Nonlinearities make a difference: comparison of two common Hill-type models with real muscle

Area of Science:

• Biomechanics
• Computational Biology
• Muscle Physiology

Background:

• Hill-type models are widely used in musculoskeletal simulations due to their simplicity and low computational cost.
• Two common models, [CC+SEC] and [CC], differ in their representation of elastic components.
• Accurate muscle parameterization is crucial for gaining insights into movement mechanics.

Purpose of the Study:

• To compare the representational accuracy of two Hill-type muscle models ([CC+SEC] and [CC]) for the cat soleus.
• To determine which model better captures the muscle's contraction dynamics.

Main Methods:

• In situ ramp experiments (isometric and isokinetic) were performed on cat soleus preparations.
• Supramaximal nerve stimulation was used to elicit muscle contractions.
• Hill-type models incorporating force-length, force-velocity, excitation-contraction coupling, and elastic components were fitted to experimental data.

Main Results:

• The force-velocity and series elastic component relations were independent of the chosen model when passive force was negligible.
• Model [CC] predictions for these relations aligned with experimental findings, unlike model [CC+SEC].

Conclusions:

• Model [CC] demonstrated superior representation of cat soleus contraction dynamics compared to model [CC+SEC].
• Model [CC] is recommended for nonlinear regression of muscle parameters and in musculoskeletal modeling applications.