ACUTE EFFECTS OF VIBRATION ON DIGITAL CIRCULATORY FUNCTION IN HEALTHY-MEN

Objectives-To investigate the local and central pathophysiological mec hanisms involved in the acute effects of unilateral vibration on the d igital circulation of healthy men. Methods-Finger blood flow (FBF) and finger skin temperature (FST) in thermoneutral conditions, and the pe rcentage change in finger systolic pressure (FSP%) after local cooling from 30 to 10 degrees C were measured in the fingers of both hands in eight men (aged 23-47 years) who were not occupationally exposed to h and transmitted vibration. The right hand was exposed for 30 minutes t o sinusoidal vibration with a frequency of 125 Hz and an acceleration of 87 degrees 5 m . s(-2) rms (root mean square). A control condition consisted of exposure to static load only (10 N) without vibration. Th e measures of digital circulation were taken before exposure to vibrat ion 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 c hanges in FBF, FST, or FSP% in either the test right or the control le ft finger. Immediately after vibration exposure, there was a temporary increase in FBF in the vibrated right finger, whereas the non-vibrate d left finger showed no vasodilation. In both the vibrated and non-vib rated fingers, FBF and FST were significantly reduced during the recov ery time. A large variability between subjects was found for FBF and, to a lesser extent, for FST. In the vibrated right hand the decrease i n FBF was significantly related to cold induced vasoconstriction in th e digital vessels. Such a relation was not found in the nonvibrated le ft hand. Conclusions-The results of this investigation suggest that ac ute vibration can disturb the function of digital vessels through two different and opposite mechanisms. Vibration seems to produce local va sodilation and to trigger a central sympathetic reflex vasoconstrictio n that can be recorded in the ipsilateral and the contralateral finger to vibration. Both local and central vasoconstrictor mechanisms are l ikely to be involved in the responsiveness to cold found in the digita l vessels of a vibrated finger.