Sodium, The Missing Link? by Wes Hobson

You, as an Ironman athlete, dedicate much of your life training for the triathlon. You sacrifice time with family and put off work obligations, which isn't always a bad thing, so you can get in the 16-25 hours of training per week necessary to not just finish, but rather to compete in the Ironman. An often overlooked aspect to the IM race is the additional supplementation of sodium (Na) to your race day nutrition plan.

Athletes should consider Na supplementation as insurance. Most likely, depending on the climate and your sweat rate, some amount of Na supplementation will benefit your ability to race at a high level. Don't be caught off guard in assuming that race day will be cool and therefore you won't need supplementation. In 2003, an elite Australian triathlete competed in the Ironman Coeur d Alene triathlon. The typical weather for that time of year was to be relatively cool with a high around 22 C. Instead, record highs were achieved and one aspect of him dropping out while in second place at the 34K mark of the run was that he had severe cramping from not taking Na supplements. All those hours of training, including $5,000 US in prize money and travel expenses, lost due to most likely not taking a couple of tablets.

In general, assumptions must be made when determining a person's necessary Na intake. Na is the primary extracellular electrolyte and the amount is tied to blood volume and thus the size of the individual. Blood sodium is very tightly controlled by the body, and the range is 135-148 mmol/L, about 3 grams of Na per liter of blood (to get from mmol to mg, multiply mmol by 23).

Sweat rate, genetics, fitness level and acclimatization will affect the amount of sodium lost during a race. A well-conditioned, heat acclimatized athlete would lose about 920-1840 mg per liter of sweat per hour of racing. If you can get an idea of your personal sweat rates, a good place to start with Na supplementation would be in the middle of that range. For example, if the average sweat rate is = 1.5 liters per hour, about 1380 mg Na per liter = 2070 mg Na (about 2 grams) is lost per hour.

We are making assumptions since we can never really know how much sodium a person looses unless tested. For instance, another elite Australian Ironman triathlete went to the Gatorade Sports Institute to determine his Na needs. Through testing, they found he needed 3,000 mg per hour! This demonstrates the wide range of Na intake between individuals. In the most recent USA Track and Field hydration position statement, it stated a modest addition of Na at the rate of 500-700 mg sodium per liter of fluid is plenty.

When determining your supplementation, make sure you know the amount of Na in the salt tablet AND the amount of sodium you will intake with any electrolyte drinks to take for your estimated losses. Some sports drinks don't contain any Na so make sure you check, before race day, to see what sports drinks will be offered during the race if you plan to use those. Many coaches recommend that athletes take between 400-1000 mg of Na per hour. You can see there is a wide discrepancy. If you do not have a clear idea of your Na depletion rate, it is recommended to not take more than 1,000 mg for each hour on the bike from drinks, foods and tablets. Let heat, humidity, body size and your experience dictate the amount. Yes, practice taking sodium before the day of the race with your long training sessions of more than four hours. Most likely you will experience no side effects such as nausea, bloating and diarrhea, but practicing will allow you to go into the race confident with your race strategy.

When taking Na such as salt tablets, it is best to wait ingesting tablets on the bike until after you have had .5 to 1 liter of water. This is usually during the first thirty minutes to one hour on the bike. In fresh water swims, just water helps the digestive tract as you have a long day of racing still ahead and you don't want to start the bike by getting a bloated stomach or feeling nauseated. Waiting to take Na is especially important if the swim was in salt water and you have ingested salt water during the swim. Seawater is 25-35 times more concentrated with Na than the recommend amount of 1gram of Na per 700-1000 mL of fluid. It would be a detriment to add more Na after ingesting so much in the swim. It may be best to delay taking in sodium supplements for one hour or so on the bike. Once you are sure there are no seawater poisoning symptoms such as nausea, vomiting, diarrhea, abdominal cramps and bloating, then sports drinks, feedings and sodium supplements can begin. Until then, you should use some caution.

For some during an Ironman, the body has a tendency to "shut down" during the latter stages of the bike and the entire run where you have no desire to eat or take in fluids. Of course, fluids are essential, but the right amount of what kind of fluids depends on how your body is reacting. If you have been guessing with your Na intake during the race, you may feel no need to drink, nauseated or a bloated feeling. If this is the case, you might have had too much Na on the bike. When Na becomes excessive in the body's system, hypernatremia may occur where the stomach pulls water from the rest of the body to restore normal Na concentrations. This may cause dehydration (no urine production) while the stomach is holding water waiting until a balance is achieved before releasing fluids (bloated feeling). If this is the case, drinking more water will allow the kidneys to excrete the excess sodium and restore the system to normal.

Determine your sodium needs as best as possible before race day so that you can eliminate a possible stumbling block for a great Ironman race. Don't rely on what other athletes are taking as each individual is different.

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Comments

[Dick Hanneman]

Right on! Too often those engaged in heavy exercise are advised to drink water but avoid salt -- and the result can be a dangerous hyponatremia.

Dick Hanneman
President
Salt Institute