Andy Blow: Sweat Testing to Hone in Hydration, Sodium Replacement Needs

January 21, 2016

Endurance athlete and hydration expert Andy Blow, of Precision Hydration, joins this show to talk further about hydration and electrolyte needs, and why sweat testing could be your answer to overcoming blow ups in races and the ticket to the best performances of your life.


  • You can take Precision Hydration‘s FREE entry-level sweat test online to get your own personalized hydration plan.Want the full advanced Sweat Test that Tawnee had? Find your nearest test center.
  • Ready to up your hydration? Use the code “ENDURANCE10” to get 10% off your first Precision Hydration product order.
  • Find more deals on trusted products we love at
  • Click here to watch Tawnee receive a sweat test with the Gatorade Sports Science Institute (GSSI) in Kona as mentioned on this podcast! The results from this cycling sweat test are discussed on the video with GSSI experts as well as Andy during this episode, and we compare the cycling test with the machine-based sweat test…

On this show

*PART 1*

  • About Andy Blow
  • Andy was an elite-level triathlete and has a few top 10 Ironman and 70.3 finishes to his name. He brought home an Xterra World Age Group title back in the year 2000. Knee surgery forced him out of competitive triathlon a few years ago, but he still competes for fun at events like Coast to Coast New Zealand and OTillO Sweden. He’s got a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams. He learnt about hydration and electrolyte replenishment the hard way, by getting things very wrong and ending up in the medical tent of more than one hot-climate endurance event. It took a lot of frustrating trial and error to get to the bottom of his hydration problems. But it was totally worth it, as Precision Hydration was born out of this struggle.
  • The Basics:
  • Should we be measuring sweat via sweat test or is ball-parking enough?
  • “Drink to thirst” like Noakes says, but Andy adds: drink what you lose (in terms of electrolytes). Why is this?
  • Does our body has buffering mechanisms for sodium and that those mechanisms correct any sodium imbalances (according to noakes and maffetone)
  • Discussion from stats and data posted on Precision Hydration’s blog:
  • “Some people losing as little as 0.2g per litre of sweat and others losing near 2.0g per litre! This means that different athletes need to take in very different amounts of sodium when sweat output is high. This variance in sweat sodium loss is largely down to genetics. Whatever the cause, it’s clear that a ‘one-size-fits-all’ approach to electrolyte supplementation doesn’t work.”
  • “Our own data (which is probably one of the most comprehensive sets available) shows a much wider variance in sweat sodium values (approximately 19mmol/l to 84mmol/l) in well trained athletes than he quotes in the book (around 20-40mmol).”
  • The truth that there’s a wide range of sweaters and it’s genetics
  • Andy discusses his thoughts on the role of health status and how it can alter sodium regulation putting one at risk, and the role of health and hormonal balance in regulating hydration and sodium/electrolytes overall.
  • When hormones are in imbalanced state, and HPA axis no functioning properly, can this cause a hydration-related issue?
  • Ultra/extreme endurance races and racing in heat:
  • Recommendation for athletes who are racing 24+ hours or multi-day and in extreme dry heat?
  • In these extremes is it unsafe to just drink water? what about water but eating food like chips and whatnot
  • Flip that to something like ironman or ultraman in hawaii (humidity!). how do things change for hydration and sodium needs in these conditions vs dry heat?
  • What do you like to have athletes use? Tabs that dissolve.
  • Are salt tab and pills too concentrated?
  • Are gatorade and/or traditional sports drinks too much (i.e. too high osmolality and sugar?)
  • Special diets:
  • Dr. Jeff Volek recommends a pretty high sodium supplementation when on the ketogenic or LCHF diet. Noakes has even conceded that Jeff Volek might be right and that when LCHF, your sodium needs are different.
  • Discussing LCHF athletes sodium needs. “I’ve tried a lower sodium diet in general and it just didn’t work. The cramps would get really bad. Especially during sleep. Even my hands would cramp. I would also get super light headed.”
  • Andy gives his analysis on Tawnee’s sweat test in Kona with the GSSI

*PART 2*

  • Live with Andy Blow to get sweat tested with Precision Hydration’s equipment!
  • We met up with Andy again, in person, after the recording of the initial podcast to receive some sweat tests using his special equipment (no exercise required). Find out what the results showed and further analysis comparing a high sweater with lots of sodium loss vs. a low sweater with little sodium loss.
  • Two tests are completed during this meeting comparing two very different kinds of sweaters–John, a high sweater who loses a lot of salt (like Andy); and Tawnee, a low sweater who doesn’t lose much sodium.
  • What we can take away from this individualized approach and information to optimize sports performance.

Further listening

Comments (4)

  • brockdorf says:

    I disagree that people should take the online test. Every single endurance athlete should take the actual sweat test. I sweat salt as much as Andy, and this knowledge has made a huge difference and possibly saved my life. Before the sweat test I had no idea what was going on. I had actually semi-passed out twice (collapsing and loosing it but staying awake enough to get thru it). One of these was only on an Olympic distance event. For those 10% of us this is a game changer, and for those taking tons of salt for no reason, it is worth the few bucks. I will also add that I have never in my life suffered from a cramp and think we associate salt loss with cramps too much.

    • Tawnee_Prazak says:

      Thanks so much for your story and testimonial, we are stoked to hear you're dialed in and doing so well now! We agree this can be a total game-changer for some athletes out there, I've seen the difference in my fiance since he's now more dialed in. I took the online test and it actually lined up very accurately with my real tests (both Andy's test on the machine and the cycling test with GSSI). If the athlete has enough basic knowledge of him or herself, the online test is a good place to start. But you're right–why not go the extra step for the real test too?! It just makes sense especially if you've suffered.

      Thanks again for sharing!!!

  • […] to athlete, and there is no one-size-fits-all approach. Find your nearest test center here (and listen to this show for Tawnee’s experience with this test). Or to start, take Precision Hydration’s free […]

  • […] to athlete, and there is no one-size-fits-all approach. Find your nearest test center here (and listen to this show for Tawnee’s experience with this test). Or to start, take Precision Hydration’s free […]

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