Let’s talk about hydration during exercise from three perspectives: why to replenish water, when to replenish water, and how much water to replenish.

Why hydrate?

It’s simple, because when we exercise, our body functions to regulate body surface temperature and achieves this purpose through sweating.

The main component of sweat is 98 to 99% mainly water, of which sodium chloride (that is, salt) is about 300 mg/100 ml. The other 1 to 2% is a small amount of urea, lactic acid, fatty acids, etc.

The main electrolytes in sweat are sodium and chloride ions, with small amounts of potassium and calcium.

If the body does not have enough water, our performance during exercise will be affected. Proper drinking water can help:

Improve metabolism and exercise performance

Accelerate the recovery of physiological functions after exercise

Maintain the body at optimal body temperature

Helps the body perform at its best

Help perspiration and detoxification

When do you need to rehydrate?

You must replenish water during the three stages of exercise: before exercise, during exercise and after exercise.

The temperature of drinking water should be close to room temperature. Drinking ice water or boiled water after intense exercise can easily irritate the respiratory and digestive systems and affect body expansion; overheated water can easily burn the mouth and esophagus, which will slow down gastric absorption.

before exercise

One of the simplest and most common methods is to rely on physical sensation. If you feel thirsty or not, if you feel thirsty obviously, you should replenish some food in advance.

In addition to feeling, we can also judge whether the body has enough water by observing the color of urine. When the urine is light yellow, it means that the body has enough water. When the urine is darker in color, it means that the body is not hydrated enough. (Except for conditions that affect the color of urine, such as when taking medication)

Urine color is the manifestation of metabolites in the body in the urine. If you drink less water, the metabolites will be concentrated and the urine color will become darker.

in motion

The water in the body is excreted with sweat. At this time, we often feel very thirsty, and the amount of water we need to drink naturally increases. But remember, you should not drink too much at one time. Drinking water too fast or too much may cause It can lead to serious consequences such as cramps, because drinking too much boiled water will dilute the electrolytes in the blood, leading to hyponatremia, thereby causing cramps.

At this time, in addition to drinking water, you can also drink some sports drinks appropriately. During long-term exercise, the lost sweat contains the most sodium, and the loss of sodium ions and chloride ions will cause the body’s inability to timely regulate physiological changes such as body fluids and temperature. At this time, replenishing water may not be enough. Cope with electrolyte loss.

after exercise

15 minutes to half an hour after exercise, remember to take a break and replenish water. Once you are severely dehydrated and feel muscle weakness, nausea, and vomiting, you can add half a teaspoon of salt to your drinking water to replenish the lost salt. When drinking water, avoid drinking too much. The correct speed of drinking water should be to drink slowly and slowly in small sips, so that the body can achieve good absorption.

For the general small amount of sweat loss, the electrolytes stored in the body will actually be automatically released into the blood to maintain the stability of electrolytes in the blood. Therefore, after a short period of exercise or sweating, you only need to replenish water.

In addition to sports drinks containing electrolytes, general fruits and juices are also foods with a high sugar content, which are also very helpful for physical recovery after exercise and maintaining electrolyte levels. There is no need to stick to sports drinks after losing sweat.

How much water is enough?

After exercise, the body loses a lot of sweat and body fluids, so it is necessary to replenish water in an appropriate amount in a timely manner to maintain optimal and normal functioning of the body. The ideal golden rule is to replace your fluid losses by 25% to 50%.

How to calculate that 25%-50%?

Weigh yourself before and after exercise. The difference in weight is a rough estimate of the amount of water and body fluid lost during exercise. The difference in kilograms is then multiplied by 1.25 or 1.5, and the resulting figure is the recommended amount of water that needs to be supplemented, that is: for every 1 kilogram of weight lost, at least 1250-1500ml (1.25-1.5 liters) of fluid must be supplemented to correct dehydration.

For example, if your weight before exercise is 68 kg and after exercise it is 67 kg, the weight difference is 1 kg. Multiply the 1 kg difference by 1.25 or 1.5. As a result, you need to give yourself 1.25 or 1.5 liters of water to properly replenish the water lost during exercise.

Generally, you can drink 200-400ml of electrolyte-containing liquid before exercise or before going out in summer. During exercise, add 150-250ml of electrolyte-containing sports drink every 15-20 minutes until the exercise or sweating stops. The remaining amount of fluid replenishment can be completed within 6 to 12 hours. At this time, the rehydration should be mainly water replenishment.

Sports drinks contain a lot of glucose, electrolytes and water, so they can also be used as a substitute for drinking water. But it is not advisable to drink too much.

When you are not exercising, it is best to drink less – because it contains more sugar, electrolytes and calories that your body does not need at this time.

Thanks for reading Garmin Jiaming’s 35th answer~ We will continue to share useful knowledge/stories about sports with you on Zhihu in the future. We look forward to your attention and interaction!