Nutrition, Podcast

Race hydration, calories and sodium – a 2020 update with Andy Blow | EP#218

 January 27, 2020

By  Mikael Eriksson

Race hydration, calories and sodium - a 2020 update with Andy Blow | EP#218

Race hydration, calories and sodium - a 2020 update with Andy Blow

Andy Blow, founder of Precision Hydration is back on the show to revisit the topic of hydration and nutrition strategies for triathlon and endurance events and races. This episode is packed with practical and actionable advice that will put you in a great spot to get your race day nutrition and hydration right.

Discuss this episode!

  • Let's discuss this episode and the topic in general. Post any comments or questions in the comments at the bottom of the shownotes. Join the discussion here!

In this Episode you'll learn about:

  • An overview on sweat rate and sweat sodium concentrations, and the vast differences in losses and replacement needs between individuals
  • Why Andy recommends separating your energy from your hydration
  • Training the gut to better tolerate nutrition and hydration during racing
  • Hydrogels like Maurten and Beta Fuel
  • Wearables that measure hydration and sweat status in real-time and non-invasively

Sponsored by:

Precision Hydration

Precision Hydration
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Inter individual differences in sweat production rate and sweat composition

04:20 - 

  • There is a significant variation between individuals in regards to sweat production rate and sweat sodium composition.

    These differences may not be that important during shorter races under fairly normal conditions, however, as the race time increases and/or if the race takes place in an extremely hot and humid environment, these individual variations become more and more significant and needs to be addressed.

  • Inter individual differences in fluid loses: There is a big inter individual variety in sweat production rate, which is also very dependent on outside temperature.


On average, a person can sweat around 1200 ml per hour, but as much as over 2000 ml per hour is not rare.

    The 1200 ml fluid loss per hour mark is interesting since most people have trouble absorbing more fluids than that.

    In order to get an opinion regarding your own sweat production rate, being as specific as possible is recommended, i.e. test your fluid loses in similar environmental conditions as your targeted race and at goal race intensity.

    Also connect your fluid intake and loses not only to changes in body weight but to your performance.

    The sweat production rate does not seem to vary that much from day to day for the same athlete, heat acclimatization can bring the production rate up, but usually those changes are minor.
  • Inter individual differences in sweat sodium composition: As we see a 4-5 time variance between individuals in fluid looses, the variance in sweat sodium composition can be up to 10-11 times, from 200 to 2000 mg sodium per liter sweat.


You can test your own sweat sodium composition in two ways: ”The trial and error way” where you use your intuition or answer a few free questions on the Internet or you can take a sweat sample.

    The sweat concentration seem to stay rather stable for the same person, so one sample is basically enough to get a good estimate of your sweat sodium composition.

    The free online questionnaires for estimating your sweat sodium concentration seem to show a higher degree of accuracy for individuals with high sweat sodium composition.

    An important indicator of a high sweat sodium concentration is salt stains on your body and/or clothes following training, however, this marker is highly dependent on the environment, a hot and dry climate tend to leave considerably more noticeable stains compared to a more humid climate.

Combining energy, fluid and electrolyte intake

20:30 -

  • Generally it is recommended to separate your fluid and electrolyte intake from your energy intake as much as possible.

    There is evidence for that you can absorb fluid and electrolytes much more efficiently if the intake is not combined with plenty of carbohydrates.

  • Recently developed energy drinks like Maurten does have a very high carbohydrate concentration but the gastric uptake is supposed to be enhanced by incapsulating the carbohydrates in a special way facilitating the gastric emptying process, however, it is still rather unclear if this technique leads to any performance gains.
  • Newly developed sports drinks that are advertised to break down the carbohydrates more slowly, leading to a more stable energy release seem to fit certain athletes well, but in the end, for most people, the most important aspect is to get the fundamentals right, i.e. to get the right proportion of components in during a specific time frame.

The most common fueling mistakes

28:50 - 

  • Drinking too much of isotonic sports drink.


For instance, Getorade Endurance that is served on the North American Ironman circuit does have a huge content of carbohydrates and much less electrolytes, leading to a skewed intake by people mainly relying on this product as their fueling.


Isotonic sports drinks with plenty of carbohydrates tend to lead to gastro intestinal distress for many athletes.
  • Don’t know exactly how much fluid, electrolytes and carbohydrates that is required to take in per hour for a given race.
  • In general, an intake of 60-90 grams of carbohydrates per hour is a good target to aim for, however, it is very important to put this amount into the perspective of what your intake has been previously, doing big changes too fast is often a good recipe for gastric upset.

High intake of carbohydrates (> 100 grams/h)

34:20 - 

  • Especially in cycling, some professional athletes state that they can consume a much higher amount of carbohydrates than what is normally consider to be physiologically possible (~90 grams/h), also at a high intensity.


These athletes may be genetically predisposed to this or might have trained themselves to this ability.
  • The composition of sugar types may affect the ability to take in the total amount of carbohydrates.
  • Intake must also be correlated to intensity, for instance, riding at 250W requires much more energy than riding at 150W and intake must be planned based on that.
  • In order to get to know where your intake limit is, testing different strategies and relating them to performance and/or any levels of gastro intestinal distress is the recommended way to go.

Metabolic testing for planning race hydration and nutrition strategy

42:55 -

  • One shouldn’t let such numbers dictate your training and racing strategies too much, but if it is used intelligently and methodologically it can be a good tool to base your strategies from.

Practicing race nutrition

48:47 -

  • Being able to increase your gut’s ability to tolerate and absorb plenty of energy seems to be very trainable, especially for unexperienced athletes.
  • In your preparations for longer distance races (typically the Ironman distance), it is absolutely paramount to getting your body and gut accustomed to your race nutrition strategy.

    Ideally, your race nutrition plan should be practiced during sessions similar to your targeted race, this could for instance be a longer brick session at close to target race pace.

    It is rather unclear if practicing taking in your planned race nutrition on more or less every single training session will have an additional effect.

Isotonic vs hypertonic gels

53:48 -

  • Isotonic gels (usually advertised as liquid gels) may be easier absorbed compared to highly hypertonic gels, particularly under hot conditions, and is recommended especially when the supply of water or hypotonic drinks are scarce on the race course.

    When there is a great supply of water and hypotonic drinks out on the course, one can wash down a hypertonic gel with some extra water to get the similar effect as an isotonic gel.

Monitoring hydration, nutrition and electrolyte parameters

57:45 - 

  • There is currently a strong development in new ways of monitoring sweat and electrolyte losses as well as other hydration, electrolyte and nutrions parameters in real time.

    As of now, all that can be done is doing fairly accurate estimates based on snap shot in times of these parameters, little is known about what the actual dynamics of these are.
  • Getorade Endurance will probably rather soon release a sweat patch that measures the sweat consumption over time, other similar gears are in the prototype stage and there will probably take a while some time before they will be commercially available.

Final recommendations/key take home messages

1:00:42 - 

  • Be thorough in regards to the basics, i.e. make sure that your intake of fluids, electrolytes and carbohydrates matches your individual losses.

    Don’t get too carried away by intense marketing such as the hydrogel technology advertised by Maurten, the gains are probably marginal at best.

Links, resources and contact

Links and resources mentioned

Connect with Andy Blow

Connect with host Mikael Eriksson


Hi! I'm your host Mikael,

I am a full-time triathlon coach and an ambitious age-group triathlete. My goal is podium at the Finnish national championships within the next few years.

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Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

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  • Interesting podcast.

    I have one question. How is consuming electrolyte fluids independent of caloric intake going to increase gastric transit time?

    I agree that strictly consuming fluids with electrolytes will have faster gastric transit times than a carbohydrate rich fluid. But this is not all that is going on during a triathlon. Whether the fluids have carbohydrates or not the athlete will need to be consuming calories which will slow the transit time no matter if they are in the same solution.

    What are your thoughts?

  • We try to estimate how much sodium you lose in our sweat.. But can we just be on safe side and consume 1500… maybe You call it overdose if an individual actual rate is 500, but what is the negative effect of such electrolyte overdose ???

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