Effect of vibration magnitude and repetitive exposure on finger blood flow in healthy subjects.

In order to study the effect of the magnitude of vibrations and repetitive exposure on finger blood flow, we exposed ten healthy subjects to three experimental conditions: (1) vibration of 3.16 m/s2 at 60 Hz, (2) vibration of 31.6 m/s2 at 60 Hz, and (3) no vibration, as a control. Under the experimental conditions, the right hand was exposed to 5-min vibration three times, with intervening 5-min rests. Meanwhile, the blood flows of both middle fingers were continuously measured with a blood flow meter based on the thermal diffusion method. Finger blood flow was significantly decreased in both hands with exposure to vibrations of 3.16 m/s2 and 31.6 m/s2. Increased magnitude of vibration tended to enhance the decrease in finger blood flow in both hands, and repeated exposure to vibration had cumulative effects on the decrease in finger blood flow in the unexposed left hand.