5.7 Study of Intensity Fluctuation Spectra of Dynamic …
425
Besides, the ratio of the estimated value of the oscillations under study and
intensity distribution in longitudinal section of the speckle should be taken into
consideration.
If the estimated maximal amplitude of the fluctuations under study does not go
beyond the linear area of intensity distribution in longitudinal section of the spectrum,
then the given informative parameters will describe the amplitude characteristics
of oscillations taking into account corresponding frequencies of the spectrum. For
example, spectrum power used during the study of contractive activity of human
skeletal muscles showed with a sufficient degree of reliability and credibility the
changes of amplitude characteristics of the vibrating biceps by the testee at changes
of the value of the applied isometric load. Relaxation time characterizing the fatigue
characteristics of muscles can also serve as an informative parameter.
This parameter was determined through registration and analysis of spectra after
relieving stress from the muscle caused by the applied physical load.
Along with this, it is possible to determine informative parameters f , S, Q not
for the whole spectral curve, but for its separate specified parts, for example, local
maxima, i.e., to change limits of integration. Search for most optimal conditions of
selection and determination of informative parameters was conducted in the process
of the study. It will be shown further during description of the experiments how these
informative parameters work during the study of dynamics of the surface blood
flow and contractive activity of muscles in different conditions. In particular, it is
reasonable to use integral characteristics of spectra: square S, average frequency F,
etc. It is obvious that it is also reasonable to complement the mentioned integral
characteristics with moments of higher orders
f
n A( f )d f as well where n = 2.3.
As an additional parameter, the dispersion can be used as well (or standard deviation of time dependence of the signal, which characterizes the average power of
intensity fluctuation in the observation plane). Besides, it is also sensible to add to the
above-mentioned characteristics some indicators of nonlinearity of transformation
with a device of pulsation spectrum of the skin into intensity fluctuation spectrum.
They can be in the form of coefficients of overtones of the main frequency of muscle
contractions. It is known that the muscle “buzzing” effect is observed at frequencies
of about 23 Hz, so the overtone coefficients can be taken into consideration as well.
When the applied isometric load is intensified up to the maximal effort developed
by the biceps of the upper arm, the increase of the average fluctuation frequency
within the limits of 23.6–23.9 Hz is observed. This dependence can be explained by
representing the muscle as a simple model of a string system [111, 154–156].
Thus, the conducted studies gave the possibility to develop a noninvasive method
of determining biomechanical characteristics of human skeletal muscles—a method
of speckle-optical myography. This allows obtaining additional information about
oscillatory activity of muscles and degree of their contractility through the registration of amplitude–frequency parameters of intensity fluctuation spectra of radiation
scattered by skin. This information cannot be obtained with traditional method of
electromyography.
That is why the developed method can be rather informative for diagnostics of
neuromuscular diseases, as it is known that disturbing factors of any genesis, both
425
Besides, the ratio of the estimated value of the oscillations under study and
intensity distribution in longitudinal section of the speckle should be taken into
consideration.
If the estimated maximal amplitude of the fluctuations under study does not go
beyond the linear area of intensity distribution in longitudinal section of the spectrum,
then the given informative parameters will describe the amplitude characteristics
of oscillations taking into account corresponding frequencies of the spectrum. For
example, spectrum power used during the study of contractive activity of human
skeletal muscles showed with a sufficient degree of reliability and credibility the
changes of amplitude characteristics of the vibrating biceps by the testee at changes
of the value of the applied isometric load. Relaxation time characterizing the fatigue
characteristics of muscles can also serve as an informative parameter.
This parameter was determined through registration and analysis of spectra after
relieving stress from the muscle caused by the applied physical load.
Along with this, it is possible to determine informative parameters f , S, Q not
for the whole spectral curve, but for its separate specified parts, for example, local
maxima, i.e., to change limits of integration. Search for most optimal conditions of
selection and determination of informative parameters was conducted in the process
of the study. It will be shown further during description of the experiments how these
informative parameters work during the study of dynamics of the surface blood
flow and contractive activity of muscles in different conditions. In particular, it is
reasonable to use integral characteristics of spectra: square S, average frequency F,
etc. It is obvious that it is also reasonable to complement the mentioned integral
characteristics with moments of higher orders
f
n A( f )d f as well where n = 2.3.
As an additional parameter, the dispersion can be used as well (or standard deviation of time dependence of the signal, which characterizes the average power of
intensity fluctuation in the observation plane). Besides, it is also sensible to add to the
above-mentioned characteristics some indicators of nonlinearity of transformation
with a device of pulsation spectrum of the skin into intensity fluctuation spectrum.
They can be in the form of coefficients of overtones of the main frequency of muscle
contractions. It is known that the muscle “buzzing” effect is observed at frequencies
of about 23 Hz, so the overtone coefficients can be taken into consideration as well.
When the applied isometric load is intensified up to the maximal effort developed
by the biceps of the upper arm, the increase of the average fluctuation frequency
within the limits of 23.6–23.9 Hz is observed. This dependence can be explained by
representing the muscle as a simple model of a string system [111, 154–156].
Thus, the conducted studies gave the possibility to develop a noninvasive method
of determining biomechanical characteristics of human skeletal muscles—a method
of speckle-optical myography. This allows obtaining additional information about
oscillatory activity of muscles and degree of their contractility through the registration of amplitude–frequency parameters of intensity fluctuation spectra of radiation
scattered by skin. This information cannot be obtained with traditional method of
electromyography.
That is why the developed method can be rather informative for diagnostics of
neuromuscular diseases, as it is known that disturbing factors of any genesis, both