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Multifractal analysis of laser Doppler flowmetry signals before and after
arm-cranking exercise in an older healthy population
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There is a lot of speculation about the role of nitric-oxide (NO) in the improvement
usually noticed in microcirculatory function, following exercise. The knowledge of the
underlying mechanisms leading to such an improvement is important as it may help in
targeting and implementing therapies for microcirculatory diseases. Through a laser
flowmetry (LDF) signal
processing study, the authors’ goal is to compare multifractal spectra
of LDF data recorded in both lower leg and forearm, during different exercise
conditions, in an older, untrained but healthy population.
Using the method suggested byHalsey
et al. [Phys. Rev. A33, 1141–1151
(1986)], multifractal spectra of LDF
signals recorded on lower leg and forearm before and after exercise (arm-cranking),
before and after acetylcholine (ACh) iontophoresis, were determined on scales in
relation with the NO-dependent endothelial activity. The width of each multifractal
spectrum was then computed through the maximum and minimum Hölder exponent values for
which the multifractal spectrum reaches its minimal values. The results were then
Following exercise and on the scales studied, the average width of the multifractal
spectra in both lower leg and forearm does not vary significantly before and after ACh
iontophoresis. Similarly, following ACh iontophoresis and exercise, the average width of
multifractal spectra remains statistically unchanged, when compared to that measured
prior to exercise, in both upper and lower body, although negative trends can be
For the authors’ population and for the type of exercise that the authors have chosen,
the authors showed that the width of the multifractal spectra of LDF signals does not
change significantly on scales in relation with the NO-dependent endothelial activity.
Future studies may involve comparisons with signals obtained in patient populations.
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