Role of ingested amino acids and protein in the promotion of resistance exercise-induced muscle protein anabolism

Paul T. Reidy, Blake Rasmussen

    Research output: Contribution to journalArticle

    • 24 Citations

    Abstract

    The goal of this critical review is to comprehensively assess the evidence for the molecular, physiologic, and phenotypic skeletal muscle responses to resistance exercise (RE) combined with the nutritional intervention of protein and/or amino acid (AA) ingestion in young adults. We gathered the literature regarding the translational response in human skeletal muscle to acute exposure to RE and protein/AA supplements and the literature describing the phenotypic skeletal muscle adaptation to RE and nutritional interventions. Supplementation of protein/AAs with RE exhibited clear protein dose-dependent effects on translational regulation (protein synthesis) through mammalian target of rapamycin complex 1 (mTORC1) signaling, which was most apparent through increases in p70 ribosomal protein S6 kinase 1 (S6K1) phosphorylation, compared with postexercise recovery in the fasted or carbohydrate-fed state. These acute findings were critically tested via long-term exposure to RE training (RET) and protein/AA supplementation, and it was determined that a diminishing protein/AA supplement effect occurs over a prolonged exposure stimulus after exercise training. Furthermore, we found that protein/AA supplements, combined with RET, produced a positive, albeit minor, effect on the promotion of lean mass growth (when assessed in >20 participants/treatment); a negligible effect on muscle mass; and a negligible to no additional effect on strength. A potential concern we discovered was that the majority of the exercise training studies were underpowered in their ability to discern effects of protein/AA supplementation. Regardless, even when using optimal methodology and large sample sizes, it is clear that the effect size for protein/AA supplementation is low and likely limited to a subset of individuals because the individual variability is high. With regard to nutritional intakes, total protein intake per day, rather than protein timing or quality, appears to be more of a factor on this effect during long-termexercise interventions. There were no differences in strength or mass/muscle mass on RET outcomes between protein types when a leucine threshold (>2 g/dose) was reached. Future research with larger sample sizes and more homogeneity in design is necessary to understand the underlying adaptations and to better evaluate the individual variability in the muscle-adaptive response to protein/AA supplementation during RET.

    LanguageEnglish (US)
    Pages155-183
    Number of pages29
    JournalJournal of Nutrition
    Volume146
    Issue number2
    DOIs
    StatePublished - 2016

    Fingerprint

    Muscle Proteins
    Exercise
    Amino Acids
    Proteins
    Skeletal Muscle
    Muscles
    Sample Size
    Ribosomal Protein S6 Kinases
    Resistance Training
    Leucine
    Young Adult

    Keywords

    • Exercise training
    • Leucine
    • MTORC1
    • Protein synthesis
    • Skeletal muscle

    ASJC Scopus subject areas

    • Medicine (miscellaneous)
    • Nutrition and Dietetics

    Cite this

    Role of ingested amino acids and protein in the promotion of resistance exercise-induced muscle protein anabolism. / Reidy, Paul T.; Rasmussen, Blake.

    In: Journal of Nutrition, Vol. 146, No. 2, 2016, p. 155-183.

    Research output: Contribution to journalArticle

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