Sports
Nutrition - Fueling your
Sport
It is common knowledge
that poor diet is a decisive factor in many conditions and
diseases, including obesity, certain types of cancer and heart
disease. The link between good health
and good nutrition has been well established, and interest in
nutrition and its impact on sporting performance is now a science
in itself. Whether you are a competing athlete, a weekend sports
player or a dedicated daily exerciser, the cornerstone to improved
performance is a well balanced diet.
Daily requirements
The basic training diet should:
• Provide adequate
energy and nutrients to meet the demands of training and exercise.
• Include
a wide variety of foods like wholegrain breads and cereals,
vegetables -
(particularly
leafy green varieties), fruit, lean meat and low fat dairy
products.
• Enable the athlete to achieve optimal body weight
and body fat levels for performance.
• Promote a quick and full recovery during exercise.
• Provide adequate fluids to ensure maximum hydration.
• Consider both the short and long term health of the
individual.
An athlete's diet should be similar to that
which is recommended to the general population. Energy intake
should divided into:
• More than 55 per cent from
carbohydrates
• About 12 to 15 per cent from protein
• Less than 30 per cent from fat.
Athletes who exercise
strenuously for more than 60 to 90 minutes daily may benefit
from increasing the amount of energy they derive from carbohydrates
to 65 to 70 per cent of energy intake. The World Health Organisation
states that athletes can comfortably consume up to 35 per cent
of energy from fat without compromising performance. Some sports
nutritionists have recently suggested that extra fat in an
athlete's diet may improve performance for endurance events
- this is a new area of thought and is currently not widely
recommended or practiced.
Carbohydrates
Foods rich in carbohydrate, particularly unrefined
carbohydrates like wholegrain breads and cereals, should form
the basis of the diet. More refined carbohydrate foods - such
as white bread, jams and lollies - are useful to boost the
total intake of carbohydrate. During digestion, all carbohydrates
are broken down into a simple sugar, called glucose.
Glucose is
the body's primary energy source and is delivered to every cell
via the blood. Excess glucose is converted into a substance called
glycogen and stored in the liver and muscle tissue. Once glycogen
stores are full, glucose is stored as fat, however, this storage
process requires a lot of energy.
Glycogen
Glycogen is the most important energy source for the body during
exercise.
When you exercise, the glucose present in the blood is used as
an energy source. The body converts the stored glycogen back
into glucose in order to fuel the exercising muscle tissue and
other body systems. Athletes can increase their stores of glycogen
by regularly eating high carbohydrate foods. This is particularly
important for athletes who exercise strenuously for more than
60 to 90 minutes daily.
If carbohydrate in the diet is restricted, a person's ability
to exercise is compromised due to poor glycogen storage. This
can result in a loss of protein tissue (and muscle), as well
as urinary loss of essential ions, such as potassium.
Glycaemic Index (GI)
The glycaemic index
(GI) ranks carbohydrate-rich foods based on their rate of digestion
and absorption. Moderate to high GI foods can efficiently deliver
carbohydrate to the body during exercise and recovery. This is
why they are increasingly used by sports people. However, it
is generally recommended that the bulk of the carbohydrate consumed
in the overall diet should have a low glycaemic index.
Eating should be tailored to maximise
the performance of the particular sport in which the individual
is involved. The type and timing of food eaten are often specific
for different sports and different individuals.
Pre-event Meal
A high carbohydrate meal three to four hours before
exercise is thought to have a positive effect on performance.
A small snack, one to two hours, before exercise may also benefit
performance. Some people's blood glucose levels may react negatively
to eating close to exercise - it varies between individuals.
The
pre-event meal should be easily digestible, high carbohydrate,
low fat, low fibre and known not to cause gastrointestinal upset.
Examples of suitable pre-competition snacks include fresh fruits
and juices, muesli bars (without the chocolate coating), bread,
toast, cereal with low fat or skim milk. Contrary to popular
belief, consuming sugary foods or drinks just before a sporting
event doesn't give your energy levels an immediate boost.
Eating During Exercise
If exercise lasts
longer than 60 minutes, it might be a good idea to eat some source
of carbohydrate during exercise to top up blood glucose levels
and delay fatigue. Low fat and low fibre food choices of a high
glycaemic index, such as lollies (without chocolate) and sandwiches
made with white bread, are ideal in these situations. Sports
drinks and very diluted cordial or fruit juice offer the benefit
of delivering both carbohydrate and fluid to the body.
Eating after exercise
To top up glycogen stores
after exercise, the best foods to eat are carbohydrates with
a moderate to high glycaemic index. This is best done in the
first half hour or so after exercise. This should then be followed
by foods high in carbohydrate, with a low glycaemic index. Exercise
should be avoided during recovery.
Protein
Protein is an important part of a training
diet. It plays a key role in post-exercise recovery and repair.
Protein needs are generally met by following a high carbohydrate
diet, because many foods - especially cereal-based foods - are
a combination of carbohydrate and protein.
The amount of protein
recommended for sporting people is only slightly higher than
that recommended for the general public.
For example:
• General public
and active people - the daily recommended amount of protein
is 0.75gmper kg of body weight (a 60kg person should eat around
45gm of protein daily).
• Sports people involved in non-endurance events - who exercise daily
for less than 60 minutes: daily protein intake should be between
0.75 to 1.0gm of protein per kg of body weight per day.
• Sports people involved in endurance events and strength events -
who exercise for longer periods (more than one hour) or who are
involved in strength exercise, such as weight lifting, should
consume about 1.24 to 1.7gm of protein per kg of body mass.
• Dietary surveys have found that most athletic groups comfortably
reach and often exceed their protein requirements by consuming
a high energy diet. Despite this, protein and amino acids (the
building blocks of protein) are popular nutritional supplements.
Water
Heavy sweating depletes the body of water. Dehydration
can impair athletic performance and, in extreme cases, can lead
to collapse and even death. Drinking plenty of fluids before,
during and after exercise is very important. The thirst mechanism
should not be relied upon as a reliable indication to drink.
Following
exercise, you should drink 500ml of water for every 0.4 to 0.5kg
of weight lost during exercise. Fluids are especially important
in warm and humid conditions. Water is the preferred fluid in
most situations. Sports drinks may be useful in ultra-endurance
events (greater than 90 minutes) or when a quick recovery is
necessary. If you prefer taking commercially prepared sports
drinks, make sure that they are low in sodium - no more than
about 30mmol (millimoles) per litre. Sodium can interfere with
glucose getting into the cells and may exacerbate dehydration.
Pregnant
women, children, adolescents and the elderly should pay particular
attention to their fluid intake.
The use of salt tablets to combat muscle cramps is no longer
advised, since it is lack of water - not lack of sodium - which
affects themuscle tissue. Persistent muscle cramps might be
due to zinc or magnesium deficiencies.
Things to remember
• Good nutrition
can enhance sporting performance.
• Carbohydrate should form the basis of the diet.
• Athletes can increase their stores of glycogen by
regularly eating high carbohydrate foods
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