shows that the effective stiffness of the ankle joints
increased with an anterior position of the body CM. The 4-cm
humanoid showed an increased initial effective stiffness. This
increased stiffness somehow allowed the humanoid to attenuate
the effect of the perturbation. The importance of the ankle stiffness
in initially compensating the perturbation, however, did not
provide a significant decrease of the muscular torque necessary
to stabilize the humanoid.