How Does Sodium Intake Relate to Hydration in Triathlon Training?

We all sweat water out of our bodies. However, did you know that key electrolytes—the most predominant of which is sodium—are also lost along with our sweat? Actually, the very definition of sweat by the National Institutes of Health website, Medline Plus, is “the release of a [salty] liquid from the body’s sweat glands.”

Most triathletes in training are aware of this nowadays. But a few decades ago nearly everyone attempted to hydrate by simply guzzling down as much water as possible.

Case in point: Jan Ripple’s (in)famous crawl at the 1987 Hawaii IRONMAN triathlon. As Torsten Abel describes on his blog, “She was leading until about mile 20 of the run until she collapsed, made the comment that she didn’t know why she fell apart late in the race – ‘I drank 12 large bottles of water on the bike …’”

There’s an issue with trying to hydrate on nothing but water. You risk succumbing to hyponatremia. Hyponatremia is the result of drinking too much water during an endurance event, causing the sodium in your body to become diluted.

For the most part, sodium loss has a direct correlation to sweat loss—i.e. not necessarily dependent on other factors. Therefore, the more you sweat, the more sodium you’re likely to lose. And when the weather is hot and humid, the more everyone sweats.

The problem with trying to hydrate solely on plain water is that when you’re low on sodium your body is unable to regulate the amount of water that’s in and around your cells. Therefore, you won’t retain the additional fluids put into your body (causing your cells to swell). Furthermore, you’ll be diluting the remaining electrolytes left in your bloodstream.

The result is excessive cramping, nausea, and heavy fatigue. In extreme cases it can lead to seizures, coma, and even death. More than likely, the triathlete’s experience with hyponatremia won’t reach these extreme levels. However, it’s easy to misdiagnose the milder symptoms as dehydration and compensate with more water, resulting in the condition worsening.

This is why it’s so important to be consuming a high sodium diet 3-4 days leading up to a long race, and especially taking in a healthy dose of sodium on race morning. When your blood is frontloaded with the sodium needed for a hot race day, you’re more equipped to absorb the required fluids when hydrating without diluting the precious remaining electrolytes in your bloodstream as well as the new ones coming in.

A word of caution. This doesn’t mean you should have a high sodium diet at all times. That would be an easy way to become hypernatremic in your daily triathlon training – having too much sodium accumulated in the blood. In this state, you’re subject to bad GI issues as your body attempts to process and purge the excessive water retention.

Moreover, depending on how much you sweat, you may need to add extra sodium in addition to your food and electrolyte hydration drink of choice during triathlon competition. This, of course, is very dependent on the athlete.

Super sweaters may need up to and even over 1200 mg of sodium per hour during a long course race. Those who don’t process salt as quickly might be fine on one sodium-concentrated electrolyte drink containing just 400-500 mg. And, of course, the weather will greatly affect your required dosage during the event. The hotter it is, the more you’ll sweat and, thus, the more sodium you’ll lose.

To generalize, most athletes require anywhere from 600-1200 mg of sodium per hour. But the best way to know how much you need is to experiment through training.

First and foremost, perform a sweat test to discover how much you sweat per hour under a given set of circumstances. TriDot coach and professional triathlete Nick Waninger suggests performing this on the bike. First, do a quick warm-up on the trainer and then record your weight. Next, perform an hour of riding attempting to simulate long course racing (average Z3 training effort). Hydrate normally during the workout and then record your weight and consumption afterwards.

With some math you can evaluate how much sweat is lost in liters or ounces per hour. According to dietician Lauren Antonucci writing for Triathlete, the typical triathlete loses 1 liter, or 32 oz per hour. This person should be consuming between 750-1,000 mg of sodium per hour. Therefore, if after the sweat test you’re above this amount, shoot for the higher end of the spectrum or more. Vice versa if you’re losing less than 32 oz in an hour. Once again, don’t forget about changes in temperature.

You should also consider how much your clothing is caked in white salt after a long training day. If the level of “whiteness” is pretty substantial, you may lose more salt per oz of sweat than the average person and will want to stay on the higher end of sodium consumption.

Long triathlon training days, especially in hot weather, are the perfect opportunities to experiment with salt supplementation (as will probably be needed on race day). Using the educated estimation from above, experiment consuming your required amount of salt per hour on a long training brick incorporating varying vessels for the sodium such as electrolyte drink mixes, food, and most importantly salt tablets when necessary.

Pay attention to the sodium content of your nutritional products of choice and determine how much and when you’ll be consuming each. As with everything, balance is key. You’ll need to practice and learn what the right combination is and how much sodium to intake in varying weather environments and at varying distances and intensities.

Once you’ve done your homework, racing with sodium becomes … well … no sweat!


Hydration for the triathlete is not done simply by drinking water. Depending on how much you sweat and, therefore, how much sodium you lose, you’ll need to counter that loss with an increased sodium intake before a big race and while out on the course.


Have you evaluated your sodium requirements for your desired triathlon race? How much do you need to consume per hour?

JARED MILAM is a professional triathlete, TriDot coach, and member of the Tri4Him Pro Team. He has 16 years of competitive running experience and 11 years of competitive triathlon experience with a half Iron PR of 3:59 and a full Iron PR of 8:30. Coaching under the TriDot system since 2011, Jared loves working with aspiring triathletes of all ages and performance levels.


Martin. Laura J. “Sweating.” MedlinePlus. National Institutes of Health, 30 April 2015. Web. 21 June 2016.

Abel, Torsten. “Ironman Traithlon Race Day Salt Intake.” T3. T3, 15 April 2014. Web. 21 June 2016.

Mayo Clinic Staff. “Hyponatremia.” Mayo Clinic. Mayo Foundation for Medical Education and Research, 28 May 2014. Web. 21 June 2016.

Metzl, Jordan D. “Sodium Advice For Triathletes.” Triathlete. Competitor Group, Inc., 16 June 2015. Web. 21 June 2016.

Antonucci, Lauren. “A Triathlete’s Guide To Salt.” Triathlete. Competitor Group, Inc., 1 Sept 2015. Web. 21 June 2016.

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