Protein is probably the most important supplement for all athletes, but it is especially indispensable for those involved in long-term, high intensity endurance training. It is the fuel for the build-up, mass and toning of the muscle. In fact, protein is essential for growth and development. The proteins that make up the human body are not obtained directly from the diet; rather, dietary protein is broken down into its constituent parts known as amino acids, which are the basic building blocks of life. That means that it is the amino acids, and not protein per se, which are essential nutrients.
Of the 20 amino acids that the body needs to make protein, eleven are designated as nonessential amino acids because they can be produced by the human body from other amino acids and do not need to be obtained from the diet. The remaining nine amino acids cannot be synthesized by the body and are, therefore, called essential amino acids. These amino acids must be obtained by degradation of the dietary protein. All of these essential amino acids must be present in the body in order for it to build and repair muscle.
The manner in which the body uses protein during and after exercise is quite different from the way it utilizes carbohydrates or fat for energy. In the hours after exercise, the body begins to build the so-called structural proteins from amino acids for muscle repair and growth, and remodeling the tissues needed for performance. This is one of the reasons that athletes should pay particular heed to nutrition for fast and complete recovery and make it an integral part of their workout regimen.