title: Myogenic, matrix, and growth factor mRNA expression in human skeletal muscle: effect of contraction intensity and feeding.
abstract: BACKGROUND
  We examined short-term (3-hour) and long-term (12-week) training effects after heavy load [HL; 70% 1RM] and light load (LL; 16% 1RM) exercise.
  
  
  METHODS
  mRNA expression of genes involved in skeletal muscle remodeling were analyzed and muscle activity (EMG measurements) was measured.
  
  
  RESULTS
  Relative muscle activity differed between HL and LL resistance exercise, whereas median power frequency was even, suggesting an equal muscle-fiber-type recruitment distribution. mRNA expression of Myf6, myogenin, and p21 was mostly increased, and myostatin was mostly depressed by HL resistance exercise. No major differences were seen in atrophy-related genes between HL and LL resistance exercise. No changes were seen over 12-week training for any of the targets.
  
  
  CONCLUSIONS
  Resistance exercise at LL and HL elevated the expression of genes involved in skeletal muscle hypertrophy, although the greatest response was from HL. However, no long-term effect from either LL or HL resistance exercise was seen on basal levels of the mRNA targets.
authors.affiliation: Institute of Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital, Denmark. jakobagergaard@hotmail.com
authors.forename: Jakob
authors.initials: J
authors.lastname: Agergaard
authors.forename: Søren
authors.initials: S
authors.lastname: Reitelseder
authors.forename: Troels G
authors.initials: TG
authors.lastname: Pedersen
authors.forename: Simon
authors.initials: S
authors.lastname: Doessing
authors.forename: Peter
authors.initials: P
authors.lastname: Schjerling
authors.forename: Henning
authors.initials: H
authors.lastname: Langberg
authors.forename: Benjamin F
authors.initials: BF
authors.lastname: Miller
authors.forename: Per
authors.initials: P
authors.lastname: Aagaard
authors.forename: Michael
authors.initials: M
authors.lastname: Kjaer
authors.forename: Lars
authors.initials: L
authors.lastname: Holm
mesh_terms: D000328:Adult; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D055435:Myostatin / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D055070:Resistance Training
chemical_list: D055435:Myostatin; D012333:RNA, Messenger