Effect of whole body vibration applied on upper extremity muscles.

The acute residual effect of whole body vibration (WBV) on upper extremity muscles and testosterone secretion was studied. Eight highly (G1), nine moderately trained gymnasts (G2) and seven physically active persons (CG) were recruited for the investigation. The intervention occurred in push-up position with the elbow flexed at 90°. G1 and G2 received 30 s, 30 Hz and 6 mm amplitude vibration repeated five times. Subjects were tested before and after one and ten minutes intervention in push-up movement. Contact time (Tc), fly time (Tf), TF/Tc ratio and impulse was measured from the ground reaction force-time curves recorded during self-selected (SSRM) and full range of motion (FRM). Testosterone level in urine was also determined. Tf increased significantly in SSRM for G1 and decreased in SSRM and FRM for G2. Tf/Tc ratio in FRM and impulse in SSRM increased significantly for G1 only. No significant alteration in testosterone level was observed. We concluded that WBV is a reasonable training modality for influencing dynamic work of upper extremity muscle, but the reaction to WBV is training and individual dependent. It seems that WBV do not influence dynamic work through increased testosterone secretion because of the relatively low mass of the involved muscles.