ABSTRACT
Within the framework of coordination dynamics (Kelso, 1995), Bardy and collaborators (e.g., Bardy et a!., 1999) analyzed the whole body joint coordination in the sagittal plane during a visual tracking task. They proposed a collective variable capturing in a simple way the complex interactions operating within the postural system: the relative phase between the ankles and the hips. Two coordination modes were observed depending on target frequency: An in-phase mode for low frequencies and an anti-phase mode for high frequencies. Furthermore, this postural task allowed the observation of several self-organized properties, such as phase transition, multi-stability, critical fluctuations and hysteresis.
