title: Resistance training alters plasma myostatin but not IGF-1 in healthy men.
abstract: OBJECTIVE
  We determined and compared the magnitude of changes in resting plasma myostatin and IGF-1, muscle strength, and size in response to whole body or local muscle resistance training in healthy men.
  
  
  METHODS
  Volunteers performed high-intensity resistance exercise of major muscle groups of the whole body (N = 11), or of the elbow flexors only (N = 6), twice per week for 10 wk. Strength was assessed by elbow flexor one-repetition maximum (1-RM) and repetitions at 80% of 1-RM, muscle cross-sectional area by MRI, and plasma IGF-1 by RIA and myostatin by Western analyses, before and after the training program.
  
  
  RESULTS
  In subjects of both groups, elbow flexor 1-RM and cross-sectional area increased (P = 0.05) by 30 +/- 8% (mean +/- SD) and 12 +/- 4%, respectively. Individual changes in myostatin ranged from 5.9 to -56.9%, with a mean decrease of 20 +/- 16%, whereas IGF-1 did not change from pre- to posttraining. There were no significant differences in any of the responses of the subjects between the two training programs.
  
  
  CONCLUSIONS
  Myostatin may play a role in exercise-induced increases in muscle size, its circulating levels decreasing with resistance training in healthy men. Exercise of the whole body versus the elbow flexors alone did not provide a supplementary stimulus in altering resting plasma IGF-1 or myostatin, or in increasing muscle strength or size. Thus, by default, growth factor responses local to the muscle may be more important than circulating factors in contributing to muscle hypertrophy with resistance training.
authors.affiliation: Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand.
authors.forename: Kylie S
authors.initials: KS
authors.lastname: Walker
authors.forename: Ravi
authors.initials: R
authors.lastname: Kambadur
authors.forename: Mridula
authors.initials: M
authors.lastname: Sharma
authors.forename: Heather K
authors.initials: HK
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D000328:Adult; D004550:Elbow / Q000502:physiology; D006801:Humans; D006984:Hypertrophy; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D009132:Muscles / Q000033:anatomy & histology / Q000502:physiology*; D055435:Myostatin; D010806:Physical Education and Training / Q000379:methods*; D018709:Statistics, Nonparametric; D016212:Transforming Growth Factor beta / Q000097:blood*
chemical_list: C525911:MSTN protein, human; D055435:Myostatin; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I