In fact, most aren’t aware of the effects dehydration (loss of body water) can have on their performance.
These include:
These include:
• an increase in heart rate, that causes needless fatigue,
• an increase in body temperature, that can endanger their health,
• an increase in perception of effort: they’ll feel like they are working harder than they actually are.
• and a decrease in motivation. They’ll want to quit.
For active kids, dehydration translates into decreased speed, technical moves, and ability to focus on the task at hand. Also, sweat losses can contribute to muscle cramping in predisposed players.
Now you may ask, how much does my child need to sweat until he feels those symptoms? Scientific research shows that a loss of as little as 1 to 2% (particularly in hot environments) of body weight during exercise is likely to impair performance! (Weight lost during a bout of exercise is primarily water.)
As so, you really must pay attention to your son/daughter’s hydration status. Teach your child to assess his/her urine color and output. If s/he urinates frequently (every 2 to 4 hours) and urine color is pale (see fig. 1) s/he is probably well hydrated. The most reliable time to check urine color is in the morning, after waking up. It will tell if s/he hydrated well the day before.
Fig.1 – Urine color chart. If the urine sample matches #3 or less in the chart, your child is well hydrated. If the urine color is #7 or darker, s/he is dehydrated and should consume fluids. (From: Casa DJ,Armstrong LE,Hillman SK,Montain SJ,Rich B, Roberts WO, Stone JA. National Athletic Trainers' Association Position Statement: Fluid Replacement for Athletes. J Athl Train 2000;35(2):212-224.)
Every athlete who aims for excellent performance must aim to be well hydrated before, during and after training/competition.
To start well hydrated, your little warrior must begin hydrating 4 hours before an afternoon game (or the day before a morning game) with 5-7ml/kg (for example, 200 to 300ml or 7 to 10 oz in a 40kg/80 lb athlete) and then s/he can monitor how often and what color is the urine passed. If the urine is still too dark two hours before the soccer event, s/he must drink another 3-5ml/kg (ex. 120 to 200ml or 4 to 7oz in a 40kg athlete), so s/he still has time to pass excessive fluids before exercise time.
To optimize your child’s hydration status during training or competition, you must estimate his/her sweat rate in both contexts, in order to replace efficiently sweat losses. To do so, you can use the following formula:
[(Pre-exercise body mass (kg) – Post-exercise body mass (kg)) + Total fluid ingestion (l)] (– Urine output (l), if the child urinated)
This tells you how much s/he sweated in the whole session (ex. 3L in a 2h session). If you divide the result by exercise time (h), you’ll have his/her sweat rate (ex. 1,5L/h or 50 oz/h) calculated. With this information in hand, you’ll be able to optimize performance by fine-tuning replacement of sweat losses. You must assess his/her sweat losses in a variety of weather conditions and type and context of exercise because these influence his/her sweating.
If you prefer to do this more intuitively, just make sure s/he weighs him/herself with minimal clothing or nude (if possible) before and after exercise. His/her final weight must be neither higher nor too much lower (loss > 2%) than initial one. To achieve this result s/he must drink regularly (120-240ml or 4-8 oz every 15-20m) during training/competition. If possible in hot weather games, water should be placed along the sidelines to be consumed during breaks in play.
Practical example:
Luis Miguel is a soccer player who weighs 45kg (90 pounds) before a training session. Immediately after exercise, he weighs in again and finds he is 44kg (88 pounds) now. He lost [(45 – 44)/45] x 100 = 2,2% of body weight, so next time he should drink about one more liter (1 kg fluid) in a similar exercise session.
After exercise, the best way to recover your child’s hydration status is to drink 150% of his/her losses (ex. If s/he loses 1L s/he must drink 1,5L).
Sports drinks vs water
If this is not your son/daughter’s case, but s/he hasn’t fueled well enough for the workout, s/he’ll feel some benefits due to the energy provided by the drink.
Sports drinks can also be helpful to recover after exercise, as I said in previous blog post. They can both re-hydrate and refuel your body.
The most rigorous criterion I suggest you to have when choosing a sports drink is the carbohydrate content. The optimum content is between 6 to 8% (i.e. 6 to 8 grams carbohydrate per 100ml). Also, make sure your child enjoys the flavor.
Attention note:
Some young players tend to over-hydrate (i.e. drink more than they lose) when water is made available. That can also be harmful! Besides the needless additional weight, drinking too much water may predispose to exercise-associated hyponatremia (i.e. sodium levels too low in bloodstream), a clinical condition characterized by symptoms that become increasingly severe and include headache, vomiting, swollen hands and feet, undue fatigue, confusion and disorientation and wheezing. In worse scenarios, low blood sodium may end in edema in the brain, coma and death.
This emphasizes the need for monitoring of sweat losses to ascertain that your son/daughter drinks neither too little nor too much fluids.
Recommended reading for more information:
- Food Guide for Soccer: Tips & Recipes from the Pros (http://www.nancyclarkrd.com)
Once again, feel free to comment this post, I'd like to know:
Do you pay attention to your child’s hydration status?
How much weight does s/he normally lose during exercise?
Has s/he ever felt the consequences of dehydration during a training session or match?
I'll be glad to answer your questions too!
Wishing you and your child the best performance ever,
Diogo Ferreira, RD
Sports Nutritionist, Lisbon, Portugal
“Promoting best health and performance through nutrition”
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