Sweat testing for athletes: is it worth it?

Understanding your sweat content helps you tailor your rehydration needs effectively on race-day

Luke McKenzie completes a fuel utilisation test at the Gatorade Sports Science Institute in Barrington © Steve Green

Sweat testing to measure performance is growing in popularity for athletes across endurance sports because understanding your sweat’s sodium content allows you to tailor electrolyte intake specifically to personal needs.

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Sweat sodium content varies by person, and is genetically determined, meaning it’s pretty stable throughout adulthood.

The simple test is painless, efficient, insightful and low in cost. Electrodes on the skin artificially stimulate sweat glands to collect a sample and results can be drawn in as little as ten minutes. But why do it?

Hannah spoke to top long-course athletes Luke McKenzie, Mirinda Carfrae, Rachel Joyce and Beth Gerdes to find out if they’re sweat testing and the valuable lessons they’ve learnt along the way.

Mirinda Carfrae, Ironman World Champion 2010, 2013 and 2014

Have you looked into sweat testing?

I have never had sweat testing done but I’m eager to partake this season ahead of Kona in October. I’ve been impressed with the technology and some of the non-invasive measures being tested for real time feedback.

Having not yet sweat tested, how do you stay on top of hydration needs?

I have tested and trained in racing and competition environments and know what works in different race formats and weather conditions. On long duration or high intensity training days I fuel with GU Roctane Energy Drink.

 Have you ever experienced any major hydration issues?

In (Kona) 2012 I dropped one of my key nutrition bottles and felt firsthand the significance of trying to execute a plan on the fly. A powerful lesson and another reason to stay focused on your intake during any race.

 How much confidence do you have in the products you use for training and racing?

Having confidence in your product is key. Racing and training with the product that works for you is just plain doing your homework. GU Energy has been a partner of mine for years and I reached to them leading into my first Ironman, starting with gels. In Kona I use Roctane Electrolyte Capsules as insurance in case I start to feel cramping.

Luke McKenzie, 2nd Ironman World Champs 2013

Have you had sweat testing done?

Yes. I recently traveled to Chicago’s Gatorade Sports Science Institute to do some extensive sweat testing. We performed 1.5 hours of Ironman race pace riding and running in a heat chamber set at Hawaii-like conditions.

 And the results?

We analysed the results, and have started creating an individual sweat replacement programme for me. As part of this I’ll be using a range of Gatorade Endurance products and this season will be working with the GSSI team to give constant feedback.

Do you expect to see a significant impact on your racing?

Absolutely. Proper hydration especially at a race like Kona (Ironman World Championships) is crucial for a top result. Last year I didn’t place enough emphasis on executing the perfect nutrition plan and the day ended with my very first DNF at Kona – I have teamed up with Gatorade Endurance in 2016 with the goal to return to Kona more prepared than ever.

Meredith Kessler, Ironman Asia-Pacific Champion 2015

What are your thoughts on sweat testing?

I sweat tested when I was just turning professional in 2010, yet I didn’t pay too much attention to it. Sixty Ironman competitions and many other 70.3 races later, trial and error has meant I am more dialed-in to my hydration needs. I would recommend using a combination of experience and a sweat test to lessen the time it takes to unlock the secret.

What’s your go to hydration plan?

I use what I find works for me in training and this carries over to race day. This is BASE electrolyte salt. Never train on something that you won’t use on race day and vice versa.

How did you find the right product for you?

Again, trial and error. What works for one person can be detrimental for another. The human body is an amazing engine ­­­­­– and everyone’s engine beats to a different drum.

Rachel Joyce, ITU Long Distance World Champion 2011

Have you ever looked into sweat testing?

I have done the sweat test analysis designed by H2Pro Hydrate – this measures your approximate sweat rate plus how much sodium (and other electrolytes generally), you are losing in your sweat.

 What output did you get from the test?

The test showed that whilst I have a very high sweat rate I lose very little sodium in my sweat.

 Have you implemented a hydration plan based on the results?

It showed that I need to drink a lot of water and weak-strength electrolyte during HIT training sessions and races. I bought some ofPrecision Hydration’s product – the tabs with fewer electrolytes.

Beth Gerdes, Ironman Switzerland champ 2015

Have you had a sweat analysis?

I just recently had my sweat tested and analysed at the Gatorade Sports Science Institute. I’m categorised as a ‘heavy sweater’ and I lose 1.7 l/hr in Kona-like conditions on the bike and run. I also lose 1400+ mg of sodium per hour.

 Your result is toward the higher end of sodium loss, are you using specific products for that?

Yes! For me, Gatorade Endurance Formula is perfect because I like the taste and it is high in electrolytes with 600mg of sodium per 24oz bottle. I shoot for one bottle of G Endurance and 1 bottle of water per hour in a long race like an Ironman.

 Are the products making a difference?

Absolutely. This is a huge focus for me this year and I’m looking forward to putting my learnings with GSSI into practice to have a foolproof hydration plan for racing and training.

You can get your sweat tested at the National Triathlon Show (April 8-10) with Precision Hydration 

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