Dehydration can cause a huge drop-off in triathlon performance, here’s how to ensure proper hydration to help you race at your best.

Dehydration is something that virtually every triathlete has had to deal with and left unchecked it can seriously impair your performance or even give you a one-way ticket to the medical tent. While there’s more to beating it than drinking lots, dehydration is one of the easiest endurance sports ailments to conquer.

What is dehydration?

Dehydration occurs when fluid intake is insufficient to match the fluid loss during exercise. As blood volume decreases through sweating, the amount of oxygen-rich blood the heart can pump to your working muscles also decreases. This means a higher heart rate is required to sustain the same pace as when you’re properly hydrated.

When it’s hot, you sweat more and therefore lose more fluid. Once you’re dehydrated, the amount of blood available to send to the skin to dissipate heat is lowered, meaning sweat rate decreases and your body struggles to lower its core temperature. Unchecked, severe dehydration can cause dizziness, nausea and heat stroke, so keeping on top of hydration is incredibly important for triathletes.

Running aid station dehydration
The ghostly pallor of the dehydrated athlete isn’t overcome by drinking plenty of water. (Photo: Triathlon Vibe)

As sodium (salt) is lost in sweat, it’s essential to replenish this along with fluids. If you consume lots of water rather than a drink containing sodium-replenishing electrolytes, it could lead to hyponatremia – over dilution of sodium in the blood. This is a much more dangerous scenario than dehydration and a major cause of fatalities in amateurs during marathons and Ironmans who heed outdated advice to drink as much water a possible.

How to deal with dehydration

The old theory that a two per cent loss in body weight during exercise equals a dehydrated state and a loss in performance has been somewhat debunked in recent years, but proper hydration is still important to race at your best, here’s how to safety drink your way to victory.

Hydration starts before you exercise

You know you’re going to sweat during your triathlon, so be prepared for it. An electrolyte drink with sodium can help ensure you’re replenishing salt and minerals lost through sweating as well as water. Starting on your electrolyte solution the day before the event – as well as race morning – can help ensure you’re properly hydrated when the gun goes off. This is because the sodium in electrolyte drinks aids fluid retention, boosting your blood plasma volume so you can call on these reserves during your race.

When it comes to pre-loading, a strong concentration of sodium is best to give maximum retention. Aim for around 1500mg per litre, drinking 500ml the night before your race and another 500ml on race morning. This high concentration means so you’ll probably need to drop a few electrolyte tablets into your bottle – or use something stronger, such as Precision Hydration’s PH1500 option.

Drink to thirst or drink to a plan?

One popular theory in the sports science community is drinking to thirst. Like all animals, humans have hard-coded instincts to avoid dehydration by drinking when thirsty. In theory, all you’ve got to do is listen to your thirst and act on it.

Practise different hydration strategies in race simulations and brick sessions to find out what works for you

Drinking when your mind naturally turns to the thought of quenching your thirst is great for lower intensity training but when it comes to racing, where emotional and physical responses are running high in the heat of competition, it can be much harder to gauge when to drink. Some sports scientists also argue that by the time you feel thirsty, you’re already well on the road to dehydration while the drink to thirst philosophy doesn’t take into account different sweat rates or concentrations, either.

Therefore, drinking to a personalised hydration plan is a great idea for triathlon competition. Practise different hydration strategies in race simulations and brick sessions to find out what works for you, logging when things go right and wrong to help you nail your hydration plan before race day.

A general rule of thumb to avoid over-hydrating is to not to drink more than 500ml per hour in cool races and 750ml per hour in warmer conditions. If it’s really hot and you’re sweating lots, 1000ml per hour is just about the maximum the body can utilise.

Pick the right hydration drink

There are lots of electrolyte drinks out there. Some are designed specifically for hydration while others are primarily carbohydrate drinks for energy with electrolytes added to the recipe. Options vary from powder-based mixes to effervescent tablets that you simply drop into your drinks bottle. Most of the big sports nutrition brands including High5, SiS and Powerbar provide electrolyte and sports drinks formulated to keep you hydrated.

Precision Hydration’s range of sodium concentrations is our go-to start point for planning race hydration. (Photo: Triathlon Vibe)

However, different brands of electrolyte drinks contain differing amounts of sodium and knowing what’s right for you can be tricky. With this in mind, Precision Hydration is a great place to start. The British hydration brand has an online survey to estimate how heavy a sweater you are and prescribe a concentration to suit. There’s also an advanced one-to-one sweat test service for even better accuracy.

Avoid dehydrating drinks

For many triathletes, a cup of coffee goes hand in hand with pre-work training, but the caffeine in your cup of joe can cause dehydration, so try to cut down during race week. Alcohol is also dehydrating, so save the beers for a post-race celebration.

Dehydration – the bottom line

By consuming electrolyte drinks before and during your race, you should be able to maintain good hydration levels whatever distance you’re competing at. There is a trial and error element to this though and individualisation is key – practising your hydration strategy with different liquid volumes and electrolyte concentrations in training and race simulations will help you get it right on the big day.

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Triathlon Vibe is the home of triathlon training advice for beginner to expert triathletes. From sprint to Ironman, we share how to swim, bike and run stronger and faster.


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