Besides calories, the other nutrient needed in greater amount by the young athlete is liquids. They are the most important part of an athlete's diet. Fluid is important to prevent overheating and dehydration. Because muscles heat up during exercise, extra fluid is needed to maintain the blood volume so that the circulating fluid can reach into the muscles and carry the heat away to the skin. The heat is released primarily by sweating. Sweating without replacement of fluids can lead to dehydration. Dehydration's first symptom is fatigue... not what a successful athlete needs for optimum performance. More than any other nutritional factor, too little fluid can effect your young athlete.
Children are particularly vulnerable to the effects of fluid imbalance. That is because they don't handle heat well, they get hotter during exercise and their hearts have a lower blood output. Be sure your child drinks water before, during and after exercise. Supply him with his own water bottle that you can see through. Check regularly to be sure he is drinking. Children may not notice the need for liquid or the signs of overheating. Careful monitoring on your part is important, especially on hot humid days when sweat does not evaporate effectively, so cooling is not as efficient. Watch out, also, if your athlete wears lots of protective clothing that may interfere with proper cooling, like football pads or hockey equipment.
The best fluid replacement is water, but if your child is more apt to drink if it is flavored, then a sports drink or a diluted juice (at least one to one) would work. A full-strength juice or juice drink is too concentrated a source of carbohydrates and could lead to nausea and cramping if drunk during an athletic event. Afterward, water-containing foods along with liquids are a good way to replace both carbohydrates and fluids. Juicy fruits like watermelon, tomatoes, grapes and oranges are good choices.
An overall balanced diet is the most important nutrition-related factor in your child's athletic performance, but that's not what the coach tends to stress. Therefore, its your job to keep track of that component. You coaches out there will want to make sure you give good advice to your players on what to eat in those crucial hours before the big event. The most important point: Your athletes must have a good supply of energy ready to go to work in their muscles. A meal relatively high in carbohydrate is the best choice. Keep the levels of fat and protein low since they take longer to digest, which can result in nausea or even vomiting.
Some athletes get so excited before an event that it interferes with digestion. It's best to exercise on an empty (not hungry) stomach. Have them eat well beforehand -- that means no closer than two to four hours before practice or competition. Digestion requires routing the blood supply to the digestive tract to pick up nutrients. By the time exercise begins, the blood should be freed of that task so it can focus on the more immediate job of carrying oxygen-rich blood to exercising muscles.