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Get Your Triathlon Hydration Strategy Right!

“Dehydration impairs performance!”

“You must drink during exercise!”

Just How True Are These Statements?

Before 1969 athletes were actually advised not to drink during exercise as it was assumed this would have a negative effect on performance.

If you have a question about your triathlon hydration please ask us

In 1965 the first sports drinks were developed and from then on, the message to athletes was: “drink as much as you can” so as not to lose weight through sweating.

But Is This Really Necessary?

It appears that some athletes can perform successfully in a race having lost as much as 12% of their body weight through sweating.



So What Should My Triathlon Hydration Strategy Be?

It seems that the levels of dehydration that an athlete can tolerate are very individualised. The guidelines below are to help you develop a triathlon hydration strategy that minimizes dehydration. Bear in mind that you are probably better off being slightly dehydrated than you are over drinking and ending up with hyponaetremia (more on this below).

You should aim to start a race or training session fully hydrated. Thereafter, aim to minimize dehydration, but don’t worry about following these guidelines exactly if you don’t feel thirsty.

Do remember though that the best way to get energy on board during a triathlon is through a sports drink and so you need to make sure you take on board enough energy.

If you have any questions about your triathlon hydration strategy then please just ask us.

How Do I Know If I Am Well Hydrated?

The most simple way to know if you are well hydrated is to look at the colour of your urine. When you are well hydrated your urine should be pale coloured. If it is dark then you probably need to drink more.

How Much Do I Need To Drink?

You can work this out by measuring your own sweat rate.

Why Do I Need To Know My Sweat Rate?

Drinking at a rate close to your sweat rate and aiming not to lose more than 2% body weight from sweat will help you to maintain hydration from training session to training session. Knowing your sweat rate will help you plan your triathlon hydration strategy.

  • A 1kg weight loss is equal to a loss of 1 litre in sweat when you’re exercising - if you haven’t consumed any food or fluid or been to the toilet during the session.
  • Sweat rate will differ between types of session - you can expect to lose less weight during a technical or resistance training session than you will during an endurance session.
  • The weather will also affect your sweat rate – you’ll obviously sweat more in the heat which is usually obvious to see. Windy days mean the sweat evaporates more quickly so you may not realize how much you have lost.
  • Clothes will affect your sweat rate – get the layers right and you’ll maintain an even temperature. Have too many layers or too thick a layer and you’ll sweat more than you would normally for the same weather conditions.

Calculating Sweat Rate

Measure body weight (in kilograms) before and after at least one hour of training.

Do this wearing minimal clothing and with no shoes. Dry with a towel after exercise and obtain body weight as soon as possible (ideally within 10 minutes).

Sweat loss (litres) = body weight before exercise (kg) – body weight after exercise (kg) + fluid consumed during exercise.

To convert to a sweat rate per hour, divide by the exercise time in minutes and multiply by 60.

After a session you should aim to drink 1.2 - 1.5 times the amount lost, starting as soon as you finish the session. You need to drink more than you lost because you will still be producing urine. You also need to replace the electrolytes (salts) lost in your sweat.

Here’s an example to illustrate how to calculate how much you need to drink after a session:

60kg person during a 2h session:

Post session 59kg = 1kg loss,

Plus they drank 500ml (equivalent of 500g) during the session so,

Total loss = 1.5kg.

Minimum amount needed to be replaced in recovery = 1.2 x 1.5 = 1.8L

For a sweat rate per hour:

(1.5 litres/120) * 60 = 750ml.
So sweat rate per hour = 750ml.

When a 60kg person loses 1.2L (2% body weight) or more, fatigue can occur. With a sweat rate of 750ml per hour, if the person had not drunk 500ml during the 2 hour session they would have exceeded 2% body weight loss and it is very likely that performance would have declined.

As a triathlete potentially doing more than one training session in a day, it is particularly important that you re-hydrate after a training session so that you don’t get progressively more and more dehydrated. Make sure you put your triathlon hydration strategy into action straight away!

Replacing Salts

It is difficult to work out how much sodium (salts) you are losing.

However if:

  • you have opaque sweat
  • your sweat tastes salty
  • your sweat leaves white marks on your clothes
  • You sweat a lot

You would probably benefit from increasing your salt intake. Ideally this would be through a sports drink after training, allowing you to replace carbohydrates at the same time.

A moderate excess intake of salt is unlikely to be bad for your health if losses through sweat are high and your fluid intake is also high.

Start A Race Or Your Training Session Well-Hydrated

Your triathlon hydration strategy should include drinking 250 – 500ml before starting a session or race. Sip this up to 1 – 2 hours before the start. Get to know how well you can tolerate fluids. Some people can drink during the hour before a session or race and feel fine, for others this can cause gastrointestinal discomfort or a stitch.

Do I Need To Drink During Training Sessions?

You will usually not be affected by dehydration until you have lost around 2% of your bodyweight (although this can vary from person to person – some people can tolerate greater levels of dehydration than others). So it is unlikely that fatigue will be due to dehydration in a session lasting up to an hour, unless it’s very hot of course.

For longer sessions your triathlon hydration strategy should involve carrying a drinks bottle and trying to take 2 – 3 large mouthfuls every 30 – 40 minutes. Sports drinks (carbohydrate-electrolyte mix) are ideal – beware of water as it is not an ideal source of hydration during exercise. It is digested less well, and doesn’t replace the electrolytes (salts) lost in sweat.

What About During A Race?

drink on triathlon bike

You should plan and practice your triathlon hydration strategy for race day. The longer the duration of the event, and the hotter the weather, the more you will have to drink to prevent dehydration and compromised performance.

If you can calculate your sweat loss in training you will be able to work out roughly how much fluid you need to drink, allowing you to develop an effective triathlon hydration strategy. Just make sure you calculate sweat loss when exercising at a similar intensity to racing, and in similar weather conditions.

A recent research study found that the average volume of water lost during an Ironman was 1.1 litres every hour. That adds up to a lot over the course of the race – and potential disaster if you don’t replace the majority of it.

The bike section is the best opportunity to take on fluids. However you don’t want to overdo it. There is a limit to the rate at which your body can absorb fluids – drink too much and it will just slosh about inside you.

A study looking at fluid absorption when cycling found that the maximal rate of absorption when cycling at 85% of VO2max (around the intensity sustained in the bike section of an Olympic distance triathlon) was 0.5l/hour.

To find out more about the ideal content of your drink, refer to the nutrition for racing page.

Drink during the bike section, but no more than 500ml every hour – and try to sip regularly rather than knocking this back in a oner!

Sports Drinks

Commercial sports drinks are widely available and are a key element in your triathlon hydration strategy. However these can be quite expensive.

Follow the recipe below to make your own (from Professor M Gleeson, www.medicdirectsport.com):

The amounts shown are sufficient for 1 litre (1000 mL) of drink.

  • 50 grams of glucose as dextrose monohydrate (available from most pharmacies).
  • 0.5 grams of sodium chloride (table salt). This works out at about 1/7th of a level teaspoon.
  • 1.5 grams of sodium bicarbonate (baking soda). This works out at about half of a level teaspoon.
  • Add the above ingredients to 500 ml of cold water. Mix thoroughly until completely dissolved.
  • Add 100ml of a commercially available sugar-free (low-calorie) fruit cordial (experiment with different flavours to see what you like best).
  • Finally add more cold water to top up to a total volume of 1 litre.

You might find the drink to be a bit too salty. If so, then instead of the table salt and baking soda, add 2.5 grams (about one level teaspoon) of sodium citrate (as trisodium citrate dihydrate). This will provide a similar amount of sodium, but without the salty taste.

Pour the drink into a bottle that can be kept airtight. Store it in the fridge if you are not going to use it on the same day. Use within 3 days.

Can I Drink Too Much?

Yes…. and this is also not good for you. If you drink too much water, this can result in your blood sodium concentration being too low. Combined with losing sodium in sweat, this can exacerbate the problem, known as hyponatraemia.

Symptoms of hyponatraemia include nausea, vomiting and headache, as well as confusion/agitation, shortness of breath and rapid breathing.

Risk factors for hyponatraemia include:

  • High fluid intake,
  • Long duration endurance events
  • Low and high BMI,
  • Less experience in racing/competing
  • Female gender,
  • NSAIDs, and
  • Higher heat stress weather conditions

The incidence of hyponatraemia seems to be higher since the surge in availability of sports drinks, and the publicity promoting the importance of drinking enough during exercise.

There is now a school of thought that the guidelines for how much to drink during exercise are flawed. This is because they are based on the logic that body weight is the only variable that is homeostatically-regulated during exercise.

However, human fluid balance before, during and after exercise is regulated to maintain constant plasma osmolality (basically keeping the concentration of different ions, such as sodium, in the blood balanced). The controller is the thirst mechanism which insures that the plasma osmolality is maintained within the correct range.

Research has shown that when athletes follow this advice, and drink according to thirst, the risk that they will over-drink and so develop exercise-associated hyponatraemia is reduced.

There is also no evidence that their performance is affected by the mild to moderate level of “dehydration” that they develop as a result. So bear this in mind when planning your triathlon hydration strategy.

Triathlon Hydration Strategy
Take Home Tips

  1. Weigh yourself before and after training to assess fluid loss. Try to limit weight loss to 1% during training and races lasting longer than 1.5 hours.
  2. Practice: Your triathlon hydration strategy is important. As with new trainers, don’t try it out in competition. Work out your fluid needs during training.You might also want to practice drinking whilst on the bike – getting your bottle in and out of the holder on your bike.
  3. Start a race or your training session well-hydrated.: Drink 250 – 500ml before starting a session or race. Sip this up to 1 – 2 hours before the start. Get to know how well you can tolerate fluids. Some people can drink during the hour before a session or race and feel fine, for others this can cause gastrointestinal discomfort or a stitch.
  4. During a training session: Have a drinks bottle readily available for longer training sessions, and take small sips of this regularly throughout the session. If you know your sweat rate then you can make sure that you do not lose too much fluid. However be aware of whether you actually feel thirsty and need to drink, and try not to over-drink. Sports drinks are best, as water is less easily digested. Also the carbohydrate in these drinks help keep your energy levels topped up, which is essential for sessions lasting more than an hour. Aim for a carbohydrate concentration of 6 – 8% as this is the most easily digestible.
  5. During a race: Practice your triathlon hydration strategy for race day. Have a bottle on your bike and make the most of fuel stations during the run. The amount you need to drink during the race will depend on the duration of the race and how hot it is. The longer the race and the higher the temperature, the more you should drink. 500ml/hour is the most you should be able to comfortably drink.
  6. Post-session: Drink 1.2 – 1.5 times the amount you have lost during the session. Again sports drinks are ideal, containing carbohydrates and electrolytes.

Got a question about your triathlon hydration strategy?
Then ask us!


















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