Biophysical Reviews and Letters

This is a commentary about the biophysics of muscle, presenting an introduction to the area, modeling muscles' biophysics, and this Issue's projects.

Automotive shocks involve various tiers’ speed for different human body tissues. Knowing the behavior of these tissues, including muscles, in different vibration frequency is therefore necessary. The muscle has viscoelatic properties. Dynamically, this material has variable mechanical properties depending on the vibration frequency. A novel technique is being employed to examine the variation of the mechanical impedance of pork muscle as a function of frequency. A force is imposed on the lower surface of the sample and acceleration is measured on its upper surface. These two parameters are measured using sensors. The sample is modeled by Kelvin–Voigt model. These measures allow deducing the change in the mechanical impedance modulus (/$Z_{\mathrm{\text{exp}}}$/ $=$ /Force: Acceleration/) of pork muscle as a function of vibration frequency. The measured impedance has a resonance of approximately 60Hz. Best-fit parameters of theoretical impedance can be deduced by superposition with the experiment result. The variation of Young’s modulus and internal damping of pig’s muscle as a function of frequency are determined. The results obtained between 5Hz and 30Hz are the same as determined by Aimedieu and al in 2003, therefore validating our technique. The Young’s modulus of muscle increases with the frequency, on the other hand, we note a rating decrease of internal damping.

The transverse thermal fluctuations of the myosin molecule are significant. This paper explores the contribution of lateral myosin bending to the developed crossbridge force and power stroke. The equipartition theorem is used to calculate the mode amplitudes for myosin bending. Crossbridge axial force $F_x$ and power stroke $\mathrm{\Delta }x$ are developed by transverse in-plane fluctuations along the $y$- and $z$-axes. Practical applications include the effects of temperature on the flexibility of the myosin molecule stiffness and tension, relevant to man-made fabrication of synthetic muscle using micromachines and nanowires. Scaling laws for the $S2$ bending amplitude depend on filament length, mode number, and stiffness, as $n^{-2},L^2$, and (EI)${}^{-1}$. This paper quantifies the effects of thermal motion on the mechanics of miniature molecular motors, including the muscle crossbridge.