We decided to find out where these categorical rules came from and how much you still need to drink in everyday life and during training.
Why 2.5 liters?
Most likely, this figure comes from the recommendations of the US National Academy of Medicine. These are scientifically-based recommendations for how much water a person should receive daily, based on gender, age, and other characteristics.
According to them, an adult needs 2.7 (women) to 3.7 (men) liters of water per day. Other categories can be found in the recommendations.
On average, people cover around 20% of their daily fluid needs with food, i.e. only around 2 to 2.5 liters are left to drink.
What is considered a source of water?
According to all the same recommendations, the source of liquid can be not only pure water itself, but also any drinks, as well as foods with a high liquid content, such as soups, watermelons, cucumbers and others fruits and vegetables.
Yes, the tea water is the same as without the tea leaves, and it also replenishes our water balance. Yes, there is water in soup, and there is water in vegetables, and there is water almost everywhere, so you probably don’t need a lot of pure water .
But we must not forget that, for example, lemonade is not only water, but also 30-40 kcal per 100 ml, plus dyes and flavors. This coffee is made up of water + caffeine, which improves its excretion and increases blood pressure. Or this soup with salad is still the same water, but with fibre, vitamins and minerals. Choose your water sources wisely.
Let’s agree on the terms
Hydration (from the ancient Greek hydro – water) – the saturation of something with water, in our case – the human body.
And all the derivatives of this word:
- dehydration – loss of water;
- rehydration – restoration of its normal amount;
- hyperhydration – excess water;
- hypohydration – lack of water.
How often to drink?
If you’re not working out right now (even if you were engaged yesterday), you can focus on feeling thirsty.
Water from food, drinks and additional drinks when thirsty fully covers the needs of a healthy adult who has no additional liquid waste.
Can I drink too much water?
Excessive water intake is called overhydration. At the same time, the concentration of all useful ions in the blood decreases, causing disruption of the heart and skeletal muscles, up to a fatal outcome.
The kidneys of a healthy adult can eliminate up to 700 ml of excess fluid per hour. If you don’t intentionally drink too much too quickly, you’re unlikely to overdose.
In the presence of kidney disease, be careful and careful (although if there is something serious with the kidneys, you are already very careful and careful).
If everything is fine with your kidneys, it is enough to take a urine test and a biochemical blood test once a year to be sure that everything is really fine. Kidney pathology can be asymptomatic for a long time, and it is much easier to treat it in the early stages.
What if I exercise?
Here everything is more complicated and interesting. We will understand using the recommendations of the National Association of Athletic Coaches in the United States.
First, we not only lose water, but also salt.
Second, sweat is hypotonic (contains fewer salts) compared to the whole body. That is, we lose a lot of water and some salts from the interstitial fluid. To compensate for these losses, water from the cells enters the intercellular space. On average, we get almost the same amount of salts in a reduced volume of liquid. Of course, it is necessary to replenish salts, but water always comes first.
Ideally, you need to know how much fluid you lose during exercise in different conditions (hot, cold, wet, long). You can calculate it like this:
Fluid loss during exercise = Weight before exercise – Weight after exercise + Volume of fluid drunk during exercise – Volume of urine excreted during exercise (if any)
For example, you can run about ten in different conditions, weigh yourself before and after (and wait while going to the bathroom until the second weigh-in to simplify the calculations), and roughly estimate your water loss per hour.
Our next goal is to ensure that fluid loss does not exceed 2% of body weight. Yes, they can be more – in hard races, in the heat, in free range, at high altitudes and in other non-standard conditions.
But 2% of body weight is already severe dehydration and the threshold for a bunch of unpleasant effects – deterioration of endurance, speed, thought disorders, muscle cramps and pains, insufficient increase in heart rate and other cardiovascular problems.
So we figured out our fluid expenditures and are working to keep them under 2% of weight.
What, how and when to drink for runners?
If you have any chronic illnesses, they should be taken into account when planning rehydration. Ideally, consult a doctor who is not afraid of the words “running” and “sport”.
The feeling of thirst is a bad guide during sport. It appears late and is hard felt with losses close to 2%. That is to say, if during the race you are very thirsty, you are already dehydrated.
During competitions or active training, you should not wait for thirst.
But! For amateur athletes who prefer a calm pace, moderate exercise, are relatively well nourished and healthy – drinking when thirsty is an adequate way to replenish fluid losses.
There is no universal recommendation on how much to drink during a workout.
Even in studies (like this one), the final recommendations were 15-34ml/kg per hour for cyclists, which could be more than double the amount. And this in a fairly homogeneous group of trained athletes!
Psychological factors also strongly influence water consumption. In the heat, cold water is much better to drink than hot water – look for volunteers with a fridge when running errands. We tend to drink more with food than without – keep the gel or bar up to the point of hydration.
Before competition with limited access to water, it makes sense to drink a little more than you want to reduce the degree of dehydration in the process.
To adequately compensate for losses after finishing , more water may be required (up to 150% loss) due to the fact that with active drinking, water is more actively excreted. If it is possible to devote more than 4 hours to recovery (and preferably more than 12 hours), then you can restore the water balance gradually in small portions, then the volume cannot be increased.
Additives in beverages
If the charging time is less than an hour and the intensity is medium or low, you will have enough clean water (and then – its need depends on the temperature).
For longer duration or high intensity interval training, carbohydrate and/or electrolyte supplementation can improve your performance.
Plus, carbohydrate and electrolyte drinks before long workouts will help you feel better in the process.
How to drink?
The recommendation is to ideally drink 200 ml of liquid every 15 to 20 minutes. But consider these factors:
- we always have a small amount of liquid in our stomach (about 400-600 ml), which ensures its normal functioning. In case of lack of water, this fluid is absorbed and its volume is then very difficult to restore. It is therefore advisable to drink little and often in order to maintain a constant volume of liquid in the stomach.
- during intense exercise, fluid absorption slows down
- the optimal concentration of carbohydrates in the drink is 3-5%
- severe water deficiency (more than 4% of body weight) significantly impairs the body’s ability to absorb it. Filling such a deficit by drinking is difficult and time-consuming.
- small amounts of caffeine in the drink during and after exercise do not interfere with rehydration
- creatine at the doses provided by the package insert does not affect rehydration
- drinks containing less than 2% alcohol do not interfere with rehydration. 2-4% is allowed under normal hydration conditions. Drinks containing more than 4% alcohol are not recommended for consumption. And in general, alcohol and sports are a rather dubious combination.
How to assess your level of hydration?
It can be very difficult to adequately assess your condition, especially in a competitive environment. The signs below are indicative, pay attention to their combination, and not to each one separately.
The thirst. Markedly increases with a loss of about 2% of body weight, may be delayed. When replenishing losses to a level below 2%, thirst is significantly reduced.
Weight. An accurate floor scale is a great way to measure your fluid loss during exercise. You should weigh yourself before and after training, or compare the weight after training with your average weight (less reliable).
Urine color. A simple, affordable, and very reliable way. Of course, ideally, you should measure the density of the morning portion and monitor its consistency (density). But if you notice too dark a color during the competition, this is a very important reason to think about more active rehydration. You can read more about colors and their meanings here.
Symptoms of Water Balance Disorders
The following signs of hypohydration in yourself or others require special attention and possibly seeking help:
- intense thirst and general discomfort
- dizziness, headache
- nausea Vomiting
- severe shortness of breath
- feeling of warmth in the neck or head
Unfortunately, the symptoms of a lack of water overlap with those of a pronounced decrease in blood sodium levels due to exercise:
- headache, dizziness
- fatigue extreme
- muscle contractions
In the case of a decrease in sodium levels, these symptoms are preceded by the consumption of a large amount of water and are accompanied by an increase in headache and swelling.
Unfortunately, the measurement of sodium levels in the blood during competitions is rarely available (and we probably never), so if there are doubts about the reasons for a person’s poor health, it is better to drink hypertonic (with a salt content of more than 9 g / l) solutions. This will help replenish lost sodium and will not harm hypohydration.
What is the result
In ordinary life – drink what you want and how much you want. Fluid needs are very individual and there are no universal guidelines for fluid intake.
Tea, coffee, drinks, soups, even fruits and vegetables also count. There may not be much left for clean water.
Under fillers, it is important to understand the costs of individual fluids. If you exercise regularly, measuring weight before and after training is a good indicator of losses that can be used to calculate fluid needs in the future.
Try to keep water loss to less than 2% of body weight. Calculate in advance how much you will need to drink during a workout/race with your average losses, and divide that amount into approximately equal portions every 15-20 minutes.
During high-intensity interval work or runs lasting longer than an hour Supplementing the electrolytes and carbohydrates in your drink can improve your performance.
For any threatening symptoms (headache, nausea, vomiting, swelling, mental symptoms) in yourself or others – be sure to seek help!