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Guide to sports drinks

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Guide to sports drinks

Sports drinks were developed to help athletes doing high-intensity exercise stay hydrated.

There are a lot of people using them who perhaps don’t need to. Nutritionists Nicole Barnett and Claire Turnbull investigate what’s in sports drinks to answer, do you need them?

Adequate fluid intake is essential for everyone to maintain good health, but it is particularly important for people who train regularly to prevent the negative effects of dehydration and help them to perform at their peak.

Sports drinks are designed for athletes who do regular, high- intensity training. Sports drinks can help people who are exercising at high intensity for an hour or more, particularly if they are sweating a lot. They have been shown to delay fatigue and improve exercise performance in numerous scientific trials.

With anywhere between 600 and 1100kJ and 10 to14 teaspoons of sugar in a bottle, however, it is very important to only use them when and if you really need them.

If you are going to the gym a couple of times a week exercising at a moderate intensity, doing a few spin classes or doing short runs and you are trying to lose weight, sports drinks really aren’t for you. Water is all you need. Drinking sports drinks, you could end up drinking more kilojoules than you have burnt off!

Sports drinks contain water, carbohydrates and electrolytes. They may also have other ingredients such as vitamins, minerals, certain amino acids and ginseng, but there is little evidence these extra additives can enhance exercise performance.

Carbohydrates

The purpose of carbohydrates in sports drinks is to provide energy for the working muscles, which helps delay muscle fatigue. The main carbohydrates used in sports drinks are glucose, fructose, sucrose (table sugar) and maltodextrins. As a rule, increasing the carbohydrate content of a sports drink using glucose, fructose or sucrose to a level higher than that found in the bloodstream will slow the rate of emptying from the stomach into the intestine where the fluid is absorbed. This means it is very important for sports drinks to have the right balance of carbohydrates to promote rapid hydration.

Electrolytes

Sodium, potassium and chloride are the three electrolytes commonly added to sports drinks to help replace those lost in sweat. Sodium also increases the amount of water taken up by the intestine, helping rehydration. Potassium helps regulate the heartbeat and optimise muscle function, and chloride helps with fluid balance. Sports drinks vary in the amounts of the different electrolytes they contain, but this is not likely to have an effect on hydration or exercise performance.

Sports drinks aren’t all the same. The ideal sports drink to be used during high-intensity exercise will have between four to eight per cent carbohydrates (that is 4-8g per 100ml). Similarly, the amount of electrolytes in each drink can vary. Typically, the sodium in sports drinks is between 23-69mg per 100ml. Athletes who lose a lot of salt in their sweat will chose products with a higher sodium content.

Sports drinks labelled ‘isotonic’ have between six to eight per cent carbohydrates. This concentration of carbohydrates is similar to the amount in body fluids and promotes a smooth flow of fluid into the bloodstream. These are ideal for those training for a prolonged period at higher intensity.

  • Examples: Powerade, Gatorade, Replace, Mizone Isopower

Sports drinks labelled ‘hypotonic’ have a lower carbohydrate level than the fluids in the body (less than six per cent carbohydrates). These are also helpful to assist with hydration and are lower in kilojoules than isotonic sports drinks so can be useful for those who need to use a sports drink but need to be mindful of their energy intake as well.

  • Example: Mizone Low Carb

These are often found in the same section of the supermarket as sports drinks but they aren’t the same. They do contain some carbohydrate and electrolytes and are often flavoured to make them taste nice but they don’t quickly hydrate you like sports drinks. They can be helpful when you are tramping or on a long recreational bike ride if you struggle to drink enough plain water. But remember: with 350-400kJ and about five teaspoons of sugar in a bottle they are not ideal to grab along with your lunch when you’re not exercising — particularly if you are watching your weight.

Drinks which have more than eight per cent carbohydrates (8g per 100ml) such as soft drinks and energy drinks (such as V, Red Bull, E2 and G Force) do not assist with rapid rehydration as they are too concentrated in carbohydrates.

Some higher carbohydrate drinks such as flat cola drinks may be used in ultra-long distant events such as cross-country running or Ironman to help these people meet their high energy needs, but for most other people these aren’t ideal during exercise. Fruit juice also fits into this high carbohydrate group so it’s best to dilute it 50:50 with water if you are giving it to your children to help them rehydrate after exercise.

The most important consideration when exercising is keeping fluids up. Even a decrease in body weight of as little as two per cent due to fluid loss is enough to have a detrimental effect on our exercise performance. Anything more than five per cent can cause heat illness. The amount of fluid a person needs to drink during exercise varies greatly between individuals, as we have differing sweat rates and proportions of water lost in the breath.

If you are serious about your training, working out your personal sweat rate can help you avoid the effects of dehydration and to perform at your best.

  • To calculate your sweat rate, record your nude weight (in kilos) before you exercise and then again afterwards, remembering to towel off any sweat in advance. Subtract your post-training weight from your pre-training weight, and multiply this by 1000 to convert it to grams. This is the total amount of fluid you have lost.
     
  • For every gram lost, you need to drink 1ml fluid to make up for it. So if you lost 700g in a 60-minute workout, you need to drink 700ml in 60 minutes to stay properly hydrated.

Exercising in the heat, for a long time or at a high intensity, as well as having a high sweat rate will increase the speed at which you dehydrate, and this needs to be taken into account when you are determining how much you need to drink.

Type of exercise Examples What do you need?
Low- intensity exercise Walking to work, walking the dog in the evening, leisurely bike ride or swim Water
Moderate- intensity exercise Brisk walking or jogging, recreational cycling, swimming Water in most cases will be fine. If you are exercising for well over an hour, you may consider a sports water
High- intensity exercise Fast paced running, cycling or swimming, high- intensity gym class or spin class etc. If this is under an hour, water may be adequate but in some cases a sports drink can be helpful. When training for over an hour a hypotonic or isotonic sports drink would be ideal

 




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