Sports drinks can be expensive to buy in the quantity you need to stay hydrated while you exercise. If you know a little more about what sports drinks are and how they work it can help you make good decisions about what to drink before, during and after exercise.
Commercial sports drinks provide energy and help people rehydrate during or after exercise. They usually contain the carbohydrate, glucose, which is needed by muscles as an energy source while they are working hard. Sports drinks also contain sodium, chloride, calcium, magnesium and potassium (electrolytes) to replace what is lost in sweat. These electrolytes are required to maintain fluid balance and to keep muscles working properly.
Sports drinks can help delay the onset of fatigue during exercise and prevent dehydration. The concentration of any drink affects how quickly it is absorbed from the small intestine. The more concentrated it is the more slowly it is absorbed.
It is important for any fluid drunk before or after exercise not to be too concentrated because it will not be absorbed very efficiently.
There are three main types of commercial sports drinks available.
Isotonic drinks contain similar concentrations of salt and sugar as in the human body. They quickly replace fluids lost through sweating and supply a boost of carbohydrate to the muscles as they work. This type of drink is ideal for runners and people involved in team sports such as football to consume during exercise.
Hypertonic drinks are more concentrated than the fluids in the body and are usually consumed after exercise. They help rehydrate the body as well as top up carbohydrate lost during exercise. A milk shake is a good example of a hypertonic drink.
Hypotonic drinks contain a lower concentration of salt and sugar than the human body.
They help to replace fluids lost by sweating and are suitable for athletes who require fluid without a carbohydrate boost, e.g. gymnasts.
Not necessarily. Before exercise drink moderate amounts of water (300 – 400 ml) and check your urine is a pale straw colour.
If you are doing an event like a half marathon you might find it useful to have a very dilute amount of fresh fruit juice. To make your own isotonic sports drink, mix: 200ml fruit squash, 800ml water and a pinch of salt.
After extensive periods of physical activity it is important to replenish fluid, carbohydrate and protein. Protein promotes muscle repair; carbohydrate replenishes glycogen stores in the liver and fluid rehydrates all the tissues in the body so that you will recover from exercise more quickly.
Milk (and plant milk) have been shown as a good post-exercise recovery drink. These milks contain vitamins and minerals that can replace those lost via sweating and enhance rehydration (sodium), as well as assisting in muscle function and bone health (potassium and calcium). Milk also naturally contains high quality protein and some carbohydrates, and is relatively cheap to buy.
Research from Northumbria University showed that chocolate milk helped people recover after prolonged periods of exercise.
The amount of fluid you need depends on lots of things including the weather, how much physical activity you do, your age and body weight. The Eatwell Guide suggest 6-8 glasses of fluid per day. This is in addition to water provided by food you eat.
Small water losses during exercise are not harmful but dehydration can be. Dehydration can affect performance during exercise and lead to collapse if left untreated.
It is important to drink regularly during exercise and to monitor the colour of your urine, which should be a pale straw colour. This is a good sign of how well hydrated you are.