Two runners have died in the US from Hyponatremia while participating in a Marathon these past couple of years. The article below, written by Carolyn McClanahan, M.D., a family physician with Jacksonville Emergency Consultants, should give you basic information to help you avoid this condition.

Prevention of Under and Over-Hydration
Rules for the Long Road

When and how to hydrate has been a controversial subject since the dawn of hard work and exercise. Back and forth the pendulum swings. Drink a lot, drink a little, don’t drink at all. We now know that there is danger in too much and in too little water. As Ben Franklin would say, the answer is moderation; but for hydration we have to add a pinch of salt.

The human body has an incredible capacity to adjust to a lack of fluid intake. The main issue with dehydration in runners is the importance of fluids in preventing heat injury. Symptoms of heat injury include swelling and tightness of the hands and feet, light-headedness, cramps, muscle spasm, dizziness, fatigue, nausea, vomiting, weakness, headache and muscle aches. More severe symptoms include irritability, bizarre behavior, combativeness, hallucinations, seizures, and coma. Even death may occur.

Over-hydration with water can lead to dilution of salt in our body fluids which causes a condition known as hyponatremia. Symptoms of hyponatremia are fatigue, weakness, cramping, nausea, vomiting, bloating, swelling and tightness of the hands and feet, dizziness, headache, confusion, fainting, seizures, coma, and even death. The symptoms are very similar to heat injury, and for doctors, the clue to telling these two conditions apart is the core body temperature and blood work. It is very important to get the correct diagnosis quickly, as the treatment for each is very different.

Hyponatremia due to exercise has previously been a very uncommon condition. However, with increased participation in marathons and other ultra-events, and the pendulum swinging to athletes over-hydrating with water, more cases are occurring. Risk factors include being female, sustained activity greater than 4 hours, excessive water intake 1 to 2 days before an event, and taking medications such as ibuprofen, naproxen or aspirin before an event. Many other types of medications can also impair our ability to conserve salt.

The key to preventing heat injury and hyponatremia is adequate hydration with appropriate fluids. Many theories abound on fluid replacement types and amounts. Basically, an athlete should replace the amount of fluids lost through sweating. Due to genetics, we all sweat at different rates. One way to determine the amount that you sweat is to weigh yourself before and after an hour of exercise. For every pound lost through sweating, drink 16 ounces per hour during your event. It is important to keep in mind that weather conditions can affect this also, so adjust accordingly. Common sense is important – if you are thirsty, you probably need to drink.

If you plan on exercising more than an hour, be sure to replace your sodium. Effective ways to do this are to increase the salt in your diet for a couple of days before your race. In addition, be sure to drink sports drinks that contain sodium. Skip the salt tablets, as the amount of sodium they contain is too high.

Avoid nonsteroidal anti-inflammatory medications such as naproxen and ibuprofen before or during your race, as these medications can impair your ability to conserve salt. If you must take a pain reliever, acetaminophen (Tylenol) is safer and doesn’t affect salt balance.

Most importantly, if during or after your race you begin to have any of the symptoms described, be sure to stop and get medical attention. We run to stay healthy and happy, and around here, there is always another race to try.

Carolyn McClanahan, M.D., is a family physician with Jacksonville Emergency Consultants.