Is it good to drink glucose while exercising?

Drink & sport : Nothing works without water

For many endurance athletes, a drop in performance during training is a familiar experience. Common reason: lack of water. Actually as banal as it is logical, after all, you don't get very far in a car without fluids. Nevertheless, the topic of "drinking" is very often neglected and underestimated by athletes. This does not only apply to endurance athletes. All athletes should ensure that they have an adequate water supply before, during and after training or competitions in order to make the most of their own performance potential.


How much water do i need?

Sufficient water, what exactly does that mean? Women need around two liters of water a day, men need around two and a half liters and competitive athletes even three to three and a half liters. And these values ​​are based on the state of rest of the body. This means that water loss - such as through sweating during exercise - does not appear in this calculation. By sweating, with which the body regulates the core body temperature, the body loses another one and a half liters per hour. Of course, these values ​​depend on the person, the training intensity and the environmental conditions. For example, at the Iron Man in Hawaii, a water loss of up to 20 liters per day was observed.

If there is a lack of water in the body because one does not drink enough, this means that the body cannot excrete substances that are subject to urine. After two to four days, dehydration can be so advanced that the blood thickens and the circulation fails. This is certainly the extreme case. But lack of water in sport means a decline in performance. Trained athletes can cope with a certain lack of water, but water must be supplied at the latest when sweat losses of one to two liters are reached. Otherwise there is a risk of weakness, muscle cramps, nausea and / or disorders of the brain functions.

The right time

For training sessions or competitions that last longer than an hour, you should ensure that you have enough water during the activity. Many people make the mistake of only drinking when one is thirsty. The thirst starts with a delay in physical exertion, so you should drink before the thirst is even noticeable. In the case of high-intensity loads of less than an hour, during which you sweat heavily, it is also recommended to compensate for the water loss during the activity.

Water and co.

It is very important to know: The amount of water drunk is not the same as the amount of water absorbed by the body! This is because a large part of water is absorbed in the small intestine. The speed with which the body can absorb drunk water depends on various factors. On the one hand, from the so-called gastric emptying rate. It determines how much water is carried from the stomach to the small intestine. On the other hand, the absorption of the liquid depends on the composition of the drink we consume, after all, many people do not only drink pure water while exercising.

If the drink contains more than five percent glucose, the gastric emptying rate slows down. If you have a drink that contains table sugar (sucrose) and a water-soluble carbohydrate mixture (maltodextrins) instead of glucose, this has no effect on gastric emptying up to a concentration of eight percent. Fats and proteins, in turn, slow down gastric emptying. Electrolytes have little effect. It is therefore worth taking a look at the label and the information on the composition of the drink in order to derive the necessary amount of liquid.

Big gulp, small gulp

The speed at which the stomach is emptied naturally also depends on how full the stomach is: the more the stomach is full, the faster the emptying into the small intestine takes place. Drinking a lot before exercise therefore has a positive effect on gastric emptying. The same applies to the periodic intake of larger amounts of drink during exercise; they are preferable to small amounts of drinks consumed at short intervals. So: It's better to take a long sip on a regular basis than just sipping the bottle all the time. Incidentally, the temperature of the drink also plays a role. Five and ten degrees Celsius are considered ideal. When it's fresher outside or even winter, the temperature of the drink can also be higher.

The fluid is released from the stomach into the small intestine, the faster the more fluid there is in the stomach. It is therefore recommended to fill the "water tank" before starting. An amount of liquid of 600 ml or 400 ml 40 or 20 minutes before the start is optimal. During exercise, a fluid intake of 200 to 250 ml every 15 to 20 minutes is recommended. That sounds like a lot - and it is. But: These values ​​are derived from the maximum gastric emptying rate and are unfortunately difficult to implement in practice.

This is how runners drink properly

If the gastrointestinal tract is exposed to vibrations, such as when running, these quantities are not suitable. Here it has proven to be useful to drink properly two hours before exercise, to take 150 to 300 ml shortly before exercise and to add 150 to 200 ml every 15 to 20 minutes during exercise. However, these details are only guidelines and can be subject to individual fluctuations. It is therefore important to practice drinking during exercise and to develop an individually optimal drinking mode.

What should I drink and what not?

When taking fluids before exercise, make sure to consume water rich in sodium. Why? The decrease in the concentration of sodium in the blood indirectly leads to the accelerated excretion of water via the kidneys. In other words: you keep running to the toilet.

The optimal drink during exercise must make water available to the body quickly. So it has to get quickly from the stomach to the small intestine and be able to be quickly absorbed by it. It should also provide carbohydrates to delay fatigue and sodium to make up for sweat loss.

Details for experts

This results in the following composition: The drink should be hypotonic to isotonic and have a carbohydrate concentration of two to eight percent and a sodium content of 400 to 1100 mg / l. It may contain a larger amount of sucrose than glucose. For the sodium concentration, an amount of 400 to 800 mg / l is recommended, and the drink will also be too salty in taste. It is not necessary to add further electrolytes, but it does not do any harm either.

Fruit spritzer and mineral water

Fruit juice spritzer mixed in a ratio of 1: 1 with high-sodium mineral water is a good drink during exercise. However, since the spritzer contains fruit acid, it has a negative effect on water absorption. It should not be drunk during endurance exercise with a competitive nature. In addition, the fruit acid can cause stomach problems. So it's not a good idea.

Drinks for endurance athletes

For long-lasting endurance exercise, we recommend drinks that contain mainly maltodextrins and soluble starch. At a carbohydrate concentration of 17%, these solutions are isotonic. The water absorption corresponds roughly to that of mineral water, but is a little slower than with fruit juice spritzers and Co. They provide more energy, albeit with a delay. Such a drink would be, for example, Lampert's maltodextrin 12, to name just one.

Tap water and mineral water without added carbohydrates and sodium are hypotonic drinks. They are only conditionally suitable for intensive endurance exercise, as they do not provide any energy and do not compensate for the loss of sodium through sweat, which is, however, absolutely necessary.

Better to do without this

Lemonade, cola drinks, energy drinks, fruit juices and malt beer are hypertonic drinks, they initially increase dehydration and the feeling of thirst. These drinks are not suitable for drinking water during exercise. Such drinks are also only conditionally recommended for balancing the water balance after exercise.

Very few isotonic thirst quenchers available on the market keep what the name promises. Many, contrary to their name, are hypertonic. Additions of minerals and vitamins have no benefit on the water absorption, but affect the content of carbohydrates, since the number of particles in the drink is defined by the specifications. High concentrations of potassium (more than 700 mg / l) impair performance, especially since the potassium concentration in the blood already increases during exercise due to the release of potassium to the muscle cells. Too high a concentration of magnesium (more than 300 mg / l) can lead to intestinal problems. The addition of fatty or amino acids also makes no sense, as they slow down the rate of gastric emptying.

Source: Schek, A., “Top performance in sport through needs-based nutrition”; Trainer library 36 (2002); Pp. 30-41)

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