Hormonal and Neuromuscular Responses to Mechanical Vibration Applied to Upper Extremity Muscles

• Published in: PloS one Vol. 9; no. 11; p. e111521
• Main Authors: Di Giminiani, Riccardo, Fabiani, Leila, Baldini, Giuliano, Cardelli, Giovanni, Giovannelli, Aldo, Tihanyi, Jozsef
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04.11.2014; Public Library of Science (PLoS)
• Subjects: Acceleration; Adult; Arm - physiology; Biology and Life Sciences; Biomechanical Phenomena; Biomechanics; Body mass index; Colleges & universities; Double-Blind Method; Electromyography; Exercise; Extremities; Fatigue; Growth hormone; Growth Hormone - blood; Growth hormones; Hand Strength - physiology; Hormones; Humans; Hypotheses; Laboratories; Load; Male; Medicine and Health Sciences; Muscle contraction; Muscle, Skeletal - physiology; Muscles; Musculoskeletal system; Position measurement; Posture; Strength training; Testosterone; Testosterone - blood; Values; Vibration; Italy; L Aquila Italy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0111521

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.