Thursday, January 21, 2010

Hydration in Soccer


Soccer players frequently prepare for matches with no consideration for their hydration status.

In fact, most aren’t aware of the effects dehydration (loss of body water) can have on performance. These include:
  • an increase in heart rate, that causes needless fatigue;  
  • an increase in body temperature, that can endanger your health ;  
  • an increase in perception of effort: you’ll feel like you are working harder than you are;  
  • and a decrease in motivation. You’ll want to quit.

  In soccer, dehydration translates into decreased speed, passing/shooting, dribbling and focusing ability. Also, sweat losses can contribute to muscle cramping in predisposed players. 

Now you may ask, how much do I need to sweat until I feel 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! (This assumes the weight you lose during exercise that lasts for less than three hours is mostly water.)

As so, you really must pay attention to your hydration status.  A good way to check it out is to assess your urine color and output. If you urinate frequently (every 2 to 4 hours) and urine color is pale (see fig. 1) you are probably well hydrated. The most reliable timing to check your urine color is in the morning, after you wake up. It will tell you if you hydrated well the day before. 


Fig.1 – Urine color chart. If the urine sample matches #3 or less in the chart, you are well hydrated. If your urine color is #7 or darker, you are dehydrated and should consume fluids.    
(Adapted 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, you must begin hydrating 4 hours before exercise with 5-7ml/kg (for example, 350 to 500ml or 12 to 17 oz in a 70kg athlete) and then monitor how often and what color is the urine you pass. If the urine is still too dark two hours before the soccer event, drink another 3-5ml/kg (ex. 210 to 350ml or 7 to 12oz in a 70kg athlete), so you still have time to pass excessive fluids before exercise time.


To optimize your hydration status during training or competition, you must know your sweat rate in both contexts, so you can replace efficiently your sweat losses. To do so, you can use the following formula:

 [(Pre-exercise body mass (kg) – Post-exercise body mass (kg)) – Urine output (l) + Total fluid ingestion (l)] 

This tells you how much you sweated in the whole session (ex. 3L in a 2h session). If you divide the result by exercise time (h), you’ll have your sweat rate (ex. 1,5L/h or 50 oz/h) calculated. With this information in hand, you’ll better understand your body and be able to optimize your performance by fine-tuning replacement of sweat losses. You must assess your sweat losses in a variety of weather conditions and type and context of exercise because these influence your sweating.  

If you prefer to do this more intuitively, just make sure you weigh yourself dry and nude (if possible) before and after exercise. Your final weight must be neither higher nor too much lower (loss > 2%) than initial one. To achieve this result you must drink regularly (120-240ml or 4-8 oz every 15-20m) during training/competition. If possible in hot weather games, place water along the sidelines to be consumed during breaks in play. 

Practical example:

Luis Miguel is a soccer player who weighs 75kg (150 pounds) before a training session. Immediately after exercise, he weighs in again and finds he has 73,3kg (146,6 pounds) now. He lost [(75 – 73,3)/75] x 100 = 2,3% of body weight, so next time he should drink a couple more gulps.

After exercise, the best way to recover your hydration status is to drink 150% of your losses (ex. If you lost 1L you must drink 1,5L). 

Sports drinks vs water   

A sports drink is basically a mixture of water, carbohydrates and electrolytes (mainly sodium). Although advertisements make it look like we need a sports drink to even catch a bus, the reality is far from that. Sports scientists conclude that only in high-intensity events of 1 hour or longer, as well as less intense exercise events sustained for more than an hour and a half, could athletes significantly benefit from sports drinks.

If this is not your case, but you haven’t fueled well enough for the workout, you’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 you enjoy the flavor.



Attention note: 

Some 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 self-monitoring of sweat losses to ascertain that you drink neither too little nor too much fluids.


Recommended reading for more information: 

  • Nancy Clark’s Sports Nutrition Guidebook (http://www.nancyclarkrd.com)
  • 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 hydration status?

How much weight do you normally lose during exercise?

Have you ever felt the consequences of dehydration during a training session or match?


 I'll be glad to answer your questions too!  

  

Wishing you the best performance ever,

 Diogo Ferreira, RD

Sports Nutritionist, Lisbon, Portugal

“Promoting best health and performance through nutrition”




8 comments:

  1. Hi Diogo,

    I am a nutrition student in Arizona, and I am currently working with a semi-pro soccer team. This post is really helpful as I advise them on hydration this summer! Since we are in a very warm climate where temperatures reach past 100 degrees, training can be a little difficult for the players, as well as games. Because it is a higher temperature, how much more water would you recommend for players to drink? I water down their gatorade closer to game days and then have them drink regular gatorade during and after the game. But my concern is the water loss they have on average due to the heat.

    Thank you!

    Chioma

    ReplyDelete
  2. Hello Chioma,

    Thank you for your feedback. The answer to your question will depend on the water losses of your players, and you must individualize the (re)hydration protocolfor each player depending on his/her water losses. You can calculate their sweat rate with the following formula:

    (pre-exercise body mass - post-exercise body mass - urine losses + total fluid intake) / exercise time

    With this in hand, you can make practical recommendations for each player :)

    Best regards,
    Diogo

    ReplyDelete
  3. I am the team manager of a boy's youth soccer team. We have one player that often has extreme calf cramping late in the game (80-85 minute games). He says he drinks tons of water, and is trying other things like sports drinks, adding salt to drinks, etc. He is 16 and is large for his age, grew fast with very large calf muscles. I recall a minor version of this with him when he was 11. He often has to come out of the game near the end. I guess this is normal, as I see pro soccer players have these problems often in their games. Noe of our other players have this type of issue. I've suggested he consult a sports nutritionist or doctor, but is there any where else he can look for information on this condition?

    ReplyDelete
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