In this chapter, we address the problem of human quiet stance regulation using a single-link inverted pendulum model in the sagittal plane, focusing on the passive and active torques at the ankle joint. The active torque arises from ankle muscle contractions activated by the delayed response of the central nervous system (neural controller). The passive torque reflects the inherent mechanical properties of the muscle-tendon-ligament complex. Consequently, an inability to sustain a quiet stance is directly attributed to the dysfunction of either or both torque mechanisms. We propose a modeling of the neural controller as a delayed proportional-derivative-acceleration controller that acts on the angular position of the ankle joint. Thereby, we consider the occurrence of the multiplicity-induced-dominancy property of the corresponding dynamical system represented by a delay differential equation as an indicator for fine behavior, and we examine both the critical time delay in motor control and the critical stiffness of the ankle joint (A preliminary version of the present work has been published in the First IFAC Workshop on Control of Complex Systems [3].)