Changes in Peripheral Circulation and Autonomic Nervous Activity in the Elderly Exposed to Acute Whole-Body Vibration

We attempted to ascertain the specific patterns of changes in peripheral circulation and autonomic nervous activity from acute exposure of elderly subjects to whole-body vibration (WBV). Thirty subjects were randomly exposed to intervention with WBV (vertical, side-alternating, three bouts of 1 min with 1 min interval between bouts) at 15, 20, and 25 Hz with corresponding A(8) values of 0.76, 1.12, and 1.41 m/s2 r.m.s., respectively, and to control condition (0 Hz). Foot skin blood flow (SBF), skin temperature (ST), and heart rate variability (HRV) were measured before and during and/or after intervention. During intervention, relative to the control condition, SBF increased significantly under all vibration frequencies (P < 0.001) with greater responses under the higher frequencies. After exposure, compared to the control condition, the increase in SBF was significant under 20 Hz and 25 Hz exposure conditions (P < 0.001), and the responses were comparable under these two exposure frequencies. On the other hand, exposure to WBV did not produce any significant change in ST or HRV during and/or after the intervention. We conclude that WBV exposure with a vibration frequency of 20 Hz and peak-to-peak displacement of 4 mm producing an A(8) value of 1.12 m/s2 r.m.s. can be used safely and effectively in inducing improvements in peripheral SBF without exerting any adverse effects on the autonomic nervous activity.