Importance of Staying Hydrated

Hydration
Water is the most abundant, yet overlooked, substance in the body. The body's fluid status is a fragile balance, so much so that experts rank water second only to oxygen as essential for life. Water plays a vital role in all bodily processes by providing a universal medium for chemical reactions, lubrication, nutrient delivery, waste disposal, heat dispersion and temperature regulation.

Exercise significantly increases fluid loss which can reach levels of up to 4 liters per hour during heavy work-outs. A loss of body mass through dehydration of as little as 2% significantly impairs performance (Armstrong et al 1985) which emphasizes the importance of the maintenance of hydration, especially during exercise.

But how does dehydration affect the body? And how does the body recognize it has a problem with fluid loss? Blood plasma is 92% water, and therefore, dehydration reduces the volume of blood in the body which makes the heart work harder to pump the blood around the body and deliver oxygen to the working muscles. Exercise feels much harder as your body's systems aren't working as efficiently as they do with good hydration and performance is impaired. As dehydration progresses, nausea and vomiting may be experienced and by 5% reduction in total body weight, performance has dropped by 30%. Fluid loss greater than 5% creates weakness, confusion and dizziness leading ultimately to coma and death if fluid isn't replaced immediately.

The World Health Organization recommends drinking 6 to 8 large glasses of water a day, but this is only to maintain normal fluid balance. This does not take into account the extra fluid demands of exercise.
Drink at least 8oz of water before exercise to ensure your fluid levels are up when you start exercising and then continue to take in as much as you can during exercise.

To the majority of recreational exercisers thirst is viewed as an indicator that they need to drink or they will become dehydrated. In fact, thirst is a sign that the person is already dehydrated; also the thirst mechanism tends to be depressed during exercise which increases the level of dehydration before thirst is sensed. This is why fluid replacement should be considered before, during and after physical activity rather than relying on thirst to determine when the body needs fluid.

If the exercise lasts for less than an hour the body should have sufficient electrolyte and carbohydrate supplies to maintain optimal performance. Therefore, for short periods of exercise water is just as good as sports drinks. Exercise that lasts for over an hour, a drink with electrolytes and carbohydrates will aid performance by supplying additional energy. Contrary to popular opinion a relatively small amount of sweat is salt (0.2 to 0.4%) therefore unless the climate is extremely hot or the activity is over an hour in duration, additional salt should not be necessary.

There is always a tendency to think that water is plain and that additional ingredients will improve it. However, in actual fact, water is the best fluid you can choose for exercise of an hour or less in duration. If you think water is just water then think again. It is worth considering what type of water to use.

Types of Water

Spring: Comes from an underground source and must meet Drinking Water in Containers Regulations and can be treated if necessary.
Purified: Can be drawn from any source and can be artificially processed and chemically treated to make it drinkable.
Tap: This water is chemically purified and on average recycled 9 times, when bottled, tap water may be termed 'purified' or 'table' water.
Practical Recommendations for Fluid Replacement


Drink one tall glass of water at every meal, plus one glass between every meal. If you follow this plan, you will be drinking 5 glasses of water throughout the day, and with about 2 cups of water per glass, this equals approximately 10 cups of water. Another plus to drinking water before, during, and after your meals is that it helps you feel satisfied while consuming less food and consequently, fewer calories. Liquid allows your food to expand in while you eat, curbing your hunger. It also helps you eat slowly, which is another important tactic for eating in moderation.


Don't rely on thirst. Drink before, during and after any physical activity. Get into the habit of taking on fluids during training as well as competition.

It is also important to realize that many foods we eat contain water. Fruits and vegetables obviously contain water, which gives them their juicy nature. Other foods, such as cooked rice and grains, dairy, casseroles, and soups are all rich in water, which again, can help you feel satisfied while consuming fewer calories and fending off excess body weight.

The best way to stay hydrated is to follow a schedule for hydrating your body, which will date back to a few hours before your sporting activity, but needs to be followed;

• Begin drinking fluids on a regular basis, 2-3 hours before your sporting activity.
• Drink 250ml 15 minutes before exercise.
• Drink 250ml every 15 minutes exercise.


References:

American College of Sports Medicine (1996) advise on fluid intake
Armstrong et al (1985) , Medicine and Science in Sports & Exercise, 17: 456-461
Davis & Brewer (1997), Journal of Sports Sciences, 15(1):44-45