A nonlinear model of passive muscle viscosity

Area of Science:

• Biomedical Engineering
• Skeletal Muscle Physiology
• Biomechanics

Background:

• Passive skeletal muscle properties are vital for function and therapeutic targets.
• Previous research on muscle viscoelasticity has emphasized elastic properties, overlooking the significant role of viscosity.
• Understanding both elastic and viscous components is crucial for comprehensive muscle characterization.

Purpose of the Study:

• To characterize the time, strain, and strain rate dependence of passive muscle stress in single mouse fibers.
• To develop and validate a nonlinear viscoelastic model for muscle fibers.
• To compare the performance of the new model against traditional linear viscoelastic models.

Main Methods:

• Single mouse muscle fibers were subjected to incremental stress relaxation tests.
• A novel nonlinear viscoelastic model was developed to describe fiber behavior.
• The developed model's predictions were compared with established linear models.

Main Results:

• The viscous component of mouse muscle fiber stress demonstrated nonlinear behavior, dependent on time, strain, and strain rate.
• The newly developed nonlinear model provided a more accurate representation of fiber stress relaxation than linear models.
• The study highlights the limitations of assuming linear viscosity in muscle tissue.

Conclusions:

• Muscle fiber viscosity is complex and nonlinear, necessitating advanced modeling approaches.
• The developed nonlinear model offers a superior tool for analyzing muscle viscoelasticity.
• This research provides a new method for investigating alterations in muscle viscous stress due to aging, injury, or disuse.