Objective: We aimed to elucidate the frequency-specific microcirculatory blood-flow (MBF) effect induced by weak vibration stimulation (VS) in healthy human subjects. Methods: VS was implemented by a rod (connected to a DC motor) hitting a water-filled bag. VS was applied to the left palm at frequencies near to the heart rate (HR) (n = 35; Group A) and 50% higher than the HR (n = 20; Group B), and laser-Doppler-flowmetry measurements were made on the back of the left hand (Site 1). A control group without applying VS was also used (n = 21). Results: The mean MBF (MMBF), pulsatile MBF, and pulse width at Site 1 only increased significantly in Group A, and the coefficient of variance of the MMBF sequence increased significantly at Site 1 in Groups A and B. Conclusion: These results illustrate the VS-induced changes in the regulatory activities of arteriolar openings, and improve- ment of the MBF near the VS application site in Group A. The improvement in MBF depended on whether the VS frequency was near to, or higher than the HR. The present findings may be pertinent to amelioration of disease induced by an abnormal MBF.
