The evolving art of carbo-loading
By Matt Fitzgerald - For Active.com
The practice of carbo-loading dates back to the late
1960s. The first carbo-loading protocol was developed by a Swedish
physiologist named Gunvar Ahlborg after he discovered a positive relationship
between the amount of glycogen (carbs stored in the muscles and liver) in the
body and endurance performance.
Scientists and runners had already known for some time
that eating a high-carbohydrate diet in the days preceding a long race
enhances performance, but no one knew exactly why until Ahlborg's team zeroed
in on the glycogen connection.
Subsequently, Ahlborg discovered that the muscles and
liver are able to store above-normal amounts of glycogen when high levels of
carbohydrate consumption are preceded by severe glycogen depletion. The most
obvious way to deplete the muscles of glycogen is to eat extremely small
amounts of carbohydrate. A second way is to engage in exhaustive exercise.
The stress of severe glycogen depletion triggers an
adaptive response by which the body reduces the amount of dietary carbohydrate
that it converts to fat and stores, and increases the amount of carbohydrate
that it stores in the liver and muscles as glycogen.
Ahlborg referred to this phenomenon as glycogen
supercompensation. Armed with this knowledge, he was able to create a more
sophisticated carbo-loading protocol than the primitive existing method, which
was, more or less, eating a big bowl of spaghetti.
The Ahlborg method
Ahlborg came up with a seven-day carbo-loading plan in
which an exhaustive bout of exercise was followed by three or four days of
extremely low carbohydrate intake (10 percent of total calories) and then
three or four days of extremely high carbohydrate intake (90 percent of total
Perform an exhaustive workout one week before a long
race (90 minutes-plus).
Consume a very low-carb diet (10%) for the next 3-4 days
while training lightly.
Consume a very high-carb diet (90%) the next 3-4 days
while continuing to train lightly.
Trained athletes who used this protocol in an experiment were able to nearly
double their glycogen stores and exhibited significantly greater endurance
in exercise lasting longer than 90 minutes.
After these results were published, endurance athletes
across the globe began to use Ahlborg's carbo-loading plan prior to events
anticipated to last 90 minutes or longer. While it worked admirably, it had
its share of drawbacks.
First of all, many athletes weren't keen on performing
an exhaustive workout just a week before a big race, as the plan required.
Second, maintaining a 10 percent carbohydrate diet for three or four days
carried some nasty consequences including lethargy, cravings, irritability,
lack of concentration and increased susceptibility to illness. Many runners
and other athletes found it just wasn't worth it.
The no-depletion method
Fortunately, later research showed that you can increase
glycogen storage significantly without first depleting it. A newer
carbo-loading protocol based on this research calls for athletes to eat a
normal diet of 55 to 60 percent carbohydrate until three days before racing,
and then switch to a 70 percent carbohydrate diet for the final three days,
plus race morning.
Perform a long workout (but not an exhaustive workout)
one week before race day.
Eat normally (55-60% carbohydrate) until three days
before a longer race.
Eat a high-carb diet (70%) the final three days before
racing while training very lightly.
As for exercise, this tamer carbo-loading method suggests one last longer
workout (but not an exhaustive workout) done a week from race day followed
by increasingly shorter workouts throughout race week. It's simple, it's
non-excruciating, and it works. Admittedly, some scientists and athletes
still swear that the Ahlborg protocol is more effective, but if it is, the
difference is slight and probably not worth the suffering and inherent
Note that you should increase your carbohydrate intake
not by increasing your total caloric intake, but rather by reducing fat and
protein intake in an amount that equals or slightly exceeds the amount of
carbohydrate you add. Combining less training with more total calories could
result in last-minute weight gain that will only slow you down.
Be aware, too, that for every gram of carbohydrate the
body stores, it also stores 3 to 5 grams of water, which leads many athletes
to feel bloated by the end of a three-day loading period. The water weight
will be long gone by the time you finish your race, however.
The Western Australia method
The newest and perhaps the best of all the carbo-loading
strategies was devised in 2002 by scientists at the University of Western
Australia. It combines depletion and loading and condenses them into a one-day
The creators of this innovative protocol recognized that
a single, short workout performed at extremely high intensity creates a
powerful demand for glycogen storage in both the slow-twitch and fast-twitch
fibers of the muscles. They hypothesized that following such a workout with
heavy carbohydrate intake could result in a high level of glycogen
supercompensation without a lot of fuss.
In an experiment, the researchers asked athletes to
perform a short-duration, high-intensity workout consisting of two and a half
minutes at 130 percent of VO2max (about one-mile race pace)
followed by a 30-second sprint. During the next 24 hours, the athletes
consumed 12 grams of carbohydrate per kilogram of lean muscle mass. This
resulted in a 90-percent increase in muscle glycogen storage.
The Western Australia
During the pre-race week, eat normally while training
lightly until the day before a longer race.
On the morning of the day before the race, perform a very
brief, very high-intensity workout.
Consume 12 g of carbs per lb. of body weight over the
next 24 hours.
Runners have cause to be very pleased by these findings. Doing just a few
minutes of high-intensity exercise the day before a competition will not
sabotage tomorrow's performance, yet it will suffice to stimulate the
desirable carbohydrate "sponging" effect that was sought in the original
Ahlborg protocol. This allows the athlete to maintain a normal diet right up
until the day before competition and then load in the final 24 hours.
The Western Australia carbo-loading strategy works best
if preceded by a proper taper -- that is, by several days of reduced training
whose purpose is to render your body rested, regenerated, and race-ready. In
fact, several days of reduced training combined with your normal diet will
substantially increase your glycogen storage level even before the final day's
workout and carbohydrate binge.
When you exercise vigorously almost every day, your body
never gets a chance to fully replenish its glycogen stores before the next
workout reduces them again. Only after 48 hours of very light training or
complete rest are your glycogen levels fully compensated. Then the Western
Australia carbo-loading regimen can be used to achieve glycogen
Having said all of this, I would like to note finally
that carbo-loading in general has been shown to enhance race performance only
when athletes consume little or no carbohydrate during the race itself. If you
do use a sports drink or sports gels to fuel your race effort -- as you should
-- prior carbo-loading probably will have no effect. But it doesn't hurt to do
it anyway, as insurance.
Matt Fitzgerald is the author of several books on
triathlon, running, and sports nutrition, including
Runner's World Performance Nutrition for
Runners (Rodale, 2005).
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