Invariant sway properties in children.

The ability to maintain upright body posture depends on the biomechanical properties of a body and on the execution of control programs. The aim of this study was to determine how the structural growth of the human body, between ages 7-18, affects spontaneous sway parameters and to determine how the visual feedback positional task changes body sway parameters. The selected parameters of postural sway were evaluated in 57 children aged 7-18, while they stood with their feet together for 30 s. The experiment consisted of two different tasks: free standing with no feedback (No feedback), and free standing with additional visual feedback (Feedback). No statistically significant correlation between sway parameters and developmental factors (body height, body mass, and age) in the No Feedback task was found. Statistically significant correlations were found between age and most of the sway parameters in the Feedback task. The execution of voluntary feedback resulted in an increase in the total sway (20%), while the total area decreased nearly two-times. The invariance of sway amplitude supports the view that the same activation patterns can be utilized by children aged 7-18, despite the changes in body dimensions.