Theoretically, we all know that we should rehydrate – even more important for athletes. But in practice it’s not so obvious anymore – we often disregard this issue. Meanwhile, the proper hydration is of cardinal importance both for our health, as well as for the quality of our training.

WATER IN THE BODY

The average healthy adult human consists in more than 60% of water. For example, 70-kg man has approx. 45 litres of water in his body. Women have slightly higher amount of fat in the body, therefore the percentage of water is somewhat lower. Water can be found in every organ – the percentage of water in the different tissues and organs is as follows:

• Blood, lymph, digestive juices – from 86 to 98%
• Kidneys, heart – approx. 80%
• Muscles – approx. 75%
• Leather – approx. 70%
• Lungs – approx. 70%
• Liver – 68%
• Connective tissue – approx. 60%
• Bones – approx. 25%
• Adipose tissue – approx. 20%

Water is involved in the transport of substances in the body and is permanently replaced. A healthy organism maintains very rigid control over the balance of fluids, as it is necessary for the efficient removal of toxins and counteracting organism overheating. With the loss of only 2% of the liquid, our physical capacity is reduced by 10%, 3% loss of fluid causes a 15% reduction in efficiency, while 4-5% loss – as much as 20-30% – this has a huge impact on the quality of our training, but also increases susceptibility to diseases.

FUNCTIONS OF WATER  IN THE BODY

• essential to maintain the appropriate blood volume and pressure
• transports essential nutrients and oxygen to all the cells of the body
• transports metabolic wastes from the cells
• removes excess heat, preventing overheating
• allows for better assimilation of nutrients by the body
• moisturizes organs, facilitates swallowing, stabilizes the nervous system and is involved in the transmission of sound through the middle ear,
• allows us to breathe by moisturizing the lugns

WATER DEMAND

Under normal circumstances we lose daily an average of about 2.5 liters of water:

• 1.4 l – we excrete in the urine
• 0.5 l – is lost through the skin
• 0,4 l – is exhaled through the lungs
• 0.2 l – is eliminated in the faeces

This amount is greater during the hot, dry and windy days, or after an intense workout and should be replenished as soon as possible. It is therefore recommended to consume about 1.5-2 liters of fluid each day. It is believed that an everage adult needs 1 ml of water per 1 kcal ingested food, although this value varies depending on the intensity of perspiration and may reach as high as 1.5 ml/kcal.

We derive water not only from beverages, but also from a solid food – approx. 1/3 of all liquids ingested during the day. Most water is found in vegetables – nearly 95% water.

Physical activity enhances water loss, and with it, the loss of electrolytes. This further reduces our efficiency during longer workouts and hinders the post-workout recovery. During physical effort, the loss of water can be as high as 2 liters per hour, which means a 30% reduction of efficiency. The metabolic rate increases as well, and with it the heat production, the excess of which is transported with blood to the skin and there excreted in the form of sweat. With very intense physical effort, water loss can stay at a higher level of 1l/h even many hours after the workout.

WHAT TO DRINK

And now the most important – what to drink to achieve the best results? We have a multitude of options at hand: water, juices, carbonated drinks, cocktails, special sports drinks, coffee, tea, etc. In general, all these drinks can be divided into 3 categories:

hypertonic drinks – simply put, these are the drinks with a higher density than the density of our body fluids. Often they are called energy drinks. Their main goal is to quickly provide glycogen and therefore supplement energy when the hydration itself is no longer that important. They are a great source of energy for people who do not tolerate solid food during exercise, yet such composition slows down the absorption of water, so they don’t rehydrate very well. This category includes eg. various kinds of juices, Coca-Cola and other similar beverages,  shakes/smoothies and some certain sports drinks.

hypotonic drinks – drinks with density lower than the density of our blood, containong no carbohydrates or 2-4g of carbs per 100 ml. These beverages replenish water level fastest, but provide less energy and electrolytes. This type of drinks include mainly water and certain sports drinks for athletes performing low-intensity exercise.
Water, even highly mineralized, complements the fluid levels in the body well, but because of the poor composition, dilutes them and doesn’t supplement the loss of crucial micro- and macronutrients. During the long effort, drinking only water impoverishes the body.

isotonic drinks – drinks with a density close to the density of blood. They contain 6-8g of carbohydrates per 100 ml of liquid and addition of adequate electrolytes such as sodium and potassium. Such drinks are designed to maintain water and electrolyte balance in the body, providing at the same continuous portions of energy, helping to maintain the appropriate level of effort for a long time. This category includes certain sports drinks, like Powerade, Oshee, 4Move etc.

Hypertonic and isotonic comparison:

• drinking a 500ml of drink containing 30g of carbohydrates (isotonic) causes that within 10 minutes, 200 ml of liquid passes from the stomach into the intestine, delivering 200 ml of water and 12g of carbohydrates
• drinking a 500ml of drink containing 60g of carbohydrates (hypertonic) causes that within 10 minutes only 150ml of liquid leaves the stomach, and as a result we deliver only 150ml of water, but in turn 18g of carbohydrates

As for the temperature, generally we should drink cool beverages, as they are quickly transported to the blood, additionaly reducing the temperature of overheated body. On the other hand, we should remember not to drink too cold beverages, as it can contribute to the formation of gastro-intestinal colic and throat inflammation.
The best temperature for our drink is 4-10 ° C. If we train in a cold environment (eg. during winter), the optimum temperature for our drink is 15-22 ° C.

During more intense workouts  we should avoid carbonated drinks – carbon dioxide acts as a relaxant on the stomach walls and inhibits the actual feeling of thirst. In addition, there is the obvious discomfort caused by hiccups.

WHEN AND HOW MUCH TO DRINK

A lot depends on the ambient temperature. The warmer it is, the more you should keep an eye on hydration. On hot days you should drink small amounts of fluid, but very often. It is good to maintain adequate hydration long before training and after the workout, obligatorily drink a full glass of liquid. For longer workouts take a drink with you on the track and don’t wait for the feeling of thirst. If we get to such point, it means it’s already too late to fill the loss. When you feel thirst, your body is already dehydrated.

Water demand depends on the duration and intensity of exercise. We, runners, should mind the adequate hydration at all times. The day should begin with a glass of water. Also, we should keep the following rules in mind:

• before training – 300-500 ml of isotonic drinks or water
• during training – approx. 200 ml every 20-30 minutes
• after training – 500-700 ml of the drink – it can be isotonic or energy drink. In addition, watch the proper hydration for at least0 a few hours after the workout

Because of the risk of dehydration during prolonged exercise, athletes often consume large amounts of fluids ‚just in case’. Acting this way is unfortunately also potentially harmful and can lead to hyponatremia. It is often the result of receiving excessive amounts of water (so-called „water intoxication”) during prolonged exercise and in extreme cases can lead to death. Hyponatremia displays in a form of nausea and weakness, and in more serious phase as headachea, altered consciousness, or even seizures and cardiac arrest.

To prevent hyponatremia, you should drink in a reasonable manner. The greatest risk occurs during marathons and triathlons when athletes have virtually unlimited access to fluids. During such efforts you should drink approx. 0.5 l of fluids/hour. Of course every body is different, so it is best to determine how much water you lose during a similar effort, by controlling body weight before and after exercise. Another good indicator of hydration is the color of urine, which should be light-straw-colored. In no case can one take up intense exercise in a state of dehydration.

HYDRATION IN A NUTSHELL

• Before workout, drink a glass of water or isotonic
• During long or intense workouts drink 200ml of fluid every 20-30 minutes
• During intensive interval training, drink small sips between consecutive sets
• After workout, drink a glass of isotonic or hypertonic to replenish fluids and glycogen and speed up recovery
• Do not drink too much so as not to wash away too many electrolytes – 0.5 l/hour is sufficient
• Every body is different – weigh yourself before and after exercise – weight loss will tell you how much water you lose in a given time and how much should be supplemented
• Do not go to training dehydrated – if the color of your urine is darker than a pale-straw, you need to replenish fluids
• It is best to drink cool beverages, but not too cold.
• Avoid carbonated drinks – carbon dioxide interferes with the feeling of thirst and can cause stomach „sensations” or colic
• Alcohol, tea and coffee are diuretics and too much consumption of them can lead to dehydration

 

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Sources:
Skarżyński Jerzy, 2012, „Biegiem przez życie”,  MEGA SPORT Jerzy Skarżyński
https://pl.wikipedia.org/
http://zdrowezywienie.edu.pl/woda.htm