Electrolyte Considerations for Ironman Athletes

By Bob Seebohar, MS, RD, CSSD, CSCS

Electrolyte consumption for Ironman athletes is a very popular topic and while somewhat individual, there are some key points to remember that will assist you in your electrolyte supplementation protocol on the big day.  Not known by all athletes is that very important fact that proper electrolyte use begins during your daily nutrition program then “spills” over onto your training and competition day nutrition plan.  There are many mistakes Ironman athletes make before race day and these can be easily avoided with a bit of background knowledge.

Dietary Sodium

It is well known that the average Western diet is very high in sodium.  Endurance athletes are known to go to extremes of adding copious amounts of salt to their foods throughout the day to try to keep up with the amount they lose.  However, if the diet contains a high amount of sodium, the body requires more sodium on a daily basis to remain in balance.  As the amount of sodium increases in the diet, the amount lost in sweat also increases to maintain an even balance.  The body eventually becomes used to this high amount of sodium and requires it day in and day out thus driving the daily need for more and more sodium.  The end result is that you need more daily sodium to keep your body functioning properly both in and out of training.

However, if less sodium is consumed in the daily diet, then it is much easier for the body to remain in balance.  Sodium is still lost through sweat during training but it is easier to maintain these levels by simply focusing on sodium supplementation strategies immediately before and during training and competition.  The ideal scenario is to follow a lower sodium daily nutrition plan and implement a training and competition electrolyte protocol that is centered on improving performance.  After training and competition is finished, follow the lower sodium nutrition plan once again.

The Electrolytes

The five main electrolytes that are often discussed when it comes to athletic performance are sodium, chloride, potassium, calcium and magnesium.  While sodium, an extracellular compound, gets much of the attention since it is probably the most important electrolyte, the other four electrolytes should not be overlooked as they all function to support physiological training adaptations and physical performance.  Here is a little information about each electrolyte:

  • Both sodium and potassium are important in nerve conduction which helps generate the signals from the central nervous system to the muscles to perform work.  Potassium, found inside of cells, also works closely with sodium and chloride in maintaining the body’s fluid balance.
  • Chloride binds to both sodium and potassium and contributes to muscle functioning.  Chloride is always found in combination with sodium and potassium.
  • Calcium is the mineral that is mostly associated with bone health.  However, what not all athletes realize is that calcium also assists with muscular contraction, the metabolism of glycogen, neuromuscular conduction and messaging between cells.
  • Magnesium is usually overlooked in the electrolyte supplementation program of Ironman athletes when in fact it can be responsible for poor performances because it is important in the generation of ATP, muscle contraction and the transmission of nerve impulses.

As can be seen, the role of electrolytes spans far greater than simply maintaining fluid balance or trying to prevent the “mystery” cramps that Ironman athletes often experience.  There are many other physiological functions that these electrolytes contribute to and all work in concert with one another to support intense physical exercise.  Having a combination of all five electrolytes is crucial for proper physiological functioning and adaptations to training.

Sodium Loading

There has been some research to suggest that acute sodium loading the night before or morning of a race can be beneficial in promoting good fluid balance and acclimating to warmer environments.  Chronic sodium loading (greater than 2 days), common among many endurance athletes, can sometimes produce bloating and weight gain the week leading up to a competition.  However, acute sodium loading has been shown to have minimal adverse effects with maximal performance benefits.  Combining acute sodium loading with low sodium diet can work to improve performance while minimizing any adverse effects.  For more information about acute sodium loading, refer to the First Endurance sodium loading protocol at www.team.firstendurance.com.


Taking into consideration all of the valuable information presented in this article, the take home messages are:

1.  Follow a lower sodium diet in your daily nutrition to improve health and reduce the amount of supplemental sodium needed during training and racing.

2.  All five electrolytes are important in concert with one another due to their role in muscle functioning, fluid balance and the formation of ATP.

3.  Acute sodium loading may prove as a successful means for improving hydration status for Ironman racing.

These small steps will provide huge dividends for any Ironman athlete but they should be implemented far in advance of the competition date.  Take a few weeks to get your daily sodium balance in check to lower amounts then try the acute sodium loading protocol at least two or three times in quality training sessions before competition day.

4 responses to “Electrolyte Considerations for Ironman Athletes”

  1. Greg Kogut says:

    “The body eventually becomes used to this high amount of sodium and requires it day in and day out thus driving the daily need for more and more sodium.”

    This development of “sodium tolerance” is interesting. Can you point me to some peer-reviewed clinical research which describes this mechanism?

  2. Greg,
    I’ve asked Bob to chime in as well. The primary mechanism for salt regulation is what is called the sodium/potassium pump. The body keeps intracellular sodium concentration within a narrow range regardless of your sodium intake. It does this by excreting or absorbing sodium via the kidneys and intestines. The adrenal gland will signal the kidneys to excrete less sodium into the urine when sodium is needed in the body.
    Consuming too much or too little salt chronically can have health issues, where too little can cause digestive and neural signaling issues. Too much salt can lead to hypertension.
    The sodium/potassium pump regulated via the adrenals, kidneys and intestines cannot work quickly enough to manage large acute changes in sodium intake or sodium loss. It is recommended that athletes adhere to a relatively low to moderate sodium diet on a day to day basis, which is not only a healthier alternative, but can also offer a distinct acute advantage when additional sodium is needed, like during a long, hot race. Because the body is ‘used’ to regulating low/moderate sodium, ingesting higher sodium content just before an event can essentially load the body with additional sodium before the body has a chance to regulate this and excrete what is not needed. Those athletes who regularly eat a high sodium diet have set their ‘regulation pump’ to constantly excrete excess at a relatively high rate. Because of this, these same athletes will require even greater levels of sodium intake on race day in order to overcome that high rate of excretion created through their daily diet.

    This sodium/potassium pump mechanism can be found in most physiology or nutrition text books. Some links to the references that help explain the mechanism are below. The last link is a nice article that explains this regulation in layman terms.







  3. Greg Kogut says:

    Thank you very much. That reading material should occupy my spare time for a while. As an athlete with an extreme sweat rate I appreciate First Endurances’ publication of scientific information in lay terms as well as the availability of the actual scientists/nutritionists to actually respond to questions.

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