title: Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis.
abstract: BACKGROUND
  Protein ingestion after a single bout of resistance-type exercise stimulates net muscle protein accretion during acute postexercise recovery. Consequently, it is generally accepted that protein supplementation is required to maximize the adaptive response of the skeletal muscle to prolonged resistance-type exercise training. However, there is much discrepancy in the literature regarding the proposed benefits of protein supplementation during prolonged resistance-type exercise training in younger and older populations.
  
  
  OBJECTIVE
  The objective of the study was to define the efficacy of protein supplementation to augment the adaptive response of the skeletal muscle to prolonged resistance-type exercise training in younger and older populations.
  
  
  METHODS
  A systematic review of interventional evidence was performed through the use of a random-effects meta-analysis model. Data from the outcome variables fat-free mass (FFM), fat mass, type I and II muscle fiber cross-sectional area, and 1 repetition maximum (1-RM) leg press strength were collected from randomized controlled trials (RCTs) investigating the effect of dietary protein supplementation during prolonged (>6 wk) resistance-type exercise training.
  
  
  RESULTS
  Data were included from 22 RCTs that included 680 subjects. Protein supplementation showed a positive effect for FFM (weighted mean difference: 0.69 kg; 95% CI: 0.47, 0.91 kg; P < 0.00001) and 1-RM leg press strength (weighted mean difference: 13.5 kg; 95% CI: 6.4, 20.7 kg; P < 0.005) compared with a placebo after prolonged resistance-type exercise training in younger and older subjects.
  
  
  CONCLUSIONS
  Protein supplementation increases muscle mass and strength gains during prolonged resistance-type exercise training in both younger and older subjects.
authors.affiliation: Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, Netherlands.
authors.forename: Naomi M
authors.initials: NM
authors.lastname: Cermak
authors.forename: Peter T
authors.initials: PT
authors.lastname: Res
authors.forename: Lisette C P G M
authors.initials: LC
authors.lastname: de Groot
authors.forename: Wim H M
authors.initials: WH
authors.lastname: Saris
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D000375:Aging; D004044:Dietary Proteins / Q000008:administration & dosage*; D019587:Dietary Supplements; D006801:Humans; D024510:Muscle Development; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000378:metabolism; D016032:Randomized Controlled Trials as Topic; D055070:Resistance Training
chemical_list: D004044:Dietary Proteins