ABSTRACT
This chapter explores the effects of exercise and food intake on utilization of amino acids for energy and synthesis of new proteins; examines the regulation of protein synthesis in skeletal muscle; and reviews present information defining protein requirements for exercise and performance. The vast majority of the amino acids in the body are in protein structures. During endurance exercise, changes in protein turnover produce net protein breakdown with release of amino acids into the free pools. A decrease in plasma branched-chain amino acids concentrations during exercise may negatively affect exercise performance via changes in serotonin. Serotonin is synthesized in the brain from the amino acid tryptophan. Muscle protein mass is determined by the relationship between the processes of protein synthesis and degradation. During periods of growth or protein accretion, protein synthesis rates exceed protein degradation rates. Several researchers have suggested that the energy state of the cell is the primary factor regulating protein synthesis.
