a conditioning
program and competition tend to become fitter, in a process
known as acquisition. If the exercise stressors are well
matched with energy intake, then the tissues being used
hard will strengthen. If the energy intake is too low,
then the same tissues will be broken down (catabolized)
and the horse will lose weight and fitness. Muscle soreness
and stiffness is generally the first outward sign other
than body weight loss. The body has a continuing choice,
depending on energy supply, to go either anabolic (builds
and repairs tissue) or catabolic (tears down tissue for
This situation is best seen immediately after a tough
race or workout. In these circumstances, muscle glycogen
and blood glucose are depleted. Since the brain needs
glucose in the blood, all systems are directed toward
raising blood glucose levels as a first priority. But
studies in humans and other mammals show that a dose of
a fast-acting carbohydrate immediately after a hard workout
or hard race solves the blood glucose problem. Then the
body doesn't have to catabolize its own tissues for energy.
The same dose of concentrated energy - a sports drink
containing glucose in humans, or a glycogen loader paste
in horses - triggers IGF-1 to go to work, rebuilding injured
tissues and overbuilding stressed tissues. The result
is faster recovery, increased acquisition, and reduced
soreness and stiffness.
We now know that, as local muscle glycogen is depleted,
the athlete must experience fatigue and slow down. This
does not mean that the muscle cell must be completely
depleted of glycogen - as little as 10% glycogen depletion
in a muscle cell will begin to cause a decrement in muscle
contraction time and power. By the time a muscle cell
is 50% depleted of glycogen, fatigue is compromising performance.
We discovered this phenomenon in racehorses and endurance
horses in experiments with glycogen loading.
We've always thought of lactic acid as being the primary
cause of fatigue in the athlete. It's not. Muscle fuel
depletion is the principal cause of fatigue, not only
in sprinters but in endurance horses as well. For example,
the first horse we documented through a glycogen loading
protocol was a Thoroughbred named Acey Mack. This horse
was trying hard coming out of the gate fast and usually
leading the race until the final quarter mile - at which
point he would slow down so quickly that the horses coming
up behind him had to get out of his way. Race after race,
Mack delivered the same kind of failing performance. Post-race
bloods demonstrated 22 millimoles of lactic acid and 350
CPK (muscle enzyme indicating muscle damage). These are
within the "normal" post race ranges.
We then loaded Mack with a product much like Vita-Flex's
CarboCharge (CarboCharge is the improved version), feeding
multiple doses each day for the four days before the race.
Mack gained 15 lengths and was second by a nose. In his
next race, he was second by a nose again. Then he won
four in a row - all of these races run under a glycogen
loading protocol. What's interesting for our discussion
is that immediately after a winning performance, CPK was
reduced to 250, but the lactic acid was so high our YSI
Sport 1500 lactate analyzer could not give us a reading
other than "higher than 35 millimoles." The
horse had double his earlier post-race lactic acid and
was winning, not slowing down. We were astonished, to
say the least.
Since that time, thousands of racehorses, Standardbreds,
Quarterhorses, and Thoroughbreds, have been glycogen-loaded
and have demonstrated the kind of improvement that brings
a horse from the middle of the pack to the winner's circle.
We have also run experiments on eventers and endurance
horses, and there is a problem. Glycogen loading tends
to make a horse feel like Godzilla on race day. This isn't
a very good situation for eventers, where control is of
primary concern during the dressage section which occurs
on the first day. A similar situation exists in endurance
horses - you don't want the athlete burning up the trail
at the start when he's got 50 to 100 miles of ground to
Still, endurance horses and eventers also need a supply
of readily available energy throughout their competitions.
Without carbohydrate, fats and proteins cannot be processed.
Vita-Flex provided CarboCharge for some experiments with
endurance horses. For this protocol we borrowed the human
science that demonstrated that periodic intake of sugar-based
drinks improved marathon performance. We fed the glycogen
loader two hours out from the beginning of the endurance
ride and then every two hours during the ride. More than
a dozen endurance riders reported back that their horses
showed improved energy and enthusiasm throughout the ride
and had superior vet checks. None reported anything negative.
Event riders have reported similar results with doses
of glycogen loader beginning immediately after dressage,
with the pre-competition doses two hours out from the
start of competition. And that leads us to another new
bit of knowledge about blood sugar; the horse will not
perform well if he starts the event with a low blood glucose.
Instead he's lethargic; sleepy. This is because the central
nervous system is slowing down metabolism in order to
preserve the blood glucose that exists. Normally, grain
or sugar will produce a peak blood glucose in 1.5 to 2
hours. Vita-Flex has designed a long-chain sugar component
for their CarboCharge so that the loader can provide some
leeway in feeding times. Still, two hours is the safest
pre-event timing we've used and, with continuing work,
maintenance doses every two hours seem to be the most
How will carbohydrate ingestion affect other performance
categories? Glycogen loading should be effective in polo
ponies. It has proven effective in barrel racers. We have
not tested the loader on cutting or reining horses, hunter-jumpers,
or show horses, but any event that can produce fatigue
in the horse should benefit from carbohydrate loading.
For example, steeplechasers and timber horses benefit
greatly from glycogen loading. The last thing these animals
need to face as they go over a jump is fatigue.
And when we talk about preventing fatigue, we're also
talking about preventing injury - not just winning an
event. In race horses, reducing or eliminating fatigue
is very important - a horse that is staggering down the
stretch is susceptible to a dozen different injuries as
biomechanical stressors multiply with missteps and shortened,
Recently there has been an over-enthusiasm for high fat
diets in performance horses. Remember this: fat is fed
to "spare" glycogen. If sufficient carbohydrate
is fed, glycogen doesn't need to be spared. The problem
with chronic fat feeding is that, over time, the muscle
cells begin to learn to use fat instead of glycogen, storing
away lipolytic enzymes instead of glycolytic enzymes.
In racehorses, this causes a slowing in performance. Fat
may be useful in endurance horses, but Dr. Gary Potter,
the author of many fat-feeding studies, tells me that
the first priority in working horses is carbohydrate intake.
He says fat can be used as a supplement, but not without
a strong carbohydrate presence and not in high percentages
of the diet (he suggests 10% max). Sure, it's interesting
that the horse can do well on three times as much fat
as he would get in a standard diet. But the old saying,
"fat burns on the flame of glycogen," still
Now, feeding enough carbohydrate to support hard exercise
can be a problem. You cannot feed a racehorse enough plain
oats to support a genuine interval conditioning program.
Corn and barley can help bring in more concentrated carbohydrates,
but even then there are situations that demand a sure-fire
energy delivery system. For example, the horse that has
been racing hard while being underfed will eventually
come up muscle sore, and then anorexic; sore horses go
off their feed. You can back off the racing/training schedule,
allowing the horse to decondition, or you can fill in
the holes of carbohydrate intake with a glycogen loader
used as an energy source every day (half doses of the
loading protocol) until the horse is back eating and feeling
Finally, one interesting side effect of carbo-loaders.
Whether it's the chromium or the long chained sugars we
don't know, but a dose of the loader tonight will eliminate
tying up tomorrow. We don't know why. In fact, we don't
really know what tying up is, exactly. But if you have
a horse in the middle of the syndrome, tying up every
day, you can break him out of it with a dose of glycogen
loader the night before the next scheduled exercise.
We are seeing that the horse's inherent preference for
dietary carbohydrates runs deeper than we thought, to
impact many realms and phases of metabolism. More information
will certainly follow. But we know enough now to start
applying these findings to improve the energy nutrition
of our carbo-centered athletes. In doing so we can reduce
the peaks and valleys of blood glucose during and after
performance, and help promote efficient, non-damaging
metabolism. And that is the biological foundation of safe
and rewarding performance.