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The Importance Of Hydration During Exercise



 65% of body weight is water and 75% of the muscle is water. Water has different functions within our body, such as transporting nutrients and metabolic waste, preventing body temperature to rise, etc. Incorrect intake of fluids during exercise will affect temperature regulation, cardiovascular function and muscular metabolism.

The amount of perspiration will depend on external factors such as the duration and intensity of the exercise, environmental conditions (temperature, humidity, wind, sun) and the clothes worn as well as the individual characteristics such as weight, genetics, level of training and acclimation. The range of variation in the perspiration rate is very wide, for this reason, it is necessary to make individual recommendations on hydration.


 Thirst is a late indicator; therefore, it is not a correct stimulus to ideally hydrate.

We drink water to satisfy the temporary need, but the water deficit remains.

Studies have shown that even though people have the fluids to drink, they are not able of keeping an ideal hydration state. When dehydrated the main alterations are:

Gastrointestinal disorder

More consumption of local glycogen

Rise in heart rate and body temperature

Decrease in:

Gastric emptying

Blood flow in the skin

Fine concentration and coordination


A tolerable dehydration involves a 2% loss of weight (in a person who weighs 70kg, it is 1.4 kg); if the loss is bigger, performance in most sports is hampered and recovery is slowed down.

This is why it is important to drink fluids, given that the loss of fluid through perspiration produces a progressive decrease of performance.

You should also not over hydrate ( complete your training with more weight than when you started training ), since it could result in hyponatremia ( a decrease in the sodium concentration in blood plasma ) that could also carry negative consequences.

After water, the main component of sweat is sodium. The losses of sodium greatly vary from individual to individual. In order to know if our sweat contains too much sodium you just have to see is there are residual white stains in your skin, or also to use dark clothing and see if these white stains are detected. It these cases, sodium dietary intake must be increased, as well as replenishment of lost sodium during exercise must be done, since it facilitates the retention of fluids helping the absorption of glucose in the intestinal system and prevents muscular cramps.

How Do I Calculate My Needs Of Liquid During Exercise?

Measure your body weight with as little clothing as possible before exercising,

when you complete your activity, dry up the sweat, and with dry clothes ( without socks, bandages, etc ) measure your body weight again ( in other words, under the same conditions than your previous body weight measurement ). Calculate the amount of liquid you consumed during your training ( for this, you should have hydrated with your own individual bottle ) If possible, when you complete your training, urinate and measure its volume ( Initial weight – Final weight )+ Ingested volume – urine volume )

Example: ( 60 Kg. – 59.2 Kg ) + 200 ml ( in this case no final measurement of urine was performed ).

Loss of liquid: 800 ml + 200 ml = 1000

Calculation of % of loss: 1/60 = 1.66%

Tolerable dehydration: 2% of 60 Kg.: 1.2 Kg ( and only 1 Kg was lost ).

During the following 2 hours, this person should ingest 1.5 lt ( 150% of weight lost )

Some Practical Tips:

Stay hydrated not only during trainings and competitions but during the whole day.

Check on your state of hydration through the smell of your urine. It should be clear and abundant.

Don’t wait until you are thirsty to drink liquid: when thirst appears, you are already dehydrated.

During exercise, hydrate yourself by alternating water with sports beverages, specially during hot and humid days or during training sessions that last more than 1 hour.

To improve your hydration is a matter of planning, it is a habit that you can train.


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