The SALT in your Sweat: The Nitty Gritty of Sodium Testing

By Dana Willett

As multi-sport athletes, we’ve pretty much all heard about the importance of salt – sodium – electrolytes – during endurance activities, especially in hot weather.

But how much? And what kind? And how often?

The go-to “test” most athletes are familiar with is a sweat rate test – weigh yourself before exercise, go hard for an hour, weigh yourself again, and do the math on how much fluid you lose (details below). Then load up with any of the many sports drinks out on the market, and try to consume close to the amount you normally sweat out.

BUT. So many different products. And they all affect our guts in different ways.

Salts and minerals that can conduct electrical impulses in the body. Common human electrolytes are sodium chloride, potassium, calcium, and sodium bicarbonate. Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost every major biochemical reaction in the body. –From Medical Dictionary

And, perhaps more importantly, the concentration of sodium in your sweat is as important to understand and utilize as your sweat rate.

My coach has recommended I use the current off season to tackle any testing and nutrition questions, so I have plenty of time over the winter and spring to integrate any changes and trial-and-error any new products. I’ve had year-over-year trouble with gut issues and muscle cramping, so salt intake is at the top of my list.

I checked in with resident expert Ryan Ignatz at Colorado Multisport, who agreed, saying, “Now is a good time to consider Sodium Composition Testing since people have more time and can start implementing their new knowledge with their bigger indoor workouts. Often we see people just drink water when they ride inside through the winter, which can actually create a bit of issue in their sodium balance after a few workouts.”

I booked an appointment at CMS for the sweat test and was surprised to learn no workout was involved. This test can be done any time, with no exercise-induced sweat necessary.

I sat comfortably in a chair, and Ryan applied a small disk to my forearm, secured with a strap.

The disk is equipped with a type of electrode that promotes a sweat reaction on the skin just below the disk.

The sweat is collected in a tiny coil of tubing inside another disk called a macroduct; once enough sweat has been collected, Ryan withdraws the fluid using a syringe and analyzes it with the Precision Hydration machine.

And just like that it’s confirmed – I am a salty sweater!

I’m in the “high” category, bordering on “very high.”

I need 1331mg of sodium for every liter of sweat that I lose.

Levels of sodium loss fall anywhere between 200mg or 2200 mg  – but the proportion each individual loses stays the same (except for hyponutremia, a condition caused by overhydrating with plain water – without sodium – and water diluting the blood stream). Thus, each athlete’s sodium concentration level is individual, similar to a blood type or VO2 max… it’s yours for life, and it does not change.

When I do a traditional sweat test (see below), I lose two pounds over an hour – so I basically need at least a full liter of fluid and 1200-1300mg of sodium for every hour of racing. Plus 200-300 calories an hour.

The immediacy, and accuracy of this data is quite reassuring, especially given my history.

During my last full Ironman, I suffered kidney trouble. I was using a well-respected endurance formula (“exclusive blend… all the electrolytes an endurance athlete needs… no need to supplement with salt tablets...”). I consumed 24 oz an hour, 240 calories, 334mg of sodium – not nearly enough sodium for me.

Unknowingly, hour after hour, I was about 1000mg shy of meeting my sodium needs, compounding every 60 minutes. Plus I supplemented with some extra water – which only further diluted my blood sodium level. No wonder mid-way through the day my kidneys weren’t working well, and after the event I experienced mild rhabdomyolysis .

The key is the sodium concentration in your sweat, and your sports drink.

Ryan reassures me, underlining the importance of ratios over quantity: “Its more about the concentration of sodium in the fluid you drink – it’s not only about how many milligrams per hour, because that varies depending upon different conditions, such as intensity, temperature, etc.; both your sodium concentration, and sweat rate are important. You need to drink to thirst, and make sure your drink contains the correct sodium concentration – that is what is important.”

Determining those formulas ahead of time is the key to solid hydration: Ryan says to look at packages, and really read the labels. “If Gatorade Endurance is on course, look at those sodium levels ahead of time and consider how much you’ll need.” Another thing to consider is everyday nutrition, and sodium intake during training sessions. “Athletes who train regularly and eat ‘clean’ tend to not add salt, and may not get enough in their everyday diet,” Ryan adds – another reason to dial in sodium levels to ensure training fluids are the proper concentration.

The next part of the sweat test included reviewing the leading products on the market, factoring the sodium levels, and taking into account past gut-checks, calories, delivery method (salt capsules, stick-licks, powders, etc.).

When you study the variety of offerings, you might be surprised. For example,  Endurolytes by Hammer – whose name indicates a product appropriate for endurance events (“Electrolyte replenishment done right“) – has only 40mg of sodium per capsule.

Do the math… for me, needing 1300mg of sodium per hour, I would need 32.5 capsules every hour. Thirty-two+ pills. Every hour.

There are different types of salt… Sodium Citrate is not as strong tasting… and Sodium chloride is table salt.

Ryan suggests drinking to thirst, and then separating your carbohydrates/calories from your fueling. He recommends dialing in your hydration: “Make sure everything that you drink has a certain concentration of electrolyte – that way, no matter what amount you drink, you always have the best ratio of sodium to fluid for your personal body chemistry. ”

Base salt… Boulder salt… Salt Stick… what’s the difference? “Mostly method of delivery,” Ryan says. “From a salt shaker kind of delivery, where you lick the dispenser, to capsules, under the tongue delivery (bypassing the stomach), to a canister with a scoop for mixing with fluid.” Other things to consider are packaging (key when you’re trying to ingest while in the aerobars or carrying on the run), and cost. Some offer better ability to measure intake-specific doses.

What if you find yourself on a course, your unsure of your sodium needs, and salt is being offered? Ryan says, if in doubt, take it. “Most of the time it’s probably a benefit because most people aren’t doing enough.”

“When we exercise the number one job the body has is to cool itself – through sweat,” Ryan points out. “It will do that above just about anything else. Sodium concentration is key to this process.”

One final point from Ryan: “Drinking to schedule can work against you – drinking to thirst, with proper ratio of electrolyte to fluid, is the best practice.” And, “Always, always, check the math!”

Contact Colorado Multisport to book your Sodium Composition Test. The cost us normally $129 – mention this article and 303Triathlon for a 10% discount plus 10% back through December 31, 2017!

A certificate for the test can make a great gift for the triathlete in your life.

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Your standard sweat check procedure is:

  1. Check your weight before and after training, and calculate weight loss.
  2. Convert any weight loss to ounces or ml of fluid.
  3. Check/measure the amount of fluid consumed during training.
  4. Add the amount of fluid lost to the amount of fluid consumed to get total fluid losses.
  5. Divide the total amount of fluid lost by the number of hours of training to get fluid losses per hour.
Originally from Ironman

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