A model of postural coordination dynamics

Prior research has shown that voluntary postural movement is characterized by stable in-phase and antiphase hip-ankle coordination modes. Prior modeling of coordination dynamics does not capture the stable fixed-points, phase transitions and hysteresis found in hip-ankle coordination. In this article a model was created to capture the dynamics of hip-ankle postural coordination. The present model follows the synergetic approach and uses two nonlinear oscillators to capture the dynamics of hip-ankle coordination. Terms for symmetry breaking and additive stochastic noise are included in the model. The model captures phase transitions from in-phase to antiphase coordination as movement frequency is scaled up and from antiphase to in-phase coordination as movement frequency is scaled down. The model also exhibits hysteresis, with phase transitions occurring at different movement frequencies as the control parameter is scaled up and down.