How to calculate your sweat rate and the amount of fluid you need to drink for your training?
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It is known to every athlete that excessive dehydration is bad for performance and must be avoided, and that we need to drink to replenish the water lost in sweat during exercise. But how much you need to drink to avoid excessive dehydration?
There is no standard answer that fits all athletes for this question, and so, each athlete should develop an understanding of his own fluid demands during exercise.
Since during exercise we mainly lose water through sweating then obviously we need to drink as much as we sweat in order to avoid dehydration.
So, how much do you sweat during exercise?
The easiest way to calculate how much you sweat per hour of exercise is through the difference in body weight before and after exercise. To calculate that, you can use the following formula:
Sweat Rate in litre per hour = (Weight before exercise – weight after exercise + fluid consumed during exercise) / duration of exercise
Let’s take an example. A cyclist weight before a training session was 75.00 kg and after the session was 72.00 and he consumed 0.5 litres of fluid during this session and the session duration was 2 hours.
So, his sweat rate per hour of exercise = (75-72.00+0.5)/2 = 1.75 litres per hour. So, this athlete should drink 1.75 litres of fluid per hour during such session of exercise. Total of 3.5 litres in 2 hours.
But it is difficult for most athletes to consume that much of fluid!
According to the American College of Sports Medicine, dehydration of more than 2% of body weight can negatively affects performance. In other words, it is okay not to drink (during the exercise) as much as 2% of your initial body weight.
Now let’s apply this to the above example and adjust the amount of fluid this athlete needs to drink.
2% of his initial weight = 75 x 2/100 = 1.5 kg. So, he may drink in a session of exercise the amount equivalent to his sweat in the whole session less 1.5 litres.
Since we calculated his sweat rate to be 1.75 litres per hour x 2 hours session = 3.5 litres – 1.5 = 2 litres. So, in a session of 2 hours he needs to drink 2 litres of fluid to avoid excessive dehydration or 1 litre per hour.
We also need to note that amount of sweat in a hot morning session can be different from a similar session in the evening or in the winter and exercising outdoor is not like indoor. So, we should make this calculation from time to time with changing training conditions to adjust fluid needs.
For accurate results it is recommended to empty bladder before each weighing and to weigh yourself with minimal clothing and without shoes.
We also need to remember that our sweat is not only water and that we lose important minerals with the sweat. Hence the recommendation for drinking for any exercise session lasting more than 1 hour is to drink a sport drink that contain important minerals like Sodium and Potassium and not just plain water.Sponser Sport Drinks like ISOTONIC, COMPETITION and LONG ENERGY provide ideal sports drinks for different needs and training demands.