As an exercise professional I come across so many people who complain of physiological problems which are connected to the effects of de-hydration, so before we really get into the height of summer please take heed of the following information.

Exercise is thirsty work and your body fluid losses can be very high. If they are not replaced quickly then this can lead to dehydration. Prevention is better than cure, so what and how much should you be drinking?

Why is drinking important?

During exercise, your muscles produce heat. This must be expelled in order to keep your body working properly. Sweating is the most important way in which this happens. For every 600 calories of heat energy your body expends, you lose around a litre of sweat. During exercise you also lose fluid through the water vapour in the air you breathe out. The harder and longer you are exercising, and the hotter and more humid the environment, the more fluid you lose. During an hour’s workout you can expect to lose up to one litre (about 2 pints) of fluid – even more in hot conditions.

What are the dangers of dehydration?

If you carry on exercising without replacing fluid loss, You will become dehydrated. This will have an adverse effect on your physical performance and health. Exercise becomes much harder to perform, and you will fatigue sooner. A loss of just 2% of your weight will affect your ability to perform muscular work. A loss of 4% and you may experience nausea and vomiting. An 8% drop will cause dizziness, laboured breathing, weakness and confusion. Any drop beyond this could have very serious consequences. If you suffer from any of the following signs and symptoms then you are suffering from de-hydration!!!!

Thirst * Decreased urine output * Dry mouth * Eyes stop making tears * Sweating may stop * Muscle cramps * Nausia and vomiting * Heart palpitations and many more problems without realising.

When should I drink?

Prevention is better than cure therefore make sure you are well hydrated before you start exercise. Drink plenty of fluid beforehand, especially in hot and humid weather. If you work out in the evenings make sure you have had enough fluid during the day (at least 1.5 litres). If you train in the morning, make sure you have plenty to drink first thing. Continue to take in fluid at suitable intervals during exercise whenever possible. Drink as much as you comfortably can – aim for about a quarter of a pint every 15 minutes. Drink freely after exercise to replace lost fluids.

Don’t wait until you feel thirsty, as this means you are already dehydrated. The message is; drink before you are thirsty and before you become dehydrated.

What should I drink?

Water is an excellent fluid replacer. After all, this is mostly what you are losing in sweat, so this is what your body needs. If you are sweating profusely or exercising for over 1 hour, a dilute carbohydrate drink (up to 8g per 100ml) will help speed up water absorption and provide extra fuel. Dilute squash, diluted fruit juice or a commercial sports drink are also suitable. Avoid more concentrated drinks such as cola during exercise as they can exacerbate dehydration. They need diluting in the stomach before thy can be absorbed so delaying absorption. Carbohydrate supplements, based on glucose polymer (maltodextrins), provide up to 20tg carbohydrate per 100ml and my benefit performance only if you are exercising intensely for more than 90 minutes and sweat losses are low.

Hypotonic, Isotonic, Hypertonic – What’s the difference?


Hypotonic drinks e.g. fruit juice diluted 1:3 are less concentrated than your body’s fluids. That is, they have fewer dissolved particles per 100ml (usually 2-3g per 100ml) they are designed to be absorbed more rapidly than water and, therefore, achieve faster dehydration.


Isotonic drinks, e.g. fruit juice dilated 1:1 have the same concentration of dissolved particles as your body fluids (usually 4-8g per 100ml). They will be absorbed either at the same speed as water or slightly faster, depending on exercise conditions.


Hypertonic drinks, e.g. undiluted fruit juice, on the other hand are more concentrated than your body fluids and will be absorbed less quickly into your body.

Chris Haney is your local Personal Trainer based at Esport gym in Hondon de los Frailes, and is always available to advise you how to correctly exercise and follow a good dietary plan. Telephone 679 008 021
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