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Research Fact Paper by the International
Association for Dance Medicine and Science.
To perform
at their best, dancers need to be well fueled for classes, rehearsals,
and performances. This paper will present a strategy for obtaining
the energy needed for dance training and the right balance of carbohydrate,
fat, protein, micronutrients, and fluids.
One important challenge facing many dancers
is ingesting sufficient quantities of food to meet the energy demands
of dance. The first step in planning a high performance diet is
to be sure that the dancer is obtaining adequate caloric intake.
The easiest rough estimate of how many calories a dancer requires
during heavy training is 45-50 calories per kilogram of body weight
for females and 50-55 calories per kilogram of body weight for males.
For a more accurate assessment, dancers should consult a dietitian.
A low caloric intake will not only compromise
energy availability, it can also lead to an under-ingestion of many
micronutrients that could affect performance, growth and health.
After calculating the number of calories needed, the next step is
to estimate the necessary amount of carbohydrate, fat, and protein,
the building blocks of the diets.
Carbohydrate
A dancer's diet should be composed of about 55-60% carbohydrate,
12-15% protein, and 20-30% fat. During heavy training and rehearsals
the amount of carbohydrate should be increased to about 65%. The
reason is that carbohydrate is the major energy source in muscles.
Ingested carbohydrate is broken down into simple sugars (glucose)
in the digestive tract then stored in muscle in the form of glycogen,
the primary fuel for energy production. Dancers who do not ingest
sufficient carbohydrate in their diet will compromise their ability
to train because of low muscle glycogen levels. They may feel more
fatigued during classes and rehearsals.
To achieve a high carbohydrate diet,
food choices should be complex carbohydrate (cereal, bread, English
muffins, pasta, rice) rather than simple sugars. This is because
complex carbohydrate has many micronutrients associated with it
(nutrient dense) while simple sugars are nutrient poor. The estimated
carbohydrate need is 6-10 grams of carbohydrate per kilogram of
body weight.
In addition to meals, other times when
carbohydrate ingestion is important are before, during, and after
class, rehearsal, or performance. About 1-2 hours prior to these
activities, a small carbohydrate snack should be consumed. This
will increase glucose levels in the circulation and "top-off"
muscle glycogen stores. A carbohydrate snack, such as a bagel or
commercially available "energy" bars, can provide the
added boost needed for optimal performance.
During long rehearsals it is also important
to eat some carbohydrate to maintain circulating levels of glucose
to prevent fatigue. A good way to ingest this carbohydrate is in
solution such as sports drinks that are specially formulated to
contain the right amount of carbohydrate (6-8% glucose) to empty
from the stomach quickly. Ingesting carbohydrate in a solution provides
the added benefit of fluid replacement.
After a period of dancing, the muscles
require an adequate supply of carbohydrate to replenish the muscle
glycogen stores. Because the fastest rate of glycogen re-synthesis
occurs in the 2 hours following exercise, it is important to ingest
carbohydrate as soon as possible after a long or strenuous exercise
period to refill muscle stores and be ready for the next activity.
Fat
Fat from the diet provides structure for all cell membranes, comprises
the insulating layer around nerves, forms the base of many hormones,
is needed for the absorption of fat soluble vitamins, and is an
important fuel for muscles. The estimated grams of fat in the diet
are about 1.2 gm per kilogram of body weight. Because ingestion
of high amounts of saturated fats is associated with chronic disease,
the recommended amount of saturated fat in the diet should be less
than 10%.
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| Muscle
and adipose (fat) tissue store fat in the form of triglycerides.
During exercise, triglycerides are broken down into fatty acids
which are metabolized to produce energy for muscle contraction.
Fatty acids are used as an energy source in the muscle for endurance
activities such as during a long rehearsal where the body is
continuously exercising for over 20 minutes at a time. A diet
too low in fat can have serious health consequences and ultimately
can impair performance.
Protein
Adequate protein ingestion is essential for all dancers who
are training. For those dancers who are not building muscle,
protein is needed to repair the breakdown of muscle fibers
that are stressed by constant use. Protein is also used as
an auxiliary fuel, and it is important for synthesizing the
many enzymes necessary for metabolism. The estimated protein
need is 1.4-1.6 grams of protein per kilogram of body weight.
For non-vegetarians, chicken or turkey without the skin are
excellent low fat protein sources. For vegetarians, tofu,
seitan (wheat gluten), and mixtures of beans and rice are
good protein choices. Protein powders are not necessary, even
for male dancers, if they are following the recommendations
above. If a protein supplement is warranted, the best choice
is milk powder. The high tech and expensive protein supplements
on the market are not any better than simple dry milk.
Micronutrients
Vitamins and minerals comprise the micronutrients in the diet.
Water soluble vitamins are the B vitamins and vitamin C. Vitamins
A, D, E, and K are fat soluble. The B vitamins play important
roles in energy production (especially thiamin, riboflavin,
niacin and vitamin B6) and in red blood cell formation (folic
acid and vitamin B12). Deficiency of these vitamins can impair
performance. Vitamins A (beta carotene), C, and E function
as antioxidants that are necessary for the repair of over-stressed
muscles and are needed to help muscles recover from strenuous
classes and rehearsals. Vitamin D is important in bone formation.
Minerals are classified into macrominerals
that are needed in levels of over 100 mg/day and microminerals
(trace minerals) that are needed in levels of under 100 mg/day.
Macrominerals are calcium, phosphorus, and magnesium, but
only calcium will be discussed because of its importance for
dancers. There are 9 trace minerals but only iron and zinc
will be discussed because of the possible deficiency of these
minerals in dancers.
Calcium is important in bone formation.
During the first 2-3 decades of life bone mass is developed,
and thereafter bone formation ceases. It is essential to ingest
adequate calcium during the bone growth years. Low bone mass
and low calcium intake are also associated with increased
risk of stress fractures. The richest source of calcium is
dairy products.
Iron is a trace mineral needed
to carry oxygen in the blood because it forms part of the
haemoglobin molecule. Oxygen is used for the production of
energy in muscle cells. Dietary iron is of two types, the
heme, found in meat, and non-heme, less absorbable type found
in plants. Dancers should include some lean red meat in their
diet to obtain adequate iron. However, if dancers are vegetarians,
then they should be careful to ingest foods rich in iron,
like whole grains. Because vitamin C increases the absorption
of non-heme iron, ingesting a source of vitamin C along with
food will maximise absorption of non-heme iron. Red meat is
also a good source of zinc which is a component of several
enzymes important in energy production and plays a role in
red blood cell production.
Dancers should be cautious about
taking vitamin and mineral supplements because supplements
containing only selected micronutrients could do more harm
than good. Excessive amounts of one can interfere with the
absorption of another, and megadoses of some vitamins and
minerals could be toxic. Adjusting the diet so that it is
rich in micronutrients is the recommended means of obtaining
necessary micronutrients. Furthermore, there are numerous
phytochemicals in food that impart important health benefits.
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To obtain all important micronutrients,
dancers should increase the amount of fresh fruit and vegetables
(recommended 5 servings of fruit or vegetables per day), whole
grains, dairy products, and lean red meat. Because not all
vitamins or minerals occur in all foods, dancers should ingest
a wide variety of foods. A calorie restricted or monotonous
diet could lead to a deficiency in some of these vitamins
and could impair the ability to train strenuously and recover.
As an insurance policy, a multivitamin/mineral supplement
containing equal to or less than the recommended level of
each micronutrient will provide a balance that is not harmful.
Read the label carefully before purchasing a vitamin/mineral
supplement.
There are many dietary supplements
on the market designed to enhance performance or decrease
body weight. Dancers should be warned that these supplements
are ineffective or even dangerous. Dietary supplements can
be marketed without adequate proof that they are effective
or safe.
Fluid
Exercise increases heat production by muscles. Cooling the
body depends on evaporation of sweat from the skin. Sweat
losses during a hard class or long rehearsal can be substantial-up
to 2 litres/hour. Fluid loss results in dehydration that can
impair performance and mental functioning, such as the ability
to quickly pick up complicated choreographic combinations
and execute them effectively. A cup (250 ml) of fluid every
15 minutes is recommended. Whenever there is a break in class
or rehearsal, the dancer should have ready access to fluid,
and they should be encouraged to drink because the thirst
mechanism does not keep up with the body's need for fluid.
A water bottle or sport drink should be part of a dancer's
"gear," and, if possible, the dancer should be able
to bring the bottle into the studio for frequent drinks. Following
class and rehearsal, dancers should continue to increase fluid
consumption for the next few hours. Avoid carbonated drinks
and large quantities of fruit juice.
A simple way to monitor hydration
is to check urine color: clear to light yellow is hydrated;
yellow to dark yellow means dehydrated. One caveat, vitamin
B supplements will result in yellow urine and make this dehydration
"test" inaccurate.
All dancers need to ingest sufficient
energy to meet the rigors of hard training. Consuming the
right amounts and types of food and fluid will provide the
body with "high performance fuel" necessary to achieve
optimal training benefits and peak performance.
Written by Priscilla Clarkson,
PhD, under the auspices of the Education Committee of IADMS.
With special thanks to Elizabeth Snell, BSc, RD.
This paper has been reproduced
for educational purposes, to provide you, as a dancer with
important nutritional information.
For further research papers and
information about the International Association for Dance
Medicine and Science visit www.iadms.org
17th Annual IADMS Meeting
25th-18th October 2007
Canberra, Australia
To register click
here
©2003-2005 International Association
for Dance Medicine and Science (IADMS)
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