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Frequency domain-based models of skeletal muscle
R V Baratta1, M Solomonow, B H Zhou
1Louisiana State University Medical Center, Department of Orthopaedic Surgery, New Orleans 70112, USA. rbarat@lsumc.edu
Summary
Skeletal muscle models using frequency response analysis reveal a second-order system with time delay best describes isometric force. These models are robust for neuroprosthesis design.
Area of Science:
- Biomechanics
- Neuroprosthetics
- Systems Biology
Background:
- Frequency response analysis has modeled skeletal muscle since the 1960s.
- Cyclic stimulation determines force/length amplitude and phase, approximated by pole-zero models.
- This bypasses complex force-length/force-velocity relationships.
Purpose of the Study:
- To characterize skeletal muscle dynamic response using frequency domain analysis.
- To develop robust models for neuroprosthesis applications.
- To investigate the influence of tendons and joints on muscle dynamics.
Main Methods:
- Sinusoidal stimulation at varying frequencies to measure muscle force and length.
- Development of second-order models with time delays for isometric and load-moving conditions.
- Analysis of tendon and joint effects on muscle frequency response.
Main Results:
- Isometric force modeled by a critically damped second-order system (corner frequency ~2 Hz) with time delay.
- Load-moving muscle response shows load-independent phase lag and load-dependent gain.
- Tendon viscoelasticity has minimal impact on isometric response but affects load-moving dynamics.
- Joints introduce phase lag and reduce high-frequency gain, but do not significantly degrade signal quality.
- Co-contraction significantly impacts joint dynamic response.
Conclusions:
- Frequency response models are robust under consistent conditions.
- Muscle architecture and function are key determinants of isometric force response.
- These models are valuable for designing dynamic muscle controllers in neuroprostheses.