Sweat Testing for Better Performance

News and Updates

We train our bodies in the disciplines of swim, bike, and run so we can perform at our best on race day, and fine-tune nutrition to make sure we don’t run out of fuel. But we also lose sodium and other minerals as we sweat, which affects how we perform.

Photo by Damir Spanic on Unsplash

How important is sodium in athletic performance?

Sodium plays important roles in the absorption of nutrients in the gut, as well as maintaining fluid balance, cognitive function, and nerve impulse transmission affecting muscle contraction.

A 2015 study found that athletes who adequately replaced the sodium lost in their sweat finished a middle distance triathlon an average of 26 minutes faster than those who didn’t. While that sort of performance gain isn’t going to be possible for everyone, it does highlight the potential impact of getting your hydration strategy right.

How much sodium do we need to replace?

Everyone’s numbers are different and can vary between 500mg to an excess of 1800mg per litre of sweat.  This number is unique to you and will not change; it is part of your genetic makeup.

The only way to really know how much you need to replace is to have your sweat collected and analysed.

Rebekah Bruhwiller has been a Sweat Test Centre in Switzerland for Precision Hydration since 2015. Currently in Australia, she has now developed a home collection kit for A$100. (The normal cost for a one-to-one sweat test is A$377.)

This will allow you to collect your sweat sample and send it in to be analysed. Then a full Precision Hydration plan will be emailed to you.


“I knew I was a heavy sweater but had no idea how much sodium I lost. With an exact measurement, I was then able to add H2Pro to my nutrition plan… The effect of getting the correct level of electrolytes, especially sodium, into my body during training & racing has been to increase my alertness, keep my focus, and recovery is also better. The test was so simple & easy to complete”.

– Julie-Ann Dillon

“Having a sweat test with Bek changed my race day and training outcomes. Cramping was a major issue for me. I’d done the conventional weigh in, train, weigh in test to understand sweat loss via weight. But Bek’s test showed me how much sodium I was not replacing via simple water or nutrition. With this info, I now train and race knowing my sodium is right to ensure I don’t cramp or dehydrate myself to a point I have nothing left on the run.”

– Lee Postlethwaite

“I did the online quiz… it returned that I was a high sweater, and sodium loss in the range of about 1500mg. So I purchased a large amount of the product and started taking the product, but never felt great during training. I always felt sluggish, bloated, and puffy. I then got chatting to Bek… She suggested I take the medical Sweat Test. WOW, the results showed that I only lost 500mg of sodium per litre of sweat. Thanks Bek, feeling much better now in training.”

– Kylie S (Elite Triathlete)

About Rebekah Bruhwiller

Rebekah Bruhwiller has represented Switzerland in age group triathlon and world championships. She was also an Australian title/state representative for track athletics (100m and 400m) and is a credited swim teacher in Australia. She has a Masters in Human Nutrition from Deakin University, a Bachelor of Commerce, and is currently working toward her personal trainer certificate III & IV. She is a member of the Nutrition Society of Australia (NSA).

While training for her first Ironman and planning her training and race nutrition, she went to get a sweat test from Precision Hydration knowing sodium plays an important role in athletic performance. She eventually trained and became the test centre in Switzerland in June 2015.

Rebekah believes hydration was one of the reasons she finished third in her age group in that first Ironman. “I ran a sub 4 hour marathon and my last 10km was at 4:45k/pace.  I was coming 10th in my Category going into the last 10km loop, and I passed 7 people to podium.”


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The Pho3nix Foundation assists and inspires children worldwide to achieve their dreams and live healthy, inspired lives through sport.

From kids triathlons and workshops to teen sports camps and assistance for aspiring Olympians, Pho3nix projects create a pathway from participation to professionalism. Pho3nix Club memberships and donations support every step on that pathway.