Hydration

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Have you ever considered how much fluid you should be taking on during a race?  If not you might want to think about it!!!!  This becomes even more critical in endurance racing.

Studies have found that a 2% drop in bodyweight as a result of fluid loss during a race can have a detrimental effect on performance, but on the other side you are limited by the amount of fluids that your body can process as you take them in.  You may find that you are losing 1,000ml of fluid an hour during exercise but your body can only process fluids at a rate of around 600-800ml per hour, and therefore there may no way to avoid losing some fluids as your race progresses.  The key is minimising the losses to minimise your performace reductions.

But, on the other side you also have to watch for the dangers of over-hydration, by taking in too much fluid or by taking on only water.  An essential part of your bodys operation is the electrolyte balance.  You lose electrolytes as you sweat and these need to be replaced or you can suffer the effects of over-hyrdation which can be as bad or potentially worse than dehydration.

You don’t need to use expensive electrolyte tablets or sports drinks, simple solutions like adding 1/2 a teaspoon of salt to a bottle of your normal juice can serve to replace the electrolytes that you lose.  Or if you don’t fancy that, foods like bananas are high in electrolytes or taking on salty snacks like crisps etc.  If you are a particularly salty sweater you will need to pay close attention to replacing the electrolytes you lose during race conditions and training.

So, where do you start when looking at your hydration strategy?  Well the first port of call is to figure out how much you sweat in each discipline, and you do this by carrying out a sweat rate test as follows.

  • Pre exercise – weigh yourself with no clothes on, but holding any hydration you will be taking in during your exercise.  e.g. holding your full water bottle(s)
  • Exercise for a set period of time, easiest if you exercise for an hour, but you can work it out for any duration of exercise
  • Post exercise – weigh yourself again with no clothes on, after drying any sweat from your body, and holding the remainder of any hydration including empty water bottles.
  • The difference between your Pre exercise weight and Post exercise weight is the the amount of fluid you have lost.  You then take that weight loss and turn it to an hourly sweat rate figure.

Lets say your pre exercise weight was 75kg, and after 40 minutes of exercise your weight was 74.4kg.  Your total weight loss was 0.6kg in 40 minutes, which is equivalent to 0.9kg in an hour.  As 1,000ml of fluid weighs 1kg, your sweat rate would be 900ml per hour.

The sweat rate test should be completed for every discipline, as sweat rates vary from swimming to cycling to running.  This rate is also affected by other factors, the primary one being the weather conditions, where your sweat rate can increase significantly during hot and humid races as your body tries to regulate temperature.

This then gives you the opportunity to plan your hydration strategy for the race, and thereby ensure that you are adequately hydrated before you start, and minimise any fluid loss during the race, and then ensure that you are taking on enough fluids and sufficient electrolytes to mitigate any potential performance losses.

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