Before you read this
factsheet, it would help in your understanding if you knew how your body
processes the food you eat. To help, why not read the
Digestive Process Factsheet?
Food energy contents
All foods are made up of the nutritional building blocks of
carbohydrates, fats, and protein plus a certain amount of water and
fibre (indigestible and without any food value).
Carbohydrates contain 4.1 Calories per gram and are the primary
source of energy for most cyclists and endurance athletes.
Fats are more important for slower endurance events and contain 9 Calories per gram.
Protein's main use (again 4 Calories per gram), is to maintain and
repair the body's cells and is rarely available as a source of energy to
an athlete. But that doesn't mean it should be ignored!
The chart below
is the replacement for the now considered outdated food pyramid.
It shows the correct ratio of what should be eaten to maintain a
balanced diet. When training, these ratios may need to be
"tweaked" and to do that you need the advice of a
Muscle energy supply
carbohydrates supply the majority of the energy for muscles during
vigorous activity, fats can be a major contributor for less strenuous
activities. Carbohydrate is stored as glycogen in muscle and liver
cells. In a balanced sports diet there is enough glycogen to support
around 90 minutes of aerobic exercise before depletion occurs. Or,
to put it another way, the fuel tanks run dry.
internal stores can be replenished "as you go" through eating
carbohydrates. Begin eating at the start of the event as eating after
the bonk has occurred is infinitely less effective and desirable from a
A shift toward
fat metabolism may be the physiological explanation for the "second
wind" that occurs during long exercise sessions or races. It
may be that, once internal carbohydrate stores have been depleted and
fatigue sets in, the body's survival instinct awakens and shifts to fat
metabolism. The "second wind" or feeling of a renewed source of
trade off is the inability to maintain performance at the same %VO2max
possible with carbohydrate supported metabolism. In other words,
you may go further but it wont be as fast as if you maintained your
Factors effecting digestion & absorption
planning a nutritional strategy to supplement the body's energy stores
for a big race, the rate of digestion and absorption of foods must be
taken into account. The time needed for the stomach to start the
digestive process, empty its contents into the small intestine, and have
the food components absorbed into the bloodstream will directly affect
how quickly any food will be available to the muscles to provide energy
for the ride.
As an athlete
you have control over four major factors that influence the digestive
▼ Solid v liquid ~ liquids are
metabolized quicker than solids
Fat content of the food ~ fat slows the
Sugar concentration ~ more than 10% slows
Physical activity level ~ digestion is
slowed over 70% VO2max
From the above
four points, it is easy to see that the optimal food for a rapid, high
energy boost during a ride would be a semi-liquid (gels) or liquid
carbohydrate with minimal if any fat.
On the other
hand, for endurance events competed at a lower VO2max (Cyclosportives,
Iron Man Triathlons, End-to-End attempts), a complex, solid form of
carbohydrate (energy bar), with some fat added to improve taste will
slow emptying from the stomach and even out absorption over a longer
period of time.
Effects of exercise on digestion
Studies have demonstrated a reduced blood flow to the digestive
system during vigorous exercise ~ an 80% reduction after 1 hour of
cycling at 70% VO2max. Exercise delays stomach emptying, and the more
vigorous the exercise, the greater the delay.
It is suspected that one component of overtraining may be a
failure to adequately replace the muscle glycogen depleted as a result
of daily training. Therefore, to minimize the risk of the short-term
bonk and long-term overtraining, it is important to maximize your body
glycogen stores through:
▼ a high carbohydrate diet in the
days and hours before your ride
▼ using carbohydrate supplements,
gels, bars & drinks, while riding
▼ making full and immediate use of
the post ride recovery interval
The good old days? As far as
the pre-race period is concerned, dismiss from your mind everything
you've heard about traditional carbo-loading. All the rage when I
started racing in the 80's, which is where it should remain. It
involved avoiding all carbohydrates for several days in the week prior
to the event, while still training hard, to ensure complete and absolute
muscle glycogen depletion. Once that point had been reached you'd
eat nothing but carbohydrates for the 3 days immediately prior to the
regimen does maximise muscle glycogen stores, the price paid was
significant physical, mental, physiological and digestive
drawbacks. Nutritional science has advanced greatly since this program
was devised. In those days we were led to believe steak was the optimal
race fuel! Sticking to a normal high carbohydrate diet, without a
depletion phase, will provide 90% of the benefits of the loading program
while avoiding digestive turmoil.
Maximizing carbohydrate replacement while competing is important for
events of more than 2 hours. Up to 2 grams of carbohydrate per minute
can be absorbed and utilized to supplement pre-ride glycogen stores and
help sustain prolonged exercise.
As a rule of
thumb, the higher the level of intensity of the ride (closer to your
VO2max), the simpler the carbohydrates (energy drinks, gels, and fruits)
On longer rides and at lower heart rates, more complex
carbohydrates and a higher fat content offer other alternatives. A
reasonable goal during high intensity rides is 200 to 300 Calories (60
grams of carbohydrate) per hour.
bars and sports drinks are often advertised as providing a particularly
potent combination of ingredients and secret "supplements".
However, they are no more effective on a gram for gram basis as an
energy booster than any other carbohydrate snack. One big
advantage is that they are pre-packed, readily available and do offer a
potentially better taste and texture option for a mid-competition snack.
Take advantage of the "glycogen window" that is open immediately
following vigorous exercise. During this interval, ingested
carbohydrate will be converted into muscle glycogen at about 3 times the
normal rate and "the earlier recovery starts the better".
during the first twenty minutes of finishing exercise gets on the
glycogen autobahn and screams into the muscles and liver at a phenomenal
rate. Your body acts like a sponge sucking up all the nutrients it can
in a mad panic before the "twenty-minute window" begins to close.
After four hours it's shut altogether and nutrient absorption returns to
it's country lane way off life.
Be careful what
you eat. Many simple carbohydrate snacks such as biscuits are more
than 30% fat and if eaten in large quantities to boost recovery (which
they wont), you might exceed your planned daily fat intake. In
contrast, complex carbohydrate foods such as pasta, bread, and rice
offer significantly more carbohydrate per gram. There are even special
drinks" available to give you what you need when you need it.
There is also
suggestive evidence that the muscle stiffness occurring after vigorous
exercise (DOMS) may be related to muscle glycogen depletion. So, rapid
repletion may have the added benefit of minimizing this day after effect
as well. Lots of "mays" there but it may work for you, so why not try
does not provide any calorific energy whatsoever. However, adequate hydration is
as important to performance as the food you eat. One of the biggest
mistakes made by new, and many experienced, cyclists is the failing to
replace fluid losses associated with exercise.
In cycling rapid
skin evaporation decreases the sense of perspiring and imparts a false
sense of only minimal fluid loss. Sweat production and loss
through the lungs can easily exceed a pint per hour. When standing
in the cold waiting for your club run to start, look at the steam coming
from your breath. That's water that is.
during exercise result in decreased plasma volumes as well as muscle
water content. Dehydration of 2% of begins to impact heat
regulation, at 3% there is a measurable effect on muscle cell
contraction and when dehydration reaches 4% there is up to a 10% drop in
You may think a
4% drop is a lot. But what happens if you come to the start line
2% dehydrated. If you work in an air-conditioned office or spend
Saturday in the garden it's very likely that you may not be fully
hydrated when you start your event. Hydration is an important part
of your race preparation. Practice until you get it right.
Nutrition and hydration strategies are as important a part of
your competition as the training you undertake, the equipment you buy
and the mental preparation you put in. You can do as much of the
others as you like but if your nutrition is wrong, it will be reflected
in your results.
Would you feed a
Grand National prospect the same food you'd give a beach-ride donkey?
Absolutely not! As athletes who train or race more days than we
rest, we can't get away by eating the same as "normal" people.
Performance humans require performance nutrition. Give the food
you eat the attention it deserves. As the old computer phrase
goes, "rubbish in ~ rubbish out".
There are two
sets of bottle cage bosses on your bike for a reason. Drink a
little often, rather than gulping mouthfuls every half-hour. Keep
topped up and keep your performance levels consistent. Eat before
you're hungry and drink before you're thirsty. By the time you
feel either, it's too late.
Money spent on
the advice of a qualified sports nutritionist may help you find that extra 1%
that you need to win races or go for your personal best. For the
price of a pair of tubs you can improve your results by factors greater
than any pair of wheels or fancy frame could ever do. Check-out
our services page to find someone who has already helped some of our
riders to improved performance.