title: Post-absorptive muscle protein turnover affects resistance training hypertrophy.
abstract: OBJECTIVE
  Acute bouts of resistance exercise and subsequent training alters protein turnover in skeletal muscle. The mechanisms responsible for the changes in basal post-absorptive protein turnover and its impact on muscle hypertrophy following resistance exercise training are unknown. Our goal was to determine whether post-absorptive muscle protein turnover following 12 weeks of resistance exercise training (RET) plays a role in muscle hypertrophy. In addition, we were interested in determining potential molecular mechanisms responsible for altering post-training muscle protein turnover.
  
  
  METHODS
  Healthy young men (n = 31) participated in supervised whole body progressive RET at 60-80% 1 repetition maximum (1-RM), 3 days/week for 3 months. Pre- and post-training vastus lateralis muscle biopsies and blood samples taken during an infusion of13C6and15N phenylalanine and were used to assess skeletal muscle protein turnover in the post-absorptive state. Lean body mass (LBM), muscle strength (determined by dynamometry), vastus lateralis muscle thickness (MT), myofiber type-specific cross-sectional area (CSA), and mRNA were assessed pre- and post-RET.
  
  
  RESULTS
  RET increased strength (12-40%), LBM (~5%), MT (~15%) and myofiber CSA (~20%) (p < 0.05). Muscle protein synthesis (MPS) increased 24% while muscle protein breakdown (MPB) decreased 21%, respectively. These changes in protein turnover resulted in an improved net muscle protein balance in the basal state following RET. Further, the change in basal MPS is positively associated (r = 0.555, p = 0.003) with the change in muscle thickness.
  
  
  CONCLUSIONS
  Post-absorptive muscle protein turnover is associated with muscle hypertrophy during resistance exercise training.
authors.affiliation: Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, TX, 77550, USA.|Department of Nutrition and Metabolism, School of Health Professions, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, 77555-1142, USA.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Reidy
authors.affiliation: Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, TX, 77550, USA.|Department of Nutrition and Metabolism, School of Health Professions, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, 77555-1142, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Borack
authors.affiliation: Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, 77550, USA.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Markofski
authors.affiliation: Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, TX, 77550, USA.|Department of Nutrition and Metabolism, School of Health Professions, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, 77555-1142, USA.|Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, 77550, USA.
authors.forename: Jared M
authors.initials: JM
authors.lastname: Dickinson
authors.affiliation: Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, TX, 77550, USA.|Department of Nutrition and Metabolism, School of Health Professions, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, 77555-1142, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Fry
authors.affiliation: Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, 77550, USA.
authors.forename: Rachel R
authors.initials: RR
authors.lastname: Deer
authors.affiliation: Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, 77550, USA.|Department of Internal Medicine/Geriatrics, University of Texas Medical Branch, Galveston, TX, 77550, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Volpi
authors.affiliation: Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, TX, 77550, USA. blrasmus@utmb.edu.|Department of Nutrition and Metabolism, School of Health Professions, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, 77555-1142, USA. blrasmus@utmb.edu.|Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX, 77550, USA. blrasmus@utmb.edu.
authors.forename: Blake B
authors.identifier: http://orcid.org/0000-0001-7854-5375
authors.initials: BB
authors.lastname: Rasmussen
mesh_terms: D015502:Absorptiometry, Photon; D006801:Humans; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D053580:Muscle Strength; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000502:physiology; D055070:Resistance Training; D055815:Young Adult
chemical_list: D009124:Muscle Proteins
keywords: Growth; Ribosome biogenesis; Skeletal muscle; Strength training; mTORC1