Reflex control of body posture in standing

Human body as a segmented inverted pendulum is an unstable system needing posture control for balancing. Using the inverted pendulum as a template representing human balance in quiet standing, neuromuscular models can be employed for understanding posture control. Feedback control is implemented in human neuromuscular systems by reflex signals. In this paper, we want to realize which type of reflex signals are the most advantageous ones in posture control. As common reflex signals, muscle length, velocity and force are examined. Simulations, stability and robustness analyses show that combination of force and velocity reflexes results in a stable system with the largest basin of attraction, the most robustness against perturbations and the best performance. In addition, a proposed model with two antagonistic muscle can explain human moderate oscillations at quiet standing, using the metabolic effort under optimal control argumentation.