Abstract
Skeletal muscle supports locomotion and serves as the largest site of postprandial glucose disposal; thus it is a critical organ for physical and metabolic health. Skeletal muscle mass is regulated by the processes of muscle protein synthesis (MPS) and muscle protein breakdown (MPB), both of which are sensitive to external loading and aminoacidemia. Hyperaminoacidemia results in a robust but transient increase in rates of MPS and a mild suppression of MPB. Resistance exercise potentiates the aminoacidemia-induced rise in MPS that, when repeated over time, results in gradual radial growth of skeletal muscle (i.e., hypertrophy). Factors that affect MPS include both quantity and composition of the amino acid source. Specifically, MPS is stimulated in a dose-responsive manner and the primary amino acid agonist of this process is leucine. MPB also appears to be regulated in part by protein intake, which can exert a suppressive effect on MPB. At high protein doses the suppression of MPB may interfere with skeletal muscle adaptation following resistance exercise. In this review, we examine recent advancements in our understanding of how protein ingestion impacts skeletal muscle growth following resistance exercise in young adults during energy balance and energy restriction. We also provide practical recommendations for exercisers who wish to maximize the hypertrophic response of skeletal muscle during resistance exercise training.
Highlights
Maintaining skeletal muscle mass throughout the lifespan is critical for the preservation of metabolic health and independent locomotion
Important to acknowledge states of disease Itasis,well as ageimportant may alter to acknowledge that states of disease as well as age may alter the kinetics of amino acid metabolism the kinetics of amino acid metabolism following protein ingestion [16,17]
Not all the constituent amino acids are utilized by the translational machinery to synthesize new proteins
Summary
Maintaining skeletal muscle mass throughout the lifespan is critical for the preservation of metabolic health and independent locomotion. In addition to the health-centric importance of maintaining skeletal muscle there is great interest, within the athletic community, in enhancing the adaptive response of skeletal muscle to exercise training (i.e., improved force production and increasing muscle size: hypertrophy) with the aim of maximizing physical performance in competitive events. Increased loading of skeletal muscle and hyperaminoacidemia following dietary protein intake, independently and synergistically exert a positive influence on NPB by modulating the relative balance between MPS and MPB [3,4]. Repetitive bouts of resistance exercise in combination with protein intake increase NPB and promote muscle protein accretion over time. In this brief review, we focus on how dietary protein is utilized in support of skeletal muscle protein remodeling and how protein may facilitate increased post-exercise MPS and impact hypertrophy. We provide a brief discussion of recent findings regarding strategies to maintain or even increase skeletal muscle mass during periods of energy restriction
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