The modification of beat to beat algorithm and its application on the assessment of muscle flexibility

Laser-Doppler Flowmetry (LDF) described by the theory related to the Doppler effect is one of the most convenient measurement techniques for routine tissue perfusion assessment. Although the LDF signal did not reveal a significant waveform in heart-beat frequency, its 'waveform' could be obtained by beat to beat algorithm, in which the R peaks of electrocardiograph (ECG) were used as a reference. Nevertheless, because the period length of heart beat varies a little bit over time even for the same person, the segments of LDF signal divided according to the peaks of ECG definitely would not have exactly the same length. In this study, we modified the beat to beat algorithm by resampling the LDF segments and normalizing them into the same length. According to the modified beat to beat algorithm, the characteristics of LDF were compared between individuals with different flexibility of lower extremities. The LDF flux of the individuals with higher flexibility revealed higher stability underwent the muscle stretching, while the blood flux from the individuals with lower flexibility was interfered and became unstable during muscle stretching. We concluded that the modified beat to beat algorithm will be a useful tool for the analysis of LDF signals.