Motion compensation strategy of preschoolers coping with tasks of stride length changes and curve turnings: in terms of centre of mass

The purpose of this study was first to disclose motion compensation strategy of healthy preschoolers according to evaluate how the stride length changes and curve turnings affected their Centre of Mass (CoM) performances; and then to comprehend the process of children develop in motion. Ten healthy children aged around 6 and 9 adults aged 23-47 were recruited in this study. The CoM was calculated based on four key markers in pelvis and its trajectory in five tasks including the stride length changes (short stride, straight walking and long stride) and curve turnings (0°-30°-60°) were first recorded; and then variables such as trajectory of CoM in sagittal and coronal plane, Unit of Energy (uEN), Energy Kinetic (uEk) and Gravitational Potential Energy (uEg) in the critical gait period were analyzed. Results show that as the stride length increase, child accordingly enlarged their motion range of CoM both in mediolateral and vertical direction to assist the whole-body movement; meanwhile, children's uEN increased as the stride length prolonged. Further, since 10%GC, child's CoM shifted gradually to the curving direction (right) as curve turning angle aggregated; while, dramatic change occurred at 60%GC, where a larger CoM deviation was found in 60° than that of 30°. The uEN of children was low before 60%GC, but it raised prominently after 60%GC. Overall, adult-like CoM were partly found in healthy preschoolers when coping with varied gait tasks, however distinctions existed which demonstrated that compensative strategies of those children were still developing.