Prolonged endurance exercise causes significant protein breakdown to provide fuel for exercise. This breakdown may be offset by adding protein to your diet. When protein is ingested, it’s broken down into amino acids that are absorbed into the blood. These amino acids, particularly leucine, are triggers that increase the rate of protein synthesis to rebuild muscle proteins broken down during exercise.
Protein augments the repair and remodeling of tissue, speeds recovery and ultimately helps maintain muscle mass and optimal functioning of muscle. If no protein is ingested, the body actually breaks down its own protein stores, a process obviously not conducive to peak performance and optimal recovery. It’s important to note that adding protein will not create huge muscles, which could be a negative for endurance athletes.
Research shows that endurance exercise, as opposed to resistance exercise, stimulates synthesis of different proteins in muscle such as mitochondria that function in aerobic metabolism and contribute less to total muscle size. Simply put, the amino acids provided by protein serve as the building blocks for building muscle proteins that contribute to enhanced performance.