Sweat Test Process

All you need to know about PF&H’s Sweat Test.

All you need to know about PF&H’s Sweat Test.

But you also need to replace the sodium the key electrolyte) you’re losing in your sweat. Sweat sodium concentration (ratio of sodium to fluid) is genetically determined and can vary significantly from person to person.

We can test your sweat by placing 2 electrodes on your forearm and stimulating your sweat glands – no exercise required.

This disc is placed on top of the now-sweating spot, and collects the sweat sample into the tube. All we need is a few rings full before it’s ready to test.

The Sweat Analyzer reads the sample and tells us the mg of sodium (converted from mmol) per litre of fluid. Based on this number, you’ll learn what the best sodium:fluid ratio is for you.

Your Sweat Test officer will ask you a few questions to help interpret the results and explain your personalised plan for optimal hydration. And then you’re ready to rock!

Athletes Frequently Ask

There’s no universally correct answer for whether you should combine your fuel, fluids and electrolytes into one bottle or keep them separate. The science is inconclusive on the subject, and you can see in our Case Studies that athletes of all abilities perform well using vastly different approaches.

What matters most is that you hit your numbers and that the method you use works from a practical perspective in the event you're trying to fuel and hydrate for.

When combining everything into a single bottle can work:

Having a super-concentrated bottle with carbs (and sometimes but less commonly electrolytes) in it is a convenient way of carrying a lot of fuel in a small space. A classic example of this is placing a PF&H Flow Gel into a PF&H Flow Flask, so you have the vast majority of the carbs you need in one place. Water and electrolytes are then carried in other bottles (or electrolytes in the form of Electrolyte Capsules) + supplemented with additional water you pick up from aid stations on the course.
Using a Carb-Only Drink Mix or Carb & Electrolyte Drink Mix. This approach provides Carbs + Fluids (and electrolytes in the latter) in a single bottle. Whilst the total amount of carb you can get from using a drink like this is much lower than using a super-concentrated gel bottle, this approach can work very well for short to medium-duration events where, typically, hourly carb and fluid intakes are slightly lower and the advantage of only having to consume liquid (i.e. not having to try to open and consume gels or chews when moving fast and breathing hard) is considerable.

When separating fueling from hydration can work:

Using a carb-based drink mix to provide all of your fluid, carb (and possibly electrolyte) needs for a long event, especially in the heat, is a potentially risky move as it removes the ability to adjust your intake of any one of the 'Three levers' - Carbs/Fluid/Sodium - independently as the race wears on. It can also increase the risk of GI issues in hot races if you have to drink very large volumes to meet your hydration needs and end up with an excess of liquid carbs in your stomach as a result.
In longer, hotter races, we generally advise athletes to 'decouple' their carbs/fluid/sodium intake, relying predominantly on gels or chews for fuel and water with electrolytes (either in effervescent tablet or capsule form). This allows the carb/fluid and sodium intake rates to be adjusted in real time based on how you're feeling and performing on the day.

That doesn't mean that combining the 'Three Levers' in one bottle can't work at all during a long race - there are plenty of examples of where people use a 'hybrid' approach in long events by utilising some drink mix along with gels, electrolyte capsules and water to meet their total fuel and hydration needs. It is, however, rare to see an athlete succeed using only a drink mix to meet 100% of their requirements in longer and hotter races.

We always recommend reviewing the characteristics of your upcoming event, along with your personal carb, fluid, and electrolyte targets, and determining which of the above approaches is most compatible.

As ever, the team at PF&H are always happy to jump on a free 20-minute Video Consultation with you to talk through a plan and troubleshoot alongside you.

If you wanted to direct your customer to learn more, we've filmed a 'How to fuel a marathon' series over on YouTube… HOW TO FUEL A MARATHON (PART 1)

Your fuel and hydration strategy still matters, no matter what the conditions.

If it’s cold out, you’re likely to sweat less, but cold, dry air increases fluid loss through breathing, and wearing extra layers often means you’re still sweating more than you realise. On top of that, thirst cues are weaker in cold weather, so a lot of athletes tend to habitually drink less. Top tip: drinking hot fluids can help.

We always recommend starting sessions well hydrated. If you’ve had a busy day or you’re heading into a longer or harder workout, having ~500ml of a strong electrolyte drink (around 1,500mg sodium per litre) 60–90 minutes beforehand can really help. This is a strategy we call preloading.

For ~60–90-minute sessions in the cold, assuming you start hydrated, you probably don’t need to drink much during. For longer sessions, especially outdoors, adding electrolytes helps you absorb and retain fluid. This really matters because chilly conditions can make you pee more (a phenomenon called cold diuresis).

Your fueling strategy shouldn’t change based on temperature. Intensity and duration determine the carb you need, not how hot or cold it is.

In summary: drink to thirst, use electrolytes during long/hard sessions, and preload if you struggle to drink when it’s cold. For fueling, aim to consume the same amount regardless of the temperature.

If you’d like to dial in your strategy further, use the free Fuel & Hydration Planner, or you can book a free Video Consultation with the fuel & hydration experts.

Not necessarily. Sweat rate (how much you lose) and sweat sodium concentration (how salty your sweat is) are two different things. Some people sweat buckets but lose hardly any sodium; others sweat very little but lose a lot of sodium. Some outliers sweat profusely and could open a salt mine after a light session!

To refine your hydration strategy, it’s worth measuring your sweat rate (which you can do at home). And estimate how salty your sweat is by looking for signs (such as salt stains on your kit) if you can’t get a Sweat Test.

Precision Fuel & Hydration have done thousands of Sweat Tests, and the average athlete loses ~991mg of sodium per litre of sweat. Which is why PH 1000 (which contains 1,000mg of sodium per litre when mixed) is typically the strength that they put out on course at events they support.

A good place to start to find out which strength of drink is right for you is to use the free Fuel & Hydration Planner.