All athletes know the importance of avoiding dehydration during exercise. When exercising for more than thirty minutes it may be useful to drink something that replaces sweat losses (water and electrolytes) and energy.
Depending on whether it is necessary for an athlete to replace fluid losses, replace energy stores or replace both fluids and energy, the athlete should choose one of three types of drinks – hypotonic, isotonic or hypertonic. These drinks can be made at home using your favourite squash or fruit juice.
Hypotonic drinks are absorbed into the body more quickly than plain water. They usually contain low levels of carbohydrates (sugars) – less than 3g per 100ml – and may have a little salt added. These drinks are thirst quenching and provide fluid but they do not provide significant amounts of energy.
Hypotonic drinks are useful when it is necessary to replace fluids quickly without a lot of carbohydrate – for example, when activity lasts less than one hour and is of low intensity. They can also be useful if a high fluid intake and low calorie intake is required – for example, when exercising in a hot climate.
Recipe #1 – 100ml fruit squash, 900 ml water, 1/5th teaspoon salt (1g)
Recipe #2 – 250ml fruit juice, 750ml water, 1/5th teaspoon salt (1g)
Isotonic drinks are absorbed as fast as or faster than plain water. In addition to replacing fluids, isotonic drinks provide carbohydrates – 5-8g per 100ml. These drinks are designed to provide some carbohydrate to fuel the muscles, and have a little salt added to enhance the absorption and retention of fluid in the body. Many commercial sports drinks fall into this category.
Isotonic drinks are good for replacing fluids and providing carbohydrates (sugars) if activity lasts more than an hour, such as team sports or endurance events. Drink before, during and after exercise.
Recipe #1 – 50-70g glucose or sugar, 1 litre water or diluted sugar-free squash, 1/5th teaspoon salt (1g) – dissolve the glucose or sugar and salt in 100ml warm water before adding the remaining 900ml cold water or sugar-free squash
Recipe #2 – 500ml unsweetened fruit juice, 500ml water, 1/5th teaspoon salt (1g)
Recipe #3 – 150ml high juice squash, 850ml water, 1/5th teaspoon salt (1g)
Hypertonic drinks have a higher carbohydrate content – usually more than 10g per 100ml – which fuels the muscles. Hypertonic drinks are absorbed more slowly than plain water. These drinks replace lost energy rather than replacing fluids and therefore are not an effective or fast way to rehydrate. Hypertonic drinks include pure fruit juice, many canned drinks and energy drinks.
Hypertonic drinks should be taken when energy replacement is a priority – for example after training or after a game. These drinks can be used to top-up your daily carbohydrate intake.
Recipe #1 – 400ml squash, 1 litre water, 1/5th teaspoon salt (1g)
Stimulant drinks – these drinks usually have a high carbohydrate content but also have other additives that supposedly provide more energy – such as herbs, caffeine, guarana, taurine, ginseng, or carnitine amongst others. There is no evidence that these additives have a beneficial effect on sports performance and they should generaly be avoided during sport.
Water – the drink of choice for many people because it is cheap and readily available. Water will replace fluid losses but will not provide any energy. Water is good for non-endurance events of low intensity, where carbohydrate replacement is not the priority. Large intakes of water will dilute the blood, which stimulates urine output and effectively dehydrates the body. Fluid overload can be minimised by adding salt to a drink.
For extreme or endurance events, such as activity in hot weather or marathon events (prolonged moderate to high intensity activity), seek specific advice regarding hydration.
Top tips for athletes
- Choose a drink that best matches your needs – water, hypotonic, isotonic or hypertonic
- Always take a full drinks bottle to training and competitions
- Cool drinks are more refreshing and palatable
- Start drinking early – about two hours before starting exercise – do not wait until you feel thirsty because by this time you will already be dehydrated
- Immediately before exercise drink about 150-350ml, then continue taking small amounts of fluid (150-200ml) every 15-20 minutes
- Start drinking as soon as possible following training or competition – after exercise athletes should aim to replace fluid losses within the first two hours of recovery (this is more important when multiple training sessions occur during the same day)
Even mild dehydration can reduce sporting performance. Dehydration can have physical effects including reduced muscular strength, increased perception of effort, fatigue and slowing of self-selected pace. Dehydration can also affect mental performance including reduced concentration, reduced skill or accuracy and reduced decision making ability.
Athletes should choose a drink they enjoy and which meets their needs to optimize sporting performance.
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Enjoy Good Food for Good Health