We caught up with exercise physiologist and medic Professor Tim Noakes for some triathlon hydration advice. 

In his new book “Waterlogged” (humankinetics.com) he challenges accepted beliefs about hydration and proposes new strategies to optimise race performance.

Q: How often should you drink during a triathlon?

One has to go back to the basics, which are that all creatures on this earth drink according to thirst and do not need to be told how much to drink. For some reason the sports drink industry decided that humans are so stupid that, unlike any other creatures on the earth, they have to be told how much to drink. They weren’t really concerned about the health of humans; they were more concerned about marketing and selling a product. They were very successful and hence a new industry was born, on the false interpretation of information.

The simple rule is that you drink to thirst. For some people, this means they will finish an Ironman having lost 12% of their body weight in water and some will finish having only lost 2%. It’s entirely dependent on your individual responses.

All the research shows that if you drink ahead of thirst, you impair your performance. It also shows that if you drink less than your thirst dictates, you impair your performance. However, if you drink according to your thirst, you maximise performance.  So the whole idea that you must drink to stay ahead of your thirst does nothing more than impair your performance.

Q: Is it possible to miss your body’s thirst signals during a race, because you’re too busy concentrating on other things?

Never. As soon as you lose a significant amount of weight [through fluid loss] you will get thirsty. Your thirst is a control mechanism. It’s your body saying: “Listen, I need water. If you’re not going to drink, I’m going to slow you down”. And that’s part of a biological response where your brain is telling you, either drink or slow down.

Q: What are the impulses that tell you need to drink?

People need to stop drinking so much and re-learn what thirst is. They need to get out on their bike or go for a run, without drinking and then wait. They’ll get to a point when they say: “Now I’m definitely thirsty!” Then drink. And it doesn’t have to be much. Otherwise you’ll have too much fluid in your body, and how can your cells do their jobs properly if they’re too full of extra liquid and weight?

A sports scientist phoned me last week from the US. They did a study where they pre-loaded guys with either 500ml of fluid or three squirts of water into the mouth. And then they did an exercise test lasting 30 minutes. The performance was impaired in the group who’d preloaded. They also studied the brain function, and that was impaired to, just by drinking 500ml before the start of 30 minutes of exercise! That’s because your body doesn’t need it.

Q: Is it possible to flush out your body’s electrolytes by drinking too much before exercise?

 You will lose electrolytes this way, but the body regulates itself well and our diets are so excessive in sodium (salt) that you couldn’t really make much difference. Technically you will lose some in your urine, but it won’t have much effect.

Q: Should triathletes take salt capsules before and during a race?

 Any salt you consume during exercise appears in your urine. The reason is quite simple. Our bodies have a massive excess of sodium and it’s essentially impossible to create sodium deficiency in modern athletes. Our diets are so full of sodium and if we were to become deficient our bodies would tell us to eat more salt by developing a craving.

There are some studies published where people exercise while drinking water or sodium-containing sports drinks. And guess what? The exact amount that they drank in the sports drink came out in their urine. It’s because the body is so tightly regulated in terms of sodium intake. It always excretes exactly what you take in the day before.

Q: Double Ironman world champion Chris McCormack says in his autobiography that he consumed extra electrolytes in the weeks leading up to his Hawaii Ironman wins. He believed that it enabled him to store more liquid in his muscles and stopped his cramping problems. What are your thoughts on this?

You have to take anecdotal evidence like that very seriously. The question is, did he do anything else as well as that? It’s always a question. Did he do more stretching, or did he change his diet in some other way? Did they tell him to eat more protein or fat? I would consider his experiences very seriously, but I would also like to know if he also did something else. This is because there’s no evidence whatsoever that electrolytes have got anything to do with cramps. They are a brain and spinal cord phenomenon, where the muscle becomes hyperactive. Normally your muscles’ activity is damped down, and what happens as you run is that you lose that dampening control. And so they become more irritable and are more likely to go into spasm. We don’t think it has anything to do with electrolytes because when we look at runners who get cramps they are no more dehydrated than anyone else and the electrolyte levels in their blood is completely normal. So we go with that model.

But then on the other hand I would never discount someone’s experience like that. What he observed is absolutely true. It’s just that the explanation for it may not be the one he’s chosen. He may have changed four or five other variables, but the point is that it worked and so he should stick with that strategy. If he drops any one of those variables he risks dropping the key one.


Q: You recommend drinking to thirst. But during a race should you also drink when you take a gel or eat an energy bar?

During a race you’ll have dryness in the mouth because you’re breathing through it, making it harder to eat. It’s not an effect of drinking too little though, and it’s normal to have a dry mouth. The only time you won’t have a dry mouth is if you’ve drunk something a few minutes beforehand. You don’t need to be full of liquid to process carbohydrates, you just need to have drunk something recently.

Interview by Phil Mosley

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