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1

An inverse procedure for characterization of material parameters of passive skeletal muscle using FEM and experimental data

Liu Shuailong, Sang Jianbing, Zhang Yi, Zhao Luming, Liu Guirong

Journal of Theoretical and Applied Mechanics

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2020

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Vol. 58 nr 1

247--259

EN

This work develops an inverse procedure which combines an improved niche genetic algorithm, finite element models and experimental data to identify material parameters of biological tissues behaving like hyperelastic materials. A novel objective function is proposed with two coefficients, which controls the contributions in a well-balanced fashion, respectively, for the small deformation stage and the large deformation stage. This allows us to obtain a global minimizer (of material constants) for the error between FEM solutions and experimental data. Moreover, simple uniaxial compression tests at two different angles (0◦ and 90◦) with respect to the muscle fiber orientation are performed on fresh muscle tissues. This enables us to obtain anisotropic properties of the muscle tissue from the present inverse procedure. The result shows that the proposed inverse procedure is stable and reliable to determine material constants in hyperelastic models for soft biological tissues like skeletal muscles considering anisotropy.

2

The tetanic depression in unfused tetani of fast motor units in mammalian muscle

Celichowski J.

Biocybernetics and Biomedical Engineering

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2005

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Vol. 25, no. 4

27-35

EN

Tetanic depression is a phenomenon that limits the force of unfused tetani in contractions evoked at unstable stimulation frequencies. In our experiments this phenomenon was visible in tetani evoked at two frequencies of stimulation: the lower immediately followed by the higher one. The force at the higher stimulation frequency was evidently depressed in relation to the force achieved during the control constant-frequency stimulations. This depression concerned the fast motor units and it was not observed in the slow units. The tetanic depression was initially found in the rat medial gastrocnemius muscle. However, it is not clear whether this phenomenon is specific only to the rat muscle or it concerns all mammals. Therefore, in the subsequent series of experiments, the tetanic depression was investigated in the motor units of the feline medial gastrocnemius, and the effect was also observed in all fast units. The maximum evoked depression exceeded 50% of the control values. Moreover, the analysis of the relationship between the amplitude of the tetanic depression and the degree of the tetanic fusion revealed that the strongest amplitude of depression was observed in the middle-fused tetani (with the fusion index in the range 0.5-0.7). The third experimental series proved that the tetanic depression could be visible in tetani evoked at a progressively increasing frequency of stimulation. Moreover, it was found that the effect of the force decrease could result from the prolongation of only one, the first interpulse interval. The amplitude of this decrease exceeded 20% of the control values. Summarizing, the tetanic depression is a phenomenon influencing the force of unfused tetani of the fast motor units at an increasing stimulation frequency. The depressive effect is present in various species of mammals, probably, including human. The amplitude of the depression depends on the fusion of the tetanic contraction. The physiological significance of tetanic depression is closely related to reduction of the importance of the motoneuronal firing rate.

3

Modelowanie i symulacja zachowania mięśnia szkieletowego o różnych własnościach dynamicznych

Wojnicz W., Wittbrodt E.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2004

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z. 24

219-224

PL

W artykule został przedstawiony nieliniowy model zachowania mięśnia szkieletowego, który uwzględnia różnorodne własności dynamiczne poszczególnych odcinków mięśnia. Opisane są zasady obliczania współczynników modelu w przypadku mięśnia wypoczętego i zmęczonego. Zaprezentowane zostały zasymulowane ekscentryczne i koncentryczne skurcze oraz bilanse energetyczne dla poszczególnych zachowań mięśnia.

EN

In the paper it has been presented the non-linear model of striated skeletal muscle's behavior which models the heterogeneity of each its part. Its have been described principles of models coefficients computations in case of rested and fatigue muscle, represented simulated eccentric - concentric muscle cramps and its energetic balances.