Spectral analysis of the laser Doppler perfusion signal in human skin before and after exercise

Spectral analysis based on wavelet transformation of the periodic oscillati ons of the cutaneous laser Doppler flowmetry (LDF) signal was used to analy ze exercise-induced changes in flow motion in humans. The measurements were performed on the forearm skin in nine healthy, less-trained subjects befor e and after exercise. Periodic oscillations with frequencies of around 1, 0 .3, 0.1, and 0.04 Hz were demonstrated, which are proposed to represent the influence of heart beat, respiration, intrinsic myogenic activity, and the neurogenic factors, respectively, on cutaneous blood now. We also demonstr ated oscillations with a frequency of around 0.01 Hz both before and after exercise. The mean spectral amplitude in the frequency range from 0.0095 to 2.3 Hz increased twofold (P = 0.004) in response to exercise. This increas e results from a significant increase in the amplitude of oscillations of a round 1, 0.3, and 0.1 Hz. The amplitude of oscillations of around I and 0.3 Hz increased onefold in response to exercise (P = 0.02 for both frequencie s), whereas the amplitude of oscillations of around 0.1 Hz increased threef old (P = 0.008). Furthermore, to evaluate relative changes of each particul ar oscillation in response to exercise, the absolute amplitude of each freq uency interval was devided by the mean spectral amplitude. In this way, the relative contribution of oscillations of around 0.01 and 0.04 Hz were show n to decrease significantly following exercise (P = 0.008 and P = 0.004, re spectively). The relative contribution of the oscillations of around 0.1 Hz increased, although not statistically significant (P = 0.08), while the re lative contribution of the oscillations of around 0.3 and 1 Hz to the total Bow motion remained unchanged in response to exercise (P = 0.84 and P = 0. 95, respectively). These findings indicate an increased contribution of the oscillations of around 0.1 I-fi to the regulation of the cutaneous blood f low following exercise, whereas oscillations of around 0.04 and 0.01 Hz con tribute less. We conclude that spectral analysis using a wavelet transforma tion of the LDF signal is a valuable tool for use in the evaluation of exer cise-induced changes in the dynamics of cutaneous microvascular blood now, but further studies are: necessary to clarify the physiological origin of t hese oscillations. (C) 1998 Academic Press.