Runners know how important it is to stay hydrated during a race, but less know about the dangers of overhydration. Symptoms often mimic dehydration, making it difficult to detect before it’s too late.
What symptoms do you have?
Swollen fingers, nausea, and stomach pain can be signs of overhydration, which occurs when you drink too much water. A combination of high fluid intake and low renal output (urine output) can cause abnormally low blood sodium levels, leading to a dangerous condition known as hyponatremia.
Sodium is an electrolyte that plays an important role in regulating many important functions in the body, such as fluid balance and supports the central nervous system.
To ensure adequate hydration on race day, runners can easily become overhydrated by drinking too much water in the days before the race, or by drinking too much water during or after the run. It often occurs after running for more than 4 hours. The idea is that the longer you’re out on the course, the more fluid you’re likely to ingest.
Slow runners tend to be more susceptible to this condition because they sweat less and have more opportunities to drink fluids easily. By comparison, fast runners only drink a few sips of water every now and then, and because of their higher heart rates, they sweat more. Therefore, you are less likely to have too much water in your body.
What is hyponatremia?
Hyponatremia can cause a variety of health problems, ranging from mild to life-threatening. Because the brain is particularly sensitive to changes in sodium levels in the body, the first symptom of hyponatremia is often confusion. Other symptoms include dizziness, headache, fatigue, irritability, muscle weakness, convulsions, nausea, and vomiting. Runners can become disoriented, lose consciousness, and even have seizures.
Too much water in the body dilutes the sodium content. This can be dangerous because sodium is a key component of osmosis, the process that regulates the amount of water in and around cells.
“Low sodium content lowers the osmolality of the blood, forcing more water into the cells,” explains Lewis James, reader in human nutrition at Loughborough University. “This causes swelling and is especially dangerous because the brain is encased in a hard shell and cannot swell permanently.” Swelling can cause problems with brain function and, in some cases, death. ”
Curiously, the symptoms of hyponatremia, dehydration, and heat stroke are very similar and can often be differentiated only by blood tests. It is very important to differentiate between the symptoms because although the symptoms are similar, the treatments are different. If you experience these symptoms again during a race or training, go to the medical tent immediately.
How to avoid hyponatremia
Drinking until thirsty is often recommended to avoid hyponatremia, but it is not foolproof. That’s because one of the symptoms of this condition is dehydration.
It is important to note that cases of hyponatremia are extremely rare, and hydration is much more common in runners than overhydration. Hyponatremia is also more likely to occur if you run for long periods of time. Therefore, people running shorter distances than a marathon rarely worry about hyponatremia.
The easiest way to avoid this condition and make sure you’re properly hydrated is to do a simple sweat test.
Normal sweat production ranges from 1 liter to 3 liters per hour, but this can vary depending on temperature, wind strength, and the intensity of your run.
Alan Ruddock, a sports and exercise scientist at Sheffield Hallam University, said the sweat test was easy to carry out at home. “Weigh yourself before and after your workout and either drink nothing or consider how much water you’ve taken in,” he explains.
Ruddock recommends calculating this after an hour of running to get a more accurate measure of how much sweat you’re sweating per hour. 1 gram of weight loss corresponds to about 1 milliliter of water, so 1 kg of weight loss corresponds to 1 liter of water. And, according to James, you don’t need to replace the exact same amount of fluid.
“If you’re losing 1 liter of weight per hour, 500 to 800 ml of water per hour is sufficient,” he says.
Also, don’t think that you can prevent hyponatremia by drinking electrolytes or chewing salt tabs instead of swilling water. James explains that while the best electrolytes are great for post-race recovery and hydration, the amount of sodium is too low to offset hyponatremia.
“The truth is that most electrolyte supplements are very low in electrolytes,” he says. “The salt content is much lower than that in the blood, so it has little effect.”
