Nutrition, Podcast, Racing

Hydration, sodium and cramping with Andy Blow | EP#49

 August 14, 2017

By  Mikael Eriksson

Hydration, sodium and cramping with Andy Blow | EP#49

Andy Blow, founder of Precision Hydration is a former elite triathlete, who suffered a lot form cramping and sodium-depletion related performance drops. Especially in hot environments in his long course racing career. So he scratched his own itch and came up with a product range that solved his issues, which led to founding Precision Hydration, a company that makes a range of electrolyte products for athletes.

In this Episode you'll learn about:

  • Why sodium is a critical component of your hydration strategy and what happens if it gets depleted
  • The massive variance in sodium requirements between individuals, and why there's no one size fits all solution
  • The free online sweat test you can take to determine your own individual sodium needs with good accuracy
  • How to take that knowledge into practice and apply it in your hydration in training, racing, and leading up to races


About Andy Blow

​03:42 -

  • ​I studied sports and exercise science leaning towards exercise physiology. I got a BSc in Sports Science from the University of Bath.
  • I was also a triathlete and raced semi-professionally for a few years. I made a lot of mistakes with hydration, especially in hot weather.
  • This eventually led me to put everything that we do now into a business which is Precision Hydration.

What hydration problems did you have in your races?

​04:52 -

  • ​When I raced longer races, and especially in hot weather, I found that something else (rather than fitness) was limiting my performance. I would often break down in races, I would get lots of cramps, I would feel very ill, nauseous and just generally unwell. I would have a horrible time and quite often end up in a medical tent.
  • It took me a long time to figure it out. It was a combination of over drinking water and sports drinks with not much electrolytes in them. And also the fact that I have a very high sweat rate. And later I found out that I have a very high concentration of electrolyte - sodium specifically - in my sweat.

When you increased your sodium intake, did your performance start to improve again and you didn’t have those cramps and issues?

​06:14 -

  • ​The difference to me was like night and day. It was so dramatic. When I started to be more aggressive in my sodium intake in long-distance races then I could keep going at full power. I felt like I used to in short races. The limitation of my performance was how fit and fast I was, not some kind of nutrition or other issue. It was a real game-changer for me.

Why is sodium so important in endurance performances?

​06:53 -

  • ​Sodium is the main electrolyte that is implicated in your blood volume, fluid balance, muscle contraction, and cellular communication.
  • When you sweat, you obviously lose water and fluid on the surface of the skin and that fluid comes from your blood plasma. And your blood plasma is very salty. So if you would sweat it out it would be very salty.
  • This in fact is what happens with people who have cystic fibrosis. Their sweat glands can’t reabsorb electrolytes. So they lose loads and loads of salt.
  • For those of us who don’t have this condition, we reabsorb some of the sodium and electrolytes when we sweat. But we do this in a varying degree.
  • So the amount of sodium that you lose has knock on effects to how well you maintain your hydration status, how well your muscles can contract and so on and so forth.
  • Sodium is definitely the key electrolyte in sweat and it’s the one that’s lost in the largest and most variable amounts.

Is sodium the only electrolyte that we need to focus on?

​08:27 -

  • ​In a sense, yes. If you’re talking about the electrolyte that is predominantly lost through sweat. About 90% of all the electrolytes that you lose through sweat is sodium. The rest is a mixture of potassium, calcium, magnesium and so on.
  • The thing is, that if you have imbalances of any of these electrolytes, it could be plausible that that causes cramping. We have people who have taken magnesium supplements and it helped with their cramping.
  • But it’s likely that if you’re getting problems related to electrolytes other than sodium, it’s more because you may have a diet deficiency or you may have low levels of those in your body anyway. You may not be absorbing them very well when you are eating them.
  • So if you are talking about sweat loss and electrolyte related issues, almost exclusively it’s going to come down to sodium loss.

Hyponatremia, muscle contraction deficiencies, and other issues related to loosing too much sodium

​10:06 -

  • Hyponatremia is a very interesting and complicated one. This is one that gets debated a lot because a lot of hyponatremia is caused more by people drinking too much and diluting the sodium levels in their blood rather than them losing a lot of sodium.
  • The people that lose a lot of salt in their sweat have a tipping point at which sodium loss also comes into the equation as well. No one knows really yet exactly what that tipping point is. But essentially, if you’re losing sodium and fluid at a very high rate and only putting low levels of sodium back in, you reach a tipping point for diluting your body a lot sooner than someone who’s sweating out more dilute sweat.
  • With regards to other issues that low sodium level cause, the main one really is contraction of your blood volume. When you’re exercising, the body tries to balance the amount of sodium in your blood. And if you lose a lot of sodium, one way that your body can balance the concentration of it in the blood is to allow you to lose fluid, and your whole blood volume contracts so your blood volume stays at the right saltiness. This makes the blood harder to pump around the body, it gives less reservoir to then sweat further, and it compromises your cardiovascular performance.

How do you know how much sodium to take?

​12:23 -

  • ​The difference in the amount of sodium that people lose in their sweat is gigantic. Some people can lose 200 mg of sodium per liter of sweat and some people can lose over 2000 mg. Then you multiply it with people’s differences in sweat rates, in which we can see up to a five- or six-fold variance in individual sweat rates.
  • How you work out how much sodium you need is an art and a science. It’s the whole picture of how your body manages sodium and fluid balance which is very complicated due to a lot of variables involved.
  • When you’re doing endurance sports, the main ones are:
    • How well hydrated and how well topped up with electrolytes are you when you start an event?
    • At what rate are you losing them?
    • How much can you physically get back in to compensate for those losses? You don’t have to put in as much as you’re losing because the body can tolerate a drop in fluid and electrolyte levels to a degree and still perform very well.
  • So it’s knowing the inputs and outputs and then play around those numbers to figure out what you can get in to replace what you’re losing.

How can you find out your sweat sodium content?

​15:32 -

  • We definitely advice athletes to measure their sweat rate and measure it in a few different conditions (environmental, exercise intensities, modes of exercise).
  • Then your sweat sodium concentration is relatively fixed and stable for you, although it varies a lot between people. Some of the literature out there supports the idea that this is not a number that fluctuates dramatically.
  • To give you an example, I lose around 1800 mg of sodium per liter of sweat which is on the very high side. And whenever I am tested, in different months and different training phases, that number has not deviated by more than 5-8%.
  • The way we test sweat sodium is we use a diagnostic equipment that is used in the medical field to help diagnose cystic fibrosis. It stimulates the sweat glands on the arm then we take a small sweat sample. And then we run it through an analyzer to look at the electrolyte composition. This really gives us a good number on what your sodium loss is.

Can you talk about the Sweat Test on your website?

​17:05 -

  • ​That’s a really good place for people to start with this process. A lot of athletes who train and compete a lot know their bodies well. And we have put a series of 8-10 questions on our website. When you answer these questions, this gives you a report which suggests whether you are likely to be a low, medium, high, or very high fluid and sodium loss athlete. And then it gives you some strategies to try off the back of it to see how you get on.
  • We’ve been doing this for 4-5 years now and we have a lot of data from athletes who have done it and compared it to athletes who have done a proper sweat test as well. We found out that if athletes know their body, we can ask questions around, “Do you see white salt marks on your skin? Do you get many muscle cramps? Do you feel that you sweat rate is low, medium, high, or very high?”. And in that picture, we can make a rough estimate, which is not as good as having an actual sweat test, but it’s much better than just you shooting in the dark.
  • These are the exact same questions we ask when you do our advanced sweat test. And we’ve used these thousands of data points to help refine the algorithm to ultimately estimate your net sodium loss which is your total sweat volume output multiplied by the sweat sodium concentration.

What are the best ways to get sodium in during exercise or racing?

​20:39 -

  • ​I usually take in sodium capsules or salt tablets. I would basically work out how many milligrams I thought I needed. In my case in an Ironman, it would usually be between 1000 mg to 1500 mg per hour, and I'd just take multiples of those tablets and wash them down with water. I find this to be effective.
  • You can get the sodium from wherever you like. Table salt, which is sodium chloride, is in lots of foods. So eating salty foods is great way of getting sodium in before and after training or an event.

What is the difference between salt and sodium? What do you need to keep in mind if you use salt to get your sodium intake?

​22:40 -

  • ​Sodium is Na - the chemical symbol. And sodium chloride is NaCl which is table salt or the standard salt that you will find in food products.
  • NaCl per unit volume is approximately 40% sodium and 60% chloride. So if you got 1000 mg of salt, you’ve only actually got 400 mg of sodium, and sodium is the important bit.
  • In some of our drinks we use sodium citrate rather than sodium chloride because it has a slightly less salty taste in the very strong products that we make but still delivers a good amount of sodium per unit.
  • We make a couple of ranges of drinks which are either in an effervescent tablet form or in a powder form that you mix with plain water and they mix up different strengths of electrolytes. We have a 250 mg sodium, which is a very light drink, half or less the standard sports drink on the market. Then we have 500 mg, 1000 mg, and 1500 mg strengths, with 1500 being about three times stronger compared to a standard sports drink.
  • We also make our own sweat salt capsules with 250 mg of sodium in it from sodium citrate. This is something that you should have in very long races. You may start the race with your own bottles, but you don’t stop during a race to mix a bottle. So you can take water bottles from aid stations and consume the relevant ratio of these sweat salt gel capsules.

Can you combine your products with a regular sports drink to get calories in at the same time as sodium or should you keep them separate?

​25:25 -

  • ​We do have a few athletes who mix our products. Especially the effervescent tablets with sports drinks which have a lot of calories in them to increase their sodium content. So they kind of make it an all-in-one solution in a bottle, so you get fluid, electrolytes, and calories in a bottle.
  • This has worked for some people but I’m not a big fan of this approach. This has never worked for me particularly. We do have a lot of athletes that struggle with this.
  • What happens when you put lots and lots of calories, and salt, and other things into the same drink, is you’re creating a drink that is thick and syrupy, and has quite a high osmolality. So it’s often very concentrated. And if it gets more concentrated than your blood, you will struggle to absorb it at a faster rate in the gut into the bloodstream.
  • I generally advice people to predominantly drink either water and take the sodium capsules or drink a very light hypotonic electrolyte drink as the source of fluids and get the calories from solid foods like bars, gels, or jellybeans. This allows you to keep the fluids very light, thin, and easy to absorb. It also allows you to dial up and down the calories versus the fluids and electrolytes on any given day based on your needs.

Can you tell us about sodium intake before and after training or races?

​30:22 -

  • Before races, especially is a huge one, because that’s where we see people’s hydration strategy start to unravel right at the start.​
  • Before big races a lot of people get nervous about hydration, especially if the weather is hot. They have a tendency to start drinking a few days before. They drink lots of water, lots of sports drinks, and drinking way too much in fact.
  • If you overdo it, what you end up with is a situation where you start to flush electrolytes out of your body. Your body kicks out a lot of urine because it’s trying not to hold on to excess fluid. You can almost end up mildly hyponatremic before you start.
  • What we recommend is to drink our Precision Hydration 1500 starting 48 hours prior. It has a high amount of electrolytes - high enough so that your body will pour some of the sodium into the bloodstream for a little bit of extra fluid in with it when you drink it, and hold it there rather than peeing it out because it’s trying to keep that blood-sodium level balanced.
  • We normally recommend something like 500 ml or 16 oz. of that the evening before a big race. And another similar amount in the morning of the race finishing it about an hour before the start.
  • After events, at first you might just want to drink plain water because the sodium concentration in the blood is high and you need to dilute it. But hours after, we usually recommend some of the stronger electrolyte drinks to rehydrate you a lot faster.

Why does cramping occur?

​33:53 -

  • ​This is a huge and controversial topic because a lot of people have different opinions.
  • Check out our blog about this: Why do athletes suffer from cramp?
  • In essence, extreme sodium dilution in the body can influence and cause muscle cramps. There are so many stories of athletes who when they get their sodium balance right, their cramping issues stop. Like myself, I find that if I get it wrong it leads to cramps, if I get it right, the cramps go away.
  • I do not suggest that electrolyte balance is the only cause of muscle cramps. I’ve had muscle cramps when I jumped into cold water at the start of the race where it’s clearly nothing to do with electrolytes. It’s something to do with your body tensing up very fast and kind of going into a shock.
  • There are muscle cramps that people get that are more related to fatigue and neuromuscular problems.
  • But I definitely think that if you get cramps, particularly when it’s hot, in long endurance events, and late during the race when you become depleted it terms of having high sweat output and having adequate replacement, then looking at your sodium fluid balance is a very good place to start.

Got questions for Precision Hydration?

​36:17 -

  • ​We at Precision Hydration don’t think of ourselves as a product or a drink company. We’re an athlete consultancy, wherein we enjoy getting questions via the website or social media from athletes.
  • I encourage everyone to interact, because we will always try and get back to you and answer you on a one-on-one basis.

Rapid-fire questions

37:03 -

Favorite book, blog, or resource related to triathlon or endurance sports:

Favorite piece of gear or equipment:

  • Power meter on the bike

Favorite race that you’ve done:

Connect with Andy and Precision Hydration

Links and resources

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Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

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