Athletes can lose between 2-3 litres of sweat during 90 minutes of intense exercise, particularly in hot and humid conditions. They can also lose as much as 2-3 kg (4½-6½ lbs) in body weight during the same period. This amount of fluid loss will certainly have a negative affect on performance.
Ideally to counteract dehydration, athletes should consume 200-400 ml (7-14 oz) of cold water or a suitable carbohydrate solution 5 to 10 minutes prior to the start of their event. During the any intervals, they should try to drink another 300-500 ml (10-17oz) of a sports drink. During hot weather or strenuous training sessions, coaches should try to provide their athletes with 150-250 ml (5-8oz) of drink about every 20 minutes.
Following a match or hard training session, it's essential that lost fluids be replaced. Water on its own is fine, but to replace fluid AND replenish energy stores, a high carbohydrate drink may be more suitable.
Drinking Before & During Competition
The right carbohydrate drink taken before and during composition can postpone fatigue and stabilize blood sugar preventing light-headiness, headaches, nausea and "jelly-like" muscles. However, not all carbohydrate drinks are created equal. Too much carbohydrate or sugar can actually hinder performance.
A solution that contains 40% carbohydrate empties the stomach much slower than plain water (which is 0% carbohydrate). This means that high sugar drinks such as Coca Cola, regular Lucozade, Exceed High Carbohydrate Source and Gator Lode (up to 40% carbohydrate) are NOT the best fluids to consume before or during exercise.
The ideal sports drink should contain 6-8% carbohydrate. It should also contain a small amount of salt. Sodium concentration in the blood can reduce due to sweating and drinking lots of diluted fluids. If it gets too low it can lead to nausea, headaches and blurred vision. Adding just a pinch of salt can offset this potential danger.
Sodium is also an electrolyte. Electrolytes help control the passage of water between body compartments and they also help to maintain the acid-base balance of the body. Electrolytes (or lack of them) have been associated with muscle cramps in the latter stages of sport games.
Here are some effective sports drinks currently on the market suitable before and during a match or training session:
Drink 200-400 ml (7-14oz) of a suitable sports drink 5 to 10 minutes before the start but no earlier unless it's several hours before the start. During any intervals drink up to 300-500 ml (10-17oz). In hot climates try to drink 150-250 (5-8oz) ml every 20 minutes or so.