In my two ‘A’ races this year – the Zell-am-See 70.3 World Championships and Chicago ITU Standard distance AG World Champs, it’s fair to say I was slightly disappointed by my results. In both instances, the results weren’t “bad”, with 7th and 5th place in the World respectively, but what was “bad” was how I raced and how I felt on the run.

In both instances, I ‘collapsed’ in the run: I ran comfortably and at target pace for 3km in both. Then I took a gel. Then 500m, my pace dropped and became seemingly impossible to pick up. Both races were on hot days, with temperatures higher than I was used to (35C in Austria). I had naively thought “oh, make sure you drink more than usual” before both. It’s not until taking the H2Pro hydrate Sweat Test and reading their blog that I realise what was more likely to be the source of my problems: too much salt, and dehydration.


Quick and Easy test – get it done with a friend!

The Test

It’s an extremely simple procedure, and takes about 20 minutes. You find out your results there and then and can discuss the implications of the results on your hydration strategy with whoever the lovely person doing the test is (in my case the knowledgable Dimity Lee-Duke).

No physical exertion is required, and no needles touch your skin!

  1. Electrodes placed on your forearms and vibrate for 5 minutes to induce sweat secretion.
  2. A small device with a tube to collect the sweat is placed on the forearm to collect the sweat until there is a sufficient volume to analyse.
  3. The sweat is passed through the analyser to give a value – mine was 20, and my friend doing it at the same time was 35.
  4. These ‘sweat values’ were then put into an equation, and the concentration of sodium in your sweat is the product.

Tube with the light blue sweat collected inside, ready for machine analysis



In my short time training in the tropics, I realised that, relative to others, I sweat a lot (high sweat rate). But what I didn’t know was in each litre of sweat, how much salt goes out. Now I do, and it’s actually considered “very low” relative to otherathletes at 409 mg of sodium per litre of sweat. Every individual has a fixed salt concentration per litre of sweat. This is genetic and does not change over time.

The Implications

I have been asked whether my level “is good or bad” multiple times. Well, it’s not really about that. It’s more about knowing what your level is to allow you to compensate for your high/low or even normal sodium level as appropriate.

In essence, for every litre of water I drink in a race, it should contain 409 mg of salt. This is assuming that

  1. I take no other gels etc with salts and;
  2. I’m staying 100% hydrated.

Of course, you still don’t know how many litres of water you should be drinking to compensate for your sweat rate. This depends on the conditions, what you are doing (intensity and duration), and who you are. This can be calculate in a pretty simple D.I.Y process, just remember weather conditions on race day are unlikely to be the same!

So just buying any salt tabs won’t do: you could be over-saltifying yourself (or more scientifically become hypernatremic). This is also dangerous and is the opposite of too little salt (hyponatremic) for an athlete, especially in an endurance race. The effects of such dehydration can seriously affect your results:  in my case several places on the run, but if it had been a longer race, potentially withdrawal.


#1 Thai athlete being tested by Dimity-Lee Duke

I would thoroughly recommend sourcing your local “sweat-tester” to find out your salt concentration – they will probably be race changing!


For those in Switzerland, I would recommend Rebekah Bruhwiller. For people in S.E Asia and Australia I would 100% suggest seeking the professional advice of pro-triathlete Dimity-Lee Duke, or check out the H2Oprohydrate for your local test centre.


One Comment on “H2Pro Hydrate Sweat Test

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