Quantifying intra-limb coordination in walking of healthy children aged three to six.

The aim of this study was first to quantify intra-limb coordination and then to explore the gender differences of 180 healthy children aged 3-6. The children's joint Euler angles and angular velocities were measured and were used to calculate the phase angle (PA) and continuous relative phase (CRP). Firstly, a portrait of the mean and standard deviation (SD) of PA and CRP was applied to quantify coordination in the knees and ankles; then five key events in walking were selected and their inter-age differences were assessed by One-way ANOVA. Finally, gender differences were evaluated by GLM-Univariate. The significance level was 0.05 and confidence interval was 95%. Our results show that similar portraits of PA and CRP were found for knees and ankles from age 3-6; SD demonstrated that the PA and CRP in the knees and ankles were consistent with the increase in age. Moreover, θ_CRP(K-A) demonstrated that the direction reversal in heels off of those two joints in children aged 5 and 6 was earlier than those of age 3 and 4 and no inter-age significant differences were recorded for PA and CRP in either gait event. Finally, gender differences exist before the age of six, particularly in the transition period such as heel contact, toe off and during the mid swing. Overall, although further development such as gait control or balance is still improving, basic principle of intra-limb coordination has formed by the age of 3 and gender differences already existed before age of 6.