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Good hydration is the key to getting you home and dry on race day, says Dr Kevin Currell.

Triathlon Nutrition - HydrationThe traditional view of hydration is that you should drink as much as possible during exercise, and certainly not wait until you are thirsty. The more recent guidelines from the American College of Sports Medicine say drink enough to prevent a 2% drop in body weight through water loss. The trouble is, how do you know when you reach that point during exercise?

There is now a view that simply following your thirst may be a valid way of making sure that you drink adequate amounts of water. Some evidence actually shows that drinking a higher amount of fluid will have no effect on performance compared to drinking to your thirst.

There was also a recent study by Professor Tim Noakes from South Africa, which even showed a correlation between dehydration and increased running performance in a French marathon. But this isn’t quite cause and effect and is not recommended, as dehydration can also reduce the effect of your sports drinks.

When you start to become dehydrated the amount of blood available to circulate around your body decreases. This reduces the ability of the gut to absorb nutrients. So the sugar you take on board to fuel your race is just going to be sitting in your intestine doing nothing. Let’s look at some strategies that might help you stay on top of your hydration.


During training it is generally best to stay on top of your hydration, and err on the side of drinking a little more than you think is needed. This is primarily due to the effect of hydration on your immune system. If you become dehydrated, your immune system comes under stress and you are more likely to get ill. If you get ill, you can’t train and therefore you can’t improve.

  • Drink at least 500ml per hour on the bike – increase this to 750ml in the summer.
  • Have 500ml per hour during swimming.
  • Monitor your hydration status in the morning. When you go to the toilet first thing in the morning, if your urine is lightly coloured, like a nice glass of champagne, you are fine. If it is dark and looks like apple juice you need to make sure you drink some more.


This should all be about performance. You need to make sure you start the race fully hydrated and ready to put out your best performance.

  • In the days leading up to the race, sprinkle a little salt on your meals to help the body to retain the water you are drinking. Sip on electrolyte drinks throughout the day to maximise fluid retention.
  • Drink 500 – 1000ml of fluid with your breakfast on race morning, continuing to sip on an electrolyte drink up until the race.
  • Plan your fluid intake on the bike around your carb intake, especially in an Olympic-distance race. So aim for 60-90g of carb on the bike. Whether you use gels or sports drinks will determine fluid intake.
  • For Ironman, drink 500-750ml per hour. Consider your size and the heat.
  • On the run, if it is Olympic-distance, swill some water around your mouth and pour the rest over your head. For an Ironman run, drink to your thirst. Keep up your carb intake.