Inter-joint coordination during Si-St and St-Si tasks in stroke patients with hemiplegia

The Si-St and St-Si tasks were performed while each subject’s joint kinematics were recorded using a three-dimensional motion capture system. Sagittal joint angles of the bilateral hip, knee and ankle joints as well as the movement duration were extracted. The angle-angle diagrams for the hip-knee, hip-ankle and knee-ankle joint were plotted to assess the inter-joint coordination. The inter-joint coordination was quantified using geometric characteristics of the angle-angle diagrams, including perimeter, area and dimensionless ratio. The coefficient of variation (CV) was performed to compare variability of the coordination parameters.The Shapiro-Wilk test was used to examine the normal distribution of the data. For normally distributed data, the paired samples t-test was used to compare bilateral coordination differences, and the independent samples t-test was used to compare group (stroke versus healthy) differences in coordination parameters. For non-normally distributed data, the Wilcoxon signed rank test was used to compare bilateral coordination differences, and the Kruskal-Wallis test was used to compare group (stroke versus healthy) differences in coordination parameters. Two-way ANOVA was used to examine the effect of movement duration and group (short versus longer duration) on coordination.