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PLoS One. 2014 Nov 4;9(11):e111521. doi: 10.1371/journal.pone.0111521. eCollection 2014.

Hormonal and neuromuscular responses to mechanical vibration applied to upper extremity muscles.

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Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila Italy.
Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
Laboratory of Chemical-Clinical and Microbiological Analysis, Giulianova Hospital, Teramo, Italy.
Department of Biomechanics, Faculty of Physical Education and Sport Sciences, Semmelweis University, Budapest, Hungary.



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.


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]).


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.


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.

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