Effect of Local Vibrations on Plantar Skin Blood Flow Responses During Weight-bearing Standing in Healthy Volunteers

Abstract

The objective of this study was to examine the effects of local vibrations on plantar skin blood flow (SBF) responses during weight-bearing standing. Wavelet analysis of plantar SBF was used to analyze microvascular regulation in response to standing with and without local vibrations. Fifteen (15) healthy participants (26.5 ± 5.7 years; 4 male and 11 female) received a local vibration intervention (35 Hz, 1 mm, 2 g vibration) and a sham vibration to the skin of the right first metatarsal head during 10-minute standing. Laser Doppler flowmetry was used to measure SBF before and after 10 minutes of standing. SBF after standing was expressed as a ratio of SBF before standing to minimize blood flow variations. The use of wavelet analysis allowed the authors to examine the frequency bands corresponding to the physiological controls in the vibration and sham areas of the foot, including metabolic (0.0095-0.02 Hz), neurogenic (0.02-0.05 Hz), myogenic (0.05-0.15 Hz), respiratory (0.15-0.4 Hz), and cardiac (0.4-2.0 Hz) regulations. Plantar SBF ratio changes in the vibration protocol (1.83 ± 0.27) were significantly higher compared with the sham protocol (0.97 ± 0.08) (P < .01). SBF before and after the 35 Hz vibrations were 41.96 ± 14.02 perfusion units (range 6.68-208.9 perfusion units) and 61.16 ± 14.74 perfusion units (range 7.76-155.37 perfusion units), respectively. SBF before and after the sham vibration were 37.32 ± 9.29 perfusion units (range 5.74-120.44 perfusion units) and 33.97 ± 8.11 perfusion units (range 6.95-108.44 perfusion units), respectively. Wavelet analysis of SBF oscillations showed a significant difference in all regulations: metabolic (P < .05), neurogenic (P < .05), myogenic (P < .05), respiratory (P < .05), and cardiac (P < .05) in response to 35 Hz local vibrations compared with the sham vibration. Local vibrations (35 Hz frequency, 1 mm amplitude) to the plantar tissues during 10 minutes of weight-bearing standing resulted in a significant increase in after-standing plantar SBF compared with sham vibration. The control mechanisms contributing to this increase in SBF were metabolic, neurogenic, myogenic, respiratory, and cardiac regulations. These findings confirm results of preclinical studies and support the need for additional research to examine the potential protective effects of local vibration to decrease the risk of plantar ulcers.