Due to the different factors such as regulating body temperature, exercise intensity and duration, the body will lose water to varying degrees. We call the loss of body fluids 1% of body weight dehydration. When the body loses water to about 2% of the body weight, symptoms such as thirst, oliguria and loss of urine potassium appear, which is mild dehydration; When the body loses water to about 4% of its weight, symptoms such as increased heart rate, increased body temperature, severe thirst, fatigue and decreased blood pressure appear, which is moderate dehydration; When the body loses water to 6%- 10% of the body weight, it may lead to accelerated breathing, muscle twitching and even coma, threatening life safety. Dehydration will affect body temperature regulation, circulatory function and exercise ability.

In order to improve and relieve the dehydration state of the body, this method of replenishing water is called rehydration. Supplementary exercise dehydration should be based on the principle of losing insufficient water and maintaining water balance of the body, and rehydration can be carried out before and during exercise. The solution used for rehydration should contain a certain proportion of sugars and inorganic salts, but the concentration is low, so it is advisable to use a low-permeability solution, and the rehydration method is better to use a small amount for many times. Generally speaking, the concentration of sugar in rehydration solution should not exceed 25g/L, and the concentration of inorganic salt should not exceed 20g/L ... Drink10-15min 150~250mL of hypotonic solution with the temperature of 6~ 12C. If you want to do endurance exercise for a long time, you can force a lot of water before exercise, because forcing water before thirst can reduce or alleviate dehydration.

Not drinking enough water before exercise and not paying attention to hydration during exercise will cause dehydration, and the degree of dehydration will increase with the extension of exercise time. Dehydration will increase the burden on the heart; The heat generated by muscle contraction cannot be distributed and accumulated in the body, which raises the body temperature; Insufficient supply of oxygen and nutrients for muscles; The excretion of metabolic waste in the body is blocked.

These hazards caused by dehydration eventually lead to the early appearance of fatigue during exercise, the decline of exercise ability and the difficulty in eliminating fatigue after exercise. This will seriously reduce the effect of athletes' training, and make the fitness exercise fail to achieve the purpose of fitness, and even endanger health. The influence of water loss on sports ability is related to the amount of water loss and training level. Dehydration usually impairs athletic ability, whether it is endurance aerobic exercise or high-intensity anaerobic exercise. Generally speaking, when dehydration reaches 2% of body weight, exercise ability is slightly impaired; When dehydration exceeds 5% of body weight, exercise ability can be reduced by 30%. It is found that long-term exercise makes the body lose about 2%. 5% of body fluids, the result is that the ability to carry out high-intensity exercise is reduced by 45%. Preventing dehydration can enhance athletic ability.