This series of articles concentrates on Taekwondo, but is applicable to any martial art...

You continuously lose fluid while exercising – mostly through sweating, but also as through breathing. Exercise produces heat which can be dangerous for your inner body which should stay at 37- 38ºC. If your temperature raise too high, normal body functions are upset. Therefore your body uses sweating as to cool you down. The amount of fluid you lose through sweat depends on how hard you are exercising; how long you are exercising for; the temperature and humidity and your individual chemistry. Obviously the harder and longer you exercise, and the hotter and humid it is, the more you will be sweating.

An average person can expect to lose about 1 litre or more of fluid in an hour of exercise. You can determine the approximate amount of fluid loss you suffer during exercise by weighing yourself before and after training. Every 1 kg of weight loss is equal to about 1 litre of fluid loss.

Fluid loss and exercise

A loss of just 2% in your body weight will affect your performance – your aerobic capacity will deteriorate by 10-20%. A loss of a further 2% may induce nausea, vomiting and diarrhoea. An excessive loss of fluid (dehydration) will adversely affect your performance. Your blood volume decreases and your body temperature rises. This places an unwanted burden on your heart, circulatory system and respiratory system. Symptoms of dehydration include sluggishness, a sense of tiredness, headaches, loss of appetite, feeling hot, feeling light-headed and nausea. Many people are unknowingly suffering from mild dehydration. I good indicator is your urine.

Dark coloured urine of a small volume is an indication that you may be dehydrated. Ideally your urine should be of good volume and a pale straw colour.

Fluid intake

Before exercise

From the discussion above it is clear that a body not probably hydrated will not perform properly. It is therefore imperative that you are well hydrated before you start exercising. It is recommended to drink approximately 500 ml of fluid or as much as you comfortably can about 2 hours before exercises.

During exercise

Apparently you can maintain optimal performance if you replace at least 80% of the fluid loss during training. Do not wait to feel thirsty or save your drink until later stages in your workout. Drink early and at regular intervals. Aim for 150-350 ml every 15 minutes. If you feel nauseous when you drink during exercise it is probably because you are already dehydrated. Avoid this by making sure you are well hydrated before you start exercising and drinking early on in your training session.

After exercise

Researches suggest drinking about 150% of the fluid lost during exercise. Using the principle of every 1 kg weight-loss being equivalent to about 1 litre of sweat you can easily calculate the amount of fluid to take after exercise. If you lost 1 kg, you would need to drink 1.5 litres of fluid. Drink as much as you comfortably can and finish the rest in divided doses.

What to drink

Before exercise

Water is an appropriate pre-exercise drink, but you can benefit from a sports drink that also provides carbohydrates. Consuming carbohydrates about 3-4 hours before exercise and then drinking water 2 hours before exercise will be equally effective.

During exercise

During low- or moderate-intensity exercise lasting less than 1 hour, your fluid losses are likely to be relatively small. You can easily top up with water during the training session. During high-intensity exercise lasting less than 1 hour you may find a sports drink3 or diluted fruit juice beneficial. During high-intensity exercise lasting longer than an hour you will benefit from rapid fluid replacement and fuel replacement. You therefore not only need fluid to keep off dehydration, but also need to avoid early glycogen depletion and low blood sugar. Drink about 1 litre of sports drink per hour. In hot and humid conditions you may be losing more than 1 litre of sweat per hour.

The typical Taekwondo training session usually spans around an hour and a half to two hours, of which about 1 hour may be high-intensity. Depending on the intensity of the exercise and the length of the training session drink a sports drink or diluted fruit juice as suggested above.

After exercise

A sports drink or diluted fruit juice (with ¼ teaspoon salt) is probably better than water directly after exercise.

What about other drinks

Many people choose soft drinks (such as Coca Cola) or fruit juice to replenish their fluid intake and provide extra fuel. These drinks are not ideal as they are too concentrated to be fluid replacers during exercise. Because of their concentration they could actually cause further dehydration! Fruit juices diluted one part fruit juice with one part water works well for rehydration and refuelling during or after exercise.

Alcoholic drinks

Some athletes may choose to consume alcohol before exercise (or competition) as it may appear to increase alertness and give confidence. Drinking alcohol before or during exercise is bad for all exercises, especially for Taekwondo. Bean (2003, 95) gives the following reasons:

• Alcohol reduces coordination, reaction time, balance and judgement.
• Alcohol reduces strength, power, speed and endurance.
• Alcohol reduces your ability to regulate body temperature.
• Alcohol reduces blood sugar levels and increases the risk of hypoglycaemia.
• Alcohol increases water excretion (urination) and the risk of dehydration.

Alcohol increases the risk of accident or injury.