Cerebral oxygenation and blood volume responses to seated whole-body vibration

Role of backrest support and hand grip contractions on regional cerebral oxygenation and blood volume were evaluated by near infrared spectroscopy in 13 healthy men during whole-body vibration (WBV). Subjects were exposed to three WBV (3, 4.5, and 6 Hz at approximately 0.9 g(rms) in the vertical direction), in a randomized order on separate days. During WBV, subjects performed right-hand maximal voluntary intermittent rhythmic hand grip contractions for 1 min. Subjects demonstrated highest oxygenation and blood volume values at 4.5 Hz, however, these responses were similar with and without backrest support (P>0.01). Compared to WBV alone, addition of hand grip exercise during WBV further increased oxygenation (0.07+/-0.11 vs. 0.004+/-0.11 od, P=0.003) and blood volume (0.156+/-0.20 vs. 0.066+/-0.17 od, P=0.000) in the right forehead. Peak oxygen uptake did not correlate to changes in oxygenation and blood volume (P>0.01). Based on the increase in ventilation volume and no change in the ratio of ventilation volume and expired carbon dioxide (P>0.01), it is concluded that WBV induces hyperventilation that might activate the pre-frontal cortical region, thus influencing cerebral responses through neuronal activation.