Use of Protein, Carbohydrate, and Fat
Protein
Protein and its constituent, amino acids, are the building blocks of muscle. Protein supplements are used by some athletes to enhance muscle repair and growth. We have established that the protein needs for teenagers and athletes generally range from 1.4 to 1.8g per kg of body weight. Studies have shown that intake in excess of that amount do not provide additional gains in strength or mass.
In some cases when it is necessary to meet the required protein demands without increasing dietary fat, protein supplements may be of benefit. This can especially be true of the vegetarian athlete. Whey protein powder has a good balance of amino acids. Soy protein powder is an option for vegan athletes to meet protein demands, but the amino acid profile is not as complete as that found in whey.
Carbohydrates
While fat stores constitute the largest reservoir of stored energy, carbohydrates are the body's main source of rapidly available energy. It has been suggested that taking proper quantities of carbohydrates at the right time could improve athletic performance by ensuring adequate energy stores are available when necessary.
It is believed that low blood glucose levels can play a role in early fatigue of athletes. Because of this, prolonged exercise does require the use of carbohydrate replacement. During exercise that lasts longer than one hour, the amount of stored carbohydrate in the muscle and liver begins to deplete and blood glucose levels drop. Depending on intensity and length of the event, carbohydrate replacement requirements can range from 250 calories per hour and up. Carbohydrate supplements typically take the form of sports drinks, gels, bars, dried fruit, and other foods such as bananas.