The effect of facing direction on static balance of children while standing on stairs

Abstract

Background: Balance control is essential to all upright activities, and can be influenced by environmental conditions and tasks. While standing on higher surface, the perception of height was changes in the adults that they might overestimate the height and adopt different strategies, such as stiffness strategy.Children need to stand and engage activities on higher surfaces occasionally, such as playing at playground or walking up/down stairs, but the immature sensory, motor and cognitive development, and insufficient experiences make them unable to balance or react as appropriate as adults. It is hypothesized that facing direction (ascending or descending) while standing on stairs would affect the height perception of children, and thus change their balance control in static stance. Purpose: To investigate the effect of facing direction on the center of pressure (COP) parameters in typically developing children aged 6–9 years while standing on a staircase. Methods: Thirteen children aged 6–9 years (6 girls, 7 boys) were recruited for the study. The average body height was 129.23 cm (SD 11.11), and body weight was 31.15 kg (SD 11.24). Foot length (FL) was measured from the heel to the tip of the big toe, and was used for normalizing the differences of body statue. Ground reaction forces were measured by a portable force plate (9286BA, Kistler Instruments Ltd, Switzerland). The data was collected when the participants maintained static standing for 20 seconds on a staircase with 90 cm in height under two conditions, facing ascending (AscD) and descending direction (DesD). BioWare 4.1 was used to calculate the center of pressure (COP). Twoway ANOVA with repeated measure (height x direction) and pairwise comparisons were employed to verify differences in total path length, sway area, root mean square (RMS) of COP displacement, RMS of COP velocity, and mean power frequency (MPF) of COP. Results:The results indicated there is no interaction effect of height and facing direction on all COP parameters. Height had significant main effect on COP displacement and mean power frequency in antero-posterior (AP) direction. Facing direction had significant main effect on total path length, and RMS of COP velocity in AP direction. While facing AscD, the normalized total path length (112.76± 7.08% of foot length) was significantly larger than DesD (107.23± 6.70% of FL); the RMS of COP velocity in AP direction was significantly larger in AsD (6.34± 0.34% of FL•sec) than that in DesD (5.99± 0.31% of FL•sec). Conclusion(s): It is expected that facing DesD should put more threats on the children than AscD, and thus the children might show increases in COP velocity when facing DesD. However, the results demonstrate that sway velocity in AP direction and total path length of COP is greater when facing AsD than facing DesD, which were not consistent with the adults’ findings. Future studies should increase age range of the participants, so at what age the children adopt the adults’ like strategies can be determined. Implications: This study may help in understanding the development of balance control in children. This matter should be taken into consideration when planning the environment for children at different age.