Hydration and how to perform at your best for longer by replacing what you lose in your sweat.
Most athletes are generally aware that replacing the electrolytes lost when you sweat is a good idea if you want to perform at your best. But exactly what electrolytes you should be taking in, why that is and – perhaps most crucially – how much to take in in order to maintain your performance is less commonly understood.
Luckily ‘sweat and hydration guru’ Andy Blow, founder of Precision Hydration, who works with top endurance athletes and sports teams to perfect their hydration strategies, has teamed up with Go Faster Food to set that straight for us. Former Team Sports Scientist for Benetton and Renault F1 teams, Andy’s got a few top 10 Ironman, 70.3 finishes and an Xterra World Age Group title to his name, as well as a degree in Sport and Exercise Science.
What you lose in your sweat and why it’s important
Your sweat only contains small amounts of potassium, calcium, and magnesium, it’s made up mostly of water and sodium. That’s why it tastes salty and you get those white marks on your kit after a sweaty workout. Your sweat can contain from around 200mg of sodium per litre to 2,000mg/l, whereas it only contains up to about 150mg of potassium per litre. Which means coconut water (which is high in potassium, but not sodium) isn’t actually all that good at keeping you hydrated (though it has other benefits and is a refreshing choice!)
Maintaining the sodium levels in your blood is crucial to performing at your best. A 2015 study found that athletes who adequately replaced the sodium lost in their sweat finished a middle distance triathlon an average of 26 minutes faster than those who didn’t.
Sodium helps you absorb and retain fluid, which keeps your blood volume up, reducing cardiovascular strain when you’re exercising.It also plays an important role in muscle contraction, maintaining cognitive function and the absorption of nutrients. Fatigue and cramps are also common when significant fluid/sodium imbalances go unchecked.
Up to a certain point, taking in plain water is enough to mitigate sweat losses. But, as those losses start to mount up, you need to replace sodium too to avoid your blood becoming diluted. This is a potentially disastrous condition called hyponatremia, which can certainly ruin your race and, tragically, has even been fatal on occasion.
Wait! I thought too much salt was bad for you?
The standard government guidelines for sodium consumption should be viewed cautiously by athletes. It’s more than possible to lose the daily 2,300mg of sodium recommended by the existing UK government guidelines in just 1 hour of exercise, if you’re sweating heavily and you’re sweating out lots of sodium.
Especially as everyone loses a different amount of sodium in their sweat. At Precision Hydration, we see athletes who lose from as little as 200mg of sodium per litre of sweat to as much as 2000mg/l. I personally lose 1,842 mg/l and I often suffered from hydration issues in hot climates as a result. It was my personal search for a solution that led to me founding the company.
Sweat rates also vary from person to person of course and when you combine differences in sweat sodium concentration with those in sweat rates, the potential difference in net sodium losses experienced from one athlete to another can be huge. Active athletes generally require significantly more sodium than the average ‘couch potato’ taken into account when creating those official recommended daily allowances.
How to replace what you’re losing in your sweat
Most of the sodium we consume is in the form of sodium chloride, or the common table salt found in food and drinks. We take salt for granted these days as we’ve developed ways to make it widely available. But in ancient times wars were fought over access to salt and wages were even paid in it. The word ‘salary’ actually derives from the fact that Roman soldiers were often paid in salt, which gives you a pretty big clue as to its importance to life!
Because your body can’t produce or store it beyond a certain point, you need to consume sodium every day to keep your levels topped up and I know Kate has some great pre/post exercise recipes for replenishing your electrolyte levels (you’re right Andy, try this watermelon & feta salad!). However, when you’re out sweating for more than a few hours your net sodium losses can really mount up, so it’s difficult to adequately replace your losses without using an electrolyte drink.
How much sodium should you be taking in?
Because sweat/sodium losses are so individual, any generic guidelines on the replacement of sodium and fluid should always viewed with suspicion. Having said that, figuring out whether your net losses are likely to be low, moderate, or high can be a great starting point for honing in on the level of sodium and fluid replacement that’ll work best for you in different circumstances.
The two main inputs that drive your personal net sodium losses are…
- The total amount you sweat. This is a factor of your sweat rate and the number of hours you spend sweating during a given timeframe.
- Your sweat sodium concentration.
Figuring out approximately what these are is a sensible place to start.
Calculating the volume of sweat you lose can be a bit awkward and hit and miss, but there are plenty of online calculators that get you to a reasonable estimate.
Your sweat sodium concentration is genetically determined and doesn’t vary much at all which means that, whilst you can only find it out by getting your sweat tested, you only need to get tested once. If that sounds too extreme, take this free online Sweat Test to get a good idea of your personal electrolyte needs in less than two minutes. Oh, and if you decide you’d like to use our all-natural, multi-strength electrolytes to personalise your hydration strategy, just use the code GOFASTER to get 15% off your first order.
Andy Blow has a few top 10 Ironman and 70.3 finishes and an Xterra World Age Group title to his name. He founded Precision Hydration to help athletes solve their hydration issues. He has a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams.