Key takeaways

1. Sweat contains water and electrolytes - especially salt (sodium chloride). It also contains protein, fat, urea, uric acid and ammonia.  
2. Sports drinks focus on replacing the water, salt and electrolytes we lose when training. However, science shows that some dehydration may be beneficial for performance, blood sodium levels increase when dehydrated and eating sodium has minimal impact on blood levels.
3. Water loss through sweat is the biggest risk to performance. For optimal performance, aim to stay between 0-2% dehydrated.
4. One way to get water into your system faster is to drink liquid with a small amount of salt and carbohydrate. It creates optimal conditions for water movement into the body

WHAT DO YOU LOSE IN SWEAT?

We all sweat, and we all know that sweat contains salt, but it also contains a number of other substances too. Here’s the list:

Water (obviously)

The primary reason we sweat is to get water on to the skin which quickly evaporates taking heat energy with it. This causes us to cool down.

Salt (sodium chloride)

The sodium in salt is key to fluid movement and balance in the body and it is thought that having salt in sweat helps get the water out of the body through the skin. 

Other electrolytes

Potassium, calcium and magnesium are probably the most well known electrolytes found in sweat. They help with a number of different processes in the body - luckily only small amounts are found in sweat.

Fat and protein

It’s normal to find small amounts of fat and also protein in sweat. Where science is still trying to figure out why, one group thinks they may work to prevent bacterial skin infections.

Ammonia, Urea and Uric acid

There are waste products showing that sweat also seems to have a detoxifying effect too. They can also make sweat smell pretty bad.

THE IMPACT ON ATHLETIC PERFORMANCE

A few of these sweat ingredients you are obviously happy to lose, but for others like water, losing too much may have a negative impact on athletic performance. In fact, if the leading sports drink brands are to be believed, you should replace electrolytes and water as soon as possible to avoid a drop in performance.  

Scientific research tells us a different story however. 

1. Dehydration (at least mild dehydration of 0-2% body weight) doesn’t necessarily impact performance in real world settings and may even improve performance as you lose body weight 
2. In a study of over 2,000 endurance athletes, Timothy Noakes, a leader in the dehydration field found that sodium levels in the blood actually increased as people became dehydrated. He also argues that consuming sodium has little impact, with individual variation being much more of a determining factor.  

So what is all the fuss about? You train, dehydrate a bit, but can still perform. 

The danger to performance comes from overshooting your dehydration to a level where the lack of body water volume starts to mess with your body - from heat regulation to getting fuel to your muscles. 

For this reason, getting water into the system should still be a priority, with the aim of staying between 0-2% dehydrated for optimal performance

HOW TO GET WATER INTO YOUR SYSTEM QUICKLY

Most of the water we drink passes into our bloodstream in the small intestines. This process happens in a few ways that rely on there being sodium and carbohydrates in the gut (if on an empty stomach, sodium is pumped out into the water to help the process). 

To get water into your system quickly then, it helps to drink something that contains at least some sodium (salt) and carbohydrate.

The purpose of the salt and carbs isn’t to replenish, it’s to simply speed up the process so you can prevent over-dehydration and remain in the 0-2% range. 

Practical Application:

To maintain your performance when training causes you to heavily sweat, you should aim to stay between 0-2% dehydrated. 

To do this, drink something with a little salt and carbohydrate in it to ensure the water enters your system quickly (We suggest sipping through training, and always drink more if you feel thirsty)

For athletes wanting help to do this we developed Hydra+, a versatile, real food based hydration drink mix. It contains the right levels of sodium and carbohydrate from natural sources to create a hypotonic drink focused on driving water into the system and avoiding drops in performance.