// The facts about dehydration

by Mizone

What is dehydration?

Dehydration is the excessive loss of water and salts from the body. Water is essential for the body to maintain blood volume, regulate body temperature and allow muscles to function properly. Along with water the body also needs electrolytes, which are salts normally found in blood, other fluids, and body cells to stay hydrated.

How do I become dehydrated?

During exercise, the core body temperature rises, blood flow to the skin increases and the body attempts to cool itself by sweating. Heat is removed from the body when beads of sweat on the skin evaporate, resulting in a loss of body fluid. Sweat production, and therefore fluid loss, increases with a rise in temperature and humidity, and with an increase in exercise intensity.

Dehydration can develop quickly under some conditions such as extreme heat, and so it is important to monitor the body and continually consume fluids before dehydration occurs. 

How can I tell if I’m dehydrated?

Some people think that thirst is the first sign of dehydration. However, by the time thirst sets in, as much as two per cent of your body’s water is already lost. The colour of urine is the simplest indication of the body’s level of hydration. If it is clear or lightly coloured, the body’s hydration levels are normal. If it is dark yellow, the body is dehydrated (or has consumed large amounts of vitamin B and/or C).

How does dehydration affect my body?

As dehydration increases, there is a gradual reduction in physical and mental performance, and the body will experience an increase in heart rate (beats per minute) and body temperature.

Common indicators of dehydration also include:

• Increased thirst, dizziness and dull headaches (thirst is the body’s way of saying it is already dehydrated).
• An increase of lactic acid in muscles (increased blood acidity), causing muscles to lose strength and tire easily.
• An increased perception of how hard the exercise feels, especially when exercising in the heat.
• Slower reaction times, concentration and decision-making ability.
• A decrease in blood volume and a thickening of the blood, forcing the heart muscles to work harder to pump oxygen and glucose to the muscles.
• Heat cramps, heat exhaustion and heat stroke.

How do I combat dehydration?

It is vital to drink before you become dehydrated. To avoid dehydration and get the most out of your body, ensure you drink plenty of fluids before, during and after any physical activity.

This can be in the form or plain water or sports water, for short or gentle exercise, but for longer and more extreme activity, the fluid should also include small amounts of carbohydrates, usually in the form of glucose.

Drinking fluids after physical activity will help your body recover, repair and rehydrate.

It is also worth remembering that improved hydration has been shown to be effective in aiding weight loss and body fat loss, enhancing the body’s ability to withstand high intensity aerobic exercise, and improving sporting performance.

How much fluid should I drink?

The amount of fluid and recommended intake timings depend on the individual and the intensity of physical activity. These factors include how much you sweat, your body size, your fitness level and the environment. Generally, bigger athletes sweat more than smaller athletes, and fitter people sweat earlier into an exercise session and in larger volumes. Sweat losses also increase in hot or humid conditions and as exercise intensity increases.

There are no set fluid guidelines on how much fluid you should drink to effectively rehydrate. It is important to monitor your own fluid loss after exercise, and the simplest way to do this is by measuring your body weight before and after exercise, with the difference being a good indication of how much fluid you have lost. Generally, one kilogram of body weight equals one litre of fluid, so aim to replace one
and a half times the fluid lost as soon as possible after you have finished exercising.

Drinking more fluid than is comfortable can interfere with good performance. In cool weather or with gentle exercise the rate of sweat loss may be lower, and is potentially dangerous to drink at rates that greatly exceed the rate of sweat loss.

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Information supplied by Mizone. For more hydration tips visit www.mizone.com.au