Fig 1.
Visualization of modelling framework.
Second-order dynamic system composed of a Hill-type muscle model in series with a damped harmonic oscillator (A). The force of the muscle is given by the sum of the active force due to the contractile element (CE) as a function of its length (B) and velocity (C), and the passive force due to the parallel elastic element (PEE) as a function of its length (B).
Table 1.
Model and equation parameters.
Table 2.
Model scaling factors.
Fig 2.
Force-velocity and force-length curves.
Normalized force-velocity (A), active force-length (B) and passive force-length (C) curves (black lines). The force-velocity curve and the active and passive force-length curves are fitted to experimental data from [47] and [48], respectively (grey points). The Bézier control points for each curve are shown as red asterisks.
Fig 3.
Muscle excitation and activation (A,F), force (B,G), length (C,H), velocity (D,I) and power (E,J) traces for two representative simulations with umax of 1, f of 1 Hz, of 5 s-1, and
of 1 (A-E) and 10 (F-J). n denotes the cycle number.
Table 3.
Output mass-specific mechanical power output P* for all simulations.
Fig 4.
Muscle work-loops showing normalized muscle force versus normalized muscle length
for each simulation. Simulations with umax of 0.1 are shown in panels A and C, and simulations with umax of 1 are shown in B and D. The non-dimensional muscle forces and lengths are identical for simulations with
of 1 (A,B) and 10 (C,D).