Acute response of finger circulation to force and vibration applied to the palm of the hand.

OBJECTIVES: This study investigated the effects of force at the palm on acute changes in finger circulation during exposure to vibration. METHODS: Ten persons attended five sessions consisting of the following five successive 5-minute periods: (i) no force and no vibration, (ii) force and no vibration, (iii) force and vibration, (iv) force and no vibration, and (v) no force and no vibration. During the second and fourth periods, the palm of the right hand applied 5 N or 20 N to a platform that vibrated (125 Hz, 64 m/s2 root mean square) during the third period. Finger blood flow was measured in the middle and little fingers of the right (exposed) hand and the middle finger of the left (unexposed) hand. RESULTS: A force of 20 N alone reduced the mean finger blood flow in the ipsilateral and contralateral fingers. Finger blood flow was also reduced by vibration, with greater reductions when vibration was combined with 20 N of force. Vibration caused vasoconstriction in the fingers of both the vibrated and nonvibrated hands. CONCLUSIONS: Force applied to the palm reduced blood flow in the fingers of the exposed hand, probably due to compression of the vascular system supplying the fingers. There was evidence that force may reduce finger blood flow in the contralateral hand, possibly due to a central sympathetic effect. Vibration at 125 Hz applied to the palm of the hand reduced finger blood flow in fingers of that hand and also in a finger of the contralateral hand. In this study, any local effects of vibration were less than those of central sympathetic origin