Athletes involved in serious training regimes may need to increase the number of calories consumed but shouldn't vary percentage breakdowns unless prescribed by a physician or nutritionist specializing in sports nutrition. Additionally, all athletes need to insure that they keep their muscles properly hydrated through the consumption of plenty of fluids before, during and after exercise. Many theories exist about high protein diets. There is no definitive evidence to support either theory. High protein diets designed to build muscle mass are ultimately just expensive.
Muscles develop from training and exercise.
Protein is used for energy when the body runs short of available carbohydrates, however protein does not provide energy to do the same things accomplished by carbohydrates. The body cannot store protein for future use. Worse, eliminating the waste created by the body's breakdown of protein can strain the liver and kidneys. Carbohydrate loading has received mixed reviews over the years. In the diet only approach, carbohydrate intake is increase for several days just before competition and training continues at normal levels.