Acute effects of vibration on digital circulatory function in healthy men

Objectives - To investigate the local and central pathophysiological mechanisms involved in the acute effects of unilateral vibration on the digital circulation of healthy men. Methods - Finger blood flow (FBF) and finger skin temperature (FST) in thermoneutral conditions, and the percentage change in finger systolic pressure (FSP%) after local cooling from 30 to 10°C were measured in the fingers of both hands in eight men (aged 23-47 years) who were not occupationally exposed to hand transmitted vibration. The right hand was exposed for 30 minutes to sinusoidal vibration with a frequency of 125 Hz and an acceleration of 87.5 m · s-2 rms (root mean square). A control condition consisted of exposure to static load only (10 N) without vibration. The measures of digital circulation were taken before exposure to vibration and static load and at 0, 30, 60, and 90 minutes after the end of each exposure. Results - Exposure to static load caused no significant-changes in FBF, FST, or FSP% in either the test right or the control left finger. Immediately after vibration exposure, there was a temporary increase in FBF in the vibrated right finger, whereas the non-vibrated left finger showed no vasodilation. In both the vibrated and non-vibrated fingers, FBF and FST were significantly reduced during the recovery time. A large variability between subjects was found for FBF and, to a lesser extent, for FST. In the vibrated right hand the decrease in FBF was significantly related to cold induced vasoconstriction in the digital vessels. Such a relation was not found in the non-vibrated left hand. Conclusions - The results of this investigation suggest that acute vibration can disturb the function of digital vessels through two different and opposite mechanisms. Vibration seems to produce local vasodilation and to trigger a central sympathetic reflex vasoconstriction that can be recorded in the ipsilateral and the contralateral finger to vibration. Both local and central vasoconstrictor mechanisms are likely to be involved in the responsiveness to cold found in the digital vessels of a vibrated finger.