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Nutrients 2016, 8(6), 331; doi:10.3390/nu8060331

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

1
Department of Biomedical Sciences, University of Padova, Padova 35131, Italy
2
Salvatore Maugeri Foundation, Pavia 27100, Italy
3
AIFeM (Italian Medicine and Fitness Federation), Ravenna 48121, Italy
4
Euganea Medica, Diagnostic Centre, Via Colombo 13, Albignasego (Padova) 35020, Italy
*
Author to whom correspondence should be addressed.
Received: 29 February 2016 / Revised: 16 May 2016 / Accepted: 19 May 2016 / Published: 1 June 2016
(This article belongs to the Special Issue Dietary Protein, Exercise and Muscle Health in an Ageing Population)
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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. View Full-Text
Keywords: nutrition; supplementation; whey protein; myosin isoform; strength training; single muscle fiber mechanics nutrition; supplementation; whey protein; myosin isoform; strength training; single muscle fiber mechanics
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Paoli, A.; Pacelli, Q.F.; Cancellara, P.; Toniolo, L.; Moro, T.; Canato, M.; Miotti, D.; Neri, M.; Morra, A.; Quadrelli, M.; Reggiani, C. 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. Nutrients 2016, 8, 331.

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