What is dehydration? Generally speaking, dehydration is the decrease in body water (fluid) volume. It may be one of the reasons for the high specific gravity of urine as a result of urinalysis. As the fluid intake increases, the density naturally decreases. With fluid loss, electrolyte (elements such as sodium, potassium, chlorine in the blood), in other words salt, may also be lost.

Fluid loss in the body causes weight reduction. Dehydration is divided into three according to the decrease in body weight.

1- Mild dehydration: It is the loss of up to 5% of body weight.

2- Moderate dehydration: It is the loss between 5-10% of body weight.

3- Severe dehydration: More than 10% of body weight is lost.

As the degree of dehydration increases, clinical findings become more pronounced. In addition to fluid loss, electrolyte loss may also occur in the body.

If fluid and electrolyte loss are equal, "isotonic dehydration", if water loss is high, "hypernatremic dehydration" and if electrolyte loss is greater, "hyponatremic dehydration" is mentioned.

Sports and Athlete

During sports activities, many athletes face the problem of dehydration. This problem is more common, especially in long-term encounters. As a dirty game of nature, sports work prevents the feeling of thirst, so you cannot understand the dehydration caused by perspiration only with the feeling of thirst.

The work of the muscles generates heat. However, with the expansion of the vessels, the blood circulation accelerates, including the vessels close to the skin, and the feeling of coolness created by the transfer of this heat to the skin and the evaporation of sweat prevents the feeling of overheating. In addition to sweating, sports also cause fluid loss in the body with breathing. Although sweating constitutes a very important part of fluid loss in high-intensity operations in hot and humid weather, especially in long-term activities, total fluid loss can reach very serious levels regardless of weather conditions.

When the lost fluid is not replaced, it is caused by the decrease in the blood volume in the circulation and hypohydration and the concentration of blood. This situation starts to put extra strain on the cardiovascular system, and the heart works faster to pump enough blood to working muscles and important organs. As the blood volume decreases, the blood flow towards the skin decreases and the amount of heat emitted from the skin decreases as the perspiration decreases accordingly. However, the body temperature that starts to rise excessively can cause cramps, collapse in body energy, and even death.

Even small amounts of liquid loss can have serious psychological effects. For example, a 2% loss in relation to body weight (only 1 kg for a 50 kg athlete) leads to a loss of performance of around 10% and the need for more effort. A loss of between 3 and 5% of body weight causes a significant decrease in performance, while it also negatively affects factors such as reaction time, concentration and decision mechanism, which are vital for all sports from high jump to American football. In impact sports such as boxing and American football, this can lead to various injuries, even serious brain damage with blows to the head.

Apart from the loss of fluid in the body, another important factor that causes premature fatigue and low performance both physically and psychologically is the excessive decrease in carbohydrate (CHO) levels. Since sufficient CHO and fluid intake will directly affect important factors such as training time and workout intensity, it enables the training to add more to you and makes one of the differences between winning and losing. It is not possible to consume liquid and food during training or competition in all sports. Although sports drinks (not energy drinks) are not the most magnificent solution in this regard, they can be used to meet these needs, as they generally meet both liquid and CHO needs together and can be easily tolerated by the body when consumed at reasonable levels.

Although there are some basic principles regarding CHO and fluid consumption required for various sports, it is better to decide individually what should be consumed when and in what amount. Each athlete can sweat different amounts and lose different amounts of fluid and CHO in the same weather and working conditions. Apart from this, many athletes also care about the taste of sports drinks that they will meet their needs and do not consume even the best thing for them if they do not find it delicious, which is a situation that can vary from person to person.

Losses by Perspiration Since

advanced levels of dehydration can lead to fatal consequences, many studies have focused on long and hard work in hot weather. While sweating increases with the intensity of training, factors such as clothing made of thick fabrics that make it difficult to expel sweat, high air temperature and humidity can increase the amount of perspiration to very high levels.

With sweating, sodium (Na) loss occurs as well as fluid. Na concentration in sweat may also differ depending on the person. In the measurements made at a temperature of 23 degrees at 70% VO2 max * level, the amount of perspiration varying between 426g and 1665g was determined. Factors such as working condition, air temperature and sweat can be removed from the body quickly affect the Na concentration. As the rate of perspiration increases, the Na ratio may also increase. While Na in sweat measurements varied between 40 and 140 mmol / liter in runners, this amount was 20 mmol / liter lower in tennis players on average.

The independence of sweating and loss from weather conditions is more than most athletes can imagine. The highest recorded sweat amount to date was 3.7 liters / hour measured at Alberto Salazar in the 1984 Olympic Marathon. While sweating between 2-3 liters / hour is considered normal in short-term heavy work, this amount is expected to be between 1.5-2 liters / hour in long-lasting endurance studies. It is considered normal for athletes to sweat up to 2 liters per hour in an American football match played at 10 degrees. In addition, it should not be forgotten that fluid loss occurs with the moisture in the breath.

Except in extreme cases, the amount of Na in the blood does not show serious changes. Most water is lost by sweating. Na lost through sweat is at a very low rate in the total Na in the body and can be replaced by normal nutrition. Severe Na levels in the blood are rare and can be seen in over eight hours of tough combat, such as the Hawaiian Ironman competition. This situation, which can be life-threatening, can also occur as a result of water poisoning caused by consuming excessive amounts of water or liquids that do not contain Na or contain insufficient amounts of Na.

CHO-Electrolyte Beverages and Performance

Since 1984, the American College of Sports Medicine has stated that water is the best drink for endurance competitions. Many studies have also shown that in addition to water, various electrolytes (most importantly, Na, which accelerates liquid absorption) and CHO consumption are also beneficial.

Drinking water suppresses the feeling of thirst, triggers the need to urinate and causes bloating. It may not be a very good option for situations that require intense fluid. Sports drinks generally contain around 10-25 mmol / liter sodium salts. This ratio is far below the ideal amount that will trigger liquid absorption, but when the ideal Na concentration is achieved, the flavor and drinkability will be lost as the beverage will approach seawater salinity. The ideal CHO amount can vary greatly depending on the physiological requirements of the sport, environmental conditions and the tolerance of the athlete. While CHO loss is the first factor that causes early fatigue in endurance-based long-term studies, it is more important to replace the lost fluid in studies where the amount of sweating is high and dehydration accelerates. In line with these differences, sports drinks sold in powder form can be prepared in different densities, which is one step ahead of those sold as liquid. Isotonic CHO-electrolyte beverages generally contain 4-8% CHO, can be absorbed at the same rate as water, even from water, and provide energy.

The benefits of beverages containing CHO are known. It has been documented that long-distance cyclists and marathon runners experience faster times when they consume CHO-electrolyte drinks instead of water, or that those who do weight training can do more repetitions with higher weights. This is actually not surprising, as the amount of glycogen decreases rapidly as the working intensity increases, so does energy production with CHO. Studies have shown that CHO support is beneficial both physically and psychologically in sports that require different skills (such as running, strength, endurance) such as ice hockey and American football. In other words, CHO not only delays fatigue, but also keeps mental alertness and decision-making.

How Much CHO?

In the light of all this information, it can be said that CHO-electrolyte sports drinks are suitable for team sports where endurance and food consumption are not possible. So how about the right CHO density? EF Coyle (see sources) recommends figures such as 30-60g CHO / hour and 625-1250 water / hour in an endurance-based study for a 68-pound athlete. This means that a beverage with a CHO-electrolyte concentration of about 4-8% is sufficient. However, in real life, some athletes find the 4% density heavy and prefer lower intensities. It is recommended to consume foods containing CHO, if possible, in case the taste of the beverage becomes boring or uncomfortable in hot weather and difficult conditions and when higher fluid consumption is required.

Drinks with a CHO concentration of 10% or more are generally not recommended for athletes. However, as sweating will be less in high-intensity work that will take around 60-90 in cold weather, replacing the consumed glycogen will be more important than providing hydration, if the athlete can tolerate, around 15% CHO concentration will have positive effects.

Why Is Dehydration Experienced?

Dehydration is the reduction of body fluids, for whatever reason, due to the faster loss of fluid intake. In some cases, athletes may come to the match already dehydrated. For example, during a long and tiring journey in hot weather, they reach the area where the activity will take place without consuming enough fluid and do not provide the necessary rehydration. Some possible reasons for not taking enough fluid during the activity are as follows.

1- Inability to understand the need for fluid; Because the amount of sweating can vary from person to person and is not taken seriously enough by many athletes, athletes cannot create a correct fluid intake plan for themselves. One method that can suggest to correct this is to measure whether they can replace the loss before and after the study without clothing.

2- Lack of opportunity or sufficient amount of drink to consume fluids. It will be beneficial to consume CHO-electrolyte sports drink 10 minutes before the start in cases where it is not possible to consume fluids while doing sports and the activity will last more than an hour.

3- The effects of not consuming fluids. As we mentioned before, exercise suppresses the feeling of thirst and the activity itself can cause the athlete to forget the need to drink water. Being dehydrated can cause a feeling of emptiness in the stomach and stomach discomfort, nausea and vomiting. This can prevent you from consuming fluid later.

4- Wrong fluid consumption timing. The nausea that many athletes attribute to fluid consumption is actually caused by fluid loss or excessive fluidity. Dehydration can be confused with a lack of CHO. Liquids containing more than 10% CHO may cause a feeling of emptiness in the stomach and may aggravate dehydration by causing the liquid to be consumed when it is not absorbed and consumed when necessary.

5- Inability to meet excessive sweating with liquid. Training above 70% VO2max suppresses the feeling of emptying in the stomach. Although the amount of gastric emptying during training is around 1-1.2 liters / hour, the highest recorded amount is 2.4 liters / hour. In some cases, the fluid stored in the stomach may also be consumed because the athlete does not take back the fluid lost by sweating with sufficient consumption.

Many athletes only cover up to 50% of their loss with their fluid intake before and during the activity. With this in mind, post-activity hydration is vital.


'Dehydration and Intravenous Fluid Therapy' Prof. Dr. Ahmet Aydin (1998), p. 45-61

'Foods, Nutrition and Sports Performance,'. C. Williams and JT Devlin (1994), pp 147-178

'Clinical Sports Nutrition,' L. Burke and V. Deakin (1994), pp 333-364

'Fluid and carbohydrate replacement during exercise: how much and why ?.' Sports Science Exchange, EF Coyle (1994) 50, vol. 7, no. 3