As teams begin preseason training for the fall season, they are likely to encounter hot, humid days. Exercise in the heat can cause excessive sweat and considerable fluid loss. If fluids are not replaced, dehydration occurs and performance can be negatively affected. More importantly, dehydration can also lead to a number of serious health consequences. Given this, what can players do to stay well hydrated and avoid the problems associated with dehydration? 

Proper hydration may be the most important piece of the soccer nutrition puzzle. Like foods eaten, beverages have a significant influence on athletic performance. However, while a weak diet may only affect performance, dehydration raises the risk of serious health consequences ranging from mild discomfort to death. This cannot be emphasized enough. The effects of dehydration can be very serious that require immediate medical treatment. Thus, always seek the advice of a medical professional with specific questions regarding dehydration. Most importantly, if a player is suspected to be suffering from dehydration or any heat-related illness, stop play and consult a medical professional as soon as possible.

Expending energy during a match or training is accompanied by heat production. Over the course of 90 minutes, body temperature can rise from 37°C (98.6° F) to above 39° C (102° F). Without adequate cooling, temperature can rise even higher, increasing the risk of heat cramps, heat exhaustion and heat stroke.  The body combats heat several ways. The most effective way to cool the body is through evaporation.  As body temperature rises during exercise, sweat is produced and it evaporates into the atmosphere. This in turn removes heat and helps cool the body.  On hot, humid days when the air is saturated with water vapor, evaporation is more difficult. As a result, cooling is compromised and the body cannot properly cool itself. This promotes more sweating and greater fluid loss. 

How much fluid is lost through sweating is often estimated by measuring body weight before and after an activity. As rule of thumb is 1 lb of weight loss after training equals about 1 pint of fluid (16 oz). Or, 1 kg equals about 1 liter. It is not uncommon for a player to lose more than 3 percentof his or her body weight during training of competing in the heat. For a 150 lb athlete (68 kg), this equals about 4.5 lbs or 2 kg.  Research shows that fluid losses equal to 1-3 percent of body weight can decrease speed, power as well as technical abilities and decision-making. Fluid losses greater than 3 percent can lead to health problems.

If fluids lost during exercise are not replaced, the athlete can enter a dehydrated state. When dehydrated, sweat production is reduced and the body loses evaporation as a method of cooling. This, in turn causes body temperature to rise quickly and the risks of heat-related health problems grow (not to mention performance suffers). The overall effect is that dehydration greatly increases the risk of heat-related health problems.      

A recent study of teams playing in the UEFA Champions League found that muscle power output declined to a greater extent when matches were played in the heat and players were dehydrated (>3% loss of body weight).  Following matches played in cooler climates without dehydration, players were better able to maintain performance.   Other studies show that fitness, dribbling and other soccer skills deteriorate after matches or training when no drinks were allowed.  When drinks are allowed, dehydration is avoided and performance is better maintained.  Thus, from a purely performance perspective, it is important to keep the body well hydrated.  Failing to do so can leave the player wanting, especially at the end of a match.

Unfortunately, dehydration is a problem with soccer players. Recent studies of youth and college players found that many players arrive at training in a hypo-hydrated state. That is, they may not be dehydrated, but their hydration status is often less than optimal for the conditions. The primary reason for this is that many players do not re-hydrate properly after training. Thus, dehydration becomes very common over the course of a pre-season training camp. Given the physical demands of a pre-season training (multiple sessions each day) dehydration probably prevent players from performing their best. Also, the risk of dehydration and health problems is probably quite high.

So, what is a player to do? How can players ensure that they well-hydrated before the start of a match or training session? By following a few simple guidelines, players can avoid dehydration which will help them maintain their performance on the field and avoid potential health problems.

• Take in 400-600 ml (15-20 oz) of fluid 2-3 hours prior to the match or training session (a typical sports drink contains about 20 oz)
• Drink during stoppages of play, especially during half-time. Cold beverages can also help cool the body
• After the match or training, replace 1.5 times the amount of weight lost through sweat.  Start by drinking 500-1000 ml (15-30 oz) within 30 min of training or a match
• Take in about 1 liter (2 quarts) of fluid every few hours after the match.  Part of this amount may be beverages consumed during the evening meal
• Drink either water or sports drinks – both are good replacement beverages.  Also, drink slowly rather than quickly gulp the entire container
• Avoid caffeinated or energy drinks as well as alcohol.  Caffeine and alcohol are diuretics that can promote more fluid loss (urination) and slow absorption of fluid from the gut.

Coaches should play a role in insuring that players are well-hydrated. Emphasize the need to drink plenty of fluids throughout the day. Allow water breaks during training, preferably under some shade. If players bring their own water bottle, check to see that the fluids are actually being consumed. Finally, make sure that they have something to drink after training.  

An important point to remember is that if you err; err on the side of more fluid rather than less. While it is possible to drink too much, the vast majority of athletes drink far less that the amount considered problematic. The bottom line is, remember to drink plenty of fluids during the summer months and especially during periods of intense training or match play. Avoiding dehydration can benefit performance. More importantly, it can help players avoid serious heat-related health consequences.

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