From Elizabeth Quinn,
Your Guide to Sports Medicine.
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High salt (sodium) diets have been linked to a number of health risks in many Americans. However, some athletes, due to their increased activity and excessive sweat production, are actually at risk of having too little sodium in their blood stream during training and competition and may have special sodium requirements. Because sodium is lost in sweat, it is more important for individuals who exercise at high intensity to get adequate sodium before, during and after exercise. This is even more critical during ultra-endurance competition.

Risks of Hyponatremia | Water Intoxication
Hyponatremia, a low concentration of sodium in the blood, has become more prevalent in ultra-endurance athletes. The Hawaii Ironman Triathlon routinely sees finishers with low blood sodium concentrations. Adequate sodium balance is necessary for transmitting nerve impulses and proper muscle function, and even a slight depletion of this concentration can cause problems. Ultra distance running events that take place in hot, humid conditions, and have athletes competing at high intensity have conditions prime for hyponatremia to develop.

Causes of Hyponatremia
During high intensity exercise, sodium is lost along with sweat. An athlete who only replaces the lost fluid with water will contribute to a decreased blood sodium concentration. As an example, consider a full glass of salt-water. If you dump out half of the contents of the glass (as is lost in sweat), and replace that with water only, the sodium concentration of in the glass is far less and the water is more dilute. This often occurs in the bloodstream of an athlete who only hydrates with water during excessive sweating. The result is hyponatremia.

Studies have shown that ultra-endurance athletes can lose 1-2 grams of salt per liter of sweat. If you consider that athletes may lose up to a liter (or more) of sweat each hour, you can see that over a long endurance event (12 hour race), it is not unimaginable that an athlete could sweat out a huge amount of sodium. Replacing this loss of sodium during the event is critical to performance and safety.

Symptoms of Hyponatremia
The early warning signs are often subtle and may be similar to dehydration; nausea, muscle cramps, disorientation, slurred speech, confusion, and inappropriate behavior. At this point, many athletes get into trouble by drinking water because they think they are dehydrated. In fact, water alone will increase the problem of hyponatremia. At the most extreme an athlete may experience seizures, coma, or death.

Treating Hyponatremia
At the first sign of nausea, muscle cramps, disorientation, an athlete should drink a sodium containing sports drink, such as Gatorade, or eat salty foods. If possible, an athlete should plan ahead and estimate his or her fluid loss and need for sodium replacement during the event, and stay on a hydration schedule during the race. If the symptoms are extreme, a medical professional should be seen.

Preventing Hyponatremia
The best way for an athlete to avoid such problems is to plan ahead. Tips and recommendations include:

• Use a sodium containing sports drinks during long distance, high intensity events.
• Eat salty foods before and during competition if possible.
• As there are no steadfast guidelines for everyone, it is important for an athlete to understand his or her individual fluid needs.
• Weigh yourself before and after training and drink enough sodium based sports drink to offset any fluid loss during exercise
• Increase salt intake several days prior to competition. The increased sodium concentration will allow additional hydration with water to remain balanced so that the dilution of blood sodium does not occur.
• Avoid use of aspirin, ibuprofen, and other non-steroidal anti-inflammatory agents as they may increase the risk of hyponatremia in athletes.
  • Many triathletes take these medications without knowing of their detrimental effect on performance. Additionally, chronic use of these medications often mask the bodies own warning mechanisms that alert athletes to pain and injury. Athletes should be discouraged from excessive use of these medications.

Keep in mind that all athletes respond differently to exercise; fluid and sodium needs will vary accordingly. Foods that provide additional sodium include chicken noodle soup, a dill pickle, cheese, pretzels, and tomato juice.

As always, it is important to consult your physician for special considerations if you have a history of any health problems or are taking any medication for a health condition.

_Source

Consensus Statement of the 1st International Exercise-Associated Hyponatremia, Consensus Development Conference, Cape Town, South Africa 2005. Clinical Journal of Sport Medicine. 15(4):208-213, July 2005.