How much should I drink during exercise?

By Abby Coleman | 4 Minute Read

The answer to the question 'how much should I drink?’ isn't as straightforward as many athletes would like it to be. 

While hydration isn't necessarily a complex topic, there's a tendency to oversimplify hydration for exercise in one of two ways:

1. By setting yourself targets - i.e. replacing an arbitrary percentage of your estimated fluid losses or by drinking ‘X’ millilitres (or fl oz) per hour. 

2. Or by ignoring any type of planning and relying solely on ‘drinking to thirst’.

Now, these approaches may have merit for some athletes in certain situations but they shouldn’t be treated as binary options.

You don’t have to choose between ‘drinking rigidly to a plan’ or ‘drinking entirely to thirst’.

In most cases, there’s a middle ground and that's where we, at Precision Hydration, like to reside. It's an area where the words ‘it depends’ get used a lot.

Contents

  1. Measure your sweat rate
  2. Why you shouldn't aim for 100%, 'like for like' fluid replacement
  3. A flexible hydration strategy
  4. Conclusion
  5. Further Reading

 

Measure your sweat rate

When trying to understand how much you should be aiming to drink, it can be useful to start by looking at how much fluid you lose when sweating.

Conducting some simple sweat rate testing can help you get a handle on your sweat losses and we've outlined how to measure your sweat rate in this blog: How to measure your sweat rate to improve your hydration strategy.

Unlike sweat sodium concentration (i.e. how salty your sweat is) - which is relatively constant within a person as it's largely genetically determined - an individual’s sweat rate can be much more variable as it's affected by environmental conditions, intensity, and many other factors.

Measuring your sweat rate gives you a decent ballpark figure of how much fluid you lose during a certain period of time, at a certain intensity of exercise, and in particular environmental conditions.

Repeating the process under different conditions will provide you with a catalogue of data to consult and learn from.

 

Andy Blow drinkingCredit: skyrise productions ©

 

Why you shouldn't aim for 100%, 'like for like' fluid replacement

Once you've measured your sweat rate, there's a temptation to think ‘right, so that’s what I gotta put back in’.

Instead, when getting a handle on your fluid losses and putting your hydration strategy in place, one of the most important factors to bear in mind is that aiming for a 100%, ‘like for like’ replacement isn't something which is necessary, nor advisable.

There are several confounding factors which make the 100% 'like for like' approach unsuitable:

  • The fact that different athletes can tolerate different levels of dehydration
  • The rate of sweat and sodium loss can outpace your gut’s absorption rate
  • Your pre-exercise hydration status
  • The availability of drinks before, during and after exercise
  • And whether you’re only hydrating to get through the current session or you’re aiming to set yourself up for a good performance during another bout of exercise later that day or the next day

Striving for a 100% fluid replacement should be seen as a flawed and damaging approach. It goes against your natural thirst instincts and makes you susceptible to hyponatremia.

Hyponatremia is the medical term for low blood sodium levels, and exercise-associated hyponatremia is most commonly associated with an excessive fluid intake. In extreme cases, the health implications of hyponatremia can be fatal. 

 

flexible hydration strategy

The most successful athletes we’ve worked with have a basic framework for their hydration strategy which they’ve honed through trial and error in training and competition but - and this is crucial - this framework is flexible enough to allow them to make adjustments on the fly.

This ‘best of both worlds’ approach is very common amongst elite performers because they tend to be in tune with their bodies and can rely more heavily on their instincts and experience.

Becoming more reliant on your instincts over time will allow you to use your intuition to guide your fluid intake and this should be a big part of the development of a robust hydration strategy.

Less experienced athletes, or athletes who struggle with remembering to drink (something we hear quite often), may benefit from leaning a bit more towards a pre-planned approach, but again, building in some flexibility is key.

Some simple signs to look out for when it comes to overdrinking include feeling bloated or experiencing ‘sloshing’ in the stomach.

On the other hand, indicators that you may be under-hydrating are feelings of thirstiness, dry mouth or difficulty swallowing.

 

Man drinking water
Credit: Mauricio Mascaro ©

 

Conclusion

As I mentioned at the start of this blog, the answer to the question 'how much should I drink?’ may not be as straightforward as many athletes would like it to be.

We feel that regurgitating the standard fluid intake guidelines (e.g. 500-750ml for runners and 750ml-1L for cyclists) is a bit of a cop-out.

These guidelines are fundamentally flawed. For example, a person’s size will play a big part in how much fluid they can tolerate, so recommending 500ml (16oz) across the board fails to consider individual differences (e.g. an athlete who weighs in at 55kg compared to someone hitting the scales at 100kg).

So, by all means use the guidelines as a starting point, but from our experience a personalised approach is best.

Combining an element of drinking to thirst, using your experience, and listening to your body offers the best route to hydration success.

If you have any questions regarding your hydration strategy, please don’t hesitate to contact our team of customer service specialists who are more than happy to help refine your plan with you at hello@precisionhydration.com.

 

Further Reading

Abby Coleman - Sports Scientist and Customer Service

Abby Coleman

Sports Scientist

Abby Coleman is a Sports Scientist who completed her BSc (Hons) degree in Sport and Exercise Science at the University of Bath and has worked at the Porsche Human Performance Centre as an exercise physiologist. She also has qualifications in nutritional training, sports massage and sports leadership.

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