WATER - REQUIREMENTS DURING EXERCISE
Loss of Body Water During Exercise
During exercise our muscles use ATP energy. Only 25%
of this energy is used by the muscle; the other 75%
is released as heat. Heat from the working muscles is
transferred to the blood. The blood flow to the skin
is increased, and the heat is lost through evaporation
- sweating. Sweat comes from the water in your blood;
you need to replace this fluid or you'll become dehydrated.
Water Needs During Exercise
On average, the human body has 2.5 million sweat glands.
The more you sweat during exercise, the more fluid you
lose and the more you need to drink. How much water
you need during exercise depends upon:
- Your natural tendency to sweat - some people naturally
sweat more than others.
- How fit you are - the fitter you are, the more
effectively you keep your body cool - so the more
- Training Intensity - Training harder and longer
- Training Ambient Environment - hotter and more
humid surroundings, will also make you sweat more.
Estimating Your Water Requirements During Exercise
How much water you should consume during exercise
can be estimated by either:
- Simple Calculation - Average loss
= one litre of fluid for each hour we exercise.
- Weight Check - Weigh yourself
before and after exercise. Each kg of body weight
loss is equivalent to a litre of fluid loss. Drink
1.5 litres of fluid for every kg of weight lost. [You'll
lose further fluid as urine]
- Urine Check - Another way is to
check your urine: if it's pale and plentiful you're
well-hydrated; if it's dark and in short supply you'd
better start drinking!
Impact of Water on Exercise Performance.
A loss of 2% of your body weight [1.4kg if you weigh
70kg] - will affect your ability to exercise. There'
is a 5% drop in performance for every 1% loss in body
Exercising without replacing the fluid lost, will
lead to dehydrated. This affects your bodys ability
to keep cool, your body temperature will start to rise,
you'll begin to feel nauseous and lightheaded, ending
up with fatigue or heat stroke.
When to Take Water During Exercise
Water should be consumed before, during and after exercise.
- Before - Drink 300 to 500ml of
fluid in the 15 minutes prior to your workout.
- During exercise - drink 150 to
250ml every 15 minutes to offset fluid losses.
- After exercise – drink at
least 500ml or more, according to the calculations
you make based on all exercise factors.
When Sports Drinks Are Better Than Water
If you are exercising at a low to moderate intensity
for less than an hour, water is great.
If you have been sweating very heavily for more than
one hour, a sports drink containing sodium will prevent
a drop in your blood sodium levels (hyponatraemia),
and speed up fluid absorption. Most sports drinks generally
contain 5 to 8g of carbohydrate in every 100ml. This
makes them 'isotonic' - a similar concentration to blood
- and therefore quickly absorbed. The added carbohydrates
also provide the vital glucose to help avoid fatigue.
Alcohol and Exercise
Do not drink alcohol just before exercise and avoid
it afterwards until you have properly re-hydrated. Alcohol
before exercise effects coordination skills and exercise
performance, increasing the risk of injury. Alcohol
can also cause dehydration and slow recovery from injury.
about water filtration systems.
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