Sweating is an inevitable and crucial (if a bit unpleasant) part of exercising. Andy Blow of hydration experts Precision Hydration explains a few things that we might not know about our sweat…

1. It’s mostly made up of water and sodium.

Your sweat only contains small amounts of potassium, calcium, and magnesium. It only contains up to about 150mg of potassium per litre, for example, whereas you can lose as much as 2,000mg of sodium per litre of sweat.

So, sodium is the main electrolyte to worry about replacing when it comes to staying hydrated and maintaining your performance.

2. Everyone loses a different amount of sodium in their sweat.

It’s not just about how sweaty you are, it’s also about how much sodium you’re losing in every drop. The average person loses about 950mg of sodium per litre of sweat. But some athletes lose as little as 200mg/l, with around 20% of athletes losing more than 1,500mg/l, according to the thousands of Sweat Tests we’ve done at Precision Hydration.

3. How much sodium you lose in your sweat is largely genetically determined.

Although how much you lose is somewhat influenced by diet, acclimatisation to heat and severe dehydration, it’s pretty much stable after infancy. 

4. The sodium in your sweat is crucial to your athletic performance.

It’s critical for maintaining blood volume, and that’s why it’s so important for athletes. When you sweat, your blood volume is gradually reduced because that sweat is drawn from your blood plasma. 

This increases the strain on your cardiovascular system, making it harder to pump blood to your working muscles and to your skin to cool your body down. Sodium boosts your blood plasma volume by helping you absorb and retain more of the fluid you consume. 

5. You need to replace the sodium lost in your sweat.

Your body can’t make or store much sodium, so you need to top it up through your diet or – if you’re sweating often or for prolonged periods – through supplementation as well.

6. If you just drink water, you can get a race-ruining condition called hyponatremia.

Whilst water is fine if you’re not sweating too much, if you don’t replace the sodium you’re losing when you’re sweating heavily you actually run the risk of further diluting your blood sodium levels and this can have some rather nasty consequences like headaches, fatigue, nausea, and vomiting. It can even be fatal in the extreme.

7. Sodium depletion can cause cramp too.

Sodium depletion is one of the major causes of exercise-related muscle cramp. Drinking a stronger electrolyte drink before, during and after intense exercise may well help you avoid/reduce instances of cramping.

Ok, so what can you do with this information?

Well, a recent study found that athletes who adequately replaced the sodium lost in their sweat finished a middle distance triathlon an average of 26 minutes fasterthan those who didn’t, so it’s well worth spending some time optimising your hydration plan before your next race!

One way to get started with personalising your hydration strategy is to take our free online Sweat Test to get some initial advice on what, when and how much you might need to drink during training and races. 

This blog on how to estimate how much sodium you lose in your sweat may come in handy when answering the questions, as might this post on how to calculate your sweat rate.

The idea is that you then refine our recommendations through some good old fashioned trial and error in training and B races.

Or, if you want to fully understand your individual hydration needs, you might consider taking the Advanced Sweat Test, which tells you exactly how much sodium you lose in your sweat to take the guess work out of the equation.

To get some personalised hydration advice, take PH’s free online Sweat Test. And, if you want to give Precision Hydration’s supplements a try in your training, just ask your Spokes coach for your exclusive 15% off Members discount code and use that on electrolyte drinks that match how you sweat at precisionhydration.com going forwards.

Get a Personalised Hydration Plan

Andy Blow founded Precision Hydration to help athletes solve their hydration issues. Hehas a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams. He also has a few top 10 Ironman/70.3 finishes and an Xterra World Age Group title to his name.

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