Muscle activation
Normalized excitation level a ∈ [0, 1]
Short definition
Muscle recruitment level; force F = a × F_max (with the force–length curve and moment arm). Static optimization minimizes Σa².
Full definition
Activation is the controlled excitation level from 0 to 1. VibroTheory/BioSim static optimization solves min Σa² subject to the required joint torque (QP or LSQ+active-set); muscle force F_i = a_i · F_max_i · f_l(l_norm). The problem is linear in the external force, so activations do not depend on its magnitude — body-part shares are identical for static and dynamic components. %MVV = activation × 100.
Examples
Biceps activation of 0.45 while holding 40 %MVC.