Protein supplementation does not further increase latissimus dorsi muscle fiber hypertrophy after eight weeks of resistance training in novice subjects, but partially counteracts the fast-to-slow muscle fiber transition

Antonio Paoli, Quirico F. Pacelli, Pasqua Cancellara, Luana Toniolo, Tatiana Moro, Marta Canato, Danilo Miotti, Marco Neri, Aldo Morra, Marco Quadrelli, Carlo Reggiani

    Research output: Contribution to journalArticlepeer-review

    6 Scopus citations

    Abstract

    The response to resistance training and protein supplementation in the latissimus dorsi muscle (LDM) has never been investigated. We investigated the effects of resistance training (RT) and protein supplementation on muscle mass, strength, and fiber characteristics of the LDM. Eighteen healthy young subjects were randomly assigned to a progressive eight-week RT program with a normal protein diet (NP) or high protein diet (HP) (NP 0.85 vs. HP 1.8 g of protein kg-1 day-1). One repetition maximum tests, magnetic resonance imaging for cross-sectional muscle area (CSA), body composition, and single muscle fibers mechanical and phenotype characteristics were measured. RT induced a significant gain in strength (+17%, p < 0.0001), whole muscle CSA (p = 0.024), and single muscle fibers CSA (p < 0.05) of LDM in all subjects. Fiber isometric force increased in proportion to CSA (+22%, p < 0.005) and thus no change in specific tension occurred. A significant transition from 2X to 2A myosin expression was induced by training. The protein supplementation showed no significant effects on all measured outcomes except for a smaller reduction of 2X myosin expression. Our results suggest that in LDM protein supplementation does not further enhance RT-induced muscle fiber hypertrophy nor influence mechanic muscle fiber characteristics but partially counteracts the fast-to-slow fiber shift.

    Original languageEnglish (US)
    Article number331
    JournalNutrients
    Volume8
    Issue number6
    DOIs
    StatePublished - Jun 2016

    Keywords

    • Myosin isoform
    • Nutrition
    • Single muscle fiber mechanics
    • Strength training
    • Supplementation
    • Whey protein

    ASJC Scopus subject areas

    • Food Science
    • Nutrition and Dietetics

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