Protein Metabolism and Endurance Exercise

Abstract

In brief: The use of proteins as a source of energy has been discounted in the past. However, current research has demonstrated that amino acids can contribute to whole body metabolism. The availability of amino acids can be increased by either elevating the rate of muscle protein breakdown or decreasing the rate of muscle protein synthesis. Research indicates that there is a substantial decrease in the rate of protein synthesis during exercise. We estimate that protein can provide up to 5.5% of the total caloric cost of exercise. Because essential amino acid requirements have been determined only for resting persons, the recommended maximum protein requirements may not be adequate for physically active individuals.