title: Hormonal and neuromuscular responses to mechanical vibration applied to upper extremity muscles.
abstract: OBJECTIVE
  To investigate the acute residual hormonal and neuromuscular responses exhibited following a single session of mechanical vibration applied to the upper extremities among different acceleration loads.
  
  
  METHODS
  Thirty male students were randomly assigned to a high vibration group (HVG), a low vibration group (LVG), or a control group (CG). A randomized double-blind, controlled-parallel study design was employed. The measurements and interventions were performed at the Laboratory of Biomechanics of the University of L'Aquila. The HVG and LVG participants were exposed to a series of 20 trials ×10 s of synchronous whole-body vibration (WBV) with a 10-s pause between each trial and a 4-min pause after the first 10 trials. The CG participants assumed an isometric push-up position without WBV. The outcome measures were growth hormone (GH), testosterone, maximal voluntary isometric contraction during bench-press, maximal voluntary isometric contraction during handgrip, and electromyography root-mean-square (EMGrms) muscle activity (pectoralis major [PM], triceps brachii [TB], anterior deltoid [DE], and flexor carpi radialis [FCR]).
  
  
  RESULTS
  The GH increased significantly over time only in the HVG (P = 0.003). Additionally, the testosterone levels changed significantly over time in the LVG (P = 0.011) and the HVG (P = 0.001). MVC during bench press decreased significantly in the LVG (P = 0.001) and the HVG (P = 0.002). In the HVG, the EMGrms decreased significantly in the TB (P = 0.006) muscle. In the LVG, the EMGrms decreased significantly in the DE (P = 0.009) and FCR (P = 0.006) muscles.
  
  
  CONCLUSIONS
  Synchronous WBV acutely increased GH and testosterone serum concentrations and decreased the MVC and their respective maximal EMGrms activities, which indicated a possible central fatigue effect. Interestingly, only the GH response was dependent on the acceleration with respect to the subjects' responsiveness.
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Di Giminiani
authors.affiliation: Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
authors.forename: Leila
authors.initials: L
authors.lastname: Fabiani
authors.affiliation: Laboratory of Chemical-Clinical and Microbiological Analysis, Giulianova Hospital, Teramo, Italy.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Baldini
authors.affiliation: Laboratory of Chemical-Clinical and Microbiological Analysis, Giulianova Hospital, Teramo, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cardelli
authors.affiliation: Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila Italy.
authors.forename: Aldo
authors.initials: A
authors.lastname: Giovannelli
authors.affiliation: Department of Biomechanics, Faculty of Physical Education and Sport Sciences, Semmelweis University, Budapest, Hungary.
authors.forename: Jozsef
authors.initials: J
authors.lastname: Tihanyi
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology; D001696:Biomechanical Phenomena; D004311:Double-Blind Method; D004576:Electromyography; D013006:Growth Hormone / Q000097:blood*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D013739:Testosterone / Q000097:blood*; D014732:Vibration
chemical_list: D013739:Testosterone; D013006:Growth Hormone