BESTZEIT sweat testing for your Personal Best

Karen Parnell June 28, 2022


BESTZEIT has been around since 2017 and was founded by an engineer called Markus Nußbaum. Markus wanted to combine his engineering background with his love of triathlon to create a product that would help athletes achieve their personal best. Hence the name “BESTZEIT” which means personal best or best time in German.

If you have done or are doing an IRONMAN® event you may see a sweat test kit from BESTZEIT in your goody bag.

They advise that you test your sweat rate two weeks after your event with an hour-long high intensity session. You put the patch on your forearm and run or cycle (I would not advise swimming!) and then put the patch in a test tube, label the box and apply for a free postage label on the website. In my case I went for a very hot run in the mountains here in Southern Spain.

If you have been given a free test kit, then your test cycle is completely free with free postage and a free App from either the Google Play store or Apple App store.

BESTZEIT Sweat Patch                                               

Test Tube packaged up to send for testing

If you don’t get a free test kit at an IRONMAN race and want to know your sweat rate you can purchase a kit for €99. This will also enable you to get free access to their App.

What’s in the box?

  • Absorbent patch to collect your sweat
  • Alcohol wipe to ensure your arm is clean to accept the patch
  • Plastic test tube to send the patch and sweat to BESTZEIT
  • Stickers to seal the test tube, seal the box and your unique QR code
  • Instructions on how to take the test and apply for free postage

The test patch, alcohol wipe, test tube and stickers

Why should I know my sweat composition?

Your sweat composition doesn't follow any rule of thumb, nor does it fit in any standard tables. During long training sessions, especially in warm and hot conditions, you lose a lot of sweat. Besides the loss of fluid, you also lose electrolytes via your sweat. How much? It depends on your individual sweat and sodium profile.

What do BESTZEIT measure?

With the sweat pack, they measure the sodium content in your sweat. The analysis is done in their lab in Germany. In the App they collect more information related to your sweating behaviour and your sweat rate to give you an individual fuelling recommendation. They only use your own and not standardized data, so their guidance is very bespoke to you.

Which method is used in the sweat pack?

Sweat testing is a well-known and validated method in science to understand more of the very individual needs of an athlete. Within the Sweat Pack the absorbent patch method is used to collect your sweat. It's the best method to collect your sweat during field testing under real conditions. After you've sent in your sweat sample, they prepare them for further analysis in their lab.

In my case I chose a very hot trail run on a mountain in Southern Spain to collect my sweat data. I started out at 8:30am when the temperature was just 28 degrees but by the end of the one hour run it had risen to 31 degrees so needless to say I had enough sweat collected!

The App supports you in creating your individual sweat profile. Based on that BESTZEIT will create your fuelling strategy based on the nutrition and hydration products you like to use, and your race type and distance. Considering your individual energy demand, your racecourse, and your personal sodium loss, they will be able to provide you a 100% individual pacing strategy.

Hydration and Sweat Loss

On race day your sweat loss will be about 2% of your body weight and this will limit your performance. So, creating your individual sweat profile and drinking within your individual fuelling zone will help greatly.

Electrolytes, especially sodium, influence your hydration balance, your energy level, heart and brain function and with the right balance can prevent hyponatremia.

Get some FREE resources including training plans here Chili Tri

What is Hyponatremia?

Hyponatremia is a low sodium concentration in the blood. It is generally defined as a sodium concentration of less than 135 mmol/L (135 mEq/L), with severe hyponatremia being below 120 mEq/L. In healthy athletes in a race, urine production normally decreases and sodium loss (via sweat) increases, setting the stage for hyponatremia if too much fluid is ingested or retained. Under these circumstances, excessive drinking will decrease your plasma sodium concentration and can lead to some dangerous situations. For endurance athletes’ mild symptoms include a decreased ability to think, headaches, nausea, and poor balance. Severe symptoms include confusion, seizures, and coma. You need to monitor your sodium loss under various conditions to understand your sweat rate and how to keep it optimal for endurance events such as IRONMAN® triathlons, marathons and Ultra events.

Pacing on Carbohydrates

The availability of energy is crucial to perform at your personal best. Did you know that your carbohydrate stores are biologically limited? Pacing on your carbohydrate combustion means not limiting yourself.  On a recent webinar with Markus he said that their maybe a tie in with Supersapiens, the glucose monitoring company, in the future to give athletes data on both sweat rate and glucose use during training and racing.


Once you have set up your profile in the App and sent your sweat patch off for analysis your will see your test results appear in the App.

From there you can scan the hydration and nutrition products you plan to use in your race, in my case it was SiS hydro tabs and OTE gel products. You can then enter your race and in this example, I added IRONMAN Vitoria. This race and product specific fuelling strategy is called “Nutrilizer” by BESTZEIT.

I also connected my Garmin Connect account so the App could understand my running and cycling stats. You can also connect your Polar account if this is your preferred training device brand. Connecting your Garmin account with your BESTZEIT App enables you to do an eDiagnostic during your cycling or running sessions. After you have completed your eDiagnostic, you will receive a detailed evaluation in the BESTZEIT app.


The eDiagnostics for your BIKE and RUN can determine your performance data, such as:

  • VO2max
  • VLamax
  • training zones
  • Carbohydrate & fat curve
  • Threshold power

Your results are one of the components of your pacing strategy.

After each training session, for example, you receive an individual drinking recommendation based on training intensity and temperature.

In order for the App to calculate your fuelling strategy you need to have a subscription. There are three levels:

-          Basic (19€/month) which gives you a sweat profile, Nutrilizer, integration of existing diagnostic and sweat test results and 1 fuelling and pacing recommendation

-          Medium (29€/month) which gives you the above plus 1 eDiagnostic for the bike and 1 for the run and 1 sweat pack a year

-          Pro (49€/month) which gives you unlimited eDiagnostics, sweat packs and fuel & pacing recommendations

All levels of subscription have a 30-day trial period. When you subscribe you get a personal 30-minute onboarding call with a BESTZEIT expert.


Images from the Bestzeit App showing your water, energy and sodium for your training session and race


If you want a deep dive in to your sweat rate and how/when to fuel your races and long training sessions based on your exact sweat rate, then BESTZEIT could be a good investment for you.

If however you want a basic home analysis of your personal sweat rate on the bike and run you can do your own sweat rate test which is detailed in my Blog here.

Sweat is natural and it's part of who we are – as men and women. Interestingly, prepubescent girls and boys sweat about the same volume. But once hormones kick in, sweating starts to vary between the sexes with men tending to begin sweating sooner and in higher volume (with activity or heat) than women.

Knowing that there is a difference in sweat rate between women and men and from person to person it is important to know your specific rate so you can plan your hydration and nutrition for your next race.

Creating a race hydration and nutrition plan gets even more important if you plan to do a long endurance race like and IRONMAN or Ultra running event. This could be the difference between a PB and a DNF at your next big race.

Get some FREE resources including training plans here Chili Tri

Karen Parnell is a Level 3 British Triathlon Coach, 8020 Endurance and IRONMAN Certified Coach, WOWSA Level 3 open water swimming coach and NASM Personal Trainer and Sports Technology Writer. 

Need a training plan? I have plans on TrainingPeaks and FinalSurge marketplace:



8020 Polarised Training Plans

I also coach a very small number of athletes one to one for all triathlon distances, open water swimming events and running races, email me for details and availability.



FAQ: The Bestzeit Sweat Test Kit

What is the Bestzeit Sweat Test Kit?

The Bestzeit Sweat Test Kit is a product designed to help athletes determine their individual sweat composition and sodium concentration during exercise. It provides insights into an athlete's hydration needs and helps tailor their hydration strategy for optimal performance.

How does the Bestzeit Sweat Test Kit work?

The Bestzeit Sweat Test Kit involves collecting a small sweat sample during exercise using the provided patches or patches designed specifically for the kit. The collected sweat is then sent to a lab for analysis. The lab measures the sodium concentration in the sweat and provides personalized recommendations based on the results.

Why is knowing sweat composition important for athletes?

Understanding your sweat composition, particularly the sodium concentration, is crucial for proper hydration during training and competition. Sodium loss through sweat varies among individuals, and replenishing sodium along with fluids is essential to maintain electrolyte balance and prevent dehydration and hyponatremia.

What are the benefits of using the Bestzeit Sweat Test Kit?

The Bestzeit Sweat Test Kit offers several benefits for athletes:

  • Personalized hydration strategy: The test results provide personalized recommendations for fluid and sodium intake based on individual sweat composition, helping athletes optimize their hydration during training and races.
  • Improved performance and endurance: By tailoring your hydration strategy to match your sweat composition, you can maintain optimal hydration levels, electrolyte balance, and performance during endurance activities.
  • Prevention of dehydration and hyponatremia: By understanding your sodium loss through sweat, you can avoid both dehydration and hyponatremia, which can negatively impact performance and health.

How accurate is the Bestzeit Sweat Test Kit?

The Bestzeit Sweat Test Kit is designed to provide accurate results when used correctly. The lab analysis of the sweat sample provides precise measurements of sodium concentration. It's important to follow the instructions provided with the kit to ensure accurate results.

Can I use the Bestzeit Sweat Test Kit for different sports?

Yes, the Bestzeit Sweat Test Kit can be used by athletes participating in various sports, including triathlon, running, cycling, tennis, and more. The kit helps athletes from different disciplines understand their unique hydration needs.

How often should I perform the Bestzeit Sweat Test?

It's recommended to perform the Bestzeit Sweat Test every 6 to 12 months or whenever there are significant changes in training volume, intensity, or environmental conditions. Sweat composition can vary over time, so periodic testing ensures your hydration strategy remains accurate and effective.

How do I interpret the results of the Bestzeit Sweat Test?

The lab analysis report provided with the Bestzeit Sweat Test Kit will include specific recommendations for fluid and sodium intake during exercise based on your sweat composition. The report will guide you on how to adjust your hydration strategy accordingly.

Can the Bestzeit Sweat Test Kit replace regular hydration practices?

The Bestzeit Sweat Test Kit is a valuable tool to optimize hydration, but it should be used in conjunction with other hydration practices. It provides personalized insights to inform your hydration strategy, but it's still important to listen to your body, monitor thirst cues, and adapt your hydration plan as needed.

Always consult with a sports nutritionist, coach, or healthcare professional for personalized advice and guidance based on your specific needs and circumstances.


Gender Differences in the Sweat Response During Spinning Exercise, Lynton Tempest HazelhurstTshwane University of Technology and Nico ClaassenUniversity of Pretoria.



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