title: Modeling human postural sway using an intermittent control and hemodynamic perturbations.
abstract: Ground reaction force during human quiet stance is modulated synchronously with the cardiac cycle through hemodynamics [1]. This almost periodic hemodynamic force induces a small disturbance torque to the ankle joint, which is considered as a source of endogenous perturbation that induces postural sway. Here we consider postural sway dynamics of an inverted pendulum model with an intermittent control strategy, in comparison with the traditional continuous-time feedback controller. We examine whether each control model can exhibit human-like postural sway, characterized by its power law behavior at the low frequency band 0.1-0.7Hz, when it is weakly perturbed by periodic and/or random forcing mimicking the hemodynamic perturbation. We show that the continuous control model with typical feedback gain parameters hardly exhibits the human-like sway pattern, in contrast with the intermittent control model. Further analyses suggest that deterministic, including chaotic, slow oscillations that characterize the intermittent control strategy, together with the small hemodynamic perturbation, could be a possible mechanism for generating the postural sway.
authors: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan. taishin@bpe.es.osaka-u.ac.jp
authors: Taishin
authors: T
authors: Nomura
authors: Shota
authors: S
authors: Oshikawa
authors: Yasuyuki
authors: Y
authors: Suzuki
authors: Ken
authors: K
authors: Kiyono
authors: Pietro
authors: P
authors: Morasso
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena; D025461:Feedback, Physiological; D006439:Hemodynamics; D006801:Humans; D055641:Mathematical Concepts; D008954:Models, Biological; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology*; D019415:Torque
keywords: Hemodynamics; Intermittent control; Noise; Postural sway; Posture control; Power law