|
Part 2: Fueling during Competition
Tips for Training and Competition:
Your body needs
carbohydrate, fluid, and electrolytes during exercise.
Weigh yourself before and
after exercise and drink enough to avoid more than 2 pounds of weight loss.
Muscle cramping is often
due to dehydration and/or excessive sodium losses. If you are experiencing
muscle cramps during exercise, make sure you’re drinking enough and taking
in extra salt.
Consume between 60-80
grams of carbohydrate per hour to keep muscles fueled.
Food is to an athlete as gasoline is to a
sports car. Every athlete seeking sports nutrition information has heard this
analogy. Just as we would not expect a car to sail through the Indy 500 on one
tank of gas, we shouldn’t expect our bodies to perform well “running on fumes.”
The analogy is also helpful because we know
that the owner of a $220,000 Lamborghini likely uses a higher-quality fuel than
the owner of a 1985 Honda Civic. However, knowing that we require fuel and that
we should be filling our tanks with high-quality fuel is the easy part. It takes
a little more digging to learn the logistics of how, what, and when to fuel. In
the first article of this series, we discussed what to do prior to competition.
In this article, we’ll focus on what to do during competition. Learning a few
key principles will help ensure that your engine is running efficiently.
Exercise Intensity and Fuel Sources:
As we learned last time, our bodies rely on
a mixture of carbohydrate and fat for energy at all but the highest exercise
intensities. Fat is plentiful but requires more than twice as much oxygen to
burn compared to carbohydrate. For this reason, our bodies will use primarily
fat during low- to moderate-intensity exercise such as walking or jogging. As
exercise intensity increases from jogging to running, so does our reliance on
carbohydrate. Carbohydrate is efficient and requires much less oxygen to burn
but our reserves are limited. Our bodies store carbohydrate in our muscles and
liver in the form of glycogen. When glycogen stores are full (carbohydrate
loaded), we have enough to fuel about 90 minutes of high-intensity exercise.
However, most athletes don’t pay much attention to the amount of carbohydrate in
their diets and their glycogen stores may only be partially full.
The term “bonking” or “hitting the wall” is
used by athletes who run out of glycogen and haven’t taken in enough
carbohydrate during exercise. Most endurance athletes are well acquainted with
this phenomenon. Team sport athletes tend to experience this less often but will
feel fatigued or may have a heavy feeling in their legs. For this reason, both
endurance athletes and team-sport athletes need to pay attention to the amount
of carbohydrate in their daily diets but also need to learn how to supplement
with carbohydrate during exercise. Many athletes shy away from taking in
calories during exercise because they fear an upset stomach. Understanding some
basics of the gastrointestinal system may help to alleviate these fears.
|
Fueling During Exercise:
Before any food or fluid can be used by the
muscle for energy, it must first empty from the stomach and be absorbed in the
small intestine. The rate at which any food or fluid empties from the stomach is
dependent upon the amount of energy (i.e. number of calories) the food contains.
In other words, a milkshake will remain in the stomach longer than a glass of
water. Therefore, the amount and composition of food or fluid is important
especially during exercise when blood is diverted to the muscles and the risk of
stomach upset increases. Research suggests that a carbohydrate concentration
greater than 6% (6 grams of carbohydrate per 100 ml of water) empties from the
stomach at a slower rate than those beverages that are 6% or less. In practical
terms, most sports drinks are formulated to be 4 - 8%. Check the label and look
for <= 14 grams of carbohydrate per 8 oz serving. Gels are popular during
sporting events and are concentrated forms of carbohydrate (~25 grams). In order
to ensure that a gel will empty from the stomach quickly, drink at least 14 oz
of water with each gel or 7 oz of water with ½ gel. This same principle applies
to food eaten during exercise. Always drink water with food to dilute the
carbohydrate content. Drinking sports drinks with food or gels adds to the
energy content and slows gastric emptying.
The same principles apply to intestinal
absorption. Lower concentrations of carbohydrate are absorbed more quickly than
high carbohydrate foods or beverages. In addition, products containing multiple
types of carbohydrate are absorbed faster than those with only one. A product
that contains multiple types of sugar (sucrose, glucose, fructose) utilizes
multiple transporters in the small intestine. As sugar is absorbed, fluid
follows allowing for better hydration, as well. Products containing only one
sugar will saturate the transporters and slow carbohydrate and fluid absorption.
Putting it all together:
It’s important to understand that
carbohydrate is the only form of energy that will be used by the body when
consumed during exercise. Fat and protein will not be oxidized to any meaningful
extent, if at all. Therefore, consuming calories that will not be used by the
muscle will only serve to slow down gastric emptying and intestinal absorption.
Finally, your body has an upper limit to
what it can absorb and use. It is not the goal during exercise to try to stay in
energy balance. In other words, if you’re cycling for three hours or running a
marathon, you may burn 2,500 kcal during that period of time. Carbohydrate is
quickly absorbed and used by the muscle; however the upper limit is between
60-80 grams per hour (240-320 kcal). Consuming more than this amount will only
increase the risk of gastrointestinal discomfort. It is possible that larger
people are able to absorb and oxidize more carbohydrate than smaller people.
However, the range of carbohydrate oxidation is relatively narrow and consuming
more than 100 grams per hour for even the largest person is not advised. Proper
fueling for training and competition helps you get the most out of your body.
There are so many factors in sports that you cannot control; it’s good to know
that nutrition does not have to be one of them. Practice in training what you
intend to do during a game or a race and you’ll be a fine-tuned machine. |
