Maturation of postural sway in young children.

The postural sway of 76 healthy young children aged from two to 14 years was investigated to identify age-related changes in the extent of sway, the effects of eye-closure, and the spectral composition of sway. Postural sway was measured from the excursions of the centre of pressure of ground reaction forces, and was analysed for both time and frequency. Within the age-range of the children tested, postural sway decreased linearly with age. Boys tended to become more stable at a faster rate than girls, but started from an initially greater level of instability. The children's Romberg quotients, which provide an index of the influence of eye-closure on sway magnitude, were remarkably low in comparison with adult values. Power spectral analysis of the postural sway showed that the principal energy was contained below 0.7 Hz for both lateral and antero-posterior sway, but that very young children had some power in the 0.8 to 2.0 Hz range. Taken together, these results confirm and extend the previously established view that children use visual information to control balance in a manner different from that of adults, and that it is not until after the age of seven years that adult-like balance-control strategies begin to appear. Also, in contrast to adults, the appearance of sway at high frequencies in children is not necessarily associated with any pathology.