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HYPONATRAEMIA
During exercise, more sodium is lost in sweat than is usually
replaced by food and fluids. Your body can tolerate a degree of
imbalance for a short period of time. If the imbalance continues
for too long, sodium in the bloodstream is diluted and
hyponatraemia (low concentration of sodium in the blood)
results. Long runs and races carry a greater risk of
hyponatraemia because of the total amount of sweat lost.
Adequate hydration and sodium intake - either via sports drinks
or food - becomes vitally important during long races (or long
training runs).
Symptoms of hyponatraemia can range from mild to severe and can
include nausea, muscle cramps, disorientation, slurred speech,
confusion, and inappropriate behaviourr.
As it progresses, seizures or coma may result. Severe
hyponatraemia is a true medical emergency.
Minor symptoms, such as nausea and mild muscle cramps, can be
treated by eating salty foods and hydrating with a sodium
containing sports drink. More severe symptoms require treatment
by qualified medical personnel. If you think you are suffering
from hyponatraemia or are unsure, seek medical attention
immediately.
Some authorities recommend drinking less water to rebalance
sodium and water intake. However, given the risk of dehydration
and heat injury, this is not a practical recommendation.
Increasing salt intake seems more prudent. By ingesting more
sodium, hydration with water is balanced and dilution of blood
sodium does not occur.
Rehearse your hydration, feeding, and salt strategy during your
training sessions. There are so many variations between
individuals that there is no single right answer. Know what your
body's' needs are.
It is best if you strive to get your sodium from both sports
drinks and salty foods - as opposed to salt tablets - for two
reasons. Salty foods stimulate thirst, and it is possible to
ingest too much salt with tablets but very difficult with food.
One litre of sports drink contains approximately 500mg of
sodium, half your hourly requirement. The remainder may come
from food sources such as half a vegemite sandwich.
If you don't think that your food and sports drink is providing
enough sodium, then consider salt tablets. But make sure you
know how much you are taking, and only do so under medical
supervision.
Some practical pointers for you to remember include:
·
Drink frequently to attempt to stay hydrated.
· During
a long, hot race, aim for a total sodium intake of approximately
1 gram per hour. Please note that this may not be appropriate
for everyone.
· During
training, heat acclimatisation, and for several days leading up
to a big race make sure sodium intake is not too low.
·
Sodium is also important for recovery.
· Anti-inflammatories,
diuretics, narcotics, and certain psychiatric medications should
be avoided during exercise, but especially during a race as they
interfere with kidney function and may contribute to the
development of hyponatraemia in athletes.
· Check
with your doctor if you have any health problems.
Kerith Duncanson
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