Visual information and multi-joint coordination patterns in one-leg stance.

This study examined the influence of visual information on the multi-joint coordination patterns in maintaining one-leg stance. 12 participants stood still on their left leg for two 1 min trials with and without visual information. The multi-joint coordination patterns in the frontal plane were examined using a frequency domain principal component analysis (PCAf) on 14 joint angular motion time series. The factor loading spectra of PC1 showed two distinct multi-joint postural coordination strategies that relate to the mechanical constraints on balance identified by Hof (2007) [7]. The more prevalent strategy was the coordination of the left ankle-left knee or the left ankle only motion that is related to the "moving the center of pressure" strategy. A 2nd multi-joint coordination strategy showed larger factor loading of the trunk and upper limbs (i.e., shoulders and elbows) in addition to the left ankle implying the role of the upper limbs to generate "counter-rotational torque against the sway of the center of mass (COM)". With eyes open, the participants predominantly utilized the 1st strategy to maintain balance but switched to the 2nd strategy when visual information was not available during the stance. The role of visual information in determining the prevalence of two dominant multi-joint coordination kinematic patterns in one-leg stance reflects the redundant and emergent properties of the postural control system that channel the biomechanical constraints on balance arising from the interaction of the task, environment and the individual.