Learn why running hyponatremia occurs scientifically and how to prevent it in runners. It's no secret that stayers can experience severe dehydration. You've probably noticed that marathon runners drink water from time to time throughout the course. However, this is not the only problem that athletes who compete in sports disciplines that require high endurance may face. Quite often, athletes develop hyponatremia while running.
Note that according to official statistics, approximately 75 percent of all finishing marathon runners experience this condition to some extent. In addition, running hyponatremia is the most common cause of death in long-distance athletes. Scientists are sure that it develops in all marathon runners without exception, but most often it occurs without pronounced symptoms.
Today we will not talk about hyponatremia from the point of view of various pathologies in which it can manifest itself in any person. Such diseases include renal and liver failure, problems with the work of the heart muscle, etc. The conversation will only go about hyponatremia when running.
Running hyponatremia: what is it?
Human blood plasma is a very complex solution from a chemical point of view. It contains both ions with a positive charge (magnesium, sodium and potassium) and negative (phosphates, chlorine, etc.). All these substances belong to the group of electrolytes. However, the blood contains a lot of non-electrolytes, for example, carbon dioxide, protein compounds, oxygen.
One of the most important indicators of plasma is osmolarity. It indicates water-electrolyte metabolism, which does not affect all the movement of fluid in our body. Osmotic pressure can be created when the solution is separated from the solvent by a membrane.
In turn, the membrane must be permeable to the solvent, but at the same time prevent the passage of already dissolved substances. The main solvent in our body, as you can easily guess, is water. It easily penetrates through all membranes in the right direction, which depends precisely on the osmotic pressure.
During normal functioning of the body, the osmotic pressure of the intra- and extracellular space is in equilibrium. As soon as the osmolarity index begins to increase in one of these spaces, water begins to flow into it from the area in which the osmolarity is lower.
To make the process described above easier to visualize, take a glass separated by a liquid-permeable membrane. On both sides of the membrane, there is a solution of water and sugar, which cannot pass through the membrane. As soon as the number of sugar molecules on one side of the membrane increases, water immediately begins to flow there, until the concentration of the entire solution is equalized. This is called osmolarity.
We have already said that plasma contains a lot of substances, among which three are distinguished - glucose, sodium and urea. It is they who are able to have the maximum effect on the osmolarity indicator. As you already understood, the movement of water through the body also depends on them.
The body always strives to maintain an indicator of osmotic pressure within strict limits, ranging from 280 to 300 mmol / liter. It is quite obvious that this pressure directly depends on the sum of the three substances. In the normal state, the amount of sodium ions in plasma is 135 to 140 mmol / liter. Among the three substances we have noted, it is sodium that has the maximum content. This suggests that the osmotic pressure of plasma mainly depends on the sodium content in it.
From all of the above, we conclude that running hyponatremia is a condition in which the concentration of sodium ions in plasma falls below 135 mmol / liter. However, it should be remembered that this rule is very relative. For example, in young people, hyponatremia most often occurs when sodium ion concentrations are below 120 mmol / liter.
In most cases, this condition in an adult is observed with an increase in the concentration of ADH (antidiuretic hormone). This substance is synthesized by the hypothalamus and acts as a water balance regulator. Note that this hormone has no effect on the concentration of salts.
The antidiuretic hormone increases the rate at which the kidneys reabsorb fluid from body tissues (reabsorption) to retain water. This reaction can be activated with significant fluid loss and the simplest way to restore the required blood volume. Here it is necessary to clarify - due to reabsorption, blood is not diluted with water, but exclusively with an electrolyte solution. Note that running hyponatremia can be caused by both dehydration and excess fluid.
Running Hyponatremia: Research Findings
Let's turn to research findings that may shed light on running hyponatremia. During the regular Boston Marathon (2002), scientists from the Massachusetts Medical Society conducted a fairly large-scale study, the purpose of which was to determine the degree of risk of hyponatremia during running.
A few days before the start of the race, more than 760 sports fans filled out the questionnaire. About 480 of them made it to the finish line, and they donated blood for analysis. In 13 percent of cases, scientists stated hyponatremia with sodium ions in an amount of less than 135 mmol / liter. At the same time, 0.6 of the study participants were rated as critical. In their blood plasma, the concentration of sodium ions fell below 120 mmol / liter.
It was also found that in most cases, the dangerous condition was the result of drinking a large amount of liquid. Athletes consumed about three liters of water throughout the distance. In 95 percent of cases, running hyponatremia was observed in slow athletes who spent four hours or more to cover the entire distance. However, they all stranded a fairly low body mass index.
A year later, 14 amateur athletes who had taken part in the marathon were delivered to medical facilities in the capital of Great Britain. All were diagnosed with hyponatremia. Note that as a result, one young runner died in the hospital. It is quite obvious that such an incident had serious consequences and scientists conducted an experiment.
88 fans of ultra-long distance running, after passing a medical examination and passing a blood test, filled out a questionnaire. As a result, 11 people (corresponding to 12.5 percent) were found to have asymptomatic hyponatremia. During the study, scientists found that they all consumed a lot of water (more than four liters). At the finish line, their body weight turned out to be higher in comparison with the starting one.
Another experiment took place in 2009 during the famous Western States Endurance Run. All athletes who reached the finish line took part in the study. Approximately 30 percent were in a state of hyponatremia. Moreover, at the same time, a decrease in the body weight of athletes by 3-6 percent was diagnosed. This fact was confirmed in further studies in which runners with significantly lower levels of training took part. As a result, we can say that in more experienced athletes, hyponatremia develops due to dehydration.
One of the largest studies in this area was carried out in the period 2000-2004. The subjects were participants in the annual marathon in the city of Houston. Approximately 22 percent of all participants were diagnosed with hyponatremia. Note that scientists again stated the direct dependence of the development of this state on the duration of being at a distance.
The slower the athlete moved, the more fluid he had to consume. This also leads to an increase in the risks of developing this condition. Also, scientists were able to identify one very interesting pattern. If an athlete lost no more than 0.75 kilograms of body weight during the race, then the likelihood of developing hyponatremia increases seven times in comparison with runners who have lost more weight.
In 1998, during the San Diego marathon, out of 26 cases of hyponatremia, 23 were among the fair half of humanity. This was confirmed in the course of other experiments, and thus allowed scientists to talk about the greater susceptibility of women to the state of hyponatremia. If the body weight exceeds normal by only four percent, then the risk of developing the condition we are considering increases by 45.
Research and triathletes have been carried out. So in New Zealand, a little more than half of the participants in the competition took part in the experiment. After passing the entire distance, the subjects donated blood to determine the concentration of hydrogen ions in the blood plasma. Approximately 18 percent of the study participants (58 people) were diagnosed with hyponatremia. It was also confirmed that women are more susceptible to this condition in comparison with men.
All this suggests that hyponatremia is possible in all sports disciplines, the main requirement for athletes is high endurance. Moreover, in the risk zone are athletes who spend more than four hours at a distance.
How to avoid running hyponatremia?
To avoid hyponatremia during a long-distance race, you must first of all follow a drinking regimen. As we learned from research results, this condition can manifest itself not only with dehydration, but also with an excess of fluid. 60 minutes before the start, you can drink as much as you want.
Do not consume more than one glass of water in 20 or 30 minutes. It's also important to eat right. Sources of all nutrients should be present in your diet. If after class you experience a strong feeling of hunger, then we recommend eating juicy fruits and vegetables.
To restore the concentration of sodium ions in the blood plasma, the water-salt balance should be normalized. Only in this case will hyponatremia be eliminated. As we said above, most often hyponatremia develops asymptomatically and only tests can determine the presence or absence of this condition.
For information on how to recognize hyponatremia, see the video below:
