Soccer Hydration

Soccer players at most levels of play and practice need extra hydration for proper health and performance. Here is a good article.

Water is the most important and critical nutrient to the survival and well being of a person. One can survive without intake of other nutrients for days, weeks, and even months but one cannot survive without water for more than a few days. In a 70 Kg person, the water content is about 40 liters (i.e. 60% of body weight). Most of the water (25 liters) is inside cells of the body and about 15 liters lie outside the cells. The blood volume is about 5 liters and the maintenance of this volume is critical to the survival of the person. For example, daily fluid intake can vary from 1-7 liters, while the blood volume must remain constant. Excess fluid intake can easily be regulated; however, a problem. arises when fluid intake is below one liter per day and blood volume starts to become lower than 5 liters (for example about volume of 4 liters and below can cause death). Under sedentary conditions skin and kidney (i.e. urine output) are the most important regulators of body water. Under the conditions of hot weather and exercises (despite fluid intake in many cases, the skin (sweating) becomes the only important regulator of body water as well as the body temperature. The daily loss of water in a heavy, prolonged exercise (3 hours marathon) can increase from 0.1 to 5 liters.(6)

Sweating is absolutely necessary in order to maintain constant body temperature. The sweat rate usually corresponds to increases in energy expenditure by the athlete. Trained athletes have a more sensitive sweating system than non-athletes due to adaptation by the repetitive exercises. Of the 5 liters of H2O, a marathon runner's losses (despite fluid intake in many cases) represent 12% of body water and 8% of body weight. Anything above 2% weight loss due to exercise induces severe demands on the thermoregulatory and cardiovascular systems.

All of the energy expenditure during exercise ends up as heat. Therefore, body temperature will rise rapidly during exercise if cooling due to sweating is not functioning. The prolonged increase in body temperature will eventually cause serious damage to the thermoregulatory system, which can result in serious damage to the brain -- the most sensitive organ. Thirst, unfortunately, is not a reliable indicator during exercise (i.e. under any stressful conditions). Therefore, athletes should drink water not just to quench their thirst, but as part of their exercise regime. Figures 3 and 4 represent a hypothetical daily water output and water intake for persons who are: sedentary, a marathon running for 3 hours, or soccer players (90-100 minutes). The numbers are rough estimates, and for illustration purpose only. The most scientific way to determine how much water intake ought to be is to weigh the player before and during the game. The loss of weight due to water loss should be adjusted by drinking the same amount of water. Remember, it is better to drink more than less water.

Children utilize a greater metabolic energy and thus produce more heat than adults to perform the same task. Fortunately, children dissipate heat better than adults due to a larger surface area to mass ratio than adults. However, when ambient temperature is hot and humid, the dissipation of heat is inhibited and thus children maybe at a greater risk than adults during exercise.

Electrolytes such as Na+, K+, Cl-, Ca2 and Mg2+ are the most important ions and their amount in the cell and the blood is critical in maintaining normal body function. As we sweat more during exercise, the amount of these ions in the sweat is less than that of the blood. In other words, the body is losing more water than ions. Under heavy exercise conditions, the body loses about 5-7 grams sodium chloride. However, there is a minimal loss of K+ and Mg2+. Under conditions of continued exercise (up to 80-90 minutes) there is a need to replenish water continuously, but not salt. If there is heavy exercise beyond the 80-90 minutes, salt replenishment is appropriate. The use of salt tablets during the early phase of exercise (in most cases of soccer) is detrimental to the body. The body fluid has a higher salt concentration after exercise than before; therefore, the body needs pure water to bring the blood composition back to normal levels.