title: Growth hormone and lactate responses induced by maximal isometric voluntary contractions and whole-body vibrations in healthy subjects.
abstract: BACKGROUND
  In contrast with maximal voluntary resistance exercise, which is allegedly considered a potent GH stimulus in young subjects, evaluation of GH response to whole-body vibrations (WBV) has yielded conflicting results.
  
  
  METHODS
  The acute effects of WBV alone (test A), maximal voluntary isometric contractions (MVC) (test B), and combination of WBV and MVC (test C) on serum GH and blood lactate (LA) levels were studied in 9 healthy adult males. Muscle soreness was assessed 24 and 48 h after exercise by a visual analogue scale.
  
  
  RESULTS
  GH responses were significantly higher after tests B and C than after test A (GH peaks: 18.8 ± 9.5 ng/ml or 20.8 ± 13.7 ng/ml, respectively, vs 4.3 ± 3.5 ng/ml; p<0.05), with no difference between tests B and C. LA concentrations significantly increased after tests A, B, and C, being significantly higher after tests B and C than after test A (LA peaks: 2.0 ± 0.5 mmol/l or 6.7 ± 2.3 mmol/l, respectively, vs 7.6 ± 0.9 mmol/l; p<0.05). Peak LA values were significantly correlated to GH peaks in the 3 tests (r=0.48; p<0.05). Muscle soreness was significantly higher 24-48 h after tests B and C than after test A, no significant differences being present between tests B and C.
  
  
  CONCLUSIONS
  WBV stimulates GH secretion and LA production, with no additive effect when combined with repeated isometric voluntary contractions. Optimization of protocols based on WBV seems important to maximize the positive effects of this intervention on the somatotropic function.
authors.affiliation: Istituto Auxologico Italiano, Laboratorio Sperimentale di Ricerche Auxo-endocrinologiche, IRCCS, Milan, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Sartorio
authors.forename: F
authors.initials: F
authors.lastname: Agosti
authors.forename: A
authors.initials: A
authors.lastname: De Col
authors.forename: N
authors.initials: N
authors.lastname: Marazzi
authors.forename: F
authors.initials: F
authors.lastname: Rastelli
authors.forename: S
authors.initials: S
authors.lastname: Chiavaroli
authors.forename: C L
authors.initials: CL
authors.lastname: Lafortuna
authors.forename: S G
authors.initials: SG
authors.lastname: Cella
authors.forename: A E
authors.initials: AE
authors.lastname: Rigamonti
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D014732:Vibration; D055815:Young Adult
chemical_list: D019382:Human Growth Hormone; D019344:Lactic Acid
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