[Interpretation of mechanical impedance of biological tissues in the three level model with the power source of vibrations]. / Interpretatsiia mekhanicheskogo impedansa biologicheskikh tkanei v trekhsloinoi modeli s silovym istochnikom kolebanii.

Theoretical expressions were derived for the mechanical impedance of a round piston on the surface of a viscoelastic triple layer with sublayers linked with each other and with the rigid base. The expressions were obtained on the assumption that the piston creates an even oscillatory pressure and does not create shear stresses. The calculations in the developed model were compared with corresponding calculations in the known strict model and with experimental values obtained on a relaxed and stressed human biceps. The results obtained suggest that models of this kind can be used for reconstructing the mechanical parameters of multilayer biological tissues.

[Possibilities of quantitative assessment of perception of weight by the muscle analyzer]. / O vozmozhnosti kolichestvennoi otsenki vospriiatiia tiazhesti myshechnym analizatorom.

The possibility of creating purely instrumental methods to study the sensory sphere was shown by an example of a muscle analyzer. The methods are necessary for the development and optimization of man-machine systems, in particular, virtual reality. Earlier the connection between a stimulus and perception was estimated by a statistical analysis of subjective answers of an examinee concerning the perception and lack perception or the difference between two similar stimuli. The novel approach proposed in this work is based on the study of the connection between the instrumentally measured value of error during the performance of a control task by the examinee and the value of the stimulus, which serves as a control signal.

[Possibilities of myotonography]. / O vozmozhnostiakh sposoba miotonografii.

The paper deals with the undamaging mode of examining the status of different elements of the human neuromuscular system, which is based on a task of test exposure and recording a response to it by recording rapid changes in the tension of appropriate muscles. Separately measured actual and imaginary constituents of complex tissue rigidity, which are recorded when a stamp vibrating at a fixed rate in the range of 10-100 Hz is pressed into them. The paper presents records of changes in the proposed characteristics of elastic and viscous properties of muscles in the following experiments: through external percutaneous electric stimulation of forearm muscles, through stimulation of knee reflex of the musculus quadriceps femoris, and through musculus gastrocnemius loading test.

[Prospects for measuring the rheologic characteristics of human soft tissues based on the recording of their transverse rigidity]. / O vozmozhnostiakh izmereniia reologicheskikh kharakteristik miagkikh tkanei cheloveka na osnove registratsii ikh poperechnoi zhestkosti.

It is shown by an example of a forearm that to determine objective characteristics of rheological properties of soft human tissues by measuring their transverse stiffness (K) one should first investigate the relation between K and the diameter of the used indentor (d). The nonlinearity of the dependence K(d) for indentor diameters from 2 to 8 mm is demonstrated and it is assumed that this nonlinearity is due to heterogeneity of tissue properties in the directions normal to the axis of force action.

[Rheological model of muscle tissue in a state of constant activation]. / Reologicheskaia model' myshechnoi tkani v sostoianii postoiannoi aktivatsii.

For cylindric sample of muscle tissue in the state of constant activation a constitutive equation was found, which permits to reproduce in first approximation the frequency relationships of muscle dynamic rigidity and phase shift between tension and deformation. The meaning of such equation seems to involve a description of the muscle contractile element via its macroscopic characteristics without looking into its inner structure.

A macroscopic description of stress relaxation in a muscle subject to stepwise deformation.

Stress relaxation regimes arising in a muscle subject to stepwise deformation are described on the basis of a recent phenomenological model of fully activated muscle tissue which is presented in the form of a second-order constitutive equation. It is shown that this model reproduces the qualitative form of relaxation curves observed experimentally. Relations between rheological parameters which correspond to different types of stress relaxation are found for the case where the jump duration is much smaller than the relaxation times of the sample. As illustrated by the simplest model of a slow length jump (linear deformation), the qualitative form of the stress relaxation depends on the jump duration in this case. This effect can lead to rough errors in determination of rheological and molecular parameters of muscle tissue in mechanical experiments in which the relation between jump duration and relaxation times is not controlled.

[Theoretical analysis of possible construction of biomechanical parameters of energy expenditures in heart muscle]. / Teoreticheskii analiz vozmozhnosti postoieniia biomekhanicheskikh pokazatelei énergozatrat serdechnoi myshtsy.

Proceeding from the data that overall efficiency of the heart muscle under constant level of contraction is estimated by the rate of fibre shortening a total expression for energy losses in the wall of the heart left ventricle is proposed. It is a concrete mathematical expression of modern concepts about the factors responsible for energy consumption by the heart. With certain assumptions the known parameters of energy expenditures are obtained: the index of heart tension (IHT known as "double product" index) and the index of time - tension TTI. More exact fulfillment of IHT is explained by the fact that it assumes certain changes of the heart contraction, while TTI is valid only at its constants level.