Wavelet-based analysis of plantar skin blood flow response to different frequencies of local vibration

Objective: The objectives of this study were to investigate the response of plantar skin blood flow (SBF) to different frequencies of local vibration (LV) and investigate the mechanisms of blood flow control in response to the different frequencies of LV using wavelet analysis. Approach: Twelve healthy participants were recruited to test the effects of three frequencies [0 Hz (sham control), 35 Hz and 100 Hz at 1 mm amplitude] of 10 min LV on the skin of the right first metatarsal head. A repeated measures design was used in this study and the order of vibration frequencies was randomly assigned to participants while they lay on a mat table. Laser Doppler flowmetry was used to measure SBF on the first metatarsal head before and after LV for 10 min. SBF after vibration was expressed as a ratio of SBF before vibration. Wavelet analysis was used to characterize changes in SBF control mechanisms. Main results: Our results showed that the SBF with the 100 Hz protocol (1.56 ± 0.19) was significantly higher than for the 35 Hz (1.29 ± 0.18, p  < 0.05) and 0 Hz (0.85 ± 0.11, p  < 0.01) protocols. Wavelet analysis demonstrated that metabolic endothelial control (SBF oscillations of 0.0095-0.02 Hz) and neurogenic control (SBF oscillations of 0.02-0.05 Hz) were associated with the increase in SBF after LV at 100 Hz. Significance: LV at 100 Hz results in a significant increase in SBF compared with 35 Hz and 0 Hz vibrations. Such an increase in SBF is related to the regulation of metabolic endothelial (0.0095-0.02 Hz) and neurogenic (0.02-0.05 Hz) controls. This is the first study to demonstrate that 100 Hz LV stimulates an increase in plantar SBF compared with 35 Hz and 0 Hz vibrations through the frequency intervals of 0.0095-0.02 and 0.02-0.05 Hz of SBF oscillations.