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Ruth James

Fluids: What To Drink, When, And Why

by Ruth James

If you want to train and race to the best of your abilities, proper daily hydration is imperative and drinking fluids at the right time before, during and after exercise is critical.

We know that a good diet is essential for maximum performance but drinking enough fluid especially water is equally as important. Water has many important roles in the body including maintaining blood volume and regulation of body temperature. During exercise the body cools itself by sweating and if this fluid (containing water and electrolytes such as sodium) is not replaced it can cause dehydration.

2% dehydration can cause at least a 10-20% reduction in performance.

The deleterious effects of dehydration on athletic and cognitive performance is well recorded and just 2% dehydration can cause at least a 10-20% reduction in performance.

Whilst thirst can be an indicator for dehydration it may not be reliable as this mechanism may kick in after you are already dehydrated.

Furthermore, some athletes are so focused on training or competing that they forget to drink. Some avoid drinking because they fear stomach troubles or being uncomfortable in the boat. 

Let’s be clear: if you are highly trained and exercising at a high intensity for long periods (more than an hour), fluids other than water e.g. commercial sports drinks, gels, protein powders and shakes (readymade or in powder form) can provide a convenient and effective way of delivering lost nutrients, carbohydrate, electrolytes to aid fluid absorption and protein for muscle recovery.

it is possible to over-drink during exercise.

The sports drinks market is the fastest growing sector in the UK soft drinks market. Its big business and there are loads of different products on the market for athletes to choose from, all with enticing slogans. They are expensive and not always formulated correctly. Most people doing recreational exercise do not need to use them.

What are your fluid needs?

Fluid requirements vary significantly between athletes and exercise situations.  Fluid losses are affected by:

  • Genetics – some people  sweat more than others
  • Body size – larger athletes tend to sweat more than smaller athletes
  • Gender -women sweat less due to a smaller body size
  • Fitness – fitter people sweat earlier in exercise and in larger volumes
  • Environment – sweat losses are higher in hot, humid conditions
  • Exercise intensity – sweat losses increase as exercise intensity increases

During long intensive exercise, the rates of sweat loss are higher than the rate you can drink, so some athletes get into fluid deficit. Therefore, guidelines suggest drinking more fluid to reduce the deficit and potential performance detriments associated with dehydration. However, it is also important to acknowledge here that it is possible to over-drink during exercise. This usually affects recreational athletes who do not sweat so much yet believe they need to take on more fluid.

You can roughly guage sweat loss by monitoring your body weight before and after training, with one litre of fluid lost equating to one less kilogram of body weight.

How much should athletes drink before exercise?

  • Hydration starts well before you train or enter an event. In the early morning, your body may be slightly dehydrated, so it is important as soon as you get up to drink a couple of glasses of water.
  • Start exercise hydrated to lower the risk of becoming dehydrated during exercise (5-10 ml/kg) 2-4 hours before exercise so an athlete weighing 65Kg would need to drink about half a litre or 500mls of fluid. Remember that food such as fruit and vegetables have high water content too.
  • Drink regularly throughout the day especially leading up to training or competition.  Have a drink with all meals and snacks

How much should athletes drink during exercise and what is the best to drink?

This will depend on the duration, frequency and intensity of the exercise .There is a big challenge if there are multiple races and it’s hot.

Practical issues such as balancing being fully hydrated against peeing in the boat is important. We do not store excess water excess well so timing intake is crucial.

If you exercise for less than 45 minutes then carbohydrate intake is probably not necessary. Plain water is an effective drink for fluid replacement.

However studies have shown that the consumption of sports drinks (with 5-8% carbohydrate) can be useful during moderate to vigorous intensity exercise in trained athletes exercising for an hour or more. They contain both carbohydrate for fuel to restore glycogen levels and flavour and also electrolytes to help the body ‘hold on to’ fluid more effectively and stimulate thirst. Athletes exercised longer and maintained better blood glucose levels better than coloured water.

water does not stimulate fluid intake to the same extent as sports drinks

Water is still a suitable option during exercise.  However, water drinkers need to be aware that water does not stimulate fluid intake to the same extent as sports drinks because they do not contain electrolytes.  Cordial, soft drinks and juice generally contain greater than 10% carbohydrate and are low in sodium.  This can slow down gastric emptying meaning they are less well absorbed and makes these drinks a less suitable choice, especially for high intensity activity.  Some athletes, exercising at low intensities may tolerate juice, soft drink and cordial but in most situations, sports drinks are the better option.

Drinks are absorbed by the body at different rates depending up on their concentrations. Osmolality is a measure that compares the concentration of the drink with the concentration of the body.  Isotonic drinks have the same concentration as the body and can be readily absorbed. This is a good concentration to maximise transport of electrolytes or carbohydrates.

choose a sport drink that has 4-8% carbohydrate, 10-20 mmol/L sodium

Excessive sweating during long events can lead to a loss of salt (sodium chloride) and this is why some additional electrolytes are usually added to sport drinks.

Recent research also recommends protein in assisting post exercise hydration and for muscle regeneration. Consuming protein (about 15-25grams protein) soon after training and then every 3-5 hrs with meals and snacks is advisable.

Which sports drink is the best?

There are loads on the market but  choose a sport drink that has 4-8% carbohydrate, 10-20 mmol/L sodium, is affordable, comes in a convenient package for you and tastes good. Glucose is the main source of CHO but evidence suggests that a mixture of sugars may be better absorbed eg glucose and fructose.

Homemade sports drinks

You can also make your own sports drink with 500mls water, 500mls fruit juice plus quarter teaspoon salt. And have a large glass of milk for recovery after for the protein benefits.

Sports drinks and dental health

Sports drinks, like other carbohydrate containing fluids, have been shown to cause to dental erosion. To help reduce the potential impact of sports drinks on dental health, athletes should:

  • Reduce the contact time the sports drink has with teeth. Do not hold or swish sports drinks in your mouth. A straw or squashy bottle can be useful by directing fluids towards the back of the mouth.
  • Where practical, consume dairy products or chew sugar free gum immediately after consumption of the sports drink.
  • Avoid brushing teeth for at least 30 minutes after consuming sports drink to allow tooth enamel to re-harden.

Purposeful fluid restriction

Lightweight rowers may use fluid restriction as part of their making weight strategy but this needs to carefully supervised by the athlete and sports nutritionist and is outside the scope of this article.

What about mouth rinses?

Recent research has reported that mouth rinses can stimulate parts of the brain and central nervous system to enhance the sense of well-being and increase work output.

What about super waters?

Super Waters e.g. coconut, bamboo, birch trees  from Latvia and cacti waters from Mexico claim to detoxify and promote performance but are expensive with no evidence that they are able to do this. Coconut is marketed as “nature’s sports drink” but recent studies comparing it alongside water and isotonic sports drink gave no difference in performance.

An athlete’s fluid and refuelling needs are highly individualised and there’s no ‘one size fits all’ approach. Best to plan a regime which works for you and try it out during training and not before competition.

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