Fig. 2.

A: nominal static properties of muscle tissues. These are determined by the active and passive isometric force-length curves. Fiber force and length values are normalized by the maximal isometric force, F^max, and optimal fiber length, l_o^m, respectively. B: nominal dynamic properties of muscle tissues. These are determined by the active force-velocity curve. Fiber force and contraction velocity values are normalized by the F^max and maximal contraction velocity, v^max, respectively. Both active force-length and force-velocity curves are depicted for different levels of muscle activation. C: solution space of the fiber force. This results from combining passive and active force-length and force-velocity curves. Note how muscle force is modulated simultaneously by activation, fiber length, and contraction velocity.