How to stay hydrated in Kona

Heading to Hawaii and worried about getting the hydration right? Former Kona competitor and hydration specialist Andy Blow explains how to get the hydration right for the Ironman World Championships in Kona

Andy competing at Kona in 2004

This article aims to help anyone preparing for the Ironman World Championships by learning from my mistakes on the Big Island back in 2004.


 Back then I was aiming to be in the top 10 in my age group, to go sub 9:30 (or maybe even sub 9 if I could find my best form from 2003). In reality I finished in 10:32:08, which put me 45th in my category and in 255th place overall. A long way off my expectations. And this was largely down to not hydrating properly. So, here are a few things I know now that I wish I knew when I was gearing up for the most important race of my life…

 1. Understand what it means to be ‘well hydrated’.

Hydration is all about balance.

Being significantly dehydrated can lead to poor performance, but over-hydration can also be very, very bad news, and this is much less talked about. Dehydration has received more than it’s fair share of bad press over the years. So much so that over-consumption of fluids before and during events is incredibly common.

 This is potentially very dangerous.

It can lead to a condition called hyponatremia, which is caused by the dilution of the body’s electrolytes when too much fluid is taken in during a short period of time. Left unchecked, hyponatremia can be fatal. Sadly, it has killed a number of competitors in marathon and triathlon events, with one recent tragedy occurring at Ironman Frankfurt. Even if it doesn’t kill you, a mild case of hyponatremia can ruin your race, through debilitating symptoms like headaches, lethargy, cramps and sickness.

Hyponatremia: causes and symptoms of low sodium levels

The aim of your hydration strategy is to achieve an optimal balance of fluids and electrolytes before getting to the start line. You then want to take in just the right amount of fluid and electrolytes during the race to minimise the negative effects of dehydration without over-doing it and running the risk of dilution and hyponatremia.

I know this now. But back in 2004 I wasn’t aware of this and I over-drank plain water in the days before the race, then further diluted my blood sodium levels during the race by drinking lots of water and Gatorade, which had nowhere near enough sodium to replace the 1842mg of sodium that I was losing per litre of sweat.* On the climb and descent either side of the turnaround point in Hawi (half way) I really started feeling ropey. I had a headache, slight nausea and a bit of a bloated stomach. Those are all symptoms of hyponatremia and my race went down hill from there.

*I now know how much sodium I lose in my sweat because I got sweat tested on my quest to learn from my mistakes in Kona 

Sweat testing for athletes: is it worth it?

2. Understand your hydration status in the lead up to the race.

Keep an eye on the colour of your urine and how often you’re peeing. If you’re going infrequently (only 2-3 times a day) and your pee is quite dark and low in volume, it’s highly likely you’re a bit dehydrated and should increase the amount you’re drinking.

If you’re peeing more than 8 times per day, the pee is clear and there’s a lot of it, you could well be over doing it and should dial your consumption back a bit. Everyone is different, but peeing 5-7 times per day, with the urine a pale but slightly yellowy colour is generally considered ‘normal’.

Again, back when I was in Kona I thought that clear pee was a good thing and something to aim for to ensure you were ‘well hydrated’.

3. Start the race hydrated

If you start to think about hydration when you start to feel dehydrated, you’ll be fighting a losing battle. You want to be toeing the line in an optimal state of hydration. Here’s some tips on how to do that:

Increase your sodium intake gradually during the final 2-3 days before the race. This can be done by adding salt to your food or by swapping some of the plain water you’d normally be taking in with electrolyte drinks. Sodium is the key electrolyte associated with hydration. Increased sodium consumption boosts the amount of fluid held in the bloodstream and reduces the amount you have to pee out

Preload the night before the start of the race with a 500-750ml dose of a very strong electrolyte drink (1500mg of sodium per litre or more). Repeat this again about 90 minutes before you start. Studies have shown this can boost endurance performance as it expands blood volume and therefore reduces cardiovascular strain. Preloading can be particularly beneficial when you’re racing in a hot climate like the one you’ll be facing in Hawaii.

Whilst people respond differently to their effects, it’s also a good idea to minimise consumption of caffeine and alcohol a few days before the race.

Does coffee dehydrate you?

4. Replace the electrolytes lost in your sweat during the race, not just the fluid.

How much sodium do you need to take in?

As well as helping you absorb and retain more fluid, sodium is involved in the smooth running of other crucial processes related to performance, including maintenance of cognitive function, effective nerve transmission and muscular contraction.

Most athletes acclimatising to the heat in Kona right now understand that electrolytes are important to their performance. But what most don’t know is that everyone loses a different amount of sodium in their sweat. Whilst one athlete approaching the finish on All’i Drive on Saturday might have been losing as little as 200mg of sodium per litre of sweat, the athlete next to them might have been losing close to 2000mg/l. I personally lose 1842mg/l and I’m no freak, about 15% of the athletes we test lose upwards of 1400mg/l.

So, it’s important to get an idea of how much sodium you lose in your sweat so you can personalise your hydration strategy by finding electrolyte drinks that match how you sweat. (There are various ways to do this, including the Sweat Tests that my company offers).

 How much do I need to drink?

Once you know how much sodium you need to replace, the next question is how much to drink. Here, learning to listen to your body and drinking to the early signs of thirst are generally a good idea once the race is underway.

However this approach alone requires you to be quite ‘in tune’ with your body. To help with that, a rule of thumb guideline for how much to drink in Kona is about 1 litre (32oz) per hour. It’s going to be very hot and humid on the Big Island and you’ll be sweating a lot. To put that into perspective, in cooler conditions, or when you’re only expecting to be sweating lightly, up to 500ml (16oz) of fluid should be sufficient for most people.

It is worth bearing in mind that 1 litre (32oz) per hour is approaching the maximum anyone can usually absorb when exercising hard, so it’s unlikely you’ll benefit from trying to take in a lot more than that, unless previous experience tells you otherwise.

You’ve probably noticed that these tips are largely about self-awareness and preparation. Like any other aspect of your race (kit, nutrition, transition, etc), hydration is all about understanding the fundamentals and tailoring those to your need individual needs. I got it wrong back in 2004, I hope learning from my mistakes helps you fare better on your Kona journey.

Andy Blow has a few top 10 Ironman and 70.3 finishes and an Xterra World Age Group title to his name. He founded Precision Hydration to help athletes solve their hydration issues, take their free online Sweat Test to get started. He has a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams.



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